If we could cure Down’s syndrome, should we do it? The media’s been abuzz with the question since scientists at UMass Medical School announced last month that they’d found a way to silence the chromosome that causes Down’s.
Humans are ordinarily conceived with 23 pairs of chromosomes (23 from mom, 23 from dad) for a total of 46. Down’s syndrome (DS) occurs when a person is conceived with 47 rather than 46 chromosomes. The extra copy occurs at chromosome 21, which is why the condition is sometimes called trisomy 21.
The extra copy causes all sorts of conditions including the familiar facial features of DS people, such as abnormally small chins, slanted eye fissures on the inner corners of the eyes, flat nasal bridges, and shorter necks. People with DS suffer mental impairment to varying degrees, from mild (IQ: 50–70) to moderate (IQ: 35–50), and more rarely severe (IQ: 20–35). They also suffer disproportionately from congenital heart defects, from an increased risk of leukemia and Alzheimer’s disease, from thyroid, eye, hearing and gastrointestinal disorders, and from infertility.
The Massachusetts researchers set out to silence the genetic expression (the activity) of the extra copy of chromosome 21. They began by producing induced pluripotent stem (iPS) cells from skin cells taken from a person with DS. Since iPScs can differentiate into most all tissue types in the human body, the cells are ideally suited for this type of research. At the site of the extra copy of chromosome 21, they inserted a gene called XIST. The natural function of the XIST gene is to silence (turn off) one of the two X chromosomes in female cells. They hoped to harness the “inactivation” power of the XIST gene in relation to the extra copy of chromosome 21. Their hopes were fulfilled.
News rapidly spread that “Down’s can now be cured!” The researchers were quick to contradict the media hype. They said their work did not target the eradication of the condition. All it did was offer proof of principle that the extra copy of chromosome 21 could be turned off in DS cells in a laboratory culture. In human beings, trisomy 21 is present from fertilization and is expressed in almost every cell in the body. Silencing its expression would mean changing the genetic activity of all these cells: “I don’t see how we could fundamentally change a person who has trisomy 21 to silence all the chromosomes in their body,” said Dr. Jeanne Lawrence, who led the research. It may not even be possible.
Nevertheless, though not a panacea, the outcome is still very significant. It is an important step towards developing therapies to overcome disabilities associated with Down’s: “We now have a powerful tool for identifying and studying the cellular pathologies and pathways impacted directly due to over-expression of chromosome 21,” said Lawrence.
The Centers for Disease Control (CDC) estimates that 1 in 700 babies born each year has DS. Mind you, that’s only counting those who are born. Nearly 75% of women who undergo prenatal diagnosis choose to abort their babies when they receive a positive test for DS. So the number of children conceived with DS each year is much higher.
If We Could, Should We?
The question, although apparently counterfactual, is still interesting: if we could cure DS, should we? In the heat of the media hype some argued that we should not. They believe that saying we should “cure” people with Down’s tells us more about our own fear of imperfection than it does about the needs of people with DS. They are often happy and content, often gentler, more affectionate and more forgiving than those without it. Caregivers and loved ones are invariably made better because of their contact with them. Indeed, the world would be a poorer place without them. Moreover, DS is a genetic condition, but not a disease in any ordinary sense from which one is cured. It doesn’t merely affect this or that organ; it not only conditions anatomical features; it runs through every cell of the body. It conditions both psyche and soma. It shapes personality. Could it be “cured” without disrupting the basic identity of the individual?
The reflections are insightful and the questions are good. (Most came from mothers of DS children.) People with DS have no less value than those without it; their beauty and moral worth is not in spite of their condition, but is integral to who they are, encompassing their whole persons, including their genetic makeup; and they’re every bit as valuable to the community as ‘normal’ kids. Moreover, they are literally an endangered species; they therefore need to be jealously guarded against the intentions of those who under the pretense of benignity are infected with the malignant view that DS babies are better off dead. They certainly should not be subjected to risks of serious harm in order to satisfy the obsession-for-normal of other people who are made anxious by their condition.
And yet, DS is a genetic disorder; it causes disability. Curing it, if such were possible, would be therapeutic. Although one’s worth does not change based upon one’s abilities, and people with disability can experience deep human fulfillment, nevertheless, disability by definition limits one’s opportunities. Most DS children will not grow up to experience the joy of marriage, parenthood, or a religious vocation, or, for that matter, Irish step dancing, water skiing, or rock climbing. Do they need these things to be happy and pleasing to God? Heck no. But are they real types of human fulfillment of which disability deprives them? You betcha (to quote Sarah Palin).
If, without subjecting them or anybody else to disproportionate risks of harm or anything intrinsically evil, we can bring God’s good order to their wounded genetic identity, then I think we should do it, just as we should try to straighten our children’s scoliosis, improve their eyesight, or overcome their learning disabilities. Genetic interventions, of course, may be much more consequential, not only to the patient but to any progeny; and so questions of safety and norms guiding ethical intervention will be more rigorous.
Moreover, even if we could completely and safely silence the activity of trisomy cells, it may very well be unethical to people after a certain point in their lives, say, after adolescence. If they’ve lived with certain limitations long enough, thrusting them into the realm of the “normal” could psychologically cripple them (recall the character of the aged Brooks in the movie Shawshank Redemption; after nearly 50 years in prison—the only world he knew—he was completely unprepared for life outside the bars; consequently shortly after being paroled he killed himself). The risks involved with attempting a “cure” for DS likely would be enormous.
We are not presently faced with this choice. But the field of clinical germ line manipulation (therapeutic genetic engineering) is poised to explode in the next twenty years. And so we jolly well should get comfortable asking the question, “if we can do X, should we do it?” Heaven knows, most scientists are not asking it.
Image credit: shutterstock.com
This article was originally published by the Culture of Life Foundation and is used here with kind permission.