Researchers in Iceland have discovered a region in the human genome that apparently increases fertility and causes longevity in people of European descent. The region in question, a DNA chain on the 17th chromosome, appears in the natives of all countries, but is more common among Europeans and its effect seems to be due to a European-environmental phenomenon.
Nicholas Wade, New York Times, Haaretz, News and Walla!
Researchers in Iceland have discovered a region in the human genome that apparently increases fertility and causes longevity in people of European descent. The region in question, a DNA chain on the 17th chromosome, appears in the natives of all countries, but is more common among Europeans and its effect seems to be due to a European-environmental phenomenon. Another rare feature is that the genetic region in question has a more ancient "genealogy" than most human genes. According to the researchers, a possible explanation for this is its entry into the human genome during "hybridization" with one of the ancient human "lineages", which developed at the same time as the modern human.
The genetic region was discovered by scientists at Decode Genetics, a biotechnology company based in the capital of Iceland, Reykjavik. The company turned the population of Iceland - on the full family tree in its health records - into one of the best "hunting grounds" for the genetic roots of common diseases and published its findings yesterday in the issue of "Nature Genetics".
The site in question was discovered during the search for the gene that causes schizophrenia, which was not found. However, according to Dr. Kari Stephenson, CEO of Decode, the company's researchers noticed that the DNA sequences they tested did not match the normal sequence in the human genome. The mismatch is caused by the fact that the site exists in two states among the Icelandic population. It is not a single gene, but a large area of DNA that is about 900 units long and is located on the 17th chromosome out of the 23 pairs of human chromosomes.
Among some of the Icelanders, the researchers found that the segment moved in the direction of the standards (as in the majority of the population), but in others a deviation was noted. Searching for physical implications, De Code scientists discovered that women who carry the inverted movable segment are mothers to more children.
According to Dr. Stephenson, several known genes were discovered on the site, none of which are related to fertility. It is not clear why the inversion affects the number of children, but it increases the rate of recombination (creating gene combinations - genetic passage through the generations), which is a main source of new genetic combinations. This may be the reason for the greater fertility.
De Code scientists discovered that the inversion in chromosome 17 is rare among Africans, almost non-existent among Asians and appears in about 20% of Europeans - a rate similar to that recorded in Iceland. The reversal was aided in the recent period by the European natural selection process - probably in the last 10,000 years. "Something caused it in the European environment, for example a nutritional phenomenon," said Dr. David Reich from the Broad Institute, which deals with population genetics.
When all known versions of a human gene are compared to each other, in most cases it turns out that they all had a common ancestor about a million years ago. However, the normal and the opposite versions on chromosome 17 have a common ancestor that dates back three million years. It is completely unlikely that two different versions of a garden would exist for such a long time; Usually one of them would disappear as part of the natural selection process.
According to the researchers, there are two explanations for the presence of the gene. The first - the normal version and the reversed version have common advantages, and for that reason it is better for a person to inherit a copy of each of them from his two parents; According to the second explanation, for many years the reverse version was part of a different genealogy of one of the ancient populations that lived before the humans we know anatomically appeared in Africa, 150 thousand years ago. As part of some kind of hybridization, a copy of the fragment entered the genealogy of modern man, who left Africa about 60 years ago.
According to Dr. Stephenson, the inversion in chromosome 17 is also associated with longevity. De Code scientists discovered among the Icelanders who participated in the study two regions of DNA that promote life expectancy. It turns out that the inversion on chromosome 17 is located on one of these regions. The findings are particularly striking among women over 95 and men over 90. "It seems that the inversion allows humans the possibility of reaching a particularly advanced age," said Dr. Stephenson.
The fact that the same genetic region is responsible for both fertility and longevity is surprising, since most animals choose one of two strategies: breed quickly for a short life or live a long life and produce a small number of offspring. "People tend to think that there is a trade-off between fertility and longevity. It seems that we are getting a 'free meal' here," concludes Dr. Alan Rogers, a genetic researcher from the University of Utah in the USA.
