Inactivation of RBP-J enhances production of photoreceptors. (A-D) Expression levels of Crx and Otx2, two photoreceptor precursor markers, are significantly increased in Chx10Cre-RBPf/fretinae (B, D) compared to wild-type controls at E13.5 (A, C). (E, F) Enhanced Crx expression is also observed in Chx10Cre-RBPf/fretina (F) relative to wild-type retina at E16.5 (E). (G, H) Expression of Thrβ2, a specific marker of cone photoreceptor precursors, is also up-regulated at E16.5 in Chx10Cre-RBPf/fretina (H) relative to wild-type retina (G). (I, J) Expressing Cre at P0 by in vivo electroporation in RBPf/+retinae does not lead to apparent morphological alterations at P14. (L, M) Expressing Cre in RBPf/fretinae at P0 results in the appearance of rosettes, an increase in rhodopsin+ photoreceptors and a decrease in bipolar and Müller glial cells at P14. (K, N) Inactivation of RBP-J by in vivo electroporation-induced Cre expression in RBPf/fretinae but not in in RBPf/+retinae at P5 results in a decrease of GS+ Müller glial cells (arrows in K) and an increase in bipolar cells at P14. Hoechst counterstaining is shown in blue. (O, P) Comparison of immunoreactive cell numbers between RBPf/+and RBPf/fretinae after inactivation of RBP-J expression at P0 and P3 (O) and P5 (P). * P < 0.05, ** P < 0.01. Scale bars, 100 μm.