Molecular characterization, expression pattern, and association analysis with carcass traits of the porcine SHIP2 gene.

Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) has been identified as 5'-inositol phosphatase that hydrolyzes PI(3,4,5)P(3) to PI(3,4)P(2), which negatively regulates insulin-induced Akt signaling in skeletal muscle. In this study, we obtained a 3,795-bp mRNA sequence of porcine SHIP2 that included the full coding region for a protein of 1,264 amino acids. With the use of comparative mapping, we mapped this gene to SSC9 p23-24, where many QTLs affect average backfat thickness, average daily weight gain (birth-10 weeks), adipocyte number, belly fat area, and mid-back fat traits. As a candidate gene for carcass traits, a novel single nucleotide polymorphism in intron 21 (A > G) was detected by PCR-RFLP. The results showed that the AA genotype had higher skin percentage, shoulder fat thickness, and m. longissimus dorsi width, but lower m. longissimus dorsi height compared with the genotype GG (P < 0.05), and that allele G appeared to be associated with an increase in the growth trait. SHIP2 was expressed abundantly in skeletal muscle tissue and was transcriptionally decreased during the proliferative phase, but increased in the intermediate stages of muscle differentiation. Analysis of the porcine SHIP2 promoter sequence demonstrated that the E2F element is involved in downregulating SHIP2 mRNA expression in proliferating myoblasts. Using RNAi, we found that the MyoD transcription factor played a role in upregulating SHIP2 expression in differentiating myotubes. In summary, we suggest that SHIP2 might play a role in the regulation of skeletal muscle development in pigs.