Study of SNPs in genes encoding for structural and proteolytic proteins in skeletal muscle of Italian Large White and Italian Duroc pigs

In pigs, several studies have been focused on structural and regulatory muscle genes and their possible relationship with meat production trait as they may play key role in muscle mass accretion. In the present work, we investigated four skeletal muscle genes, calpain 1 (CAPN1), calpastatin (CAST), myopalladin (MYPN) and titin (TTN). These genes were mapped on porcine chromosomes 2p14-p17, 2q21-q24, 14q25-q29 and 15q23-q26, respectively, and located in regions where quantitative trait loci for carcass traits were found. The calpain protein (coded by CAPN1 gene and expressed in skeletal muscle and other tissues) is involved in the early post mortem protein degradation promoting the initial disruption and destabilization of the myofibrillar structures. Calpastatin is a specific inhibitor of ubiquitous calpains and its post mortem activity influences meat tenderization process. Myopalladin is a sarcomeric protein which has central roles in the organization and assembly of the Z-line and seems to affect regulatory mechanisms of muscle gene expression. TTN encodes a large abundant protein of striated muscle that is involved in muscle assembly and ultrastructure and it is also implicated in muscle elasticity. To evaluate the putative effects of these four genes on carcass quality traits, we analysed single nucleotide polymorphisms (SNP) identified in the 3’ untranslated regions (MYPN and TTN) and in introns (CAST and CAPN1) in 272 sib tested Italian Large White (ILW) pigs and 114 sib tested Italian Duroc (ID). General linear model procedure of the SAS package was used to search for association between the SNPs and the productive traits average daily gain (ADG), backfat thickness (BFT), lean cuts (LC), ham weight (HW), feed conversion ratio (FCR) for both breeds and visible intramuscular fat (VIF) only for the ID breed. Statistically significant results for the association analyses were found for CAST in the ILW breed, with ADG, LC and FCR (P < 0.05) and in the ID breed with ADG, LC, BFT, HW (P < 0.05). Moreover, in the ID breed, the MYPN gene was associated with all considered traits (P < 0.01). The results confirm that CAST and MYPN could be considered positional and biological candidate genes affecting carcass traits, as previously reported in literature.