Category Archives: Medicine/Healthcare

Science (Indeed, the World) Needs Fewer, Not More, Icons.

by Kenneth W. Krause.

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes frequently to Skeptic as well. He can be contracted at krausekc@msn.com.

The Sims statue and its protestors.

To the extent we are rational, we share the same identity.—Rebecca Goldstein.

September was an awkward month for Nature, perhaps the most influential and well-respected science publication on the planet.  In August, a group peacefully protested, and vandals subsequently defaced, a Central Park statue of J. Marion Sims, a 19th-century surgeon and founder of the New York Women’s Hospital often referred to as the “father of modern gynecology.”  Sims’ likeness was left with fiendish red eyes and the word “RACIST” scrawled across its back.

The quarrel stemmed from the mostly undisputed facts that, although Sims helped develop life-saving surgical techniques to help women recover from particularly traumatic births, he also experimented on female slaves without providing anesthesia, and after seeking consent only from their owners. Unsurprisingly, commentators contest whether Sims’ methods were consistent with the customs and scruples of his time (Washington 2017).

Nature’s first inclination was to publish an editorial originally titled, “Removing the Statues of Historical Figures Risks Whitewashing History,” arguing that we should leave such icons in place to remind passers-by of the important historical lessons they might provide (The Editors 2017). The piece also recommended the installation of additional iconography to “describe the unethical behavior and pay respect to the victims of the experimentation.”

Given then-recent events in the ever-emotionally explosive and divisive world of American popular culture especially, vigorous dissent was inevitable. A flurry of indignant letters descended on Nature’s editors.  Several writers suggested that, at least in America, the primary if not sole purpose of public statuary is to honor its subjects, not to inform curious minds of their historical significances (Comment 2017).  One contributor noted that the history of Nazi Germany has been well-documented in the very conspicuous absence of Nazi iconography.  Another reasoned that because written documentation always precedes statuary, removal of monuments would have “no impact on our understanding of the historical failings of those individuals.”

Other letters offered less restrained and, frankly, less disciplined commentary. One author submitted that the editorial “perpetuate[d] racist white supremacy.”  Two more branded it simply as “white privilege at its height” and as a “racist screed.”  Another found the article in support of “unethical science” and to inform Nature’s minority readers that they “remain unwelcome in science because of their race.”

Vandals defaced the Sims likeness with red paint.

But more importantly for my purposes here, many writers contributed thoughts on the Sims monument itself that reveal quite plainly our human tendencies to interpret the inherent ambiguity of statues—indeed iconography and other symbolic expressions more generally—consistent with our fears, personal agendas, or ideological mindsets. One author, for example, confided that the Sims statue bid her to “Go away, woman.  You have no authority here,” and to “Go away, woman of African descent.  You cannot have the intellect to contribute to the science of your own healthcare” (Green 2017).  Another saw Sims’ likeness as a “signal” that the “accomplishments of a white man are more important than his methods or the countless people he victimized,” and that “the unwilling subjects of that research … are unimportant and should be washed away.” (Gould 2017; Comment 2017).  Yes, all of that from a motionless, voiceless sculpture.

In the end, Nature’s guests called consistently for the icon’s swift removal.  And given its and any other statue’s essential ambiguity, I agree.  Take it away, melt it down, and donate its metal to a more fruitful purpose.  But, regrettably, many writers also petitioned for additional iconography—this time to honor accomplished females in medicine and the victims of sexist and racist medical practices.  In other words, they would display more monuments of more humans, no doubt all with potentially hideous skeletons lurking in their so far sealed closets, likely to be scrutinized and challenged by any conceivable number of equally fault- and agenda-ridden human interpreters to come.

In the rush to colonize others’ minds, or perhaps to cast painful blows against cross-cultural enemies, has anyone actually taken the time and effort to think this through? Both duly and thoroughly reproved, Nature’s editors quickly apologized and revised their article, including its title, to comply with reader objections (Campbell 2017; The Editors 2017).  But glaring similarities between the Sims controversy and more widely publicized events involving statues of Confederate generals, for example (at least one of which resulted in meaningless violence), have attracted the attention of the general media as well.

Police protect Charlottesville’s statue of General Lee.

Writing for The Atlantic, Ross Anderson aptly observed that “the writing of history and building of monuments are distinct acts, motivated by distinct values” (Anderson 2017).  No serious person ever suggested, he continued, that statuary “purport[s] to be an accurate depiction of its history.”  So far, so good.  At that critical point, Anderson appeared well on his way to advancing the sensible argument that inherently simplistic and ambiguous iconography can only divide our society, and perhaps even inspire (more) pointless violence.

Unfortunately, that was also the point where the author stumbled and then strayed onto perhaps well-worn, but nevertheless unsustainable trail. The legitimate purpose of a society’s statuary, he argued, is “an elevation of particular individuals as representative of its highest ideals,” a collective judgment as to “who should loom over us on pedestals, enshrined in metal or stone ….”  But, honestly, no credible history has ever instructed that any individual, no matter how accomplished, whether male or female, black or white, can ever represent our “highest ideals.”  And is there anything about recent American history to suggest we could ever agree on what constitutes those ideals?  And, come to think of it, how do people tend to react when others choose which monuments and symbols will “loom over” them?  Indeed, wasn’t that the problem in Charlottesville, Virginia?

White supremacists march on Charlottesville.

According to Anderson, the activists demanding removal of the Sims statue and its replacement with iconography of presumptively more deserving subjects ask only “that we absorb the hard work of contemporary historians … and use that understanding to inform our choices about who we honor.” But, as any experienced historian knows, historical facts can be, and often are, responsibly parsed and interpreted in many different ways.  And why should common citizens blindly accept one credible historian’s perspective over that of any other?  Regardless, shouldn’t we encourage the public to consult the actual history, rather than convenient, but severely underdeveloped and necessarily misleading shortcuts?

Author Dave Benner argued, instead, that we should preserve our monuments (Benner 2017). Pointing to the New Orleans statue of Franklin Roosevelt, which, to this point, remains free of public derision and vandalism, Benner reminded us of Executive Order 9066, by which FDR displaced 110,000 American citizens of Japanese ancestry into internment camps, without due process, in “one of the saddest and most tyrannical forms of executive overreach in American History.”  Should the FDR monument (indeed, the dime) be purged according to the same reasoning offered by Nature’s revised editorial and those who oppose the Sims statue?  By such a standard, would iconography depicting any of the American founders survive?

Perhaps not. But to what supposedly disastrous end?  By Benner’s lights, the removal of cultural iconography would “simply make it harder for individuals to learn from the past.”  But, again, as the many dissenter’s to Nature’s original editorial observed, the purpose of statuary is not to inform.  And let’s be completely candid here: nor is it to “honor” the dead and insensible subjects of such iconography who no longer hold a stake in that or any other outcome.  Rather, the unspoken object is no less than to decree and dispense value judgments for the masses.

And some would no doubt argue the propriety of that object in the context of politics and government. But can and should science do better?  “As the statues and portraits of Sims make clear,” offers Harriet Washington, award-winning author of Medical Apartheid, “art can create beautiful lies” (Washington 2017).  “To find the truth,” she advises, “we must be willing to dig deeper and be willing to confront ugly facts.  No scientist, no thinking individual, should be content to accept pretty propaganda.”

Science’s battle is not with any particular ideological foe. It stands against all ideologies equally.  It has no interest in turning minds to any individual’s, or any coalition’s social cause because it has no agenda beyond the entire objective truth.  Science is incapable of pursuing ambiguity or any shortcut, especially where the potential for clarity, completion, and credibility persists.  And science certainly doesn’t need more icons; it needs fewer, or none.

 

A final thought on symbolic expression:

Yes, American history is saturated with political symbolism, from the flags of the colonial rebellion to the Tinker armbands and beyond.  As I wrote this column, however, the discussion of alleged “race” in America grew increasingly inane—dominated, in fact, by Donald Trump, our Clown in Chief, on one side, and mostly mute and under-studied NFL football players on the other.  The social, popular, and activist media, along with their rapacious followers, of course, seemed thoroughly enchanted by this absurd spectacle.

I take no position on this “debate,” if it can be so characterized. Indeed, comprehension of the contestants’ grievances is precluded by their irresponsible methods.  The President’s very involvement is inexplicable.  But, for me, it’s the players’ exclusively symbolic expressions that cause greater concern.  Again, not because I disagree with whatever they might be trying to say.  Rather, because their gestures are so ambiguous and amenable to any number of conceivable interpretations that, in the end, they say nothing.  Is this the future of all public discourse?

Waving or burning flags just isn’t impressive. Nor is standing, or sitting when others stand.  Nor is raising a fist or locking arms.  Because these expressions require no real investments, they amount to cheap, lazy, conveniently vague, and, thus, mostly empty gestures.  I’m old enough to know that they’ll persist, of course, and no doubt dominate the general public’s collective consciousness.  I only hope we can manage to maintain, perhaps even expand, spaces for more sober, motivated, and responsible discourse.  In any case, I’d prefer not to spend my remaining years watching them being torn down, especially from within.

 

References:

Anderson, R. 2017. Nature’s Disastrous ‘Whitewashing’ Editorial. Available online at https://www.theatlantic.com/science/archive/2017/09/an-unfortunate-editorial-in-nature/538998/; accessed September 27, 2017.

Benner, D. 2017. Why the Purge of Historic Monuments Is a Bad Idea. Available online at http://www.intellectualtakeout.org/23021; accessed September 27, 2017.

Campbell, P. 2017. Statues: an editorial response. Nature 549: 334.

Comment. 2017. Readers Respond to Nature’s Editorial on Historical Monuments. Available online at http://www.nature.com/news/readers-respond-to-nature-s-editorial-on-historical-monuments-1.22584; accessed September 26, 2017.

Gould, K.E. 2017. Statues: for those deserving respect. Nature 549: 160.

Green, M.H. 2017. Statues: a mother of gynaecology. Nature 549: 160.

The Editors. 2017. Science must acknowledge its past mistakes and crimes. Nature 549: 5-6.

Washington, H. 2017. Statues that perpetuate lies should not stand. Nature 549: 309.

Advertisements

Editing the Human Germline: Groundbreaking Science and Mind-numbing Sentiment.

by Kenneth W. Krause.

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes frequently to Skeptic as well. He can be contracted at krausekc@msn.com.

The CRISPR Complex at work.

