(A and B) H&E staining of sagittal midline cerebellar sections (A) at P0 (scale bar: 100 μm) and (B) at P7 (scale bar: 200 μm). For P0 cerebellar anlages, anterobasal (red), anterodorsal (green), central (blue), posterior (yellow), and inferior (white) cardinal lobes are marked with dash lines in their respective color. Note that the 4 principal fissures at the vermis of Ptch1^–/+;3nSD cerebella were deeper than those of Ptch1^–/+ or WT ones. Mature cerebellar lobules are marked by Roman numerals, and principal fissures are marked by asterisks. pc, preculminate; pr, primary; sec, secondary; pl, posterolateral fissure (67). For each mouse line, 4 newborn pups were analyzed (n = 4). (C) Anti-Ki67 and (D) anti-NeuN immunofluorescence staining of P0 cerebellar sections at the pc fissure are shown with DAPI or anti-NeuN as counterstaining, respectively (scale bar: 20 μm). Combined images from both channels are shown, but the cells were counted in individual channels. (E) Ratio of proliferating GCPs (Ki67⁺ cells) and (F) total number of GCPs (Pax6⁺ cells) in a fixed EGL area surrounding the pc fissure (circled by the dash line). For each data point, 1 cerebellar section per mouse was stained and quantified, and total numbers of animals used were 3 for WT or 4 for Ptch1^–/+ and Ptch1^–/+;3nSD mice, respectively. Data represent mean ± SD, and the 1-way ANOVA with Tukey’s multiple comparisons test was used for statistical analysis in E and F. *P < 0.05; **P < 0.01; ***P < 0.001.