Smad2 is not required for cerebellar granule cell proliferation but is required for maturation and migration. A–D, immunodetection of PCNA is shown in sagittal cerebellar sections of P7 and P12 mice. PCNA labeling shows the presence of similar proliferating cell numbers in the EGL in both control and Smad2-CNS-KO mice. E and F, H&E staining of P12 sections shows the EGL is three to four cell layers thick in control mice, and six to eight cell layers thick in mutants. G and H, at P16, the EGL has been depleted in control mice, but one cell layer is still present in Smad2-CNS-KO mice. Insets, high magnification images taken from areas indicated by rectangles. I, measurement of PCNA-positive cells per inset area in P7 and P12 mice EGL. Values are expressed as the mean ± S.D. per section of five sections per animal, three animals per group. NS, not significant. J, RT-PCR analysis indicating changes in the abundance of GABAR subunits expressed in the control and Smad2-CNS-KO mice. β-Actin was used as an internal control. K, changes in GABAR subunit expression were quantified using ImageJ. Gabra6 and Gabrd were down regulated by 0.23- and 0.27-fold, respectively, whereas Gabr2a was up-regulated by 1.72-fold. Statistical analyses (t test) were carried out by using Microsoft Excel. Error bars indicate S.D. NS, no significant. An asterisk represents p values <0.05. L and M, immunodetection of NeuN is shown in sagittal cerebellar sections of P12 mice. l and m, high magnification images were taken from the areas indicated by rectangles. Arrowheads highlight the spindle-shaped morphology of migrating NeuN-positive cells in the molecular layer. A–H, L, and M (scale bar), 200 μm. Insets (l-m), scale bar, 50 μm. N, the percentage of NeuN-positive cells in the IGL area per cerebellum in P12 mice. O, measurement of the spindle-shaped morphology of migrating NeuN-positive cells per inset area in P12 mice ML. An asterisk represents p values <0.05. Double asterisks represent p values < 0.01. Values are expressed as the mean ± S.D. per section of five sections per animal, three animals per group. Black dashed line indicates division between two lobes. Black bar, control; gray bar, Smad2-CNS-KO mice.