Should biologists use new gene-editing technology to modify or “correct” the human germline? Will our methods soon prove sufficiently safe and efficient and, if so, for what purposes?  Much-celebrated CRISPR pioneer, Jennifer Doudna, recently recalled her initial trepidations over that very prospect:

Humans had never before had a tool like CRISPR, and it had the potential to turn not only living people’s genomes but also all future genomes into a collective palimpsest upon which any bit of genetic code could be erased and overwritten depending on the whims of the generation doing the writing…. Somebody was inevitably going to use CRISPR in a human embryo … and it might well change the course of our species’ history in the long run, in ways that were impossible to foretell.

(Doudna and Sternberg 2017). And it didn’t take long.  Just one month after Doudna and others called for a moratorium on human germline editing in the clinical setting, scientists in Junjiu Huang’s lab at Sun Yat-sen University in Guangzhou, China published a paper describing their exclusively in vitro use of CRISPR on eighty-six human embryos (Liang et al. 2015).  Huang’s goal was to edit mutated beta-globin genes that would otherwise trigger a debilitating blood disorder called beta-thalassemia.

But the outcomes were mixed, at best.  After injecting each embryo with a CRISPR complex composed of a guide RNA molecule, a gene-slicing Cas-9 enzyme, a synthetic repair DNA template, and a “glow-in-the-dark” jellyfish gene that allows investigators to track their results as cells continue to divide, Huang’s team delivered a paltry five percent efficiency rate.  Some embryos displayed unintended, “off-target” editing.  In others, cells ignored the repair template and used the related delta-globin gene as a model instead.  A third group of embryos turned mosaic, containing cells with an untidy jumble of editions.  Part of the problem was that CRISPR had initiated only after the fertilized egg had begun to divide.

By using non-viable triploid embryos containing three sets of chromosomes, instead of the usual two, Huang avoided objections that he had destroyed potential human lives.  Nevertheless, both Science and Nature rejected his manuscript based in part on ethical concerns.  Several scientific agencies also promptly reemphasized their stances against human germline modification in viable embryos, and, in the US, the Obama Administration announced its position that the human germline should not be altered at that time for clinical purposes.  Francis Collins, director of the National Institutes of Health, emphasized that the US government would not fund any experiments involving the editing of human embryos.  And finally, earlier this year, a committee of the US National Academies of Sciences and Medicine decreed that clinical use of germline editing would be allowed only when prospective parents had no other opportunities to birth healthy children.

Meanwhile, experimentation continued in China, with similarly grim results. But this past August, an international team based in the US—this time led by embryologist Shoukhrat Mitalipov at the Oregon Health and Science University in Portland—demonstrated that, under certain circumstances, genetic defects in human embryos can, in fact, be efficiently and safely repaired (Ma et al. 2017).

Embyologist Shoukhrat Mitalipov.

Mitalipov’s group attempted to correct an autosomal dominant mutation—where a single copy of a mutated gene results in disease symptoms—of the MYBPC3 gene.  Crucially, such mutations are responsible for an estimated forty percent of all genetic defects causing hypertrophic cardiomyopathy (HCM), along with ample portions of other inherited cardiomyopathies.  Afflicting one in every 500 adults, HCM cannot be cured, and remains the most common cause of heart failure and sudden death among otherwise healthy young athletes.  These mutations have escaped the pressures of natural selection, unfortunately, due to the disorder’s typically late onset—that is, following reproductive maturity.

Prospective parents can, however, prevent HCM in their children during the in vitro fertilization/preimplantation genetic diagnosis (IVF/PGD) process.  Where only one parent carries a heterozygous mutation, fifty percent of the resulting embryos can be diagnosed as healthy contenders for implantation.  The remaining unhealthy fifty percent will be discarded.  As such, correction of mutated MYBPC3 alleles would not only rescue the latter group of embryos, but improve pregnancy rates and save prospective mothers—especially older women with high aneuploidy rates and fewer viable eggs—from risks associated with increasing numbers of IVF/PGD cycles as well

With these critical facts in mind, Mitalipov and colleagues employed a CRISPR complex generally similar to that used by Huang.  It included a guide RNA sequence, a Cas-9 endonuclease, and a synthetic repair template.  In one phase of their investigation, the team fertilized fifty-four human oocytes (from twelve healthy donors) with unhealthy sperm carrying the MYBPC3 mutation (from a single donor), and injected the resulting embryos eighteen hours later with the CRISPR complex.  The result? Thirteen treated embryos became jumbled mosaics.

Mitalipov changed things up considerably, however, in the study’s second phase by delivering the complex much earlier than he and others had done in previous experiments—indeed, at the very brink fertilization. More precisely, his colleagues injected the CRISPR components along with the mutated sperm cells into fifty-eight healthy, “wild-type” oocytes during metaphase of the second meiotic division.  Here, the results were impressive, to say the least.  Forty-two treated embryos were normalized, carrying two copies of the healthy MYBPC3 allele—a seventy-two percent rate of efficiency, no “off-target effects” were detected, and only one embryo turned mosaic.

Mosaicism and Off-target Effects.

Mitalipov’s team achieved a genuine breakthrough in terms of both efficacy and safety.  Perhaps nearly as interesting—and, in fact, the study’s primary finding, according to the authors—is that, in both experimental phases, the embryos consistently ignored Mitalipov’s synthetic repair template and turned instead to the healthy maternal allele as their model.  Such is not the case when CRISPR is used to edit somatic (body) cells, for example.  Apparently, the team surmised, human embryos evolved an alternative, germline-specific DNA repair mechanism, perhaps to afford the germline special protection.

The clinical implications of this repair preference are profound and, at least arguably, very unfortunate.  First, with present methods, it now appears unlikely that scientists could engineer so-called “designer babies” endowed with trait enhancements.  Second, it seems nearly as doubtful that CRISPR can be used to repair homozygous disease mutations where both alleles are mutant.  Nevertheless, Mitalipov’s method could be applied to more than 10,000 diseases, including breast and ovarian cancers linked to BRCA gene mutations, Huntington’s, cystic fibrosis, Tay-Sachs, and even some cases of early-onset Alzheimer’s.

At least in theory.  As of this writing, Mitalipov’s results have yet to be replicated, and even he warns that, despite the new safety assurances and the remarkable targeting efficiencies furnished by his most recent work, gene-editing techniques must be “further optimized before clinical application of germline correction can be considered.” According to stem-cell biologist George Daley of Boston Children’s Hospital, Mitalipov’s experiments have proven that CRISPR is “likely to be operative,” but “still very premature” (Ledford 2017).  And while Doudna characterized the results as “one giant leap for (hu)mankind,” she also expressed discomfort with the new research’s unmistakable inclination toward clinical applications (Belluck 2017).

Indeed, within a single day of Mitalipov’s report, eleven scientific and medical organizations, including the American Society of Human Genetics, published a position statement outlining their recommendations regarding the human germline (Ormond et al. 2017).  Therein, the authors appeared to encourage not only in vitro research but public funding as well.  Although they advised against any contemporary gene-editing process intended to culminate in human pregnancy, but also suggested that clinical applications might proceed in the future subject to a compelling medical rationale, a sufficient evidence base, an ethical justification, and a transparent and public process to solicit input.

And of course researchers like Mitalipov will be forced to contend with those who claim that, regardless of purpose, the creation and destruction of human embryos is always ethically akin to murder (Mitalipov destroyed his embryos within days of their creation).  But others have lately expressed even less forward-thinking and, frankly, even more irrational and dangerous sentiments.

For example, a thoroughly galling article I can describe further only as “pro-disability” (In stark contrast to “pro-disabled”) was recently published, surprisingly to me, in one of the world’s most prestigious science publications (Hayden 2017).  It begins by describing a basketball game in which a nine-year-old girl, legally blind due to genetic albinism, scored not only the winning basket, but, evidently—through sheer determination—all of her team’s points.  Odd, perhaps, but great!  So far.

But the story quickly turns sour, to the girl’s father who apparently had asked the child, first, whether she wished she would have been born with normal sight, and, second (excruciatingly), whether she would ever help her own children achieve normal sight through genetic correction. Unsurprisingly, the nine-year-old is said to have echoed what we then learn to be her father’s heartfelt but nonetheless bizarre conviction: “Changing her disability … would have made us and her different in a way we would have regretted,” which to him, would be “scary.”

To be fair, the article very briefly appends counsel from a man with Huntington’s, for instance, who suggests that “[a]nyone who has to actually face the reality … is not going to have a remote compunction about thinking there is any moral issue at all.”  But the narrative quickly circles back to a linguist, for example, who describes deaf parents who deny both their and their children’s disabilities and have even selected for deafness in their children through IVF/PGD, and a literary scholar who believes that disabilities have brought people closer together to create a more inclusive world (much as some claim Western terrorism has).  The author then laments the fact that, due to modern reproductive technology, fewer children are being born with Down’s syndrome.

To summarize, according to one disabilities historian, “There are some good things that come from having a genetic illness.”  Uh-huh.  In other words, disabilities are actually beneficial because they provide people with challenges to overcome—as if relatively healthy people are incapable of voluntarily and thoughtfully designing both mental and physical challenges for themselves and their kids.

I think not. Disabilities, by definition, are bad.  And, as even a minimally compassionate people, if we possess a safe and efficient technological means of preventing blindness, deafness, or any other debilitating disease in any child or in any child’s progeny, we also necessarily have an urgent ethical obligation to use them.

 

References:

Belluck, P. 2017. In breakthrough, scientists edit a dangerous mutation from genes in human embryos. Available online at https://nyti.ms/2hnZ9ey; accessed August 9, 2017.

Doudna, J.A., and S.H. Sternberg. 2017. A Crack in Creation: Gene Editing and the Unthinkable Power to Control Evolution. Boston: Houghton Mifflin Harcourt.

Hayden, E.C. 2017. Tomorrow’s children. Nature 530:402-05.

Ledford, H. 2017. CRISPR fixes embryo error. Science 548:13-14.

Liang, P., Y. Xu, X. Zhang, et al. 2015. CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes. Protein and Cell 6(5):363-72.

Ma, H., N. Marti-Gutierrez, S. Park, et al. 2017. Correction of a pathogenic gene mutation in human embryos. Nature DOI:10.1038/nature23305.

Ormond, K.E., D.P. Mortlock, D.T. Scholes, et al. 2017. Human germline genome editing. The American Journal of Human Genetics 101:167-76.

The Delectable Myths of Healthy and Healthier Obesity.

by Kenneth W. Krause.

