Meteorin is a novel secreted protein that is expressed in undifferentiated neural progenitors and in the astrocyte lineage, including radial glia. It plays important roles in the differentiation of glial cells and also in axonal network formation during neurogenesis. Meteorin selectively promoted astrocyte formation from mouse cerebrocortical neurospheres in differentiation culture, whereas it induced cerebellar astrocytes to become radial glia. Meteorin also induced axonal extension in small and intermediate neurons of sensory ganglia by activating nearby satellite glia.