Molecular characterization and expression regulation of Smyd1a and Smyd1b in skeletal muscle of Chinese perch (Siniperca chuatsi).

Smyd1 is a SET and MYND domain-containing protein, which functions as a histone methyltransferase for control of gene expression and regulates the skeletal and cardiac muscle differentiation. In this study, the full-length cDNA sequences of Smyd1a and Smyd1b were cloned from Chinese perch, and their molecular structure and expression profile in response to nutrition supply and in vivo IGF treatments were also analyzed. The cDNA sequence of Smyd1a and Smyd1b consists of 1862 and 1802 base pairs (bp), encoding 479 and 476 amino acids, respectively. The SET domains of the two proteins were split into two segments by the MYND domain. Furthermore, the amino acid sequence of Smyd1a contains an extra 13-aa insertion in the SET domain in comparison with Smyd1b. The two genes apparently exhibited temporal and spatial differential expression status. In adults, the two genes showed the higher expression level in the muscle and heart than in other testing tissues. During the post-embryonic developmental stages, the higher expression of Smyd1a was detected at 150 days post-hatching (dph), whereas the expression of Smyd1b peaked at 50 dph. It was indicated that they have potential function in muscle developmental regulation. The mRNA levels of Smyd1a and Smyd1b were sharply up-regulated within one day after refeeding in the Chinese perch juveniles following fasting for a week. Moreover, IGF-1 treatments in vivo significantly stimulated their expression in the skeletal muscle. Together, these data provide us with further understanding of the molecular characterization and expression regulation of the two genes upon internal and external stimuli.