Notch has multiple roles during cochlear development. All explants were labeled with Gfi1 (green), Sox2 (red), and Prox1 (blue). A, B, Notch inhibition with DAPT of E12.5 explants shows a disruption in the formation of the sensory epithelium. A’, B’, Higher magnification of boxed inset in A and B, respectively. A”, B”, Same as A’ and B’, respectively, showing Sox2 labeling alone. C, E13.5 control explants. C’, Higher magnification of boxed inset in C. D, DAPT treatment at E13.5 shows dual effects: blocking lateral inhibition in the base to mid-base region (arrow) and prosensory inhibition at the apex (D’). S, Saccule; B, base; Ap, apex. Scale bars, 200 μm.