Sunday, December 20, 2009

Coincidence or adaptation?   posted by Razib @ 12/20/2009 01:48:00 AM

Different Evolutionary Histories of the Coagulation Factor VII Gene in Human Populations?:
Immoderate blood clotting constitutes a risk factor for cardiovascular disease in modern industrialised societies, but is believed to have conferred a survival advantage, i.e. faster recovery from bleeding, on our ancestors. Here, we investigate the evolutionary history of the Coagulation Factor VII gene (F7) by analysing five cardiovascular-risk-associated mutations from the F7 promoter and nine neutral polymorphisms (six SNPs and three microsatellites) from the flanking region in 16 populations from the broader Mediterranean region, South Saharan Africa and Bolivia (687 individuals in total). Population differentiation and selection tests were performed and linkage disequilibrium patterns were investigated. In all samples, no linkage disequilibrium between adjacent F7 promoter mutations −402 and −401 was observed. No selection signals were detected in any of the samples from the broader Mediterranean region and South Saharan Africa, while some of the data suggested a potential signal of positive selection for the F7 promoter in the Native American samples from Bolivia. In conclusion, our data suggest, although do not prove, different evolutionary histories in the F7 promoter region between Mediterraneans and Amerindians.

The primary aim of this research seems to have been to figure out if the variance in a medical trait (prevalence in cardiovascular disease) could be traced to variance in this coagulation factor gene. Doesn't seem like that panned out. But their "Native American" sample happened to consist of Bolivian highlanders, Quechua and Aymara speakers. There are long haplotypes amongst these populations for the variant which seems result in increased risk for cardiovascular disease. I don't know much about physiology, but I immediately wondered if modulating traits which effect hematological system might have nasty side-effects. The populations of the Andes of course have developed some genetic tricks to optimize their functioning at high altitudes, bt tricks often have trade-offs. Of course this doesn't necessarily mean it's selection which drove up the frequency of the variant in question. Native populations of the New World seem to have gone through a population bottleneck, which can generate some of the same patterns. But there are enough non-highland groups whereby one could check to see if they have the high risk variant and a long haplotype as well.

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