Genome-wide scans for signatures of selection in North African sheep reveals differentially selected regions between fat- and thin-tailed breeds.

Abstract

North Africa counts several sheep breeds that can be categorized as fat- and thin-tailed. The former are well adapted to dryland environments. In this study, we used 50K genome-wide single nucleotide polymorphism profiles from 462 animals representing nine fat-tailed and 13 thin-tailed sheep breeds across North Africa to localize genomic regions putatively under differential selective pressures between the two types of breeds. We observed genetic clines from east to west and from north to south. The east-west cline separates the fat- and thin-tailed breeds, with the exception of the fat-tailed Algerian Barbarine, which is closely related to a genetically homogeneous cluster of Moroccan and Algerian thin-tailed breeds. Using a combination of three extended haplotype homozygosity tests, we detected seven candidate regions under divergent selection between fat- and thin-tailed sheep. The strongest selection signals reside on chromosomes 1 and 13, with the latter spanning the BMP2 gene, known to be associated with the fat-tail phenotype. Overall, the candidate regions under selection in fat-tailed sheep overlap with genes associated with adaptation to desert-like environments including adipogenesis, as well as heat and drought tolerance. Our results confirm previously reported candidate genes known to be a target of fat-tail selection in sheep but also reveal novel candidate genes specifically under selection in North African populations.