Meeting Abstract

P2.95  Wednesday, Jan. 5  Molt inhibition by limb bud autotomy in the blackback land crab, Gecarcinus lateralis: effects on hemolymph ecdysteroid titers and expression of myostatin and R-Smad in skeletal muscle COSENZA, K.S.*; MACLEA, , K.S.; CHANG, E.S.; MYKLES, D.L.; Colorado State University; Colorado State University; UC Davis Bodega Marine Lab; Colorado State University kcosenza@rams.colostate.edu

In the blackback land crab, G. lateralis, the claw muscles undergo an atrophy that enables the withdrawal of the claw through the small basi-ischial joint at ecdysis (molting). Molting is induced by multiple limb autotomy (MLA), as lost limbs can only be regenerated during the premolt period. Furthermore, premolt can be suspended 2-3 weeks by limb bud autotomy (LBA), which allows regeneration of a secondary limb bud. When the secondary regenerate reaches the size of the primary regenerates, premolt processes resume and animals molt with a full complement of legs. Titers of molting hormone (ecdysteroids) remain the same or decrease during premolt suspension. Previous work showed that myostatin (Mstn) mRNA level is negatively correlated with hemolymph ecdysteroid titer and global protein synthetic rate. The increased rate of protein turnover is associated with restructuring of the contractile apparatus as claw muscle fibers are reduced in size. Mstn, which activates Smad transcription factors, is a negative regulator of protein synthesis in mammals. This suggests that ecdysteroids suppress Mstn expression, which results in an increase in protein synthesis during premolt. In order to test the hypothesis that ecdysteroids are a negative regulator of Mstn/Smad signaling, we determined the effects of LBA on Mstn and R-Smad expression using real-time PCR (qPCR). The hypothesis predicts that LBA would preferentially increase Mstn and R-Smad mRNA levels in claw muscle compared with thoracic muscle, which does not undergo a molt-induced atrophy. Supported by NSF (IBN-0618203).