Skeletal muscle and kidney enriched inositol phosphatase (SKIP) was identified as a 5'-inositol phosphatase that hydrolyzes PI(3,4,5)P3 to PI(3,4)P2 that negatively regulates insulin-induced phosphatidylinositol 3-kinase signaling in skeletal muscle. In this study, we obtained a 1575-bp mRNA sequence of porcine SKIP that included the full coding region encoding a protein of 450 amino acids. With the use of comparative mapping, we mapped this gene to SSC12 q1.3, where many QTLs affect Backfat thickness at 10th rib, carcass yield, the number of muscle fibers, and ham weight traits. As a candidate gene for growth and carcass traits, a novel single nucleotide polymorphism in exon 12 (G>A) was detected by PCR-RFLP. The results showed that the GG genotype had higher skin percentage (SP), carcass length to first spondyle (CL1), carcass length to first rib (CL2), but lower intramuscular fat (IMF) as compared with genotype AG (P<0.05), and allele G seemed to be associated with an increase in the growth trait. Porcine SKIP was expressed abundantly in skeletal muscle tissue and was transcriptionally upregulated during skeletal muscle differentiation. Analysis of the porcine SKIP promoter sequence demonstrated that MyoD was involved in regulating SKIP mRNA expression in myotubes, partly via the cis-acting elements in SKIP promoter. In summary, we suggested that SKIP might play a role in the regulation of skeletal muscle development in pigs.

Sarcoendoplasmic reticulum Ca2+-ATPase 1 (SERCA1) as a Ca2+ release channel plays a key role in the relaxation of skeletal muscle through pumping cytosolic Ca2+ into the SR (sarcoplasmic reticulum). In this study, a novel single nucleotide polymorphism (SNP) in exon 8 (C > T) was detected by tetra-primer ARMS-PCR and the tissue expression pattern of SERCA1 was analyzed in eleven tissues. A model of primary skeletal muscle cells in vitro exposed to dexamethasone (DEX, a synthetic corticosteroid) was also employed to determine whether stress hormones cause an increase in intracellular Ca2+ concentration that is associated with alteration in SERCA1 and in turn subsequently affect meat quality. The results showed that the CC genotype has lower content intramuscular fat and higher water than pig carrying the genotype CT and CC. In addition, the additive effects were both significantly (P < 0.05) and allele T seemed to be associate with increase in intramuscular fat, while decrease in water content. Accompanied with previous studies, the high abundance of porcine SERCA1 was found in skeletal muscle tissue. DEX markedly down-regulated the expression of SERCA1, leading to Ca2+ overload. Furthermore, the imbalance of Ca2+ homeostasis up-regulated the transcription level of Calpain1. Taken together, we demonstrated a novel mechanism that the changes in expression of SERCA1 potential disturb the normal Ca2+ channel as well as the balance of Ca2+ homeostasis and which in turn finally activated Ca2+-dependent proteases such as Calpain1 which could affect meat quality.