Expression of alternatively spliced transcripts for a myostatin-like protein in the blackback land crab, Gecarcinus lateralis

Three complete cDNAs for the first myostatin-like gene identified in a crustacean species were cloned from the land crab, Gecarcinus lateralis. Sequence analysis demonstrates a high degree of conservation with myostatin orthologs from vertebrates. The furin cleavage site is identical to that of human myostatin, and all nine cysteines critical to the structure/function of mature myostatin peptides are conserved. Message levels for transcripts encoding the complete crustacean preproprotein were highest in skeletal muscle and heart. Lower levels of expression were observed in nervous tissue, gill, gonad, and hepatopancreas. This expansive distribution is similar to that observed for teleost myostatin, vertebrate GDF-11, and amphioxus GDF8/11, and indicates a potentially broad functional repertoire for the land crab ortholog. In addition to one cDNA encoding a complete preproprotein, two cDNAs encoding C-terminal truncated proteins lacking a mature peptide domain were identified. Expression of these truncated splice variants was restricted to skeletal muscle and heart. Myostatin is a potent negative regulator of muscle mass in mammals, and strong expression of this TGF-β factor in skeletal muscle during intermolt indicates that a myostatin-like gene product could regulate muscle mass in crustaceans when growth is physically restricted by a calcified exoskeleton.