Identification of candidate genes associated with growth and development of sheep from a crossbred population using genome-wide association studies

The article presents the results of a search for genome-wide associations with phenotypic traits characterizing the growth and development of sheep from a crossbred population obtained from crossing Romanov sheep and F1 hybrid rams (Romanov sheep x Katahdin). The phenotype database included ten body measurements (withers height, sacral height, back height, chest depth, chest width, ischial tuberosity width, body length, oblique body length, chest girth, pastern girth) recorded at the age of 6 days, 3, 6 and 9 months. Genotyping of sheep was carried out using high-density DNA chips containing about 600,000 SNP markers. Genome-wide association studies (GWAS) were performed using regression analysis in the STATISTICA 10 program. The search for candidate genes localized in the SNP region was performed using Ensembl genome browser 110. There was carried out an analysis of the matches of the identified SNPs with known quantitative trait loci (QTLs) described in the Sheep Quantitative Trait Locus Database. There were found SNPs that were significantly associated with the studied phenotypic traits overlapped with the QTLs, among which the most common categories were “Body weight (slaughter)”, “Muscle weight in carcass”, “Body weight (live)” and “Bone weight in carcass”. There has been established that SNPs significantly associated with exterior traits were localized within or in the immediate vicinity of 64 genes. There were found potential candidates regulating the growth of muscle (FOXO3, PRKAG3, MYOZ2, and ANKRD1) and cartilage tissues FGF12) and involved in metabolic processes, which were critical for the growth of lambs (CLDN, ALB, and MRC1). Along with the known in sheep functional candidates (CAST and SCD5) , there were identified genes that were not previously described in sheep, but regulated growth and development processes in other livestock species including genes RAB28, PRKAG3 and  FOXO3. The identified SNPs can be recommended for inclusion in marker-guided selection programs in sheep breeding.