FGF signaling gradient maintains symmetrical proliferative divisions of midbrain neuronal progenitors

► The loss of FGF signaling in the midbrain leads to increased neurogenesis. ► FGFs maintain Hes1 expression in midbrain ventricular zone. ► FGF-deficient progenitors begin to form symmetrical neurogenic divisions. ► FGFR1/2- signaling affects neuronal progenitors cell-autonomously. ► FGF8-protein gradient localizes in the basal lamina.