Fig. 7. Upregulation of Bhlhb5 and NeuroD expression in the Math5-LacZ cell lineage in Math5-null retina. (A-H) Retinal sections immunolabeled with anti-Bhlhb5 (green) and nuclei counterstained with PI (red) show that loss of Math5 results in a large increase in Bhlhb5⁺ displaced amacrine cells and a significant decrease in Bhlhb5⁺ bipolar cells. (A,E) Low magnification of retinas at P21. (B,F) Enlarged view of the corresponding boxed regions in A and E, respectively. (C,G) Confocal sections of Bhlhb5⁺ displaced amacrine cells in the GCL. (D,H) Confocal sections of Bhlhb5⁺ cells in the INL. (I-P) Co-immunolabeling of Bhlhb5 (red) and LacZ (green) indicates that loss of Math5 results in a significant increase in the number of cells expressing Bhlhb5 in E13 retina and that a majority of these Bhlhb5⁺ cells express Math5-LacZ. The boxed areas in K and O are shown at high magnification in L and P. (Q-X) Similarly, an increase in retinal cells expressing Math5-LacZ and NeuroD is observed in E13.5 Math5-null mice. The boxed areas of S and W are shown at high magnification in T and X. The Math5-GFP fluorescence is undetectable under the fixation and detection conditions used and all green signals are derived from either LacZ or anti-Bhlhb5 staining. Scale bars: in A, 200 µm for A and E; in all other panels, 100 µm.