Meeting Abstract
Regeneration is a phenomenon common across metazoan taxa. Decapod crustaceans including the blackback land crab, Gecarcinus lateralis, regenerate lost limbs in tandem with their molt cycle. Circulating steroid hormones or ecdysteroids regulate this process. The initial differentiation and proliferation of the blastema occurs during intermolt, when ecdysteroid titers are low. The resulting differentiated limb bud undergoes hypertrophic growth during premolt, as ecdysteroid titers rise and the animal prepares to molt. We hypothesize that ecdysteroid responsive genes mediate the differentiation and growth of limb regenerates. The mRNA levels of ecdysteroid receptor (EcR/RXR), E75, and HR3 at eight limb regenerate stages (four basal differentiation and four proecdysial growth) were quantified by qPCR. All four genes were significantly upregulated during the basal phase (4 and 15 days post-autotomy). During this time the average ecdysteroid titers remained low (9.4 ± 0.4 pg/µl on day 4 and 8.3 ± 0.6 pg/µl on day 15). Interestingly, only HR3 and E75 were significantly upregulated in the late proecdysial stages when the animals were preparing to molt. The ecdysteriod titers at this stage peaked at 73.4 ± 10.2 pg/µl. Future work will quantify the expression of four additional ecdysteroid responsive genes (E74, HR4, BR-C, and FTZ-F1) during differentiation and growth phases and determine the effects of the suspension of limb bud growth by limb bud autotomy on the expression of all eight genes. Supported by NSF (IOS-1257732).
