Molecular characterization, expression analysis of the myostatin gene and its association with growth traits in sea cucumber (Apostichopus japonicus)

Myostatin (MSTN), also referred to as growth and differentiation factor-8 (GDF-8), is a member of the transforming growth factor-β superfamily (TGF-β) and an important negative regulator for skeletal muscle development and growth in vertebrates. However, its function is not clear in invertebrates. In this study, we cloned and analyzed the MSTN gene (Aj-MSTN) from sea cucumber (Apostichopus japonicus). The full-length cDNA sequence of Aj-MSTN gene was composed of 2912 bp, which contained a 5′ UTR of 487 bp, an ORF of 1356 bp encoding 452 amino acids and a 3′ UTR of 1069 bp. The structure of Aj-MSTN included a putative signal peptide, a TGF-β propeptide domain and a conserved TGF-β domain. Phylogenetic analysis showed that the Aj-MSTN gene was clustered in the same subgroup with the MSTN-like gene found in Strongylocentrotus purpuratus. Quantitative real-time PCR detection results indicated that the Aj-MSTN gene expressed widely in adult tissues and the highest expression level was observed in the body wall. At different developmental stages, the expression levels were increased significantly at early auricularia and doliolaria stages, and reached the peak at juvenile stage. Six SNPs were identified in 5′ flanking region and exons of the Aj-MSTN gene. Association analysis showed that SNP-1, SNP-2 and SNP-4 had significant effects on dry body weight. The results suggested that Aj-MSTN gene could be used as a candidate gene for the selective breeding of A. japonicus.