Meeting Abstract

P1.119  Sunday, Jan. 4  Molting Down-Regulates Myostatin Expression in the Land Crab, Gecarcinus lateralis: Implications for the Regulation of Claw Muscle Atrophy BADER, BD*; COVI, JA; CHANG, ES; MYKLES, DL; Colorado State Univ., Fort Collins; Colorado State Univ., Fort Collins; UC Davis Bodega Marine Lab, Bodega Bay; Colorado State Univ., Fort Collins Brandon.Bader@gmail.com

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. Myostatin (Mstn), a member of the TGF beta family of growth factors, is a negative regulator of muscle growth in mammals and birds. Our hypothesis is that ecdysteroids increase the expression and/or activation of Mstn signaling, leading to the expression of genes required for the degradation of myofibrillar proteins. Real-time RT- PCR was used to quantify the expression of Mstn in claw and thoracic muscles during the molting cycle. Molting was induced by multiple limb autotomy. Mstn mRNA levels decreased during premolt and remained low at 2 and 10 days postmolt in both muscles. The reduced Mstn expression was associated with an accelerated protein turnover, which may facilitate changes in myofilament packing as fibers atrophy. Supported by NSF (IBN-0618203) and scholarships to B.D.B from the Arnold and Mabel Beckman Foundation and the College of Natural Sciences Undergraduate Research Institute.