Signatures of selection in the human olfactory receptor OR5I1 gene

Abstract

The human olfactory receptor repertoire is reduced in comparison to other mammals/nand to other non-human primates. Nonetheless, this olfactory decline opens an opportunity for/nevolutionary innovation and improvement. In the present study, we focus on an olfactory/nreceptor gene, OR5I1, which had previously been shown to present an excess of amino acid/nreplacement substitutions between humans and chimpanzees. We analyze the genetic/nvariation in OR5I1 in a large worldwide human panel and find an excess of derived alleles/nsegregating at relatively high frequencies in all populations. Additional evidence for selection/nincludes departures from neutrality in allele frequency spectra tests but no unusually extended/nhaplotype structure. Moreover, molecular structural inference suggests that one of the/nnonsynonymous polymorphisms defining the presumably adaptive protein form of OR5I1/nmay alter the functional binding properties of the olfactory receptor. These results are/ncompatible with positive selection having modeled the pattern of variation found in the OR5I1/ngene and with a relatively ancient, mild selective sweep predating the “Out of Africa”/nexpansion of modern humans.