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes frequently to Skeptic as well. He can be contracted at krausekc@msn.com.

obesity-paradox1

Why, sometimes I’ve believed as many as six impossible things before breakfast.–The Queen, to Alice in Through the Looking Glass.

Wouldn’t it be splendid to have our cakes and eat them too? Arguably, both ideology and popular culture allow their followers to do just that.  Until they don’t, of course.  At that point, when facts and logic can no longer be denied, the rudely awakened find themselves confronted with difficult choices.

The concept of healthy obesity, for example, has gained much traction during the last fifteen years. At one end of the continuum, members of the popular but clearly flawed “Healthy at Every Size (HAES)” movement profess the nonexistence of excess adiposity and suggest that even the most obese people can lead perfectly healthy lives (“Every size”—really?).  On the other end, and somewhat more credibly, others allege the existence of an “obesity paradox” and a “metabolically healthy obesity.”  Such are the tantalizing subjects of this column.

Cardiologist and obesity researcher, Carl J. Lavie, has described the paradox as follows: “Overweight and moderately obese patients with certain chronic diseases … often live longer and fare better than normal-weight patients with the same ailments” (Lavie 2014). In addition to his own research, Lavie’s conclusions are based on a revolutionary and, in some circles, much-celebrated JAMA study led by Katherine Flegal at the US Centers for Disease Control and Prevention, who reviewed 97 studies of more than 2.88 million individuals to calculate all-cause mortality hazard ratios for standard body mass index (BMI) classifications (Flegal et al. 2013).

Katherine Flegal

Katherine Flegal

Flegal’s team reported as follows: Relative to normal weight, all combined grades of obesity were associated with an 18 percent higher incidence of all-cause mortality. In cases of more extreme of obesity, the association rose to 29 percent.  By itself, however, the mildest grade of obesity was not correlated with a significantly elevated risk, and the overweight but not obese category was actually associated with a 6 percent lower incidence of all-cause mortality.  Predictably, the popular media quickly seized on the overweight population’s presumed appetite for these tempting results.

bmi

Metabolically healthy, or “benign,” obesity, on the other hand—which Lavie dubs the “ultimate paradox”—appears to have no standard definition or list of qualifying criteria, but is often characterized generally as “obesity without the presence of metabolic diseases such as type 2 diabetes, dyslipidemia or hypertension” (Munoz-Garach et al. 2016). Retained insulin sensitivity, however, is the hallmark trait of this subpopulation.  Researchers have assigned up to 32 percent of the obese population to this phenotype.  It applies more prevalently to women than men, but is thought to decrease with age among both sexes.  Researchers have yet to determine whether these obese are genetically predisposed to decreased risks of disease or mortality.  But their existence, along with that of the metabolically unhealthy normal-weight population, suggests that factors other than excess adiposity are at play.

All of which might sound at least somewhat comforting to the now 600 million obese worldwide (and still growing) who have been told for decades that obesity per se will significantly increase one’s susceptibility to heart disease, stroke, cancer, diabetes, and arthritis, for example. Preferences and popular reports aside, however, it appears we may yet be forced to choose between possessing our cakes and consuming them, because an impressive body of new and well-conceived research has called both the paradox and healthy obesity into serious question.

Consider, for example, a truly enormous international meta-analysis published last July in The Lancet by the Global BMI Mortality Collaboration (GBMC 2016).  Led by Harvard professor of nutrition and epidemiology, Frank Hu, this study poured over data from more than 10.6 million participants who were followed for up to 14 years.  239 large studies conducted in 32 countries were included.  Importantly, the Collaboration attempted to control for a “reverse causation bias,” in which low BMI was the result, rather than the cause, of an underlying or preclinical illness by excluding current or former smokers, those who suffered from chronic disease at the study’s inception, and those who died during the initial five years of follow-up.  In other words, Hu’s team addressed the potential for potent confounders that Flegal’s team, for lack of data, was forced to ignore.

The Collaboration’s results were startling. Interestingly, Hu “was able to reproduce [Flegal’s results] when conducting crude analyses with inadequate control of reverse causality, but not when [he] conducted appropriately strict analyses.”  In the end, then, the Collaboration found that, worldwide, participants with a normal BMI in the 22.5 to 25 range enjoyed the lowest risk of mortality and that such risk increased significantly throughout the overweight and obese ranges.  In fact, every five units of BMI in excess of 25 was associated generally with a 31 percent greater risk of premature death—specifically, 49 percent for cardiovascular-related, 38 percent for respiratory-related, and 19 percent for cancer-related mortality.  According to Hu, his team had succeeded in “challeng[ing] previous suggestions that overweight and grade 1 obesity are not associated with higher mortality, bypassing speculations about hypothetical protective metabolic effects of increased body fat in apparently healthy individuals.”

Frank Hu

Frank Hu

Consider too, a large prospective cohort study published last October in the BMJ in which about 115,000 participants—free of cardiovascular disease and cancer at baseline—were followed for up to 32 years (Veronese et al. 2016).  Evaluating the combined associations of diet, exercise, alcohol consumption, and smoking with BMI on the risk of all-cause and cause-specific mortality, this study was also designed to address Flegal’s peculiar 2013 results.  A lead author here as well, Frank Hu first noted, once again, that previous examinations suggesting an obesity paradox, including Flegal’s, had allowed for potentially confounding bias by failing to distinguish between healthy normal-weight individuals and a “substantial proportion of the US population” in which “leanness is driven by other factors that can increase risk of mortality,” including existing or preclinical chronic diseases and smoking.

Contrary to the alleged paradox, Hu discovered that when lifestyle factors were taken into serious consideration, the lowest risk of all-cause and cardiovascular mortality was enjoyed by participants in the slightly low-to-normal, 18.5 to 22.4 BMI range—that is, when those subjects also displayed at least three out of four healthy lifestyle factors, including healthy eating, adequate exercise, moderate alcohol intake, and no smoking. In the end, according to Hu’s team, “the U-shaped relation between BMI and mortality observed in many epidemiological studies is driven by an over-representation in our societies of individuals who are lean because of chronic metabolic and pathological conditions caused by exposure to smoking, a sedentary lifestyle, and/or unhealthy diets.”  The optimal human condition, in other words, is not overweight of any kind or to any degree, but rather “leanness induced by healthy lifestyles.”

So much for the obesity paradox, at least for now. But what of its somewhat less voracious cousin, the notion of metabolically healthy obesity?

Recognizing prior support for so-called “benign obesity,” a trio of Canadian diabetes researchers led by Caroline Kramer conducted a systematic review and meta-analysis of eight studies evaluating over 61,000 subjects—many of whom were classified as metabolically healthy obese—for all-cause mortality and cardiovascular events (Kramer et al. 2013). When all studies were considered, regardless of follow-up duration, the healthy obese subjects displayed risks similar to those of healthy normal-weight participants.  However, when considering only those studies that followed-up for at least ten years, Kramer and colleagues discovered that the purportedly healthy obese were significantly more likely than their normal counterparts to perish or suffer serious cardiovascular trouble.

Caroline Kramer

Caroline Kramer

Should we infer, then, that the healthy obese are, in fact, healthy until circumstances render them otherwise a decade later? Not according to Kramer.  Regardless of metabolic status, she warned, even in the short term, obesity is associated with subclinical vascular disease, left-ventricular abnormalities, chronic inflammation, and increased carotid artery intima-media thickness and coronary calcification.  In the end, the Canadians found no support for the “benign obesity” phenotype and declared with no uncertainty that “there is no ‘healthy’ pattern of obesity.”

Most recently, however, a diverse and impressively creative group of Swedish scientists used transcriptomic profiling in white adipose tissue to contrast responses to insulin stimulation between never-obese, unhealthy obese, and, again, supposedly healthy obese subjects. (Ryden et al. 2016). Led by Mikael Ryden at the Karolinska Institutet, this group revealed, first, clear distinctions between the never-obese and both groups of obese participants, and, second, nearly identical and abnormal patterns of gene expression among both insulin-resistant and insulin-sensitive obese subjects, independent of other cardiovascular or metabolic risk factors.

Said Ryden during a post-publication interview: “Insulin-sensitive obese individuals may not be as metabolically healthy as previously believed.” (ScienceDaily 2016). His team’s findings, he continued, “suggest that vigorous interventions may be necessary for all obese individuals, even those previously considered … healthy.”

To Lavie’s credit, he generally acknowledges obesity’s proven hazards. He also recognizes serious and consistent exercise as the most reliable strategy for attaining and maintaining good health.  Far less defensible, however, is Lavie’s insistence that exercise can render obesity a benign condition.  First, as much of the research presented here demonstrates, the chronic diseases strongly associated with obesity are, by definition, progressive and apt to cause damage down the road.  Second, in the real world, excess adiposity always leaves meaningful exercise a far more difficult and, thus, far less likely prospect.

obesity-paradox

Obese or not, our health continues to be undermined by the popular, ever-emotion-manipulating media, the misguided and oppressive forces of political correctness, and, most crucially, our own subjective prejudices and appetites. But as their numbers continue to swell, the overweight and obese grow increasingly vulnerable to seductive messages inviting self-deception and failure.  As in all other contexts, their liberation from these influences derives only from an unflinching appreciation for the methods of science—that is, empiricism, rationality, candor, and the assumption of responsibility for individual experimentation.  In a word, skepticism.

References:

Flegal, K.M., B.K. Kit, H. Orpana, et al. 2013. Association of all-cause mortality with overweight and obesity using standard body mass index categories. Journal of the American Medical Association 309(1): 71-82.

Global BMI Mortality Collaboration. 2016. Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. The Lancet 388: 776-786.

Kramer, C.K., B. Zinman, and R. Retnakaran. 2013. Are metabolically healthy overweight and obesity benign conditions? Annals of Internal Medicine 159(11): 758-769.

Lavie, Carl J. 2014. The Obesity Paradox: When Thinner Means Sicker and Heavier Means Healthier. NY: Plume.

Munoz-Garach, A., I. Cornejo-Pareja, and F.J. Tinahones. 2016. Does metabolically healthy obesity exist? Nutrients 8: 320.

Ryden, M., O. Hrydziuszko, E. Mileti, et al. 2016. The adipose transcriptional response to insulin is determined by obesity, not insulin sensitivity. Cell Reports 16: 2317-2326.

ScienceDaily. 2016. More evidence that “healthy obesity” may be a myth.” 18 August 2016. https://www.sciencedaily.com/releases/2016/08/160818131127.htm>.

