Expression and effect of Calpain9 gene genetic polymorphism on slaughter indicators and intramuscular fat content in chickens.

Calpain 9 (CAPN9) is expressed in the stomach and small intestine. CAPN9 has regulatory roles in hypertension, heart disease, gastric mucosal defense, and kidney disease. The involvement of CAPN9 has not been reported in the development of chickens. CAPN9 mRNA was found in adipose and muscle tissue in this study. Two linkage single nucleotide polymorphisms (SNP; G7518A and C7542G) in intron 4 were screened from 160 birds of the D2 chicken line. The 2 mutation sites were associated with carcass weight, evisceration weight, abdominal fat weight (AFW), abdominal fat percentage (AFP), and breast muscle percentage (all P < 0.05). Intramuscular fat (IMF) content was not significantly different in the 3 genotypes. But, the AA(7518)/GG(7542) genotype had the highest IMF content, highest breast muscle weight, and lower AFW and AFP. Moreover, the mRNA level of CAPN9 in abdominal fat tissue was significantly different (P < 0.05 or P < 0.01) between any 2 genotypes, consistent with AFW and AFP. In summary, the expression of CAPN9 in adipose and breast muscle tissue is reported for the first time. CAPN9 affected production performance of chickens. As a marker, the linkage G7518A and C7542G polymorphisms in intron 4 of CAPN9 could affect the production traits by regulating mRNA expression. The findings concerning the marker enrich the theoretical foundation for molecular breeding of high-quality broilers.