Proper central nervous system development is critical for survival and depends on complex intracellular and extracellular signaling to regulate neural progenitor cell growth and differentiation; however, the mechanisms that mediate molecular crosstalk between pathways during neurogenesis are not fully understood. Here, we explored the integration of the Hedgehog (Hh) signaling pathway with the two critical developmental pathways, Receptor Tyrosine Kinase (RTK) and Notch signaling, in the growth and maintenance of neural progenitors in the developing neuroretina. We found combined and sustained RTK and Hh signaling was sufficient to establish long-term retinal progenitor cell (RPC) cultures and these cells maintained neurogenic and gliogenic, but not retinogenic, competence in vitro and in vivo. In addition, we identified crosstalk between Notch and Hh signaling, where Notch is required for Hh-mediated proliferation and Gli protein accumulation, and gain-of-function of Notch is sufficient to extend the window of Hh responsiveness in a subset of Müller glia. Both Hh-RPC monolayer establishment and Notch mediated Hh-responsiveness required Gli2. Taken together, we identified molecular cross-communication between the Hh pathway and two major pathways, Notch and RTK, during retinogenesis, advancing our understanding of mechanisms that influence Hh to control neural progenitor growth.

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