Fgf15-mediated control of neurogenic and proneural gene expression regulates dorsal midbrain neurogenesis

► We have analyzed Fgf15−/− mice on an outbred genetic background. ► Dorsal midbrain neural progenitors fail to exit the cell cycle in these mutants. ► Neurogenic bHLH transcription factor genes were up-regulated in Fgf15−/− embryos. ► Proneural bHLH transcription factor genes were down-regulated in Fgf15−/− embryos. ► Fgf15 controls the initiation and proper progression of dorsal midbrain neurogenesis.