Veronese, N., L. Yanping, J.E. Manson, et al. 2016. Combined associations of body weight and lifestyle factors with all cause and cause specific mortality in men and women: prospective cohort study. BMJ. DOI:10.1136/bmj.i5855.

Obesity: “Fat Chance” or Failure of Sincerity?

by Kenneth W. Krause.

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes frequently to Skeptic as well. He can be contracted at krausekc@msn.com.

popular culture3

Man is condemned to be free.—Jean-Paul Sartre.

Beginning about five years ago, the chronically overweight and obese were offered a new paradigm, one more consistent with their majority’s shared experiences in the twenty-first century. Emerging science from diverse fields, certain experts argued, complicated—perhaps even contradicted—the established view that weight maintenance was a straightforward, if not simple, matter of volitional control and balancing energy intake against energy expenditure.

As a host of potential complexities materialized, the frustrated members of this still expanding demographic were notified that, contrary to conventional wisdom, they had little or no control over their conditions. The popular literature especially began to hammer two captivating messages deeply into the public consciousness.  First, from within, the overweight and obese have been overwhelmed by their genomes, epigenomes, hormones, brains, and gut microbiomes, to name just a few.  Second, from without, their otherwise well-calculated and ample efforts have been undermined, for example, by the popular media, big food, government subsidies, poverty, and the relentless and unhealthy demands of contemporary life.

In a 2012 Nature opinion piece, Robert Lustig, Laura Schmidt, and Claire Brindis—three public health experts from the University of California, San Francisco, compared the “deadly effect” of added sugars (high-fructose corn syrup and sucrose) to that of alcohol(1).  Far from mere “empty calories,” they added, sugar is potentially “toxic” and addictive.  It alters metabolisms, raises blood pressures, causes hormonal chaos, and damages our livers.  Like both tobacco and alcohol (a distillation of sugar), it affects our brains as well, encouraging us to increase consumption.

Apparently unimpressed with Americans’ abilities to control themselves, Lustig et al. urged us to back restrictions on our own choices in the form of government regulation of sugar. In support of their appeal, the trio relied on four criteria—“now largely accepted by the public health community,”—originally offered by social psychologist Thomas Babor in 2003 to justify the regulation of alcohol: The target substance must be toxic, unavoidable (or pervasive), produce a negative impact on society, and present potential for abuse.  Perhaps unsurprisingly, they discovered that sugar satisfied each criterion with ease.

Robert Lustig.

Lustig, a pediatric endocrinologist and, now, television infomercial star, contends that obesity results primarily from an intractable hormonal predicament. In his wildly popular 2012 book, Fat Chance, Lustig indicted simple, super-sweet sugars as chief culprits, claiming that sucrose and high-fructose corn syrup corrupt our biochemistry to render us hungry and lethargic in ways fat and protein do not(2).  In other words, he insisted that sugar-induced hormonal imbalances cause self-destructive behaviors, not the other way around.

Lustig’s argument proceeds essentially as follows: In the body, insulin causes energy to be stored as fat.  In the hypothalamus, it can cause “brain starvation,” or resistance to leptin, the satiety hormone released from adipose tissue.  Excess insulin, or hyperinsulinemia, thus causes our hypothalami to increase energy storage (gluttony) and decrease energy consumption (sloth).  To complete the process, add an increasingly insulin-resistant liver (which drives blood insulin levels even higher), a little cortisol (the adrenal stress hormone), and of course sugar addiction.  In the end, Lustig concludes, dieters hardly stand a chance.

Journalist Gary Taubes, author of the similarly successful Why We Get Fat, was in full agreement(3).  Picking up the theoretical mantle where Lustig dropped it, Taubes expanded the list of nutritional villains considerably to include all the refined carbohydrates that quickly boost consumers’ glycemic indices. In a second Nature opinion piece, he then blamed the obesity problem on both the research community, for failure to fully comprehend the condition, and the food industry, for exploiting that failure(4).

Gary Taubes with Dr. Oz.

Gary Taubes with Dr. Oz.

To their credit, Lustig and Taubes provided us with some very sound and useful advice.  Credible nutrition researchers agree, for example, that Americans in particular should drastically reduce their intakes of added sugars and refined carbohydrates.  Indeed, most would be well-advised to eliminate them completely.  The authors’ claims denying self-determination might seem reasonable as well, given that, as much research has shown, most obese who have tried to lose weight and to keep it off, have failed.

On the other hand, failure is common in the context of any difficult task, and evidence of “don’t” does not amount to evidence of “can’t.” One might wonder as well whether obesity is a condition easily amenable to controlled scientific study given that every solution—and of course many, in fact, do succeed(5)—is both multifactorial and as unique as every obese person’s biology.  So can we sincerely conclude, as so many commentators apparently have, that the overweight and obese are essentially powerless to help themselves?  Or could it be that the vast majority of popular authors and health officials have largely—perhaps even intentionally—ignored the true root cause of obesity, if for no other reasons, simply because they lack confidence in the obese population’s willingness to confront it?

Though far less popular, a more recently published text appears to suggest just that.  In The Psychology of Overeating, clinical psychologist Kima Cargill attempts to “better contextualize” overeating habits “within the cultural and economic framework of consumerism”(6).  What current research fails to provide, she argues, is a unified construct identifying overeating (and sedentism, one might quickly add) as “not just a dietary [or exercise] issue,” but rather as a problem implicating “the consumption of material goods, luxury experiences, … evolutionary behaviors, and all forms of acquisition.”

Kima Cargill.

Kima Cargill.

To personalize her analysis, Cargill introduces us to a case study named “Allison.”  Once an athlete, Allison gained fifty pounds after marriage.  Now divorced and depressed, she regularly eats fast food or in expensive restaurants and rarely exercises.  Rather than learn about food and physical performance, Allison attempts to solve her weight problem by throwing money at it.  “When she first decided to lose weight,” Cargill recalls, “which fundamentally should involve reducing one’s consumption, Allison went out and purchased thousands of dollars of branded foods, goods, and services.” She hired a nutritionist and a trainer.  She bought a Jack Lalanne juicer, a Vitamix blender, a Nike Feulband, Lululemon workout clothing, an exclusive gym membership, diet and exercise DVDs and iPhone apps, and heaping bags full of special “diet foods.”

None of it worked, according to the author, because Allison’s “underlying belief is that consumption solves rather than creates problems.”  In other words, like so many others, Allison mistook “the disease for its cure.”  The special foods and products she purchased were not only unnecessary, but ultimately harmful.  The advice she received from her nutritionist and trainer was based on fads, ideologies, and alleged “quick-fixes” and “secrets,” but not on actual science.  Yet, despite her failure, Allison refused to “give up or simplify a life based on shopping, luxury, and materialism” because any other existence appeared empty to her.  In fact, she was unable to even imagine a more productive and enjoyable lifestyle “rich with experiences,” rather than goods and services.

Television celebritism: also mistaking the disease for its cure.

Television celebritism: also mistaking the disease for its cure.

Like Lustig, Taubes, and their philosophical progeny, Cargill recognizes the many potential biological factors capable of rendering weight loss and maintenance an especially challenging task.  But what she does not see in Allison, or in so many others like her, is a helpless victim of either her body or her culture.  Judging it unethical for psychologists to help their patients accept overeating behaviors and their inevitably destructive consequences, Cargill appears to favor an approach that treats the chronically overweight and obese like any other presumably capable, and thus responsible, adult population.

Compassion, in other words, must begin with uncommon candor.  As Cargill acknowledges, for example, only a “very scant few” get fat without overeating because of their genes.  After all, recently skyrocketing obesity rates cannot be explained by the evolution of new genes during the last thirty to forty years.  And while the food industry (along with the popular media that promote it) surely employs every deceit at its disposal to encourage overconsumption and the rejection of normal—that is, species appropriate—eating habits, assigning the blame to big food only “obscures our collusion.”  Worse yet, positioning the obese as “hapless victims of industry,” Cargill observes, “is dehumanizing and ultimately undermines [their] sense of agency.”

Education is always an issue, of course. And, generally speaking, higher levels of education are inversely associated with the least healthy eating behaviors.  But the obese are not stupid, and shouldn’t be treated as such.  “None of us is forced to eat junk food,” the author notes, “and it doesn’t take a college degree or even a high school diploma to know that an apple is healthier than a donut.”  Nor is it true, as many have claimed, that the poor live in “food deserts” wholly lacking in cheap, nutritious cuisine(7).  Indeed, low-income citizens tend to reject such food, Cargill suggests, because it “fails to meet cultural requirements,” or because of a perceived “right to eat away from home,” consistent with societal trends.

Certain foods, especially those loaded with ridiculous amounts of added sugars, do in fact trigger both hormonal turmoil and addiction-like symptoms (though one might reasonably question whether any substance we evolved to crave should be characterized as “addictive”).  And as the overweight continue to grow and habituate to reckless consumption behaviors, their tasks only grow more challenging.  I know this from personal experience, in addition to the science.  Nevertheless, Cargill maintains, “we ultimately degrade ourselves by discounting free will.”

popular culture4

Despite the now-fashionable and, for many, lucrative “Fat Chance” paradigm, the chronically overweight and obese are as capable as anyone else of making rational and intelligent decisions at their groceries, restaurants, and dinner tables. And surely overweight children deserve far more inspiring counsel.  But as both Lustig and Taubes, on the one hand, and Cargill, on the other, have demonstrated in different ways, the solution lies not in mere diet and exercise, per se.  The roots of obesity run far deeper.

Changes to basic life priorities are key. To accomplish a more healthful, independent, and balanced existence, the chronically overweight and obese in particular must first scrutinize their cultural environments, and then discriminate between those aspects that truly benefit them and those that were designed primarily to take advantage of their vulnerabilities, both intrinsic and acquired.  Certain cultural elements can stimulate the intellect, inspire remarkable achievement, and improve the body and its systems.  But most if not all of its popular component exists only to manipulate its consumers into further passive, mindless, and frequently destructive consumption.  The power to choose is ours, at least for now.

References:

(1)Lustig, R.H., L.A. Schmidt, and C.D. Brindis. 2012. Public health: the toxic truth about sugar. Nature 482: 27-29.

(2)Lustig, R. 2012. Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease. NY: Hudson Street Press.

(3)Taubes, G. 2012. Treat obesity as physiology, not physics. Nature 492: 155.

(4)Taubes, G. 2011. Why We Get Fat: And What to Do About It. NY: Knopf.

(5)See, e.g., The National Weight Loss Control Registry. http://www.nwcr.ws/Research/default.htm

(6)Cargill, K. 2015. The Psychology of Overeating: Food and the Culture of Consumerism. NY: Bloomsbury Academic.

