Between the sixth century and the eighteenth century, successive epidemics of plague killed a third or even half of the population on the mainland, but survivors have given rise to a population with increased resistance to disease. Here, a painting by Micco Spadaro plays plague in Naples.
A romanian research participation found that genes trigger alert of the plague in body – and sees possible implications for other diseases.
Waves of plague that decimated medieval Europe and frightened centuries ultimately selected the most resistant individuals. Successive epidemics killed a third or even half of the population on the mainland, but survivors have given rise to a population with high immunity to this disease.[adsenseyu1]
A multidisciplinary team from research centers in the Netherlands, Romania, Spania and India had the idea to look for genes altered by exposure to bubonic plague in a population of un-european origin, but who lived in Europe in the last thousand years: the Gypsies.
Arriving from North India between 900 and 1100 AD, rroms ( traditionally called Gypsies ) continue to live in Europe, wearing a genetic baggage practical unchanged. ” We found that among european rroms and an ethnic group from northern India, are small genetic differences. Instead, there are big differences between them and european populations, both in the West and the East. Historical and social conditions have made the rroms interfere very little with local people for over 1,000 years “- says Michael Netease, who led the published study last month in the Journal of the National Academy of Sciences USA ( PNAS ).
But just DNA differences between rroms and european populations were the study key. Because the team found genes that have undergone identical changes in the last millennium in both groups. The similarities could only have come from evolutionary pressure environment.
To decipher these DNA changes, the researchers collected blood samples from 100 individuals of european descent and 100 individuals of rrom origin, both groups from Romania, and from 500 individuals from North India, the home geographical for rroms – for comparison.
Applying mathematical models, they made a short list of genes from modified DNA as a result of external pressure from romanian and rroms, but not from indians.
From this list, we identified three genes which previous studies have suggested that have the role of recognizing the bacteria. What major pressure factor was manifested in the last thousand years in Europe, but not in India? The authors assumed that it was lethal Yersinia pestis, the plague bacillus, brought by infected rats from Asia and transmitted by fleas, and later from human to human.
There was a set of molecular studies to verify the hypothesis.
It turns out that the same set of immune receptors (TLR – toll-like receptors) that recognize Y. pestis were altered in parallel, to european and rroms, in what is called convergent evolution. (Convergent evolution is, for example, how man and octopus eyes have come to very similar, total separated ways). Indian population, the same receptors were not altered.
“First I bought kidney cells grown in the laboratory, which didn’t showed these receptors, and have shown that they do not react to Y. pestis. Then we transfected receptors and it reacted “- explained Mihai Netea immunologist at Radboud University in Nijmegen, Netherlands. TLR 01.06.10 sights plague bacillus recognize infection and triggers a counterattack (ie induce white cells to produce certain proteins, proinflammatory cytokines, which signal the immune system to intervene).
Netea says that two things have become clear from the study: “TLR receptors 1.6.10, have been under evolutionary pressure and what was unknown so far, they are the ones who respond to Yersinia pestis infection and triggers immune response. ” it remains, however an assumption that if the plague was the sole cause of their change.
Although the plague is no longer haunting, the study is of great interest because gene variants selected in european populations by this evolutionary pressure may play a role in the detection of infectious diseases or modern inflammatory or in development of autoimmune diseases. The researchers now intend to check whether the same receptor changes the susceptibility to Crohn’s disease, rheumatoid arthritis or septicemia.