Genome-wide search for signatures of selection in three major Brazilian locally adapted sheep breeds

The study of locally adapted breeds has the potential to underpin the discovery of genes involved in economically and ecologically important traits. Brazilian locally adapted sheep breeds have distinctive characteristics that could be of value for specialized production systems. Therefore, the main objective of the present study was to identify genomic regions that may have been under selection and therefore may explain ecological and production differences observed among three important Brazilian locally adapted sheep breeds. Animals from the Brazilian Creole, Morada Nova and Santa Ines breeds were genotyped using the Illumina Ovine SNP50 BeadChip. The identification of selection signatures was based on two groups of methodologies: differentiation among populations (FST) and linkage disequilibrium (iHS and RsB). Taken together, these analyses allowed for the identification of 86 candidate genes. Functional analysis revealed genes related to immunity, nervous system development, reproduction and sensory perception. A number of genes are of particular interest including: RXFP2, which has recently been associated with the presence/absence and morphology of horns in sheep; the TRPM8 gene, involved in regulation of body temperature at low temperatures; DIS3L2, PLAG1 and NIPBL, associated with height variation; and finally, SPEF2 and SPAG6, important for spermatogenesis. Selective sweeps were identified using multiple methods, and in a number of cases sweep regions contained genes with a demonstrated role in phenotypic variation. The genomic distribution of the sweep regions differed between populations, suggesting that breed specific signatures were successfully identified that may reflect the consequence of local adaptation.