Peer Review #2 of "Sociality genes are associated with human-directed social behaviour in golden and Labrador retriever dogs (v0.2)"

Abstract

Background. Dogs have human-directed social skills that allow them to communicate and cooperate with humans. We have previously identified two loci on chromosome 26 associated with human contactseeking behaviours during an unsolvable problem task in laboratory beagles (Persson et al., 2016). The aim of the present study was to verify the SNPs in additional dog breeds and investigate possible associations to other social skills. We also studied how the allele frequencies have changed during domestication and recent selection. Methods. Dogs of two breeds, 61 golden retrievers and 100 Labrador retrievers, were phenotyped and genotyped, and 19 wolves were genotyped. The Labrador retrievers were divided into common and field type by pedigree data to make it possible to study the effects of recent selection. All dogs were tested in an unsolvable problem task where human-directed social behaviours were scored. DNA from dogs (buccal swabs) and wolves (blood or brain tissue) was analysed for genotype on two of the previously identified SNP markers, BICF2G630798942 (SNP1) and BICF2S23712114 (SNP2), by pyrosequencing. Results. There was genetic variation for SNP1 in both dog breeds whereas the wolves were fixed for this polymorphism, and for SNP2 there was variation in both dogs and wolves. For both SNPs, Labrador retriever types differed significantly in allele frequencies. We found associations between SNPs and human-directed social behaviour in both dog breeds. In golden retrievers, SNP1 was associated with physical contact variables, for example with the duration of physical contact with the owner (F 2,56 = 4.389, p = 0.017). SNP2 was associated with several behavioural variables in both breeds, among others owner gazing frequency in both golden retrievers (F 2,55 = 6.330, p = 0.003) and Labradors (F 1,93 = 5.209, p = 0.025). Discussion. Our results verify the association between the previously identified SNPs and humandirected social behaviour scored in an unsolvable problem task. Differences in allele frequencies suggest that these loci have been affected by selection. The results suggest that these genomic regions are involved in human-directed social behaviour in not only beagles but in other dog breeds as well. We hypothesise that they may have been important during dog domestication.