AN ESSENTIAL ROLE FOR RETINOID SIGNALING IN ANTEROPOSTERIOR NEURAL PATTERNING

The vertebrate central nervous system (CNS) is induced by signals eman ating from the dorsal mesoderm, or organizer, that divert the ectoderm away from an epidermal and towards a neural fate. Additional signals from the organizer pattern the neural ectoderm along the anteroposteri or axis. We devised highly specific methods utilizing constitutively a ctive or dominant negative receptors to evaluate the role of retinoids in neural patterning, Microinjection of these reagents either augment s or reduces retinoid signaling in specific regions of the embryo. We show that increased receptor activity suppresses anterior neural struc tures while dominant negative receptors lead to anterior enhancement, Similarly, microinjection of the dominant negative receptor leads to t he loss of posterior marker genes, We demonstrate that retinoid recept ors comprise a critical component in neural posteriorization and are r equired for proper neuronal differentiation. These results support a q uantitative role for retinoid signaling in regionalization of the CNS.