Genetic polymorphism detection of two α-Casein genes in three Egyptian sheep breeds

Sheep milk is an excellent raw material for the milk processing industry especially in cheese production. The protein content and composition of sheep milk are important in the cheese manufacturing. The casein fraction of ruminant milk proteins consists of four caseins, namely αs1, αs2, β and κ-Casein. Casein genetic polymorphisms are important due to their effects on quantitative traits and technological properties of milk.This study aimed to detect the genetic polymorphism of αs1- and αs2-Casein genes in three native Egyptian sheep breeds; Rahmani, Barki and Ossimi. PCR-SSCP and PCR-RFLP were used to detect the genetic polymorphism of αs1-CN and αs2-CN genes, respectively.A 223-bp fragment of αs1-CN gene was amplified by PCR and SSCP results recorded the presence of three different patterns; TT, TC and CC; in 87 tested sheep animals. The sequence analysis of two homologous patterns showed a single nucleotide polymorphism (SNP) (T → C) at position 170. The frequencies of three patterns in the tested sheep breeds were 43.33%, 50.00%, and 6.67% in Rahmani; 83.33%, 13.33%, and 3.33% in Ossimi and 74.07%, 22.22%, and 3.70% in Barki, respectively. Our nucleotide sequences of αs1-CN T and C alleles were submitted to GenBank with the accession numbers KF018339 and KF018340, respectively.The restriction digestion of αs2-CN PCR product (1300-bp) by Tru1I endonuclease revealed three different genotypes; AA, AG and GG with frequencies of 66.67%, 30.00%, and 3.33% in Rahmani; 96.67%, 3.33%, and 0.00% in Ossimi and 96.15%, 3.85%, and 0.00% in Barki, respectively. The sequence analysis revealed the presence of a single nucleotide polymorphism (A → G) in intron 6 of αs2-CN gene. Our nucleotide sequence of αs2-CN gene was submitted to GenBank with the accession number JX080380.