Meeting Abstract

P1.66  Jan. 4  Effects of elevated ecdysteroids on myostatin expression in the land crab, Gecarcinus lateralis: Implications for the molt-associated atrophy of claw muscle COVI, J.A.*; WASMUNDT, N.M; KIM, H.W.; LEE, S.G.; CHANG, E.S.; MYKLES, D.L.; Colorado State Univ; Colorado State Univ; Colorado State Univ; Colorado State Univ; UC Davis Bodega Marine Lab; Colorado State Univ joseph.covi@colostate.edu

While it is well accepted that molt-induced atrophy of claw muscle is under the control of steroid molting hormones, the signaling responsible for this critical molting event remains elusive. The role of myostatin (mstn) as a negative regulator of muscle mass is well characterized in vertebrate species, but largely unknown within the invertebrates. Here we present data which strongly suggests that mstn acts as a link between the elevated ecdysteroids associated with premolt in crustaceans and the increased expression of calpain proteases responsible for claw muscle atrophy. Phylogenetic analysis of a putative mature peptide sequence from land crab demonstrates the identification of a mstn-like member of the transforming growth factor beta superfamily. Examination of message abundance for this gene using real time-PCR clearly shows low constitutive expression of mstn mRNA in skeletal muscle during intermolt, as would be predicted for a negative regulator of muscle mass. Both the Ecdysone Receptor (EcR) and mstn mRNA levels increase in claw muscle, but not thoracic muscle, in response to elevated ecdysteroid levels induced by eyestalk ablation. Pulse treatment with exogenous 20-hydroxyecdysone elevated hemolymph ecdysteroid titers in intermolt animals to that expected during late premolt, but this acute treatment did not have a significant effect on either EcR or mstn mRNA expression. The presence of mstn in mammals, fish, birds, mollusks, and crustaceans indicates that this pathway for the regulation of muscle mass is highly conserved. Much as is the case for mammalian mstn the crustacean homologue could also be a target of interest to improve muscle quality and yield. Supported by NSF IBN-0618203