(7)Maillot, M., N. Darmon, A. Drewnowski. 2010. Are the lowest-cost healthful food plans culturally and socially acceptable? Public Health Nutrition 13(8): 1178-1185.

The Laws of Immunity.

by Kenneth W. Krause.

[Notable New Media]

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes frequently to Skeptic as well.  He can be contracted at krausekc@msn.com.

So how did humans overcome smallpox? Well, that’s an interesting story.

Toward the end of the 18th century, Edward Jenner noticed that, after recovery from infection with the cowpox virus (vaccinia), milkmaids rarely contracted smallpox. Importantly, vaccinia is very closely related to variola, the smallpox virus.

Edward Jenner

Edward Jenner

So in 1796, Jenner extracted fluid from the pustules on one Sarah Nelmes, suffering from cowpox, and injected it into a healthy James Phipps. After Phipps recovered from a mild case of cowpox, Jenner then intentionally injected him with fluid from the pustules of a smallpox patient. Phipps didn’t develop signs of smallpox infection because the cowpox virus (and the process of “adaptive immunity”) had protected him.

Jenner’s methods obviously wouldn’t pass ethical muster today. But such practices were not uncommon in the 18th century, and understandably so. Smallpox was responsible for more human deaths than any other infectious agent.

Regardless, smallpox vaccination became common in Europe and infection rates dropped dramatically by 1820. In 1853, the UK required every healthy child to be so vaccinated within 3 or 4 months of birth. By 1980, smallpox was formally declared eliminated worldwide.

Read more about the subject generally in William Paul’s new book, Immunity (Johns Hopkins University Press 2015).

Immunity

The Serengeti Rules.

by Kenneth W. Krause.

[Notable New Media]

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes frequently to Skeptic as well.  He can be contracted at krausekc@msn.com.

Serengeti

Science has saved countless lives in strangely uncelebrated ways. How did military doctors first learn to treat shock? Well, that’s another interesting story.

In the early 20th century, Harvard physiologist, Walter Cannon, coined the term “fight-or-flight” following his observations in animal studies that digestive functions were strongly affected by stress. The sympatheric nervous system, he surmised, works in concert with the adrenal glands to modulate body organs during tough times.

As casualties mounted during WWI, Cannon was asked to figure out why the wounded so often went into shock and died. These soldiers exhibited some of the same symptoms as his beleauguered animal subjects–rapid pulse, dilated pupils, and heavy sweating. He quickly volunteered to treat injured casualties overseas in the Harvard Hospital Unit.

Cannon decided to measure the soldiers’ blood pressure, instead of just their pulse. Shock patients, he discovered, had abnormally low BPs–usually under 90 mmHg. After measuring the concentration of bicarbonate ions in their bloodstreams, he found it similarly lacking. The patients’ normally alkaline blood had become more acidic, and the more acidic it was, the lower the patients’ BPs.

So, to raise their pH levels, Cannon began adminsitering sodium bicarbonate to shock victims. And it worked. Innumerable soldiers were saved before WWI finally came to a grisly end. Later emphasizing how most bodily organs receive dual nervous system inputs that generally oppose one another, he coined another term–“homeostasis.” This dual regulation, he concluded, “is the central problem of physiology,” and thus the physician’s role was to reinforce or restore homeostasis.

University of Wisconsin-Madison professor of molecular biology, Sean B. Carroll, uses this story and others to illustrate a worthy point. Regulation is critical to not just human health, but the health of entire ecosystems as well. Also the author of “Endless Forms Most Beautiful” (one of my all-time favorites), Carroll’s new book, The Serengeti Rules: The Quest to Discover How Life Works and Why It Matters (Princeton University Press 2016), explains why the overarching logic of the small and familiar also applies to the large and far-flung.

Carroll

CRISPR-Cas9: Not Just Another Scientific Revolution (Special Report).

by Kenneth W. Krause.

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, he writes regularly for Skeptic magazine as well.  He may be contacted at krausekc@msn.com.

Poised to transform the world as we know it, a new gene-editing system has bioethicists wringing their hands, physicians champing at the bit, and researchers dueling with demons.

CRISPR6

Is it possible to overstate the potential of a new technology that efficiently and cheaply permits deliberate, specific, and multiple genomic modifications to almost anything biological? What if that technology was also capable of altering untold future generations of nearly any given species—including the one responsible for creating it?  And what if it could be used, for better or worse, to rapidly exterminate entire species?

Certain experts have no intention of veiling their enthusiasm, or their unease. Consider, for example, biologist David Baltimore, who recently chaired an international summit dedicated primarily to the technology’s much-disputed ethical implications.  “The unthinkable has become conceivable,” he warned his audience in early December.  Powerful new gene-editing techniques, he added, have placed us “on the cusp of a new era in human history.”

If so, it might seem somewhat anticlimactic to note that Science magazine has dubbed this technology its “Breakthrough of the Year” for 2015, or that its primary developers are widely considered shoo-ins for a Nobel Prize—in addition, that is, to the US$3 million Breakthrough Prize in Life Sciences already earned by two such researchers.  All of which might sound trifling compared to the billions up for grabs following imminent resolution of a now-vicious patent dispute.

Although no gene-editing tool has ever inspired so much drama, the new technology’s promise as a practical remedy for a host of dreadful diseases, including cancer, remains foremost in researchers’ minds. Eager to move beyond in vitro and animal model applications to the clinical setting, geneticists across the globe are quickly developing improved molecular components and methods to increase the technology’s accuracy.  In case you haven’t heard, a truly profound scientific insurrection is well underway.

Adapting CRISPR-Cas9.

Think about a film strip. You see a particular segment of the film that you want to replace.  And if you had a film splicer, you would go in and literally cut it out and piece it back together—maybe with a new clip.  Imagine being able to do that in the genetic code, the code of life.—biochemist Jennifer Doudna (CBS News 2015).

Genetic manipulation is nothing new, of course. Classic gene therapy, for example, typically employs a vector, often a virus, to somewhat haphazardly deliver a healthy allele somewhere in the patient’s genome, hopefully to perform its desired function wherever it settles.  Alternatively, RNA interference selects specific messenger RNA molecules for destruction, thus changing the way one’s DNA is transcribed.  Interference occurs, however, only so long as the damaging agent remains within the cell.

Contemporary editing techniques, on the other hand, allow biologists to actually alter DNA—the “code of life,” as Doudna suggests—and to do so with specific target sequences in mind.  The three major techniques have much in common.  Each involves an enzyme called a programmable nuclease, for example, which is guided to a particular nucleotide sequence to cleave it.

Then, in each case, the cell’s machinery quickly repairs the double-stranded break in one of two ways. Non-homologous end joining for gene “knock out” results when reconstruction, usually involving small, random nucleotide deletions or insertions, is performed only by the cell.  Here, the gene’s function is typically undermined.  By contrast, homology-directed repair for gene “knock in” occurs when the cell copies a researcher’s DNA repair template delivered along with the nuclease.  In this case, the cleaved gene can be corrected or a new gene or genes can be inserted (Corbyn 2015).

But in other ways, the three editing techniques are very distinct. Developed in the late 1990s and first used in human cells in 2005, zinc-finger nucleases (ZFN) attach cutting domains derived from the prokaryote Flavobacterium okeanokoites to proteins called zinc fingers that can be customized to recognize certain three-base-pair DNA codes.  Devised in 2010, transcription activator-like effector nucleases (TALENs) fuse the same cutting domains to different proteins called TAL effectors.  For both ZFN and TALENs, two cutting domains are necessary to cleave double-stranded DNA (Maxmen 2015).

The third and most revolutionary editing technique, and subject of this paper, consists of clustered regularly interspaced short palindromic repeats (CRISPR) and a CRISPR-associated protein-9 nuclease (Cas9). Introduced as an exceptionally precise editing technique in 2012 by Doudna at the University of California, Berkeley, and microbiologist Emmanuelle Charpentier at the Max Planck Institute for Infection Biology in Berlin, CRISPR-Cas9 is actually the bacterium Streptococcus pyogenes’ adaptive immune system that confers resistance to foreign elements, like phages and plasmids.

CRISPR3

CRISPR thus refers to short bits of DNA seized from invading viruses and stored in the bacterium’s own genome for future reference, and Cas9 is the enzyme S. pyogenes uses to cleave a subsequent invader’s double helix.  In other words, in its native setting, CRISPR-Cas9 is the system a certain bacterium uses to recognize and disable common biological threats.  Unlike ZFN and TALENs, CRISPR-Cas9 does not rely on the F. okeanoites cutting domain and, as such, can cleave both strands of an interloper’s double helix simultaneously with a single Cas9 enzyme.

But what makes the CRISPR system so special, in part, and so adaptable to the important task of gene-editing, is its relative simplicity. Only three components are required to achieve site-specific DNA recognition and cleavage.  Both a CRISPR RNA (crRNA) and a trans-activating crRNA (tracrRNA) are needed to guide the Cas9 enzyme to its target sequence.  What Doudna and Charpentier revealed six years ago, however, were the seminal facts that an even simpler, two-component system could be developed by combining the crRNA and tracrRNA into a synthetic single guide RNA (sgRNA), and that researchers could readily modify a sgRNA’s code to redirect the Cas9 enzyme to almost any preferred sequence (Jinek et al. 2012).  Today, a biologist wanting to edit a specific sequence in an organism’s genome can quickly and cheaply design a sgRNA to match that sequence, order it from a competitive manufacturer for US$65 or less, and have it delivered in the mail (Petherick 2015).

None of which is to suggest that a CRISPR system is always the best tool for the gene-editing job, at least not yet. Critically, CRISPR-Cas9 is relatively easy to program and remains the only technique allowing researchers to “multiplex,” or edit several genomic sites simultaneously.  But TALENs have the longest DNA recognition domains and, thus, tend so far to result in the fewest “off-target effects,” which occur when nucleotide sequences identical or similar to the target are cut unintentionally.  And ZFNs are much smaller than either TALENs or CRISPR-Cas9, especially the most popular version derived from S. pyogenes, and are therefore more likely to fit into the tight confines of an adeno-associated virus (AAV)—currently the most promising vector for the delivery of gene-editing therapies.

