Characterization and Gene Expression Patterns of Calpain Family in Striped Catfish

Calpains are calcium-dependent intracellular neutral cysteine proteases that have been known to play an important role in post-mortem proteolysis and meat tenderisation in fish. In this study, the calpain family (CAPN) in striped catfish (Pangasianodon hypophthalmus) which is one of major aquaculture species in Vietnam was characterized. Firstly, the catfish genome database was searched for calpain gene family, then, classification, phylogenetic relationship and gene structure were analyzed. In striped catfish genome, 14 calpain genes were found that are orthologs to other vertebrate species, which were classified into typical and atypical calpains according to their structures. Next, the transcriptional gene expression of typical CAPN-1, -2, -3, -11, -13 genes in muscle, liver and brain tissues of the striped catfish were examined. The results showed that gene expression of CAPN-2 and CAPN-13 genes was barely detectable, while that of CAPN-1, ‑3, -11 genes was widely detected in all three types of tissues. In striped catfish muscle tissue, CAPN-3 transcript abundance was nearly three and 27 fold greater than CAPN-11 and CAPN-1, respectively. Our results suggest that CAPN-3 in P. hypophthalmus is also a muscle-specific calpain, which had been reported in other species. The results of this study provide a data resource for further research on the function of calpain genes and their genetic diversity that might be correlated with muscle texture in striped catfish.