Figure 9.
Alteration of synaptic contact and intrinsic activity of SCA7 PCs. A, Western blot analyses of SCA7140Q/5Q and WT cerebella show decreased level of vGLUT2 in SCA7 mice at 34 weeks, whereas the vGLUT1 is not affected. GAPDH and histone H3 protein levels are used as loading controls. Molecular weight in kDa. B, vGLUT1 and vGLUT2 immunostaining of lobule VI of the vermis in WT and SCA7 mice. GCL, GC layer; PCL, PC layer. Scale bar, 30 µm. C, Left, Measurement of vGLUT2-labeled area in the MCL of lobule VI and X of the vermis shows reduced width size in SCA7140Q/5Q (n = 3) compared with WT mice (n = 3). Data are mean ± SEM. Two-tailed Student's t test. Right, Coimmunostaining of vGLUT2 and CALB1 showing aggregation of vGLUT2 contact points located along large dendritic arborization of PC in SCA7 cerebellum. Scale bar, 10 µm. D, Top, Schematic of a sagittal cerebellar section where cerebellar lobules are numbered from I to X and orange lines indicate the locations of PC intrinsic activity recording sites (left). Middle, Schematic of juxtacellular recording of PC pacemaking activity. Representative traces of spontaneous firing in PCs located in lobule VI from WT or SCA7140Q/5Q mice (right). Middle, Box plots represent the values of CV2 of adjacent ISI in lobule VI and IX/X in WT and SCA7 mice. Dashed and solid lines indicate mean and median values, respectively: 22-week-old WT (n = 27) and SCA7 (n = 65); 38-week-old WT (n = 33 in lobule VI and 34 in IX/X) and SCA7 (n = 41 in lobule VI and 36 in IX/X). Bottom, Same representation as in middle panel for ISI values. Statistical analysis was performed using Mann–Whitney rank-sum test. ns. not significant.