Three-parent babies should make us examine our instinct for offspring who share our genes

How much control should we have over our children’s genes?
How much control should we have over our children’s genes?
Image: AP Photo/Sakchai Lalit
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When it comes to the genetic lottery, I’ve been lucky in a lot of ways—and unlucky in others. I was bequeathed my mother’s connective tissue anomalies, the celiac disease that runs on her side, and my father’s asthma, along with assorted other miseries. I was born by Caesarean section because my mother had a septate uterus, as do I. Sometimes I wonder if that uterine cleft may have been nature’s way of saying, “I don’t think you’re a fit specimen, let’s end it here.”

Without modern medicine, I’d never have made it out alive. I’m forever grateful I did. That’s what I think about every time I read fresh reports on the ways we can now tinker with our genes—the ever-expanding ability of scientists and doctors to save us from suffering and untimely death.

These days, using the tiniest surgical and biological scissors, we can snip away bad genes and insert good ones. We can prevent fatal inherited disorders by altering embyros. Gene therapy has allegedly cured one boy of sickle cell anemia (an inherited blood disease that affects millions worldwide) and more trials are underway. We are tweaking pigs so they can grow human organs for transplant, and genetically engineering mice so they won’t carry Lyme disease. There’s no doubt that there are enormous potential benefits to these gene therapies, once the techniques are honed and proven safe. But we are still in early days, and we need to be aware of the dangers, too.

The most astonishing gene therapy news this year has been the crafting of three-parent babies. The in-vitro fertilization practice, known as “mitochondrial replacement therapy,” is meant to help women who carry genes for mitochondrial diseases have babies without passing the disorders onto their children. The futuristic technique literally lifts the birth mother’s nucleus out of her egg, leaving behind almost all of her egg’s defective mitochondria. (Mitochondria are self-contained structures that carry their own DNA, separate from that of the nucleus.)

The nucleus is then transplanted into an egg from an unrelated, healthy female donor, which has had its own nucleus removed. That hybrid egg is then fertilized by the father’s sperm. And thus, devastating, heritable diseases can be bypassed with three parents’ DNA.

Last year, New York-based reproductive endocrinologist John Zhang made headlines when he announced that he had successfully used this technique to help a 36-year-old mother have a healthy baby boy. But the technique has yet to undergo rigorous scientific testing, and the risks are unknown. Because it is not approved in the United States, Zhang had to perform it in Mexico.

The procedure was not perfect. In his latest paper, published a few weeks ago in the journal Reproductive Biomedicine Online, Zhang notes that the boy carries between 2.36% percent to 9.23% of the mother’s defective DNA, according to sampling of his hair follicles, circumcised foreskin and umbilical blood. For the disease carried by the mother, called Leigh’s Disease, those percentages are low and rarely result in symptoms. Physical exams of the boy have shown him to be perfectly normal. But there is a chance that as he grows up, those defective mitochondria will multiply. If something goes wrong, the public may never find out: The parents have said they do not plan to have the boy’s mitochondria monitored regularly.

The fact that the boy will grow up without monitoring perturbs many people. “We don’t know what the implications are for babies at this level of manipulation,” warns bioethicist Jeff Botkin of the University of Utah, who participated in an Institute of Medicine committee last year that issued a call for more animal research on the technique. Because the procedure was performed outside of regulatory procedures, “we don’t know the long-term prospects for following up to demonstrate whether this worked or didn’t.”

Still others think the technique is valid and ethical—but that we still need to have a conversation about why parents want and need a baby who shares their genes in the first place.

“A colleague of mine coined the phrase ‘genetic idolatry,’” says Linda MacDonald Glenn, a bioethicist at California State University in Monterey Bay. “Why is it so important for us to have a genetic connection to our children when people have adopted children and done wonderfully with them? We are the product of epigenetics as well as genetics.” Curing devastating diseases by safely altering the germline—the sperm and eggs that power future generations—seems a valid reason to pursue this research. But it’s worth questioning our societal bias toward having biological children when adoption is an option.

MacDonald says people often say of the desire to have a biological child, “It’s just hardwired in me.” But, she says, “lots of things are hardwired that we try to avoid, like rage. And other things are not hardwired, that we try to cultivate, even something as simple as brushing your teeth. I’m just skeptical of that answer.”

And then there is the time-worn bugaboo of eugenics. Geneticists and ethicists worry that genetic replacement therapies might be used by the wealthy to reduce diversity (selecting for, say, tall, athletic, blond babies) and enhance things like intelligence and physical prowess, producing a generation of look-a-like “transhumans” who are far more powerful than people who lack the means and money to do the same.

There are two sides to that argument, says MacDonald. “There are many people who revel in diversity, so I don’t think we’re going to run of risk of everybody saying they want the same thing. But this issue does require thoughtful discussion, because what underlies it is once again, the idea of survival of the fittest.” That Darwinian concept, says MacDonald, is a description of how evolution works. But it’s not the measure of a compassionate and humane society that takes good care of its most vulnerable members.

And that’s why I’m all for gene therapy—within proper scientific and ethical constraints. In a much less medically advanced era, I was lifted out of my mother’s belly, with the help of anesthesia and aseptic techniques, and gifted with life. Every day, the practice of medicine keeps people alive who would otherwise die. If we only apply the logic of “survival of the fittest” to genetic therapy, we might wind up culling valuable lives that human ingenuity could save.