Tuesday, July 4, 2017

"The Brave New World of Gene Editing"

Three reviews from the New York Review of Books. The reviewer. Matthew Cobb, is Professor of Zoology at the University of Manchester. His most recent book is Life’s Greatest Secret: The Race to Crack the Genetic Code. (July 2017) .

A Crack in Creation: Gene Editing and the Unthinkable Power to Control Evolution
by Jennifer A. Doudna and Samuel H. Sternberg
Houghton Mifflin Harcourt, 281 pp., $28.00
http://www.nybooks.com/wp-content/uploads/2017/06/cobb_1-071317.jpgIn recent years, two new genetic technologies have started a scientific and medical revolution. One, relatively well known, is the ability to easily decode the information in our genes. The other, which is only dimly understood by the general public, is our newfound capacity to modify genes at will. These innovations give us the power to predict certain risks to our health, eliminate deadly diseases, and ultimately transform ourselves and the whole of nature. This development raises complex and urgent questions about the kind of society we want and who we really are. A brave new world is just around the corner, and we had better be ready for it or things could go horribly wrong.
The revolution began in benign but spectacular fashion. In June 2000, President Bill Clinton and Prime Minister Tony Blair announced the completion of the first draft of the human genome. According to a White House press statement, this achievement would “lead to new ways to prevent, diagnose, treat, and cure disease.” Many scientists were skeptical, but the public (who footed much of the $3 billion bill) probably found this highly practical justification more acceptable than the mere desire to know, which was in fact a large part of the motivation of many of the scientists involved.
During the 2000s, Clinton’s vision was slowly put into practice, beginning with the development of tests for genetic diseases. As these tests have become widespread, ethical concerns have begun to surface. Bonnie Rochman’s The Gene Machine shows how genetic testing is changing the lives of prospective parents and explores the dilemmas many people now face when deciding whether to have a child who might have a particular disease. Some of these technologies are relatively straightforward, such as the new blood test for Down syndrome or the Dor Yeshorim genetic database for Jews, which enables people to avoid partners with whom they might have a child affected by the lethal Tay-Sachs disease (particularly prevalent in Ashkenazis). But both of these apparently anodyne processes turn out to raise important ethical issues.

Whether we like it or not, the Dor Yeshorim database and other similar initiatives, such as genetic tests for sickle-cell anemia, which largely affects African-Americans, are enabling us to deliberately change the frequency of certain human genes in the population. This is the technical definition of eugenics and might seem shocking, since eugenics is forever associated with the forced sterilization of the mentally ill and Native Americans in the US or the murder of those deemed genetically defective by the Nazis. But the ability to use genetic testing when deciding whether or not to have children is clearly a form of soft eugenics, albeit one carried out voluntarily by those affected and clearly leading to a reduction of human suffering. With the best of intentions and, for the moment, the best of outcomes, we have drifted across a line in the sand.

The new genetic test for Down syndrome also hides ethical traps. The test detects tiny amounts of fetal DNA in the mother’s bloodstream, and in the US it has largely replaced the widespread use of invasive alternatives (amniocentesis or chorionic villous sampling, in which cells are taken from the placenta) that involve a risk of miscarriage. The advent of a safe way to detect Down is a positive development (in the UK it is predicted that the test will prevent up to thirty invasive test–induced miscarriages each year), but some women feel that its simplicity means they are being inadvertently pressured into having a test for Down, and potentially into having an abortion if the test result is positive.

It is extremely difficult to obtain reliable data on how often identification of Down syndrome in a fetus has led to a decision to terminate a pregnancy, but a recent study in Massachusetts suggested that prior to the introduction of the safer test in 2011, around 49 percent of such pregnancies were aborted. Since many parents opted not to have an invasive test for fear of miscarriage (in the UK the figure was around 40 percent), it is reasonable to expect that an increased rate of identification of fetuses with Down syndrome will lead to more abortions. This has led to criticism from families with Down syndrome children, who understandably want to emphasize the joy they feel living with a child who has the condition. Rochman navigates these difficult waters with skill and compassion, drawing on conversations with families and physicians and setting out the ethical challenges and the range of solutions adopted by different people, without being preachy or moralistic.

In the last few years, genetic testing has entered the commercial mainstream. Direct-to-consumer testing is now commonplace, performed by companies such as 23andMe (humans have twenty-three pairs of chromosomes). Much of the interest in such tests is based not only on the claim that they enable us to trace our ancestry, but also on the insight into our future health that they purport to provide. At the beginning of April, 23andMe received FDA approval to sell a do-it-yourself genetic test for ten diseases, including Parkinson’s and late-onset Alzheimer’s. You spit in a tube, send it off to the company, and after a few days you get your results. But as Steven Heine, a Canadian professor of social and cultural psychology who undertook several such tests on himself, explains in DNA Is Not Destiny, that is where the problems begin.

Some diseases are indeed entirely genetically determined—Huntington’s disease, Duchenne muscular dystrophy, and so on. If you have the faulty gene, you will eventually have the disease. Whether you want to be told by e-mail that you will develop a life-threatening disease is something you need to think hard about before doing the test. But for the vast majority of diseases, our future is not written in our genes, and the results of genetic tests can be misleading.

For example, Heine reveals that according to one test, he has “a 32 percent increased chance” of developing Parkinson’s disease. Behind this alarming figure lurks the reality that his risk is only slightly higher than the small likelihood that is found in the general population (2.1 percent for Heine, 1.6 percent for the rest of us). That does not sound quite so bad. Or does it? What does a risk of 2.1 percent really mean? People have a hard time interpreting this kind of information and deciding how to change their lifestyle to reduce their chance of getting the disease, if such an option is available. (It is not for Parkinson’s.)

Even more unhelpfully, different companies testing for the same disease can produce different results. Heine was told by one company that he had a higher-than-average risk of prostate cancer, Parkinson’s, melanoma, and various other diseases, whereas another said his risk for all these conditions was normal. These discrepancies can be explained by the different criteria and databases used by each testing company. Faced with varying estimates, the average customer might conclude that contradictory information is worse than no information at all. As Heine puts it, “The oracle’s crystal ball is made of mud.”

More troublingly still, however imperfect its predictive value, the tsunami of human genetic information now pouring from DNA sequencers all over the planet raises the possibility that our DNA could be used against us. The Genetic Information Nondiscrimination Act of 2008 made it illegal for US medical insurance companies to discriminate on the basis of genetic information (although strikingly not for life insurance or long-term care). However, the health care reform legislation recently passed by the House (the American Health Care Act, known as Trumpcare) allows insurers to charge higher premiums for people with a preexisting condition. It is hard to imagine anything more preexisting than a gene that could or, even worse, will lead to your getting a particular disease; and under such a health system, insurance companies would have every incentive to find out the risks present in your DNA. If this component of the Republican health care reform becomes law, the courts may conclude that a genetic test qualifies as proof of a preexisting condition. If genes end up affecting health insurance payments, some people might choose not to take these tests.

But of even greater practical and moral significance is the second part of the revolution in genetics: our ability to modify or “edit” the DNA sequences of humans and other creatures. This technique, known as CRISPR (pronounced “crisper”), was first applied to human cells in 2013, and has already radically changed research in the life sciences. It works in pretty much every species in which it has been tried and is currently undergoing its first clinical trials. HIV, leukemia, and sickle-cell anemia will probably soon be treated using CRISPR.....MUCH MORE