CSMD3-deficient mice display abnormal cerebellar PCs morphology. A, Representative images showing the biocytin-labeled PCs (red) and the 3D reconstruction of PCs morphology (gray) in the WT (left) and CSMD3^−/− (right) mice. Scale bars: 50 µm (red); 30 µm (gray), respectively. B, Sholl analysis of the biocytin-labeled PCs. Left, Representative PC with concentric circles used for the Sholl analysis. The radius interval between the circles was set to 20 μm/step, ranging from 40 to 200 μm, from the center of the neuronal soma to the end of the dendrites. Right, Quantified analysis of the numbers of dendritic intersections per circle (n = 5 cells from 3 mice/group; CSMD3^−/− vs WT: F_(21,168) = 1.92, p = 0.0086). C, D, Quantified analysis of dendrite terminals (C) and total dendrite length (D) in the wild-type and CSMD3^−/− mice (n = 5 cells from 3 mice/group; t₍₈₎ = 3.0, p = 0.0172 (C); t₍₈₎ = 3.24, p = 0.0119 (D), CSMD3^−/− vs WT). E, Representative images showing the spines on EGFP-positive PC dendrites in the WT (top) and CSMD3^−/− (bottom) mice. Scale bar, 2 µm. F, Quantified analysis of dendritic spine density in the wild-type and CSMD3^−/− mice (n = 20–21 dendrites from 7–8 mice/group; t₍₃₉₎ = 4.99, p < 0.0001). G, Quantified analysis of dendritic spine length in the wild-type and CSMD3^−/− mice (n = 164–231 spines from 3 mice/group; t₍₃₉₃₎ = 12.27, p < 0.0001). H, Quantified analysis of dendritic spine head width in the wild-type and CSMD3^−/− mice (n = 164–231 spines from 3 mice/group; t₍₃₉₃₎ = 8.61, p < 0.0001). I, Representative images showing the immunofluorescent staining with calbindin (the cerebellar PC marker; red) and DAPI (the nuclear marker; blue) in sagittal cerebellar sections obtained from the wild-type (left) and CSMD3^−/− (right) mice. Scale bar, 10 µm. J, Quantified analysis of PC density in cerebellar Crus I/II lobules in WT and CSMD3^−/− mice (n = 10–19 slices from 3–5 mice/group; CSMD3^−/− vs WT: t₍₂₇₎ = 0.03, p = 0.9767). Data are presented as the mean ± SEM. *p < 0.05, **p < 0.01, and ***p < 0.001, two-way repeated-measures ANOVA with Sidak's post hoc test (B); two-tailed unpaired t test (C, D, F, G, H, J).