Meeting Abstract
Many decapod crustaceans including the blackback land crab Gecarcinus lateralis (G. lat.) are able to regenerate limbs. In G. lateralis, autotomy of five or more walking legs induces molting. Completion of the molting process is required for successful limb regeneration, suggesting that molting and limb regeneration are regulated in tandem. Cell division and differentiation of the blastema occur during basal growth, which takes place during intermolt, when ecdysteroid levels in the hemolymph are low. During premolt, rising ecdysteroid titers stimulate limb bud growth. Both molting and limb regeneration are regulated by steroid hormones that bind to the nuclear heterodimer receptor EcR and RXR. Ecdysteroids are synthesized in and released from the molting gland, or Y-organ (YO), and bind to EcR/RXR, regulating transcription of downstream genes that direct development, differentiation, and growth. Two genes of interest are the early response gene E75 and the early-late gene HR3. E75 can repress the activity of HR3 by heterodimerization. In Drosophila, expression of HR3 is required for successful embryogenesis and is also an inhibitor of ecdysone production by the prothoracic gland. Full-length sequences of Gl-EcR, Gl-RXR, Gl-E75, and Gl-HR3 were identified in a YO transcriptome constructed from the de novo assembly of RNA-seq data. The four genes were expressed in limb regenerates. Real-time PCR is being used to quantify gene expression during blastema differentiation at 4, 6, 10, and 15 days post-autotomy and during premolt limb bud growth. Supported by NSF (IOS-1257732).
