22 October 2008

Preimplantation diagnostics: sorting embryos

Sergey Avilov, Telegraph "Around the World":
The Spartan method of embryo cultivationIn one book by Stanislaw Lem (1921-2006), a Robot asked a Person: "How do you program children?".

Until recently, it was clear to everyone that the famous science fiction writer was joking. Today, the "programming" of children is no longer fiction. Parents who resorted to artificial insemination had the opportunity to choose which of several embryos to give life to.

The method of "programming" childrenThere is no fiction in "programming children": the strategy is simple, like the techniques of a cattle breeder.

First, several eggs are artificially fertilized. Then genetic screening of the resulting embryos is carried out — the genes responsible for the appearance of a particular trait are identified, and a "good" embryo is left, that is, an embryo that has or does not have a certain gene.

In practice, this is done as follows. With the help of injections of female sex hormones, the maturation of several eggs in the patient's ovaries is artificially stimulated. Then, under the control of ultrasound, a special needle penetrates into the ovary and "sucks" out the follicles — formations inside which the eggs mature. Then, in a laboratory dish, the eggs are separated from the "accompanying" cells and mixed with prepared spermatozoa. After fertilization, the eggs (now called zygotes) are placed on a special nutrient medium, where they begin to divide — the future children began to grow.

After 2-3 days, the "best" of the embryos (usually no more than two) are returned to the uterus, and if at least one is attached to its wall, then pregnancy occurs. The question is how to select this or these "best" embryos. Modern medicine is able to perform preimplantation genetic screening, that is, to determine the presence of a number of genes that will lead to the development of serious hereditary diseases. Among them are hemophilia, sickle cell anemia, Huntington's disease, beta-thalassemia and many others. For the existing hypersensitive methods of genetic analysis, one cell is enough, which is "plucked" from the embryo. This usually occurs at the stage when it consists of eight cells; oddly enough, such a "mutilation" does not affect the further development of the embryo. Screening should be done very quickly: the embryo should be placed in the uterus no later than the fifth day after fertilization. So, the "lucky one" is given the right to life, and the rest of the embryos are eliminated — in other words, they are killed.

The roots of the problemIt all started with such an achievement of medicine as in vitro fertilization.

Infertile couples have the opportunity to have children. The technique is not always successful, so usually several eggs are fertilized at once: at least with one, but everything will work out. Then another quite humane achievement is preimplantation screening to detect hereditary "defects" in embryos before their implantation into the uterus. Previously, it was possible to detect defects only of the fetus already growing in the uterus and recommend an abortion. Any doctor will say: the earlier a hereditary disease is detected, the better.

However, these achievements of modern medicine have created a serious ethical problem. There are several embryos, and the mother can usually only carry one or two. So which one to choose? This problem concerns not only infertile couples: artificial insemination can be used by any couple to have several embryos in the "assortment" to choose from.
The health of the nation or the genocide of the deaf and dumb?

It is this choice that concerns the Bill on Human Fertilization and Embryology (Human Fertilization and Embryology Bill), which is currently being considered in the House of Commons of the British Parliament and may be adopted in October. Serious disputes have flared up around the future law, in which public organizations are actively involved. One of the provisions states: if it is known that this embryo has some hereditary "defect", and at the same time there is another embryo, "non-defective", then it is impossible to choose an embryo with a "defect".

It seems that this is generally a reinsurance: who would want a child with a hereditary anomaly to be born? But there were people and even public organizations who began to actively protest against this provision. The fact is that deafness has been included in the list of serious hereditary diseases, embryos with which cannot be selected for implantation. It turned out that people who are deaf from birth do not consider their deafness a disease. They form their own separate community, communicate in their own language and have their own unique culture. For example, Tomato Lichy, an activist of one of the deaf-mute organizations, said in an interview with BBC Radio 4: "In order for you to understand me here, you need an interpreter, but if you get to a meeting of deaf-mutes, then you will already have problems. You can't appreciate the poems in our language, you don't understand our humor."

The ban on choosing an embryo from which a deaf child will grow up is considered by deaf-mute organizations to be a manifestation of discrimination and even genocide: fewer and fewer deaf people will be born, and the original community will eventually disappear. Some (and maybe many) deaf-mute families want their children to be born deaf. In their opinion, a child who hears and talks with the help of a voice, does not understand his "finger-speaking" parents, turns out to be a stranger in their special world.

However, arguments like: "A hearing child will not understand sign language" seem somewhat far-fetched. Sign language translators understand both the deaf and the hearing! Moreover, young children learn so easily — in international families they easily master two native languages at once. Why can't they learn sign language — for their parents, and ordinary language — for the hearing world? It turns out that parents condemn children to live in their own specific world, cut off their way to the rest of the world. This is at least very selfish: a hearing-deprived child, of course, will be more attached to parents like him. But how much more difficult it will be for such a child outside the parental home, despite all the struggle against discrimination against the deaf (more correctly, the hard of hearing). And most importantly, a hearing person can learn sign language in order to join the culture of deaf-mutes, and a deaf-mute cannot "learn" to hear.

