Mutations in two genes are associated with increased ovulation rate and litter size in progeny of Lacaune meat sheep

Abstract : A new autosomal major gene affecting ovulation has been evidenced by a statistical approach in the Lacaune population. A full genome scan localized this autosomal prolificacy gene (FecL) on sheep chromosome 11. Further investigations allowed the reduction of the localization interval between markers BM17132 and FAM117A, corresponding to one synteny block of human chromosome 17 of 1.1 megabases, containing 20 genes. This fine mapping is still going on. The expression of those 20 genes was tested by qPCR and no difference was found in homozygous mutants versus wild type, in four tissues (granulosa and theca cells, hypothalamus and pituitary gland). A particular haplotype was associated with the FecL mutation, which allowed marker associated classification of animals as carriers or non-carriers of the mutation. In addition, ewes with extreme ovulation rate have been isolated in the Lacaune population and it was hypothesized that another mutation was segregating in the population. A new mutation has been evidenced in the Bmp15 coding sequence (chromosome X). This mutation is a non conservative substitution (C53Y) that prevents the processing of the protein. Synergic action of the two mutations (in FecL and Bmp15 genes) on both ovulation rate and litter size was demonstrated.