Tameness QTL Sequence Capture
Tameness QTL Sequence Capture
The identification of the causative genetic variants in quantitative                 trait loci (QTL) influencing phenotypic traits is challenging,                 especially in crosses between outbred strains. We have previously                 identified several QTL influencing tameness and aggression in two lines                 of wild-derived, outbred rats (Rattus norvegicus) selected for their                 behavior towards humans. Here we use targeted sequence capture and                 massively parallel sequencing of all genes in the strongest of these QTL                 in an attempt to accelerate the identification of putatively causative                 alleles. We identify many novel sequence variants, several of which are                 potentially functionally relevant. The QTL contains several regions                 where either the tame or the aggressive rats contain no sequence                 variation, and two regions where alternative haplotypes are fixed in the                 lines. A re-analysis of the QTL signal showed that the causative site is                 likely to be fixed among the tame founder animals, but that several                 causative alleles may segregate among the aggressive founder animals.                 Using a formal test for the detection of positive selection, we find ten                 putative positively selected regions, some of which are close to genes                 known to influence behavior. Together, these results show that the QTL                 is probably not caused by a single selected site, but may instead                 represent the joint effects of several sites that were targets of                 polygenic adaptation.