RETINOID RECEPTORS PROMOTE PRIMARY NEUROGENESIS IN XENOPUS

Retinoid receptors, which are members of the nuclear hormone receptor superfamily, act as ligand-dependent transcription factors. They media te the effects of retinoic acid primarily as heterodimers of retinoic acid receptors (RARs) and retinoid X receptors (RXRs). To analyse thei r function, xRXR beta synthetic mRNA was injected into Xenopus embryos in combination with normal and mutated xRAR alpha transcripts. Two in formative phenotypes are reported here. Firstly, over-expression of xR XR beta with xRAR alpha results in the formation of ectopic primary ne urons, Secondly, blocking retinoid signalling with a mutated xRAR alph a results in a lack of primary neurons. These two phenotypes, from con tra-acting manipulations, indicate a role for retinoid signalling duri ng neurogenesis.