Ptch1-mediated dosage-dependent action of Shh signaling regulates neural progenitor development at late gestational stages

► Shh enhances the transition from VZ progenitors to IPCs during cortical neurogenesis. ► Ptch1 is required in VZ progenitors for their self-renewal capacity. ► Cortical VZ progenitors are competent to response to Shh signal at late gestation. ► Shh and Ptch1 determine proper neural cell number and identity during neurogenesis.