Supplying β-catenin restores retinal laminated structures in RBP-J deficient retina. (A-D) In vivo electroporation-induced Cre expression in RBPf/fretinae at P0 results in a loss of β-catenin at the apical surface of the retina at P3 (arrowheads in B, D), whereas this manipulation does not lead to detectable changes in β-catenin distribution in RBPf/+retinae (A, C). (E-H, O) Expressing Cre (G) and both of Cre and β-catenin (H) in RBPf/fretinae reduces the proportion of Sox2+ cells in the total Cre+ cells compared with RBPf/+retinae electroporated with Cre (E) and both of Cre and β-catenin (F). Statistical comparison of the percentages of Sox2+ cells in the total Cre+ cells is shown in (O). **P < 0.01. (I, L) Expression of Cre in RBPf/fretina at P0 results in the appearance of rosettes (arrows) at P14. (J, M) Overexpression of β-catenin prevents the formation of rosette-like structures in Cre-electroporated RBPf/fretinae. (K, N) Overexpression of β-catenin and Cre in RBPf/+retinae. Note that there are few EGFP+ cells in the inner nuclear layer (INL) and the vast majority of EGFP+ cells are located in the outer nuclear layer (ONL) in Cre and β-catenin expressing RBPf/fretinae (J), as compared with Cre and β-catenin misexpressing RBPf/+retinae (K). (P) Comparison of rod photoreceptors, bipolar cells, amacrine cells and Müller glia cells at P14 between RBPf/+and RBPf/fretinae after in vivo misexpression of Cre and β-catenin at P0 (* P < 0.05, ** P < 0.01). Hoechst counterstaining (blue) is shown to reveal the retinal layers. Scale bars, 100 μm.