Regulation of banded hedgehog signaling in Xenopus neural crest development

TRISTÁN H. AGUERO; JUAN P. FERNÁNDEZ; GUILLERMO VEGA LÓPEZ; MANUEL J. AYBAR

San Diego, California, USA

Congreso; 37th Annual Meeting of the Society for Neuroscience; 2007

Society for Neuroscience (USA)

The neural crest (NC) is an embryonic cells population with a highly migratory and multipotent capacity, generating many cell derivatives including neurons, glia, melanocytes, craniofacial cartilage, etc. Several signals (BMP, Wnt, FGF, Notch and RA) are involved in the initial induction of this tissue; however the participation of other cell signaling pathways has not been established. The Hedgehog (Hh) pathway presents a high conservation degree in their functions in different species. In Xenopus laevis (Xl) there are three secreted morphogens of the Hh family, sonic, cephalic and banded hedgehog (Bhh). These morphogens direct a wide range of developmental processes like cell fate determination, pattern formation, cell proliferation, and differentiation in many tissue types. The aim of our work is to study the role of this pathway in NC development. We have previously shown that Bhh and Gli3 expression patterns overlap with NC markers and functional experiments have shown that both genes participate in the NC induction increasing the expression of specific markers. In this work, we focus our analysis in regulatory aspects of the pathway in NC development. We have cloned for the first time two regulatory members of the intracellular Hh signalling complex, the Xenopus homologous of Costal2 (Cos2) and Suppressor of fused (Sufu). The expression pattern of both genes demonstrated a correlation with NC markers. To evaluate the regulatory role of the genes in the development of the NC we followed a gain-of-function approach in which the overexpression of Cos2 produces a decrease in the NC markers suggesting that it negatively regulate the pathway. We also show that Gli3-morpholino was able to block the increase in NC markers produced by Bhh indicating that the control of specification by Bhh is mediated by Gli3. In addition, the temporal requirements of Hedgehog signaling for NC induction has been analyzed by grafting cyclopamine-soaked beads into the neural fold from late gastrula stage. We also carried out rescue experiments in which the inhibitory effects of loss-of function approaches were suppressed by the coinjection of full length Bhh, Gli2 and Gli3. Our results demonstrate that this pathway is required for normal development and provide new insights into the possible molecular regulation of Bhh pathway in the NC.