No "genetically modified" girls!
Reports about an ordinary event at the present time, most of the media have inflated and distorted to the best of their strength and imagination. What are some headlines worth: from variations on the theme of "a genetically modeled girl" to the piquant "Not Dolly, and not a sheep. The first child with an artificial gene system is preparing to be born." And in the very first lines – "The birth of the first genetically modified child will take place in a week in the capital of Great Britain", "a 27-year-old woman, whose name is not yet called for security reasons, will give life to a girl with a gene seized by doctors, which in case of development could lead to breast cancer..."
In fact, no one has genetically modified the girl, who will be born any day in the clinic of the University of London (University College Hospital), not to mention the creation of an "artificial gene system" unknown to science. And no one has withdrawn the gene from her, especially since it would probably be even worse to simply "remove the cancer gene": normally, the BRCA1 and BRCA2 genes (BRCA – breast cancer susceptibility gene) are involved in DNA repair processes and are suppressors of tumor growth. If a mutation occurs in the structure of the tumor suppressor gene (as a result of congenital causes, under the influence of environmental factors or during aging), it ceases to perform its functions, as a result of which cells are able to grow and divide uncontrollably and may eventually form a tumor. In the family of the girl's father, women in three generations fell ill with cancer after the age of 20, and just such a defective copy of the BRCA1 gene got into one of his pair of 17 chromosomes.
Test systems for detecting BRCA type 1 and type 2 genes have been used for several years. But until now, genetic testing for variants of the BRCA1 and BRCA2 genes has been carried out only for adult women. One of the options that is offered with a positive test result is a preventive mastectomy. Some women prefer such an operation to live in constant fear.
Preimplantation genetic screening for in vitro fertilization is not only common, but also mandatory. However, until now, embryos have been tested for chromosomal defects like Down syndrome and the presence of genes that necessarily lead to the development of serious hereditary diseases. The BRCA1 gene does not fit this definition: it does not guarantee, but only increases the probability of getting breast cancer by almost 3 times – up to 36% during life (for the entire population, this indicator does not exceed 13%). Another similar gene, located on the 13th chromosome BRCA2, is even more dangerous: the probability of illness for its carriers is 85%. Certain variants of the BRCA1 and BRCA2 genes also correspond to a 16 and 60 percent risk of ovarian cancer with an average risk of 1.7% for the general population.
The "sensational" girl will be born without the risk of dying from breast cancer as a result of not "modeling an artificial gene system", but the usual selection for in vitro fertilization of one of several embryos – the one who was lucky enough not to receive from his father a defective gene for susceptibility to breast cancer, BRCA1.
The only unusual thing about the situation is that the girl's parents were the first to take advantage of the 2006 decision of the British Committee for Human Fertilization and Embryology (HFEA) that doctors can also test so–called predisposition genes, for example BRCA1.
Preimplantation diagnosis of several three–day-old embryos was carried out according to the usual method - one of the eight cells was carefully plucked off (this does not affect the development of the embryo) and checked for the presence of mutant variants of the BRCA gene. One or two healthy embryos were implanted into the uterus. Everything is as usual with IVF – except that this was the first case of preventing a possible hereditary disease in an unborn child. Although, of course, in the girl's genome there are many imperfect variants of other genes that increase the possibility of many other diseases. And with the same breast cancer, she (ugh-ugh) can get sick for reasons unrelated to BRCA.
But the event is still significant: the first truly "designer" child will be born one of these days. There is no doubt that more and more such children will be born every year. And someday it will surely come to what the current headlines promised us in advance: preimplantation gene therapy.
A Healthy Skeptic
Portal "Eternal youth" http://www.vechnayamolodost.ru/23.12.2008