Cyclic GMP is not involved in neural induction inXenopus laevis.

Recent evidence indicates an important role for cell-surface mediated signal transduction in embryonic induction. We, therefore, started a systematic search to identify signal transduction pathways which are activated during embryonic induction and specifically during neural induction. We showed previously that the protein kinase C and cAMP pathways mediate neural induction inXenopus laevis. Here, we investigated whether cGMP is also involved in the early development of the nervous system. We measured the cGMP content of whole embryos at embryonic stages which mark important events in the early development of the nervous system, as well as in the developing neural tissue itself, after this was induced from ectoderm by dorsal mesoderm. No changes in cGMP content were found, either in whole embryos at different developmental stages, or in developing neural tissue from these stages. We also found no evidence for the presence of nitroprusside stimulatable guanylate cyclase in these developmental stages. A cGMP analogue, 8-Br-cGMP, was not able to induce neural tissue, either alone or in combination with known neural inducers, the phorbol ester TPA and 8-Br-cAMP. 8-Br-cGMP also had no negative influence on the neural inducing ability of dorsal mesoderm or TPA, alone or in combination with 8-Br-cAMP. We conclude that cGMP has no role in the early development of the central nervous system inXenopus laevis. This conclusion underlines the specificity of the signal transduction pathways (PKC and cAMP pathways) that do mediate neural induction.