A southern California couple is suing a fertility clinic for implanting an embryo with a defective gene. Both parents had family histories of early onset cancers, and both had tested positive for genes that caused these cancers. They chose in vitro fertilization to avoid having a child with any of their cancer causing genes.
With in vitro fertilization, the eggs from the mother are inseminated with sperm from the father outside the mother’s body, and the embryos that develop, which may consist of little more than a small cluster of cells, can be checked for potentially lethal or cancerous errors in their genes before any of them is implanted in the mother’s uterus (womb). This couple was especially concerned about a gene carried by the husband that had caused stomach cancers in him and several of his relatives. He needed to undergo removal of his stomach and chemotherapy to deal with the cancer, and several of his relatives had died while still relatively young from these cancers.
The fertility clinic assured them that the embryo they implanted had been checked for and was free of the cancerous gene, but the clinic staff inadvertently implanted an embryo that had the unwanted gene and subsequently altered their records to conceal the error. This misadventure is a tragedy for the couple involved, but it highlights the enormous advances made in gene recognition and management in recent years.
Humans have about 25,000 genes. These are chemical words written in letters made of a material called DNA. This collection of chemical information is referred to as the human genome. Our genes and to some extent the environmental factors they face account for everything from our eye color to our attitudes. They provide the instructions for making the building blocks of life and for assembling, maintaining, and utilizing those materials. Unfortunately, many of us have misspelled genetic words that cause illnesses, like sickle cell anemia, Tay-Sachs disease, breast cancer, and a multitude of other hereditary problems. Advances in reading our genes and understanding the mechanisms that lead to viable organisms have enabled commercial facilities to check for specific errors in our gene “instruction manual.” Knowing the proper or improper “spelling” of problematic genes allows facilities, like the fertility clinic in the above case, to avoid using embryos that carry lethal or crippling genes.
When efforts to decode all of the good, bad, and indifferent human DNA began, investigators recognized ethical dilemmas that would arise with completion of the task. Not only could Mother Nature’s mistakes be recognized and avoided, but techniques, including embryo selection, could be used to help foster certain traits, such as height, visual acuity, memory, hearing, skin color, etc. Once the function of various genes or gene combinations was identified, parents would have the option of designing their offspring.
By the end of 2023, a complete, consistent, validated listing of the more than 2.3 billion chemical letters (nucleotides) that make up the human genome, the DNA that enables us to live and destines us to die, will be available. Given this long sought chemical code, we are at the threshold of what has been a dream but may well be a nightmare: gene spellcheck and repair. We already know what errors cause many diseases and what corrections are needed to avoid those diseases. We have techniques to modify genes in single cells and may soon have the wherewithal to alter the genetic code of human embryos and eventually that of adults as well. What we do not know and cannot know until we tinker with various elements of our gene code is what changes to the code may place us on the road to extinction.
Mother Nature has spent hundreds of millions of years experimenting with innumerable gene codes to come up with versions that have populated our planet with billions of different life forms. Her tweaking one branch of this enormous tree of life over the past few hundred thousand years resulted in us and our ancestors. Random changes to the gene code have enabled us to survive malevolent forces in our environment, such as plague epidemics. Even what appears to be a genetic error, such as the miscoding of the hemoglobin gene that leads to sickle cell anemia, provides a survival advantage for people with the error living in regions with malaria. One of the many challenges arising with our knowledge of the gene code and our ability to modify it is avoiding unintended consequences. Can we get into this engine of life with the tools available to us without messing up this hugely complicated and profoundly delicate mechanism? We shall soon find out.
Nature is indifferent to our misery. It allows changes to our genes that are often disadvantageous and occasionally lethal. This ever shifting gene encyclopedia has assured the continuation of life on our changing planet. It has allowed or enabled the extinction of billions of magnificent plants and animals and facilitated the endurance of much repulsive (to humans) stuff. An early twentieth century biologist J.B.S.Haldane was asked what his decades of study of life had taught him about the Creator. He answered, “If there is a Creator, he must have an inordinate fondness for beetles.” There are hundreds of thousands of species of beetles, survivors of hundreds of millions of years of evolution. What succeeds and what fails in this struggle for life is not necessarily what we would expect or prefer.
We are relatively new arrivals to the struggle, and the flexibility of our genetic formula will determine if we have the endurance of the beetle or the fragility of the dodo bird. We think we know how to improve the human gene code. We shall soon find out if we are correct. Mother Nature is watching from the wings. Perhaps she is applauding us. Perhaps she is shaking her head in disbelief.
Dr. Lechtenberg is an Easton resident who graduated from Tufts University and Tufts Medical School in Massachusetts and subsequently trained at The Mount Sinai Hospital and Columbia-Presbyterian Medical Center in Manhattan. He worked as a neurologist at several New York Hospitals, including Kings County and The Long Island College Hospital, while maintaining a private practice, teaching at SUNY Downstate Medical School, and publishing 15 books on a variety of medical topics. He worked in drug development in the USA, as well as in England, Germany, and France.
