Communication à un colloque
Résumé : The Dmrt (doublesex and mab-3 related transcription factor) genes encode a large family of evolutionarily conserved transcription factors whose function in sexual development has been well studied. In vertebrates, some Dmrt genes also function in nongonadal tissues. For example, Xenopus Dmrt4 is essential for neurogenesis in the olfactory system. We have isolated and characterized Xenopus Dmrt5. Dmrt5 is coexpressed with Dmrt4 in the developing olfactory placodes. As Dmrt4, Dmrt5 is positively regulated in the ectoderm by neural inducers and negatively by proneural factors. Both Dmrt5 and Dmrt4 genes are also strongly activated by the combined action of the transcription factor Otx2, broadly transcribed in the head ectoderm and of Notch signaling, activated in the anterior neural ridge. Knockdown of Dmrt5 impairs neurogenesis in the embryonic olfactory system. Dmrt5 deficiency also disrupted Noggin-mediated activation of neuronal differentiation markers in animal caps, a phenotype that can be rescued by overexpression of Dmrt5 or Dmrt4. Consistent with these findings, Dmrt5 upregulates the expression of the proneural Ngnr1 and Ebf2 genes and promotes Ath5 induced neurogenesis in animal caps. Together, these data identify Dmrt5 as a novel important upstream regulator of neurogenesis and suggest redundant roles for Dmrt4 and Dmrt5 during olfactory system development.