Meeting Abstract

P1.61  Jan. 4  Cloning and Expression of Myostatin in Green Crab, Carcinus maenas: Implications for the Regulation of Muscle Atrophy. BADER, B.D.*; COVI, J.A.; MYKLES, D.L.; Colorado State University; Colorado State University; Colorado State University bbader@simla.colostate.edu

Molting is the periodic shedding of the exoskeleton required for organismal growth in arthropods. Ecdysteroid hormones initiate cellular processes necessary for successful exuviation. One process is a programmed atrophy of the claw muscle, in which the mass is reduced 2-3-fold. This allows the claws to be pulled through the small joints of the appendage at molt. How ecdysteroids induce claw muscle atrophy is poorly understood. In mammals, glucocorticoids increase the expression of myostatin (Mstn), followed by reductions in muscle mass. Mstn, a member of the TGF&beta family of growth factors, is a negative regulator of muscle growth in mammals and birds. We have cloned cDNAs encoding Mstn in scallop and land crab muscles, which suggests that Mstn also controls the size of invertebrate muscles. Our hypothesis is that ecdysteroids increase the expression and activation of Mstn, leading to the expression of genes required for the degradation of myofibrillar proteins. A partial cDNA (175 bp) encoding a 58-amino acid sequence of the green crab mature Mstn was cloned using RT-PCR. The amino acid sequence shares an 84.5% sequence identity with that of land crab (Gecarcinus lateralis) and 31.8% identity with that of scallop, while it also shares a 44.8% sequence identity with Drosophila myoglianin and human Mstn sequences for the same region. Importantly, cysteine residues found in Mstns in that region, which are important in stabilizing the native conformation of the protein, are also present in the same positions in the green crab Mstn. 3 and 5 RACE are being used to obtain the rest of the Mstn sequence. Tissue expression in response to elevated ecdysteroid will be quantified by using end-point and real-time PCR. Supported by NSF (IBN-0618203) and an Undergraduate Research Institute Scholarship to B.D.B.