General and Comparative Endocrinology · Nov 4, 2026

Differential expression of ecdysteroid signaling transcription factors in regenerating limb tissues of the blackback land crab (Gecarcinus lateralis)

By Gaudreault BN, Benrabaa SAM, Shephard RJ et al.

Decapod crustaceans regenerate lost limbs in tandem with the molt cycle. Circulating steroid molting hormones (ecdysteroids) regulate both processes. In Gecarcinus lateralis, molting and regeneration are induced by multiple leg autotomy (MLA). Basal regeneration involves proliferation and differentiation of the blastema during intermolt, when hemolymph ecdysteroid titer is low, and results in the formation of the basal regenerate, or limb bud (LB). In response to rising ecdysteroid titers during premolt, the differentiated LB undergoes hypertrophic growth. LB autotomy (LBA) in early premolt suspends the growth of the remaining LBs by lowering circulating ecdysteroids. We hypothesize that ecdysteroid signaling transcription factors mediate LB differentiation and growth. The mRNA levels of 8 ecdysteroid signaling genes (Gl-EcR, Gl-RXR, Gl-HR3, Gl-HR4, Gl-E74, Gl-E75, Gl-Br-C, and Gl-Ftz-f1) were quantified at 4 blastemal stages (4, 6, 10, and 15 days post-MLA) and 4 molt cycle stages (IM, intermolt; EP, early premolt; MP, mid-premolt; and LP, late premolt). The mRNA levels of all 8 genes increased during basal regeneration, reaching their highest levels at 15 days post-MLA. Gl-EcR, Gl-RXR, Gl-E74, Gl-E75, Gl-HR4, Gl-Br-C, and Gl-Ftz-f1 mRNA levels at the 4 molt stages were significantly lower than the 15 days post-MLA mRNA levels. Gl-RXR, Gl-E74, Gl-E75, Gl-HR3, Gl-Br-C, and Gl-Ftz-f1 mRNA levels were significantly higher at LP than at MP. Only the Gl-HR3 mRNA level was positively correlated with ecdysteroid titer. LBA decreased hemolymph ecdysteroid titers at 2 and 7 days post-LBA and decreased mRNA levels of all 8 genes in growth-suspended LBs by 7 days post-LBA. Taken together, these data suggest that basal regenerates are more sensitive to ecdysteroid-dependent inhibition during intermolt. By contrast, ecdysteroid-dependent LB growth is sustained by increased Gl-HR3 expression and constitutive expression of the other 7 genes during premolt.

doi.org/10.1016/j.ygcen.2026.115041PubMed 42982139Mechanisms