by Maurice Bernstein, MD
Babies are born with a progressive neurometabolic disorder with a general onset in infancy or childhood, often after a viral infection, but can also occur in teens and adults. The disease is seen on MRI as dead or dying tissue within the brain and though the child appears normal at birth, in a few months to two years of age, though earlier or later, there is loss of basic skills and finally the child may have heart, kidney, vision and breathing complications. What is this disorder? It is a congenital disease carried by the mitochondrial DNA genes of the mother and called Leigh’s Disease. Another disorder found in mother’s egg (oocyte) mitochondria are the Creatine Deficiency Syndromes characterized in the child by mental retardation, expressive speech and language delay, autistic like behavior, hyperactivity, epilepsy and movement disorders. And there even many more congenital disorders expressed by abnormal mitochondria and some are described at the United Mitochondrial Disease Foundation website.
A problem in anticipating these disorders is that the women carrying these abnormal mitochondrial diseases may be healthy. The possibilities of a mitochondrial DNA abnormality may only be suggested by analysis of the woman’s oocyte. If thought to be present, then what? Can the woman ever expect to deliver healthy babies? And this is where a technique of assisted reproduction, developed in the recent years in animals, may yield an answer to this question but does involve ethical dilemmas if performed in humans. It is all about creating a healthy child by removing the mother’s healthy oocyte DNA and placing it within another (donor) woman’s oocyte from which the cellular genetic material has been removed but what remains is that woman’s healthy mitochondrial DNA. Then in vitro fertilization is performed using the husband’s sperm thus introducing the husband’s DNA and then followed by implantation of the finally fertilized egg cell into the mother for the hopeful creation of a healthy baby.
In addition to the prevention of a child born with a mitochondrial genetic abnormality, there are suggestions that a reason for women after the age of 30 to be infertile was because of changes in their mitochondrial DNA with time and that perhaps the same technique would allow these women to have their child with the use of the donor’s “fresh” mitochondrial DNA.
It is this creation of a “three parent embryo” that provides a controversy regarding the ethics of performing this procedure for future therapy or even now to begin research in humans. The controversy is discussed in a comprehensive news article in the February 21 2014 issue of “Science”. According to the article, the use of this technique for human research has been cautiously approved within the United Kingdom but is currently still being considered in the United States by the Food and Drug Administration which has safety and effectiveness responsibilities regarding gene therapy in general.
So , what are the ethics issues involved? Should it be permitted to use a technique, with the purpose to avoid a serious disease for the future child (and future generations), that will result in a genetic modification that will be inherited? if we are using nuclearDNA from one woman and the mitochondrial DNA from another woman to be included in an ovum to be fertilized by a male to create a healthy child are we also introducing into the genetic germ line a “new human” which would never have previously existed and, when mature, part of that “new human’s” DNA would be carried on through future generations? And would this be the first step on a slippery slope allowing genetic modification also of nuclear DNA? If cloning “new humans” from designed nuclear genetic material is already said to be unethical and is not allowed, shouldn’t this nuclear DNA transfer be likewise forbidden? Finally, from a legal viewpoint, should the resultant child be said to have three parents and would the “third” parent (donor) have to be identifiable and have any further obligations to the “family”?
I don’t have all the answers but think only about the question of humans themselves introducing scientifically created changes in the genetic germ line through DNA transfer or even frank cloning which would not have been created by “Mother Nature” through evolution. Couldn’t all this messing with evolution be exactly what evolution was intending: developing us humans to a point when, through our intellect and science, we could add our own “two cents” to the process of evolution? Therefore, to me, no problem.