Cloning And Polymorphisms Analysis Of CAPN3Gene And Their Associations With Carcass And Meat Quality Traits In Yak

The Calpains (CAPNs)， belonging to the papain superfamily， are a group ofcalcium-dependent cysteine neutral proteases. They are found in cytoplasm in almost alleukaryotes.Calpains can be classified into ubiquitous and tissue specific, on the basis of theirmodes of expression.CAPN3，also known as p94, is a member of the CAPN large subunitfamily and predominantly expressed in skeletal muscle. CAPN3plays a key role in musclegrowth and the post-mortem tenderization of meat in animals.Variation in the CAPN3genehas been associated with limb-girdle muscular dystrophy2A in human (LGMD2A), but todate variation of yak CAPN3gene has not been reported.The CDS region and partial sequence of3’UTR of the yak CAPN3gene were clonedfrom total RNA using RT-PCR with specific primers that designed according to cDNAsequence of bovine CAPN3gene in the GenBank. The polymorphism of exon1and intron2ofCAPN3in Gannan yak, Tianzhu white yak and Datong yak were investigated by PCR-SSCPso as to analyze the associations between CAPN3gene mutations with carcass and meatquality traits. The results were showed as follows：(1) The yak CAPN3gene contained a2469bp CDS region (GenBank accession no:JX112349.1) and encoded a putative proten consisting of822amino acids (GenBankaccession no: AFP73395.1). Ten SNPs and corresponding three amino acid mutations infunction regions of CAPN3were identified through alignment with bovine CAPN3genesequence.The putative molecular weight and theory isoelectric point of CAPN3in yak were94.58kD and5.70, respectively. There was a hydrophobic region in Ⅲ region of yakCAPN3. The putative secondary structure of CAPN3was mixed type with mainly α-helicesand random coil. Deduced amino acid sequences of CAPN3gene between yak and bovine,sheep, wild boar and other species were quitely high on homology and the phylogeneticdistance consistent with their genetic relationship.(2)Four PCR-SSCP patterns representing four alleles A-D were identified in exon1ofCAPN3gene in Gannan yak. Allele A was the most common allele and genotype AA was thedominant genotype. The SNP T>G at exon1was non-synonymous and resulted in amino acidmutation (p.Met18Arg).The exon1region of CAPN3gene showed low polymorphism in Gannan yak as PIC value was less than0.25. Three SNPs representing three allelic variantsA-C were detected in intron2of CAPN3gene in Gannan yak. Allele A and genotype AA wasthe most common allele and genotype, respectively. The intron2of CAPN3gene showedmoderate polymorphism in Gannan yak as PIC value was between0.25and0.5. No variationwas found in exon1and intron2of CAPN3gene in Tianzhu white yak and Datong yak.(3)Variations in the intron2of CAPN3gene had significant effects on partial carcassand meat quality traits in Gannan yak. These castrated yak with the presence of allele A had asignificantly lower value of carcass weight and significant higher value of WBS than thesethat didn’t possess this allele at the age of three (P<0.05), respectively. Meanwhile, thesefemals with the presence of allele A and castrated yak with the presence of allele C had asignificantly higher and lower value of cooking rate than these that didn’t possess those twoalleles (P<0.05), respectively. Collectively, in Gannan yak, the elimination of individual withpresence of CAPN3A may increase carcass and improve the muscle tenderness, but couldhad a negative effect on cooking rate. On the other hand, the eliminationthe of individualwith presence of CAPN3C may increase cooking rate.