Even so, CRISPR research continues to progress at breakneck speed. In 2014, the number of gene-editing kits ordered from Addgene, a supplier based in Cambridge, Massachusetts, for research using ZFN and TALENs totaled less than 1000 and less than 2000, respectively.  During that same year—only two years after the new technology was introduced, the number of kits ordered for CRISPR research totaled almost 20,000 (Corbyn 2015).  More importantly, rapidly increasing orders seem to have translated into significant results.  As 2015 ended and a new year began, new studies announcing the creation of smaller guide RNAs and, especially, the reduction of off-target effects began to dominate science headlines.

Building a Better Mousetrap.

At some point everyone needs to decide how specific is specific enough. The idea that you would make a tool that has absolutely no off-target effects is a little too utopian.—bioengineer Charles Gersbach (Ledford 2016).

It’s cheap, easy to use, and remarkably efficient, but CRISPR-Cas9 is not perfect. In early experiments, in fact, pathologist Keith Joung at the Massachusetts General Hospital in Boston, discovered that his enzymes were cutting unintended as often as targeted sequences (Servick 2016).  The U.S. Food and Drug Administration has yet to announce requirements for clinical use of the new technology.  But to help future clinicians safely repair defective, disease-causing genes, for example, researchers are exploring various means of reducing off-target effects that could harm patients in any number of ways, including through uncontrolled cellular growth and cancer.

A CRISPR-Cas9 system “licenses” a DNA sequence for cleavage through a two-stage recognition process (Bolukbasi et al. 2016). Even the most basic details are somewhat technical, of course, but very illuminating.  First, a Cas9-sgRNA complex will attach and remain attached to a DNA sequence only if an appropriate protospacer-adjacent motif (PAM) is nearby.  PAM sequences are very short, often only a few base-pairs long.  In the case of an S. pyogenes Cas9, an NGG PAM is much-preferred, but NAG and NGA PAMs are sometimes inefficiently recognized (“N” represents any nucleobase followed by two guanine, or “G” nucleobases).

CRISPR2

Second, and only if an appropriate PAM is recognized, the sgRNA will interrogate the neighboring DNA sequence through Watson-Crick base pairing in a 3′-to-5′ direction. For an S. pyogenes Cas9, the guide sequence will measure twenty nucleotides long.  If the 3′ end of the programmed guide sequence is complementary to the DNA sequence near the PAM element, “R-loop” formation is initiated.  In zipper-like fashion, further complementarity of the DNA is assessed through extension of the R-loop.  If a complete target sequence is confirmed, allosteric activation of the Cas9 enzyme—actually, activation of Cas9’s two nuclease domains, RuvC and HNH—will result in dual cleavage and, accordingly, a complete double-stranded break in the target sequence.

Unsurprisingly, then, the specificity of a CRISPR-Cas9 system is determined in two ways. In large part, off-target effects are managed through careful design of the sgRNA.  Ideally, the guide sequence would match the target sequence perfectly, and show no homology elsewhere in the genome.  More realistically, however, at least partial homology will often occur at other genomic sites where, unfortunately, off-target cleavage could ensue.  Researchers have developed algorithms that help predict sufficient homology, but have yet to clearly and comprehensively define how closely guide and DNA sequences must harmonize before licensing occurs.  Nevertheless, nuclease activity has been observed at off-target sites displaying up to four or five nucleotide mismatches.

So, careful design of the sgRNA is critical. But one team of researchers, including Joung, recently confirmed that truncating the guide sequence can also help (Fu et al. 2014).  Shortening their guides to as few as seventeen nucleotides, instead of the usual twenty, Joung’s group was able to not only decrease nuclease activity at many off-target sites, but to preserve nearly thorough activity at the majority of intended sites as well.

Other groups have achieved similar success by inactivating one of the two nuclease domains, thus creating a “nickase” that cleaves only one strand of the target sequence (Ran et al. 2013). Here, a double-stranded break can still be achieved by joining two Cas9 nickases with two different sgRNAs targeting adjacent sites on opposing DNA strands.  Importantly, the obligatory use of two active nickases decreases the likelihood of off-target cleavage.

Perhaps the latest and most significant progress in this area, however, has been achieved through modification of the unaltered, or “wild-type,” Cas9 nuclease. Last December, for example, synthetic biologist Feng Zhang at the Broad Institute of MIT and Harvard University announced that he and his colleagues had engineered the Cas9 to render it less likely to act at genomic sites presenting mismatches between RNA guides and DNA targets (Slaymaker et al. 2015).  Appropriately, Zhang dubbed his new enzyme an “enhanced specificity” S. pyogenes Cas9, or eSpCas9 for short.

Feng Zhang

Feng Zhang

Knowing that negatively charged DNA binds to a positively charged groove in the Cas9 enzyme, Zhang’s team predicted that by replacing only a few among the 1400 or so positively charged amino acids with neutral equivalents they could temper the wild-type Cas9’s enthusiasm for binding to and cutting off-target sites. They created and tested several new versions of enzyme that reportedly reduced unintended activity at least tenfold, while maintaining robust on-target cleavage.

Earlier this year, however, Joung and colleagues claimed to have bested Zhang’s results by bringing “off-target-effects to levels where we can no longer detect them, even with the most sensitive methods” (McGreevey 2016). Like Zhang, Joung focused on points of interaction between Cas9 and DNA sequences.  His team created fifteen new enzyme variants by replacing up to four long amino acid side-chains that bind to DNA with shorter chains that do not (Kleinstiver et al. 2016).

Joung then tested each of his Cas9 variants in human cells, and found that one three-substitution and one four-substitution version rejected mismatched sites while maintaining full on-target activity. The latter variant, subsequently named SpCas9-HF1—“HF” denoting “high-fidelity,” induced targeted activity as reliably as a wild-type Cas9 when deployed with eighty-five percent of the thirty-seven different guide RNAs tested.  Similarly, SpCas9-HF1 generated no detectable off-target mutations with six of seven guide RNAs (and only one mutation with the seventh) compared to twenty-five such effects produced by the wild-type Cas9.

Keith Joung

Keith Joung

Joung’s group also tested their hi-fi creations at less typical genomic locations that are particularly difficult to control for off-target effects due to the inclusion of repeat sequences. But even there, his supplemental variants, since designated HF2, HF3, and HF4, appeared to eliminate off-target activity that tended to persist following use of the HF1 version.

It’s too early to judge which of these innovations will prove most valuable or, in fact, whether all of them will soon be superseded by modifications or entirely different systems yet to be introduced. But much progress has already been made and, importantly, at this point, many of the foregoing strategies and designs can be used in concert to bring us closer yet to the day when CRISPR gene-editing becomes a clinical convention.

Breaking Barriers.

This is now the most powerful system we have in biology. Any biological process we care about now, we can get the comprehensive set of genes that underlie that process. That was just not possible before.—biochemist David Sabatini (Yong 2015).

CRISPR-Cas9, of course, is only one among many prokaryotic CRISPR systems that could, at some point, prove useful for any number of human purposes. Use of Cas9 variations, however, has already resulted in successes far too numerous to review liberally here.  Even so, two recent applications in particular reveal the extraordinary, yet strikingly simple, means by which researchers have achieved previously unattainable outcomes.

In the first, three different teams confronted Duchenne muscular dystrophy (DMD), a terrifying disease that affects about one in every 3500 boys in the U.S. alone (Long et al. 2015, Nelson et al. 2015, and Tabebordbar et al. 2015). DMD typically stems from defects in a gene containing seventy-nine protein-coding exons.  If even a single exon suffers a debilitating mutation, the gene can be rendered incapable of producing dystrophin, a vital protein that protects muscle fibers.  Absent sufficient dystrophin, both skeletal and heart muscle will deteriorate.  Patients usually end up confined to wheelchairs and dead before the age of thirty.

CRISPR12

Traditional gene therapy, stem cell treatments, and drugs have proven mostly ineffective against DMD. Scientists have corrected diseased cells in vitro, or in a single organ—the liver.  But treating muscle cells throughout the body, including the heart, is a far more daunting task, because they can’t all be removed, treated in isolation, and then replaced.  And given current ethical concerns, most researchers are prohibited from even considering the possibility of editing human embryos for clinical purposes.

As such, researchers here decided to employ CRISPR-Cas9 technology to excise faulty dystrophin gene exons in both adult and neonatal mice by delivering it directly into their muscles and bloodstreams using non-pathogenic adeno-associated viruses. AAVs, however, are too small to accommodate the relatively large S. pyogenes Cas9, so each team opted instead to deploy a more petite Cas9 enzyme found in Staphylococcus aureus.

Neither group’s interventions resulted in complete cures. But dystrophin production and muscle strength was restored, and little evidence of off-target effects was observed, in treated mice.  One lead researcher later suggested that, although clinical trials could be years away, up to eighty percent of human DMD victims could benefit from defective exon removal (Kaiser 2015).

Remarkably, each of the three teams obtained results comparable to those of the others. Perhaps most impressively, however, these experiments marked the very first instances of using CRISPR to successfully treat genetic disorders in fully-developed living mammals.

But an ever-growing population needs to protect its agricultural products too. Plant DNA viruses, for example, can cause devastating crop damage and economic crises worldwide, but especially in underdeveloped regions including sub-Saharan Africa.  More specifically, the tomato yellow leaf curl virus (tomato virus) is known to ravage a variety of tomato breeds, causing stunted growth, abnormal leaf development, and fruit death.

CRISPR11

Like DMD, the tomato virus has proven an especially intractable problem. Despite previous efforts to control it through breeding, insecticides targeting the vector, and other engineering techniques, we currently know of no effective means of managing the virus.  Undeterred, another group of biologists decided to give CRISPR-Cas9-mediated viral interference a try (Ali et al. 2015).

In this study, the investigators chose to manipulate a species of tobacco plant, well-understood as a model organism, which is similarly vulnerable to tomato virus infection. The experiment was completed in two fairly predictable stages.  First, the group designed sgRNAs to target certain tomato virus coding and non-coding sequences and inserted them into different, harmless viruses of the tobacco rattle variety.  Second, they delivered the newly loaded rattle viruses into their tobacco plants.  After seven days, the plants were exposed to the tomato virus and, after ten more days, they were analyzed for symptoms of infection.

The group agreed that the CRISPR-Cas9 system had reliably cleaved and introduced mutations to the tomato viruses’ genomes. Fortuitously, every plant expressing the system had either abolished or significantly attenuated all symptoms of infection.  The investigators concluded further that the technique was capable of simultaneously targeting multiple DNA viruses with a lone sgRNA, and that other transformable plant species, including tomatoes, of course, would be similarly affected.

