Exon 2 Ovar-DRB1 gene polymorphism in the Iranian Sangsari sheep

ABSTRACT

The major histocompatibility complex [MHC] plays a central role in the control of disease resistance and immune response. Extensive genetic diversity in MHC genes provides a valuable source for genetic improvement, via selection, in many domestic animals. Exon 2 of the class II MHC, termed Ovar-DRBl in domestic sheep [Ovis aries] has been suggested as important disease resistance and immune response gene. We characterized Ovar-DRBl in DNA samples from 138 individuals of a population of the Iranian Sangsari sheep breed using PCR-RFLP. Eight DRB1 alleles were identified among Iranian Sangsari sheep, including one previously unrecognized allele. Eight homozygous genotypes were observed a, b, c, d, f, g, h andN. Genotype bb was the most common pattern [46 of 138]. Heterozygous genotypes [ag, cb, cd, bf, and bN] were also observed. The observed homozygosity and heterozygosity values were 0.6377 and 0.3623, respectively, vs expected values of 0.220 and 0.779. Iranian Sangsari population deviate significantly from the theoretical proportions [FIS = 0.5283; p = 0.0005]. In conclusion, PCR-RFLP analysis allows rapid identification of Ovar-DRBl types and discrimination of homozygous and heterozygous genotypes. This study indicates that the exon 2 region of the Ovar-DRBl gene is highly polymorphic in the Iranian Sangsari sheep breed