Ghaskadbi, S. | bioRxiv Science

bioRxiv2019

VEGF and FGF signaling during head regeneration in hydra

BackgroundVascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) signaling pathways play important roles in the formation of the blood vascular system and nervous system across animal phyla. We have earlier reported VEGF and FGF from Hydra vulgaris Ind-Pune, a cnidarian with a defined body axis, an organized nervous system and a remarkable ability of regeneration. We have now identified three more components of VEGF and FGF signaling pathways from hydra. These include FGF-1, FGF receptor 1 (FGFR-1) and VEGF receptor 2 (VEGFR-2) with a view to deciphering their possible roles in regeneration.\n\nMethodsIn silico analysis of proteins was performed using Clustal omega, Swiss model, MEGA 7.0, etc. Gene expression was studied by whole mount in situ hybridization. VEGF and FGF signaling was inhibited using specific pharmacological inhibitors and their effects on head regeneration were studied.\n\nResultsExpression patterns of the genes indicate a possible interaction between FGF-1 and FGFR-1 and also VEGF and VEGFR-2. Upon treatment of decapitated hydra with pharmacological inhibitor of FGFR-1 or VEGFR-2 for 48 hours, head regeneration was delayed in treated as compared to untreated, control regenerates. When we studied the expression of head specific genes HyBra1 and HyKs1 and tentacle specific gene HyAlx in control and treated regenerates using whole mount in situ hybridization, expression of all the three genes was found to be adversely affected in treated regenerates.\n\nConclusionsThe results suggest that VEGF and FGF signaling play important roles in regeneration of hypostome and tentacles in hydra.

cell biology↗

bioRxiv2019

Differential expression of BMP antagonists, gremlin and noggin in hydra: antagonism between Wnt and BMP pathways

Mechanisms regulating BMP and Wnt signaling pathways have been widely studied in many organisms. One of the mechanisms by which these pathways are regulated is by binding of extracellular ligands. In the present study, we report studies with two BMP antagonists, gremlin and noggin from Hydra vulgaris Ind-Pune and demonstrate antagonistic relationship between BMP and Wnt pathways. Gremlin was ubiquitously expressed from the body column to head region except in the basal disc and hypostome. During budding, gremlin was expressed predominantly in the budding region suggesting a possible role in budding; this was confirmed in polyps with different stages of buds. Noggin, on the other hand, was predominantly expressed in the endoderm of hypostome, base of the tentacles, lower body column and at the basal disc in whole polyps. During budding, noggin was expressed at the sites of emergence of tentacles suggesting a role in tentacle formation. This was confirmed in alsterpaullone-treated polyps, which showed noggin expression as distinct spots where ectopic organizers and ectopic tentacles eventually formed. Using RT-PCR, we found that up-regulation of Wnt is accompanied with down-regulation of BMP5-8b demonstrating antagonism between the two pathways. Down-regulation of noggin and gremlin, however, occurred only after 24 h recovery. The data suggest that inhibition of BMP pathway by Wnt signaling in hydra does not directly involve noggin and gremlin. Our findings indicate that the BMP/Noggin antagonism evolved early for setting up and/or maintaining the head organizer while involvement of these BMP antagonists during vertebrate axial patterning are recent evolutionary acquisitions.\n\nSummary statementWe show that setting up of the Organizer by BMP/Noggin antagonism and role of BMP inhibitors in tissue patterning are evolutionarily ancient, probably arising for the first time in hydra

developmental biology↗