Norrin (NDP)

Activates the canonical Wnt signaling pathway through FZD4 and LRP5 coreceptor. Plays a central role in retinal vascularization by acting as a ligand for FZD4 that signals via stabilizing beta-catenin (CTNNB1) and triggering LEF/TCF-mediated transcriptional programs.

Acts in concert with TSPAN12 to activate FZD4 independently of the Wnt-dependent activation of FZD4, implying the occurrence of a Wnt-independent signaling that also promote accumulation the beta-catenin (CTNNB1). May be involved in a pathway that regulates neural cell differentiation and proliferation.