Epigenetic imprints of childhood

Methylated because of a difficult childhood
A person carries the genetic imprint of childhood all his lifeDmitry Malianov, Newspaper.
RuLow social origin and a difficult childhood leave an imprint on human genes that is well recognized in adulthood, Canadian and British geneticists have established.

Can the oligarch's genes "remember" that as a child he was chronically malnourished and always squelched his nose due to the lack of a warm coat, living in a communal apartment in an ecologically disadvantaged suburb? Thirty years ago, any geneticist would have answered this question in the negative. He will also answer now, but at the same time he will ask to clarify what exactly is meant by "remember", and if a geneticist comes across quite advanced, then what exactly is meant by "genes". Such clarifications became necessary after the discovery of additional – epigenetic – inheritance mechanisms that do not affect the DNA molecule – the genetic program hidden in the cell nucleus.

From the point of view of nuclear DNA – the basic repository of hereditary information of the cell – various heartbreaking facts that its carrier for many years ate one potato as a child and suffered from cold are not of great interest, since bad food, leaky galoshes and an apartment without a toilet are not able to change the sequence of nucleotides in the DNA itself – the main genetic program of the development and functioning of the body.

But if we compare DNA with the score, and the life of the organism with its orchestral performance, then the sound of the opus will consist of how exactly the notes of the score (genes) will be read and performed by the musicians – mechanisms responsible for their expression.

The musicians themselves are not able to change the text of the score, but there are ways to vary – and sometimes quite strongly – the sound of the notes. These methods of information transmission, additional to the hereditary genetic program – DNA score, are called epigenetic (that is, additional to the actual genes). And now molecular geneticists are accumulating more and more data in favor of the fact that epigenetic, that is, mechanisms regulating the activity of genes can be very responsive to the effects of external factors, and the effect of such influences can be traced not only throughout the life of one organism, but also in its descendants.

DNA methylation – the main of the already discovered epigenetic scenarios – regulates the expression of the hereditary "score" through the attachment of a methyl radical -CH ₃ to certain DNA sites, which disrupts the transcription process, that is, as if blocking the gene with a universal methyl "cap".

Methylation controls the process of the emergence of new organs, turning on and off certain sections of DNA during the growth of the embryo. The further functioning of tissues, as well as the body as a whole, also depends on different schemes of DNA-containing chromatin methylation in the nuclei of already differentiated cells, and violation of these schemes can be accompanied by serious systemic dysfunctions – activation of "sleeping" genes (cancer), chronic metabolic disorders (diabetes), etc.

It turned out that the methylation function is very plastic and makes even identical twins, whose genetic "scores" are completely identical, be different from each other.
Apparently, the methylation scheme regulating gene expression influences the process of adaptation of the hereditary program to environmental changes, but neither the principle of operation of this mechanism nor its role in evolution is still unclear.

All the more intriguing are the observations of a group of Canadian and British geneticists who reported in a collective article published in the International Journal of Epidemiology (Borghol et al., Associations with early-life socio-economic position in adult DNA methylation that the pattern of methylation varies greatly in people not only from different social classes, but especially strongly among who grew up in different economic and living conditions. In other words, diametrically different conditions in which children from wealthy and poor families grow up are imprinted – "remembered" – in their organisms at the genetic level for the rest of their lives.

This fact was discovered by comparing the DNA profiles of 40 people, since 1958, that is, from the moment of their birth, participating in a long-term medical and scientific monitoring program covering a total of 10 thousand Britons. 45-year-old representatives of diametrically opposite social groups in terms of the level and quality of life, as well as those whose childhood was spent in extremely cramped conditions bordering on poverty, and those who were brought up "in the best homes in England" were specially selected for DNA research.

Methylation levels were measured in 20 thousand DNA control sites. To the surprise of geneticists, the differences in levels turned out to be very large in a rather impressive group of 6 thousand genes, while a group of methylated DNA belonging to people from higher social strata stood out inside it.

Most of the differences in methylated DNA (1252) accumulated between those who had a different childhood – "very difficult" and "very prosperous". But when comparing the methylated DNA of people with different living standards (for example, CEOs of companies and laborers), but who grew up in approximately the same conditions, the differences turned out to be more than two times less – 545.

Thus, the authors of the article believe, the genetic profiles of people who were born some "princes" and others "beggars" demonstrate a greater number of differences in the mechanism of genetic regulation than the genes of people who became such by the age of 45. In other words, all our lives we literally carry the genetic imprint of childhood, which affects our health and our character, given how closely mental activity can be connected with hormonal, enzyme and other regulatory subsystems.

The authors note that the purpose of their research was to find out the very fact of the relationship between the socio-economic factor and the genetic picture within the life of one generation of people. What specific diseases and deviations are fraught with genetic imprints inherited from a difficult childhood by "oligarchs" and "poor people", it remains to be found out (it is also possible that in the case of a "difficult" childhood, epigenetic regulators play just a protective function, therefore the number of differences is greater). It also remains to be seen whether epigenetic innovations that do not affect the structure of DNA migrate in generations.

Portal "Eternal youth" http://vechnayamolodost.ru25.10.2011