One can only guess, at this point, how certain interests might receive these and other types of genome-edited crops. Will nations eventually classify them as GMO or, alternatively, as organisms capable of developing in nature?  Will applicable regulations focus on the processes or products of modification?  Regardless, one can hardly ignore these commodities’ potential windfalls, especially for those in dire need.

Given recent innovations in specificity, for example, CRISPR-based disease research will likely continue to advance quickly toward clinical and other more practical applications. So long as it affects only non-reproductive somatic cells, such interventions should remain largely uncontroversial.  Human gametes and embryos, on the other hand, have once again inspired abundant debate and bitter division among experts.

Moralizing Over Science.

Genome editing in human embryos using current technologies could have unpredictable effects on future generations. This makes it dangerous and ethically unacceptable.—Edward Lanphier et al. (2015).

To intentionally refrain from engaging in life-saving research is to be morally responsible for the foreseeable, avoidable deaths of those who could have benefitted.—bioethicist Julian Savulescu et al. (2015).

The results of the first and, so far, last attempt to edit human embryos using CRISPR-Cas9 was published by a team of Chinese scientists on April 18 of last year (Liang et al. 2015). Led by Junjiu Huang, the group chose to experiment on donated tripronuclear zygotes—non-viable early embryos containing one egg and two sperm nuclei—neither intended nor suitable for clinical use.  Their goal was to successfully edit endogenous β-globin genes that, when mutated, can cause a fatal blood disorder known as β-thalassemia.

Junjiu Huang

Junjiu Huang

By his own admission, Huang’s outcomes were less than spectacular. Eighty-six embryos were injected with the Cas9 system and a molecular template designed to affect the insertion of new DNA.  Of the seventy-one that survived, fifty-four embryos were tested.  A mere twenty-eight were successfully spliced and, of those, only four exhibited the desired additions.  Rates of off-target mutations were much higher than expected too, and the group would likely have discovered additional unintended cuts had they examined more than the protein-coding exome, which represents less than two percent of the entire human genome.

In all fairness, however, the embryos’ abnormality might have been responsible for much of the total off-target effect. And, of course, Huang was unable to take advantage of many specificity-enhancing upgrades to the CRISPR system yet to be designed at the time of his investigations.  In any case, his team acknowledged that their results “highlight the pressing need to further improve the fidelity and specificity” of the new technology, which in their opinions remained immature and unready for clinical applications.

Nevertheless, the Chinese experiment ignited a brawl among both scientists and bioethicists over the prospect of human germline modification with the most powerful and accessible editing machinery ever conceived. Similar quarrels had accompanied the proliferation of technologies involving recombinant DNA, in vitro fertilization, gene therapy, and stem cells, for example.  But never had the need to address our capacity to reroute the evolution of societies—indeed, of the entire species—seemed so real and immediate.

Leading experts, including Baltimore and Doudna, had previously met in Napa, California, on January 24, 2015 to discuss the bioethical implications of rapidly emerging technologies. In the end, they “strongly discouraged … any attempts at germline genome modification for clinical application in humans,” urged informed discussion and transparent research, and called for a prompt global summit to recommend international policies (Baltimore et al. 2015).  A surge of impassioned literature ensued.

A small group led by Sangamo BioSciences president, Edward Lanphier, was one of the first to weigh in (Lanphier et al. 2015). Calling for a “voluntary moratorium” on all human germline research, Lanphier first expressed concerns over potential off-target effects and the genetic mosaicism that could result, for instance, if a fertilized egg began dividing before all intended corrections had occurred.  He also found it difficult to “imagine a situation in which use of human embryos would offer therapeutic benefits over existing and developing methods,” suggesting as well that pre-implantation genetic diagnosis (PGD) and in vitro fertilization (IVF) were far better options than CRISPR for parents carrying the same mutation for a genetic disease.  In any case, he continued, with so many unanswered questions, clinicians remained unable to obtain truly risk-informed consent from either parents looking to modify their germlines or from affected future generations.  Finally, Lanphier implied that even the best intentions could eventually lead societies down a “slippery slope” toward non-therapeutic genetic enhancement and so-called “designer babies.”

Edward Lanphier

Edward Lanphier

Francis Collins, evangelical Christian and director of the National Institutes of Health (which currently refuses to fund human germline research), expressed similar views regarding the sufficiency of PGD and IVF, the impossibility of informed consent, and non-therapeutic enhancement (Skerrett 2015). Additionally, Collins worries that access to the technology would be denied to the economically disadvantaged and that parents might begin to conceive of their children “more like commodities than precious gifts.”  For the director, given the “paucity of compelling cases” in favor of such research, and the significance of the ethical counterarguments, “the balance of the debate leans overwhelmingly against human germline engineering.”

On the other hand, Harvard Medical School geneticist, George Church, urges us to ignore pleas for artificially imposed bans, “encourage the innovators,” and focus more on what he deems the obvious benefits of germline research (Church 2015). Responding to Lanphier and Collins, he argues as well that, without obtaining consent, parents have long exposed future generations to mutagenic forces—through chemotherapy, residence in high-altitudes, and alcohol intake, for example.  We have also consistently chosen to enhance our offspring and future generations through mate choice, among many other things.  Church also points out that PGD during the IVF procedure is incapable of offering solutions to individuals possessing two copies of a detrimental, dominant allele, or to prospective parents who both carry two copies of a harmful, recessive allele.  Moreover, in most instances, PGD cannot be used to avoid more complex polygenic diseases, including schizophrenia.   Nor can we presume that new technology costs will always create treatment or enhancement inequities.  In fact, according to Church, the price of DNA sequencing, for example, has already plummeted more than three million fold.  Finally, germline editing is probably not irreversible, Church contends, and certainly not as error-prone at this point as many have suggested.  “Senseless” bans, he concludes, would only “put a damper on the best medical research and instead drive the practice underground to black markets and uncontrolled medical tourism.”

George Church

George Church

Taking a slightly different tack, Harvard cognitive scientist, Steven Pinker, censures bioethicists generally for getting bogged down in “red-tape, moratoria, or threats of prosecution based on nebulous but sweeping principles such as ‘dignity,’ ‘sacredness,’ or ‘social justice’” (Pinker 2015a). Imploring the bioethical community to “get out of the way” of CRISPR, Pinker reminds them that, once decried as morally unacceptable, vaccinations, transfusions, artificial insemination, organ transplants, and IVF have all proven “unexceptional boons to human well-being.”  Further, the specific harms of which moratorium proponents warn, including cancer, mutations, and birth defects, “are already ruled out by a plethora of existing regulations and norms” (Pinker 2015b).  In the end, he advises, both scientists and everyday people need and deserve a well-diversified research portfolio.  “If you ban something, the probability that people will benefit is zero.  If you don’t ban it, the probability is greater than zero.”

Such were among the arguments considered by a committee of twelve biologists, physicians, and ethicists during the December, 2015 International Summit on Human Genome Editing, organized by the U.S. National Academies of Science and Medicine, the Royal Society in London, and the Chinese Academy of Sciences. The Summit was chaired by David Baltimore.  Doudna and Charpentier, winners of the US$3 million Breakthrough Prize in Life Sciences, attended with Zhang—a now much-celebrated trio considered front runners for a Nobel Prize, though also entangled through their institutions in a CRISPR patent dispute potentially worth billions of dollars.

Doudna, Charpentier, and Zhang

Doudna, Charpentier, and Zhang

After three days of discussion, the Summit’s organizing committee issued a general statement rejecting calls for a comprehensive moratorium on germline research (NAS 2015). The members did, however, advise without exception against the use of edited embryos to establish pregnancy.  “It would be irresponsible to proceed,” they added, “with any clinical use of germline editing” until safety and efficacy issues are resolved and there exists “a broad societal consensus about the appropriateness of the proposed application.”  In conclusion, the committee called for an “ongoing forum” to harmonize the current global patchwork of relevant regulations and guidelines and to “discourage unacceptable activities.”  This forum, the members judged, should consist not only of experts and policymakers, but of “faith leaders,” “public interest advocates,” and “members of the general public” as well.

Wasting little time, the UK’s Human Fertilization and Embryology Authority approved on February 1, 2016, the first attempt to edit healthy human embryos with the CRISPR-Cas9 system.  The application was filed last September by developmental biologist, Kathy Niakan, of the Francis Crick Institute in London.  Niakan intends to use CRISPR to knock out one of four different genes in a total of 120 day-old, IVF-donated embryos to investigate the roles such genes play in early development.

Kathy Niakan

Kathy Niakan

Her research could help identify genes crucial to early human growth and cell differentiation and, thus, lead to more productive IVF cultures and more informed selection practices. It could also reveal mutations that lead to miscarriages and, one day, allow parents to correct these problems through gene therapy.  Following careful observation, Niakan intends to destroy her embryos by the time they reach the blastocyst stage on the seventh day.  Under British law, experimental embryos cannot be used to establish pregnancy.

But the human germline is not the only, or even most pressing, subject of CRISPR controversy. Some, for example, warn of the creation of dangerous pathogens and biological warfare (Greely 2016).  But many others, including Doudna, urge that we quickly address “other potentially harmful applications … in non-human systems, such as the alteration of insect DNA to ‘drive’ certain genes into a population” (Doudna 2015).

Driving DNA.

Clearly, the technology described here is not to be used lightly. Given the suffering caused by some species, neither is it obviously one to be ignored.—evolutionary geneticist Austin Burt (2003).

In broad terms, a “gene drive” can be characterized as a targeted contagion intended to spread through a population with exceptional haste. Burt pioneered the technology through his study of transposable elements—“selfish” and often parasitic DNA sequences that exist merely to propagate themselves.  Importantly, transposons can circumvent the normal Mendelian rules of inheritance dictating that any given gene has a fifty percent chance of being passed from parent to offspring.

Thirteen years ago, Burt envisioned the use of a microbial transposon-like element called a “homing endonuclease” for humanity’s benefit. When inserted into one chromosome, the endonuclease would cut the matching chromosome inherited from the other parent.  The cell would then quickly repair the cut, often using the first chromosome as a template.  As such, the assailed sequence in the second chromosome would be converted to the sequence of the selfish element.  In a newly fertilized egg, the endonuclease would likewise convert the other parent’s DNA and, eventually, drive itself into the genomes of nearly one-hundred percent of the population.

CRISPR1

 

Burt believes we can use gene drives to weaken or even eradicate mosquito transmitted diseases like malaria and dengue fever. If scientists engineered just one percent of a mosquito population to carry such a drive, he calculates, about ninety-nine percent would possess it in only twenty generations.  In fact, Burt announced five years ago that he had created a homing endonuclease capable of locating and cutting a mosquito gene (Windbichler 2011).  But his elements were difficult to program for precise application.

