The isolation and characterization of myostatin gene in Japanese flounder (Paralichthys olivaceus): Ubiquitous tissue expression and developmental specific regulation

Myostatin (MSTN) is a negative regulator of skeletal muscle growth and development. In the current study, the MSTN gene was cloned from one of flatfish species, Japanese flounder (Paralichthys olivaceus). In the 5520-bp genomic sequence, three exons, two introns, and 5' and 3' flanking sequences were identified. The putative amino acid sequence was 377 residues long, including a signal peptide, nine conserved cysteine residues, and a RXXR proteolytic processing site. The overall amino acid sequence of the P. olivaceus MSTN (pMSTN) was highly conserved with that of other organisms. Phylogenetic analysis suggested the evolutionary relationships of pMSTN with other known MSTN and GDF-11 genes. There were four microsatellite sequences identified in noncoding regions and 19 SNPs identified in coding sequences. Expression analysis revealed that pMSTN gene was expressed not only in the skeletal muscle, but also in other tissues, including cartilage, which has not been reported in fish previously. Although pMSTN was expressed in gill, no transcript could be detected in FG-9307, a continuous gill cell line from P. olivaceus. Quantitative RT-PCR analysis indicated that the expression of pMSTN appeared to be developmentally regulated. The pMSTN mRNA detected in unfertilized eggs indicated the maternal deposit. Considering of the ubiquitous tissue distribution and the continuous expression of pMSTN during the whole embryonic development in Japanese flounder, MSTN gene in fish may play different roles in comparison with that in mammals.