Abnormal morphology of dendrites and spines of the Purkinje cells in <i>ts3</i> mutants.

<p><b>A)</b> Representative ultra-high voltage electron microscopy (UHVEM) images of Purkinje cell dendrites in <i>ts3</i> mutant and WT mice (2000x). The arrow in the lower panel indicates isthmic portions of dendrites observed in <i>ts3</i> mutants. Note the significant difference in morphology between <i>ts3</i> and WT cerebella. Whereas the bulbous shape of dendritic spines is observed in WT controls, dendritic spines in <i>ts3</i> mutants are smaller and irregularly-shaped, as indicated by arrowheads. Scale bar indicates 5 µm. <b>B)</b> Dendritic spine density (number of spine/µm²) was comparable in <i>ts3</i> and WT controls. <b>C)</b> Morphology of the dendritic spines is significantly different in <i>ts3</i> mutants when compared to that of WT controls. Whereas stubby or mushroom-shaped spines, which are characteristic of normal and mature PCs, are commonly observed in WT cerebella, thin (filopodia-like or headed) spines, representing a deficit in spine maturation, are predominant in <i>ts3</i> mutants. Double-headed spines, including branched spines, were rarely observed in either genotype. “Unknown” indicates spines that could not be categorized from HVEM images by gross observation due to high density of dendritic spines in PCs. The χ² test indicated that the difference in dendritic morphology between two genotypes is statistically significant (<i>p</i><0.01).