Enter CRISPR-Cas9. As we’ve seen, Cas9 is an eager endonuclease and guide RNAs are easy to program and can be quickly synthesized.  In April of last year, biologists Valentonio Gantz and Ethan Bier revealed that they had used CRISPR-Cas9 to drive color variation into Drosophila fruit flies (Gantz and Bier 2015).  Though they labeled it a “mutagenic chain reaction” at the time, it was the first gene drive ever deployed in a multicellular organism.

Today, researchers sort potential gene drives into two major groups. Replacement drives seek only to displace natural with modified populations.  Suppression drives, by contrast, attempt to reduce or even eradicate populations.  At this point, no drives have been released into the wild.  Nevertheless, researchers have lately designed one of each type to affect mosquitos carrying the deadly human malaria parasite, Plasmodium falciparum.

The first study was led by microbiologist Anthony James, who collaborated on the project with Gantz and Bier (James et al. 2015). Focusing on the prevention of disease transmission, this group engineered Anopheles stephensi mosquitos, highly active in urban India, to carry two transgenes producing antibodies against the malaria parasite, a CRISPR-Cas9-mediated gene drive, and a marker gene.  Because the very lengthy payload rendered insertion a challenging process, James was able to isolate only two drive-bearing males among 25,000 larvae.  But when mated with wild-type females, these and subsequent transgenic males spread their anti-malaria genes at an impressive rate of 99.5 percent.  Transgenic females, on the other hand, processed the drive quite differently and passed it on at near-normal Mendelian ratios.

Despite its overall success, James doesn’t imagine that his team’s replacement drive could eliminate the malaria parasite independently. Instead, he envisions its use to reduce the risk of infection and to compliment other strategies already being employed.  Even so, because such drives would not exterminate P. falciparum or its mosquito vector, they would potentially allow the parasite to one day evolve resistance to their transgene components.

mosquito-anopheles

The second study’s goal was quite different. Here, molecular biologist, Tony Nolan, along with Burt and others, first identified three genes in the Anopheles gambiae mosquito, active in sub-Saharan Africa, that when mutated cause recessive infertility in females (Hammond et al. 2016).  Second, they designed a CRISPR-Cas9 gene drive to target and edit each gene.  Following insertion, they bred their transgenic mosquitos with wild-types and found that nearly all female offspring were born infertile.  In a subsequent experiment, Nolan released 600 vectors—half transgenic, half wild-type—into a cage.  After only four generations, seventy-five percent of the population carried the mutations, exactly what one would expect from an effective gene drive.

A suppression drive like Hammond’s could, in theory, eliminate a parasite’s primary vector. In such a scenario, the parasite might find another means of conveying the disease to humans—more than 800 species of mosquito inhabit Africa alone, for example.  But it might not.  The loss would also substantially alter the relevant ecosystem.  But despite other methods of controlling the disease, malaria still claims more than a half million lives every year, mostly among children under five.

Even in theory, no gene drive is a panacea. They function only in sexually reproducing species, and best in species that reproduce very rapidly.  Nor would their effects be permanent—most transgenes would prove especially vulnerable to evolutionary deselection, for example.   But neither would they turn out as problematic as some might imagine. They can be easily detected through genome sequencing, for instance, and are unlikely to spread accidentally into domesticated species.  And if scientists sought for whatever reason to reverse the effects of a previously released drive, they could probably do so with the release of a subsequent drive.

As Church and others have recently suggested, it “doesn’t really make sense to ask whether we should use gene drives. Rather, we’ll need to ask whether it’s a good idea to consider driving this particular change through this particular population”  (Esvelt et al. 2014).

References:

Ali, Z., A. Abulfaraj, Ali Idris, et al. 2015. CRISPR/Cas9-mediated viral interference in plants. Genome Biology 16:238 DOI:10.1186/s13059-015-0799-6.

Baltimore, D., P. Berg, M. Botcham, et al. 2015. A prudent path forward for genomic engineering and germline gene modification. Science 348(6230):36-38.

Bolukbasi, M.F., A. Gupta, and S.A. Wolf. 2016. Creating and evaluating accurate CRISPR-Cas9 scalpels for genomic surgery. Nature Methods 13(1):41-50.

Burt, A. 2003. Site-specific selfish genes as tools for the control and genetic engineering of natural populations. Proceedings of the Royal Society B 270:921-928.

CBS News. 2015. Could Revolutionary Gene-editing Technology End Cancer? Available online at http://www.cbsnews.com/news/crispr-jennifer-doudna-gene-editing-technology-diseases-dangers-ethics/; accessed January 25, 2016.

Church, G., 2015. Encourage the innovators. Nature 528:S7.

Corbyn, Z. 2015. Biology’s big hit. Nature 528:S4-S5.

Doudna, J. 2015. Embryo editing needs scrutiny. Nature 528:S6.

Esvelt, K., G. Church, and J. Lunshof. 2014. “Gene Drives” and CRISPR Could Revolutionize Ecosystem Management. Available online at http://blogs.scientificamerican.com/guest-blog/gene-drives-and-crispr-could-revolutionize-ecosystem-management/; accessed February 6, 2016.

Fu, Y., J.D. Sander, D. Reyon, et al. 2014. Improving CRISPR-Cas nuclease specificity using truncated guide RNAs. Nature Biotechnology 32:279-284.

Gantz, V.M., and E. Bier. 2015a. The mutagenic chain reaction: A method for converting heterozygous to homozygous mutations. Science 348(6233):442-444.

Gantz, V.M., N. Jasinskiene, O. Tatarenkova, et al. 2015. Highly efficient Cas9-mediated gene drive for population modification of the malaria vector mosquito Anopheles stephensi. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1521077112.

Greely, H.T. 2016. Are We Ready for Genetically Modified Animals? Available online at http://www.weforum.org/agenda/2016/01/are-we-ready-for-genetically-modified-animals; accessed February 3, 2016.

Hammond, A. R. Galizi, K. Kyrou, et al. 2016. A CRISPR-Cas9 gene drive system targeting female reproduction in the malaria mosquito vector Anopheles gambiae. Nature Biotechnology DOI: 10.1038/nbt.3439.

Jinek, M., K. Chylinski, I. Fonfara, et al. 2012. A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science 337:816-821.

Kaiser, J. 2015. CRISPR Helps Heal Mice With Muscular Dystrophy. Available online at http://www.sciencemag.org/news/2015/12/crispr-helps-heal-mice-muscular-dystrophy; accessed January 30, 2015.

Kleinstiver, B.P., V. Pattanayak, M.S. Prew, et al. 2016. High-fidelity CRISPR-Cas9 nuclease with no detectable genome-wide off-target effects. Nature 529:490-495.

Lanphier, E., F. Urnov, S.E. Ehlen, et al. 2015. Don’t edit the human germline. Nature 519:410-411.

Ledford, H. 2016. Enzyme Tweak Boosts Precision of CRISPR Genome Edits. Available online at http://www.nature.com/news/enzyme-tweak-boosts-precision-of-crispr-genome-edits-1.19114; accessed January 28, 2016.

Liang, P., Y. Xu, X. Zhang, et al. 2015. CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes. Protein Cell 6(5):363-372.

Long, C., L. Amoasii, A.A. Mireault, et al. 2015. Postnatal genome editing partially restores dystrophin expression in a mouse model of muscular dystrophy. Science DOI: 10.1126/science.aad5725.

Maxmen, A. 2015. Three technologies that changed genetics. Nature 528:S2-S3.

McGreevey, S. 2016. High-fidelity CRISPR. Available online at https://hms.harvard.edu/news/high-fidelity-crispr; accessed January 29, 2016.

National Academies of Science. 2015. International Summit Statement. Available at http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=12032015a; accessed January 2, 2016.

Nelson, C.E., C.H. Hakim, D.G. Ousterout, et al. 2015. In vivo genome editing improves muscle function in a mouse model of Duchenne muscular dystrophy. Science DOI: 10.1126/science.aad5143.

Petherick, A. 2015. Nature outlook genome editing. Nature 528:S1.

Pinker, S. 2015a. The Moral Imperative for Bioethics. Available online at https://www.bostonglobe.com/opinion/2015/07/31/the-moral-imperative-for-bioethics/JmEkoyzlTAu9oQV76JrK9N/story.html; accessed February 2, 2016.

Pinker, S. 2015b. Steven Pinker Interview. Available online at https://www.ipscell.com/2015/08/stevenpinker/; accessed February 2, 2016.

Ran, F.A., P.D. Hsu, C. Lin, et al. 2013. Double nicking by RNA-guided CRISPR Cas9 for enhanced genome editing specificity. Cell 154:1380-1389.

Savulescu, J., J. Pugh, T. Douglas, et al. 2015. The moral imperative to continue gene editing research on human embryos. Protein Cell 6(7):476-479.

Servick, K. 2016. Researchers Rein In Slice-happy Gene Editor, CRISPR. Available online at http://www.sciencemag.org/news/2016/01/researchers-rein-slice-happy-gene-editor-crispr; accessed January 28, 2016.

Sherkow, J.S. 2015. The CRISPR Patent Interference Showdown Is On. Available online at https://law.stanford.edu/2015/12/29/the-crispr-patent-interference-showdown-is-on-how-did-we-get-here-and-what-comes-next/; accessed January 29, 2016.

Skerrett, P., 2015. First Opinion. A Debate: Should We Edit the Human Genome? Available online at http://www.statnews.com/2015/11/30/gene-editing-crispr-germline/; accessed February 2, 2016.

Slaymaker, I. M., L. Gao, B. Zetsche, et al. 2015. Rationally engineered Cas9 nucleases with improved specificity. Science 351(6268):84-88.

Tabebordbar, M., K. Zhu, J.K.W. Cheng, et al. 2015. In vivo gene editing in dystrophic mouse and muscle stem cells. Science DOI: 10.1126/science.aad5177.

Windbichler, N., M. Menichelli, P.A. Papathanos, et al. 2011. A synthetic homing endonuclease-based gene drive system in the human malaria mosquito. Nature 473:212-215.

Yong, E. 2015. The New Gene-editing Technique that Reveals Cancer’s Weaknesses. Available online at http://www.theatlantic.com/science/archive/2015/11/a-revolutionary-gene-editing-technique-reveals-cancers-weaknesses/417495/; accessed on January 30, 2016.