The way in which deaf-mutes want to provide replenishment to their community resembles a story invented by Herbert George Wells (1866-1946). The hero finds himself in the land of the blind and tries to explain to its inhabitants what the visible world is. They consider him crazy and decide to blind him: let him be the same as the rest of the society. It was hard to imagine that in the XXI century in the homeland of the classic there would be those willing to realize his dark fantasy.

Improving the human breedThe most surprising thing is that the British public is not arguing about whether it is ethical to make a choice at all: "this is to live, and this is not."

The only question that causes controversy is how to make such a choice correctly.

In the first half of the twentieth century, eugenics was popular — the doctrine of improving the human breed. It was proposed, for example, to prohibit or not recommend having children to people suffering from hereditary diseases. For the benefit of humanity, of course, so that there will be fewer such diseases in the next generation. It became clear what the large-scale implementation of eugenics ideas could lead to when one particularly fanatical eugenist came to power in Germany in 1933. Then the "Law on the prevention of the offspring of people with hereditary diseases" was adopted. Forced sterilizations and extermination of people with various anomalies that were considered hereditary, such as mental illness, deafness, hereditary blindness, severe alcoholism, were carried out on a large scale.

After that, the eugenic doctrine was greatly discredited. Humanity seems to have recognized that even a good goal does not justify interference in the appearance of offspring. Now organizations of deaf-mutes are called (more precisely, called) eugenics prohibition to deliberately choose an embryo that does not have a deafness gene. But deliberately choosing an embryo that has a deafness gene is the same eugenics, only the ideas of what is good and what is bad are reversed. It turns out that in the conflict about the deafness gene, eugenics is approved by both disputing parties, but they differ only on the question of preferences: which embryos to choose "correctly" and which ones not. It may not be by chance that preimplantation screening of embryos (and hence their choice to your taste) is prohibited in Germany, which has experienced practical eugenics.

Is everything the will of Allah?In Arab countries, there is no question whether it is possible to conduct preimplantation screening and select embryos.

Here the answer is obvious: it is not possible, but necessary. The fact is that in these countries there are traditionally many marriages between relatives (up to 50% in the UAE and two thirds in Saudi Arabia). Probably because of this, children with congenital anomalies are born much more often than in Europe or America, which was proved by the Center for Arab Genomic Studies in the UAE. There are high hopes for preimplantation screening, as it will allow identifying and "culling" embryos with "defective" genes.

The mass introduction of preimplantation screening and mandatory genetic testing of the bride and groom is seen as a more realistic prospect than the eradication of the tradition of related marriages. So far, there is one institution in the entire Arab world where preimplantation screening is performed — the King Faisal Hospital in Saudi Arabia.

"We decided that it would be a boy..."The genetically predetermined trait of the embryo that is easiest to determine is gender.

Although neither gender is a pathology, many parents would very much like to choose whether it will be a boy or a girl.

If there are approximately the same number of couples in society who choose one or the other gender, there are no problems. However, in some countries, for example, in India and China, boys are traditionally preferred. If parents have the opportunity to choose the sex of the child, then a serious bias may appear in the next generation. According to the draft law, which will be considered by the Indian Parliament at the end of 2008, choosing the sex of an embryo without medical indications (so-called sex-linked diseases) will be considered a criminal offense.

The Jewish SolutionPreimplantation screening of embryos is considered acceptable from the point of view of the morality of Judaism, if we are talking about a serious hereditary disease.

For orthodox Jews, this is probably the only solution. The fact is that on the one hand, the Torah prescribes all couples to try to have their own (not adopted) children, even if both parents have some kind of hereditary disease gene and there is a high probability that the child will be sick. On the other hand, Jewish morality approves abortions only in case of a threat to the health of the mother. That is, it is impossible to kill the fetus (to have an abortion) due to the fact that a hereditary disease has been detected.

It turns out that embryo selection based on preimplantation screening is the only stage at which it is possible to prevent the appearance of children with hereditary diseases. However, another radical way is possible for those hereditary diseases that are inherited according to the so-called recessive principle: the disease manifests itself only if the child has received copies of the "defective" gene from both parents.

In the traditional Jewish community, the first date of the future spouses should be preceded by an official presentation with the mediation of a matchmaker. An organization called Dor Yeshorim tests future spouses for the presence of hereditary disease genes before they meet and reports the results (only to the matchmaker!) if it turns out that both potential spouses have the same hereditary disease gene. In this case, the matchmaker simply will not introduce them. Mental trauma, fear of the birth of a sick child, worries about their "inferiority" are excluded - the gene carriers themselves can not be informed about the results of testing.

Portal "Eternal youth" www.vechnayamolodost.ru22.10.2008

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