05 April 2010

Why do we need to decode the genome?

Deciphered to believeNatalia Leskova, "Results" No. 14-2010

Recently, a law on genomic registration has been in force in our country. With the help of a special DNA study, a picture resembling a barcode is obtained. By the number and location of the strips, it is possible to uniquely (except for identical twins) identify the owner of this DNA information. In many countries, such registration has been used for a long time, but in Russia everything is just beginning. However, it is already clear: DNA identification is invaluable in criminology, applicable in professions associated with risk. But is it necessary for an ordinary person to decode his genome and why? The director of the N. I. Vavilov Institute of General Genetics of the Russian Academy of Sciences, corresponding member of the Russian Academy of Sciences Nikolai Yankovsky was asked about this "Results".

– Nikolay Kazimirovich, genetics for many people is something from the category of theoretical sciences. Can they feel her achievements in practice?– The ultimate goal of genetics is not theoretical, but purely practical – to make the life of each of us more comfortable and longer.

Genetics has achieved outstanding results in a number of practical areas – in computer analysis of genetic tests, in the search for disease genes, in biotechnology. Already today it is possible to determine the predisposition to more than three hundred hereditary diseases. Soon this list will expand significantly. Based on the conducted fundamental research, a screening program for these ailments is being implemented. With an increased risk of some hereditary diseases – say, oncology – an operation is performed in advance, and there will be no cancer. There are also more gentle recommendations for a high risk of developing diseases – for example, to follow a special diet or take appropriate medications that effectively help a particular patient. Of course, social issues of access to treatment immediately arise here, but this is no longer a matter for scientists, but for statesmen. In the coming years, we will be able to eliminate the symptoms of some genetic defects, such as diabetes, with the help of gene therapy. And what is not a good thing to return a lost leg or arm to a disabled person by growing "spare parts" from their own tissues? Or to rejuvenate a person without any "means of Macropoulos"?

– Today, almost at every step they talk about the decoding of the genome. Is it possible to find out fate by deciphering your genome?– I would say this: in most cases, not fate, but one of its variants.

Decoding of the individual's genome is possible, but for now, instead of a complete decoding of the genome, DNA diagnostics is used - the identification of changes in some DNA sites that lead to the disease. Such a diagnosis is especially important in the case when the risk of getting sick for a given person is approaching 100 percent – in other words, the disease will necessarily develop with age. There are a lot of such diseases – several thousand, and the total number of sufferers from these diseases worldwide is about 10 million people. However, each specific of this set of diseases is quite rare. For example, less than one case per 100 thousand newborns. Therefore, children are tested for predisposition only to the most common diseases, such as cystic fibrosis, phenylketonuria and a number of others. Probably, total DNA diagnostics based on the complete decoding of the human genome will become available in practical healthcare, if not in our lifetime, then in the lifetime of our children. But the main number of diseases, and those that occur most often, cannot be predicted with 100 percent certainty, even with the fully known structure of the individual's genome. For example, breast cancer is very common. But there are only 3 percent of cases when it is possible to predict with a very high probability that a woman will develop this disease. For the remaining 97 percent of the affected women, even prior knowledge of the genome structure would indicate only an increased likelihood of developing breast cancer compared to other women. However, we can confidently say that most women will never get sick with this disease, even if they have exactly the same genome structure as those who are ill. Therefore, with the mass diagnosis of this disease, a significant number of women will live in constant fear, and the harm caused by the check, just in case, will harm the health of society rather than help.

– How to distinguish in which case to carry out the decoding of the genome, and in which – not?– This question is open to everyone – for geneticists, bioethicists, and health officials, since DNA diagnostics, and even more so the establishment of the complete structure of individuals' genomes, is a lot of money.

I believe that today genetic diagnostics should be recommended only for those cases already known to science when the connection of the genetic constitution with the development of the disease is close to 100 percent, and the disease is fatal or leading to severe disability. In this case, on the basis of DNA diagnostic data and, of course, consultation with a geneticist, parents, for example, may decide to terminate pregnancy. Of course, this is terrible, but at least they have a choice – after all, with a probability of at least 75 percent, the next pregnancy of the same couple will lead to a healthy baby!

– When I, at the age of 40, carrying my third child, came to the doctor, I only heard that at my age Down syndrome and all other horrors were provided for the heir. But it worked out…– The frequency of birth of children with Down syndrome increases with the age of the mother from 1/2000 in 20 years to 1/12 in 50 years.

But even for women in labor at the age of 50, eleven out of 12 children will be healthy. In addition, Down syndrome is usually associated with a genetic defect of the germ cell that occurred before fertilization. Therefore, DNA diagnosis of this disease is possible at the earliest stages of pregnancy, even before the embryo is inserted into the uterine wall. Technologically, the accuracy of such an analysis is extremely high, but diagnostic errors can also occur for reasons that have nothing to do with science… The rest of the diseases, and their absolute majority, are not inherited so easily. Their manifestation requires the participation of several genes at once in combination with the action of certain environmental factors. These ailments are manifested, as a rule, in adulthood and old age. For example, hypertension and diabetes. Even knowing the entire structure of the genome of a particular organism, we will not be able to say whether a person will get sick with them for sure or not.

– Have you personally decoded your genome?"Not mine.

What is "written" there are predispositions. I think I have all of them implemented. But it would be useful for a child. Risk zones can be identified. But the irony is that in response to the question of what to do with them, you can only give long-known recommendations: do not drink, do not smoke, do not be nervous, do not overeat, lead a mobile lifestyle. So far, no one has come up with anything better. And I guess he won't. Of course, there are acute diseases, but there are only 2-3 percent of them.

– Is it true that it is for genetic reasons that the same food can be useful to some people and harmful to others?– Yes, it is an established fact.

Let's take milk and bread for example. It would seem that what could be harmful in them? However, our study of the ability to assimilate milk sugar – lactose – has yielded surprising results for many: due to genetic characteristics, about 30 percent of the adult population of the Central part of Russia, and in particular Moscow, does not digest lactose. The use of whole milk in such people can lead to nausea, digestive problems, and poor health. No one has yet figured out how this feature affects children of transitional age. And the consumption of ordinary white bread in some children can lead to digestive disorders and dementia. This disease, called celiac disease, occurs in every hundredth inhabitant of Ireland. In other European countries, it is not so obvious – about one case in a thousand.

– What should we do with our addiction to alcohol?– In the laboratory, which I head, work is underway to study the genetic factors predisposing to alcoholism.

Russians, in comparison with other Europeans, do not have any peculiarities of alcohol metabolism that make us drink. So we have nothing to complain about bad genetics in connection with drunkenness.

– In which direction is the development of the science of genetics moving today?– In the future, we hope to move from the level of understanding what genes cause the disease to the level of understanding how it occurs – how genes work and how they interact with each other.

This will give us the opportunity to get closer to a more accurate prediction of diseases. Another interesting direction concerns the effect of drugs. It turns out that for each person the speed of this action, and hence the effectiveness, is individual. This is also a genetically determined fact. This rate with a certain degree of confidence can also be predicted by gene analysis. Thus, knowledge of the genetic constitution will allow us to determine what we need for treatment and in what dose.

Portal "Eternal youth" http://vechnayamolodost.ru05.04.2010

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