Positive selection in the major histocompatibility complex class III region of cynomolgus macaques (Macaca fascicularis) of the Philippines origin.

The cynomolgus macaque (Macaca fascicularis) is a model of choice among primates for the study of local adaptation processes because of its mixed and wide insular and continental distribution. In a previous study, by using 12 markers [5 microsatellites located in the major histocompatibility complex (MHC) region and 7 outside MHC], we have detected a signal of positive selection on the microsatellite DRACA located inside the gene DRA. In order to refine the location of this signal of positive selection in the MHC region, we studied the genetic diversity of 36 markers (18 microsatellites spread across the MHC region and 18 autosomal microsatellites outside MHC) in a sample of 254 individuals from four populations (Vietnam, Java, the Philippines, and Mauritius). We estimated for each locus the deviation of F(st) from a neutral model by using two methods based on contrasted demographic models. The two approaches showed a signal of positive selection in the MHC class III region that is much more significant than the one previously reported for the marker DRACA which could have been influenced by a hitchhiking effect due to its proximity with the class III region.