Aberrant CF innervation of PCs in Pclo^gt/gt rats compared with Pclo^wt/wt. A, B, Images of sagittal sections of Pclo^wt/wt and Pclo^gt/gt cerebella at 3 months of age stained with antibodies against VGluT1 and Piccolo demonstrate the loss of Piccolo in the ML (A) and the GCL (B) in Pclo^gt/gt rats. C, Images of sagittal sections of Pclo^wt/wt and Pclo^gt/gt cerebella at 3 months of age stained with antibodies against calbindin and VGluT2. The CF synapses, immunopositive for VGluT2, are increased in the ML of Pclo^gt/gt cerebella compared with Pclo^wt/wt controls (C,D). When Piccolo is absent, PF synapses in the ML, immunopositive for VGluT1, do not appear overtly different between Pclo^wt/wt and Pclo^gt/gt (A). However, MF and CF synapses are altered (B–D; see Fig. 5). D, Quantification of the percentage of the ML (dashed lines) immunopositive for VGluT2 from C (Pclo^wt/wt = 3.521 ± 0.160, n = 128 images; Pclo^gt/gt = 4.377 ± 0.241, n = 112 images; n = 3 independent experiments; Mann–Whitney U test, U = 5987, *p = 0.0278). Animals used in this experiment are as follows: wt7, wt8, wt10, wt11; ko6, ko7, ko9, ko10. Scale bars, 20 μm. Error bars indicate SEM. Data points represent images taken from lobes I, III, V, VII, and IX; 4 sections per animal.