Extrinsic signals in the developing nervous system: the role of neurokines during neurogenesis.

Vertebrate neurogenesis involves many distinct differentiation stages that are regulated by extrinsic signals. Survival and differentiation effects on cultured neurons of several lineages are elicited by members of the neurokine family of growth factors, ciliary neurotrophic factor (CNTF) and the related avian factor, growth promoting activity (GPA). The selective actions of these factors are mediated through the activation of heteromeric receptor complexes and depend on the presence of the ligand-binding receptor subunits CNTFR alpha and GPAR alpha. The in vivo localization of CNTFR alpha and GPAR alpha is consistent with the previously assigned biological functions but also suggest novel functions for these receptors and their ligands during neurogenesis.