The Polymorphisms In CAPN4 And CAST And Their Association With Carcass And Meat Quality Traits In Yak

Calpain hydrolytic system, a highly complicated regulation system existed in the body of humans and animals, is mainly composed of calpain(CAPN), calpastein(CAST) and specificity calpain of skeletal muscle(P94). CAPN is a kind of endopeptidase and its endogenous inhibiting protein is CAST. The major function of CAPN is degrading myofibril of muscle cells, which was inhibited by CAST. Calpain hydrolytic system plays an important role in regulating mammalian muscle growth, meat mature and tenderness after animal was slaughtered.Polymorphisms of the promoter-intron1 of CAPN4 and intron3 of CAST were detected by using PCR-SSCP in Gannan yak, Tianzhu White yak and Datong yak, and effects of these two genes on the carcass and meat quality traits of Gannan yak were analyzed in this study. The results are as follows:(1) Polymorphisms were high in the detection regions of CAPN4 and CAST among three yak populations. Alleles A and B were detected in the promoter of CAPN4 in which one SNP(a.-1222G>A) was discovered; four alleles A, B, C and D were detected in the region of promoter-intron1 of CAPN4 and seven SNPs were identified, they were a.-596A>C, a.-538 T>C, a.-498C>A, a.-425A>T, a.-422T>C, a.-379G>C and a.-347G>A, respectively; six alleles A, B, C, D, E and F were detected in the intron3 of CAST with seven SNPs.(2) Polymorphisms of the promoter of CAPN4 affected carcass and meat quality traits of different age-grouped Gannan yak. The cooked meat percentage of 4 and 6-year-old individual yak with genotype BB was significantly higher than that with genotype AA and AB(P<0.05); water loss rate of 3 and 6-year-old individual yak with genotype AB was significantly higher than that with genotype AA and BB(P<0.05), while water loss rate of 5-year-old individual yak with genotype BB was significantly higher than that with genotype AA(P<0.05); loin muscle area of 3 and 5-year-old individual yak with BB was significantly higher than that with genotype AA and AB(P<0.05). We can conclude that allele A has negative effect on cooked meat percentage, water holding capacity and eye muscle area of Gannan yak.(3) Polymorphism of the promoter-intron1 of CAPN4 affected eye muscle area and meat tenderness of different age-grouped Gannan yak. The eye muscle area of 3 and 7-year-old individual yak with genotype BB was significantly higher than that with genotype AB(P<0.05). Allele A had negative effect on eye muscle area of 3-year-old individual yak, while allele B had the trend of increasing eye muscle area of 7-year-old yak and improving meat tenderness at different ages.(4) Polymorphism of the intron3 of CAST affected meat tenderness of 6-year-old Gannan yak. Each genotypes of CAST had no significant effect on cooked meat percentage, water loss rate, eye muscle area, meat tenderness and carcass weight of 6-year-old individual Gannan yak, but the meat tenderness of those with allele D was significantly lower than those of without allele D(P<0.05). That is, allele D has positive effect on improving meat tenderness of yak.