Molecular Characterization and Expression Patterns of Serine/arginine-rich Specific Kinase 3 (SPRK3) in Porcine Skeletal Muscle

SRPK3 is a protein kinase belonging to serine/arginine protein kinases (SRPK) family, which phosphorylates serine/arginine repeat-containing proteins, and is controlled by a muscle-specific enhancer directly regulated by MEF2. In this study, a full-length cDNA of the porcine SRPK3 gene encoding a 566 amino acid protein was isolated. It contains 14 exons over approximately 4.3 kb. The deduced amino acid sequence of porcine SRPK3 contains a bipartite kinase domain, and shows high similarities to their corresponding human and cattle homologues. Tissue distribution analysis indicated that porcine SRPK3 mRNAs are highly expressed in heart and skeletal muscle especially in uterus and parorchis, but at low level in brain, stomach, small intestine, and ovary. Expression pattern of SRPK3 was similar in Large White and Chinese Meishan breeds. Both the two breeds had the highest expression levels at fetal 65 days (P < 0.01), and decreased while the age increased until 60 days old, then increased at 120 days (P < 0.01) and decreased at 180 days (P < 0.05). However, at fetal 65 days, the mRNA abundance of SRPK3 in Large White was 12.5-fold higher than in Meishan pigs (P < 0.01), whereas at 180 days, the abundance in Meishan was 3.4-fold higher than in Large White pigs (P < 0.01). These results suggest that the SRPK3 gene might be an important gene of skeletal muscle development and also provides basic molecular information useful for further studies on its roles in porcine skeletal muscle.