Meeting Abstract
P2.71 Friday, Jan. 4 Identification of inhibitory and receptor-regulated Smads in three species of decapod crustacean: implications for the regulation of muscle mass by myostatin COVI, JA*; BRIER, L; MARTIN, L; MYKLES, DL; Colorado State University; Colorado State University; Colorado State University; Colorado State University joseph.covi@colostate.edu
In decapod crustaceans, reversible atrophy of the propodus (claw) muscle is imperative for successful withdrawal of this relatively large structure at ecdysis. The execution of this regulated atrophy is dependent on the expression of calpain proteases and is under the control of steroid molting hormones. We previously presented data which support a role for myostatin in mediating the atrophic response to elevated ecdysteroids in claw muscle of the land crab, Gecarcinus lateralis. Myostatin is a member of the TGF-β superfamily well known for its role as a negative regulator of muscle mass in mammals. Transduction of the myostatin signal between its membrane-bound receptor and the nucleus is dependent on a family of transcription factors known as Smads. Phosphorlyation of a receptor-regulated Smad (R-Smad) by the TGF-β receptor initiates the response to ligand (myostatin) binding. Inhibitory Smads (I-Smad) limit the duration of the myostatin signal by antagonizing the action of R-Smads. To the best of our knowledge, no Smad family member has previously been identified in crustaceans. Here, we report the identification of both R and I-Smad message in the claw muscle of 3 species of decapod crustacean: G. lateralis, Carcinus maenas, and Homarus americanus. Sequence analysis demonstrates a high degree of conservation between crustacean and mammalian Smads at the amino acid level, and suggests the conservation of two putative transcription start sites in the crustacean I-Smad lineage. Identification of these transcription factors in crustacean skeletal muscle represents a significant advance in our understanding of the regulation of muscle mass by myostatin. Supported by NSF (IBN-0618203).
