EpidemicsGenes of Gypsies show traces of convergent evolution in response to Black Death
The Black Death once exterminated up to 30-50 percent of Europeans. Researchers have identified immune system genes in Europeans and Gypsies that likely underwent convergent evolution during Europe’s deadly epidemics. Immune system genes evolve under the influence of infectious diseases, but few studies have attempted genome-wide assessments of infection-driven evolution.
Researchers have identified immune system genes in Europeans and Gypsies that likely underwent convergent evolution during Europe’s deadly epidemics. Immune system genes evolve under the influence of infectious diseases, but few studies have attempted genome-wide assessments of infection-driven evolution. A PNAS release reports that to investigate the effects of epidemics on immune system evolution, Mihai Netea and colleagues exploited the fact that two ancestrally distinct populations — Romanians, of European ancestry, and Gypsies, of North Indian ancestry — have cohabited Romania during the last millennium, exposed to epidemics such as the Black Death, which once exterminated up to 30-50 percent of Europeans.
The authors used microarrays to assay 196,524 genetic variants called single nucleotide polymorphisms, or SNPs, in the genomes of three groups, namely 100 people of Romanian descent, 100 people of Gypsy ethnic background, thought to have descended from Northwest Indians who immigrated to Europe about a millennium ago, and, for comparison, 500 present-day Northwest Indians.
The authors report that a gene cluster called TLR1/TLR6/TLR10, which encodes immune receptors, adaptively evolved in Romanians and Gypsies but not in present-day Northwest Indians, suggesting an effect of selection pressure specific to Europe. When the authors exposed peripheral blood mononuclear cells from 101 present-day Europeans to Yersinia pestis, the plague bacterium, and Y. pseudotuberculosis, a precursor of the plague bacteria, SNPs in the TLR1/TLR6/TLR10 cluster — but not in a different receptor called TLR4 — appeared to influence immune responses against both bacteria.
According to the authors, the findings might help uncover the origin of differences in the susceptibility of Europeans and other populations to some modern diseases.
— Read more in Hafid Laayouni et al.,”Convergent evolution in European and Rroma populations reveals pressure exerted by plague on Toll-like receptors,” Proceedings of the National Academy of Sciences (3 February 2014) (doi:10.1073/pnas.1317723111)
