16 September 2013

Map of human genetic variability


Geneticists have archived people
Results of the largest human genome study
presented by a large group of scientists in the journal NatureThe sequencing of the human genome, which was announced in 2003, is only a reproduction of a sequence of letters in a text that we cannot yet read.

Therefore, molecular geneticists never use the word "decoding" at the same time. So far, for us, this is exactly what encryption is, over the meaning of which geneticists and bioinformatics have been struggling for more than a decade.

Understanding how the genome works is probably the most important challenge for biologists today.

Scientists are taking small steps towards this understanding. After they got the sequence of letters of the same genome, they found that many DNA sections differ from one person to another. The most common difference is the replacement of one nucleotide (the brick from which DNA is built) with another. This is the so-called single nucleotide polymorphism (SNP). Biologists began to study it from different people and have already created a huge database containing more than one million "snips". This database has become a very useful tool for searching for genetic variations associated with any diseases (the GWAS method is a genome-wide association search).

To date, geneticists have found a great many such associations, but they do not always lead to understanding the mechanism of the disease and finding ways to treat it. Because all these are structural differences in the genome, and there are also functional ones. Different people differ not only and not so much in the structure of their genes, but in how these genes work (are expressed).

And it depends on the mechanisms of regulation, which scientists have just begun to understand. To understand why we are all so different, it is not enough to even read the genomes of all people living on Earth, because the same letter sequences can be read differently by different people.

"The interpretation of millions of variations in the human genome is essential for understanding the genetic base of external and internal differences of individuals," the authors write in the journal Nature, where they published a map of genetic differences between people (Reproducibility of high–throughput mRNA and small RNA sequencing across laboratories). This work was carried out by an international team of more than 50 employees of nine research centers led by researchers from the University of Geneva. It is part of the large project GEUVADIS (Genetic European Variation in health and Disease) – "European genetic variations in health and diseases", part of the Seventh Framework Program of the European Commission.

This is the largest study that presents sequencing and analysis of two types of RNA – matrix RNA (mRNA) and microRNA.

The first plays a key role in protein synthesis, as information from a section of the DNA molecule is rewritten to it. The second performs regulatory functions. Since mRNA is synthesized only from those genes that are currently being expressed, RNA analysis in the cell indicates which genes were currently active.

The authors examined the RNA of 462 people for whom DNA sequencing data from the 1000 Genomes project was already known. These people belonged to five different populations. Scientists received unique data on individual variations in gene activity, and, to their surprise, the spread of these data turned out to be very wide. Until now, knowledge about RNA in different human populations has been very superficial. By combining the results of RNA and DNA analysis, one can understand some of the reasons for such differences. In other words, to see how differences in the structure of genes affect the degree of their expression.

The researchers were able to establish a large number of cause-and-effect relationships and, on this basis, get an idea of why some variations lead to an increase, weakening or loss of gene activity.

This is a step towards incorporating this information into a personalized genome. The results of this analysis will allow us to get closer to personalized medicine. They show how the genetic profiles of different people affect the switching on and off of certain genes. In some cases, this causes the disease. Knowing which genetic variations lead to changes in gene activity can be the key to the diagnosis and treatment of diseases.

All the data obtained are freely available in the functional genomic archive EMBL-EBI. This will allow independent researchers to use them in their work and supplement them.

Portal "Eternal youth" http://vechnayamolodost.ru16.09.2013

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