Figure 2. Purkinje cell degeneration in homozygous tippy mutant mice cerebella.

A,B, Control (A) and tippy mutant (B) mice cerebella stained with PEP19 (green) and ubiquitin (red) demonstrate ubiquitin-positive degenerating Purkinje cell somas (B, arrowhead) and degenerating dendritic arbors (B, arrows) in tippy mutant mice while there is no ubiquitin signal in control Purkinje cells (A). C–F, PEP19 immunostaining further reveals tippy mutant Purkinje cells with dysmorphic, degenerating spiny branchlets (C, arrows) and axonal spheroids (torpedoes) in the initial axonal segment (D, arrows) as well axonal spheroids in the deep granular layer (E, arrows) and white matter (F, arrows) of mutant cerebella indicating whole-cell degeneration. Crossed-arrow in panel (C) points to the arbor of a neighboring, normal Purkinje cell. G–I, Fluro-Jade C stained sections demonstrate degenerating Purkinje cell bodies (H, arrowhead), dendrites (H, arrows) and several white matter axons (I, arrows) in tippy mutant cerebella but no degeneration signal in the cerebellar cortex of control mice (G). J–M, Semithin (1–2 µm) resin sections stained with toluidine blue illustrate delicately stained Purkinje cells of normal morphology, with the nucleolus being the only dense organelle in control cerebella (J). In contrast, tippy mutant cerebella demonstrate multiple densely stained Purkinje cell somata (K,M arrows) and severely dysmorphic dendritic arbors (K–M, arrowheads) in varying stages of dark degeneration. Asterisks indicate Purkinje cell somas. ml, molecular layer; gl, granule cell layer; wm, white matter. Scale bars: A–E, H, J–L, 20 µm; F, G, I, 30 µm; M, 10 µm (scale bar in B, E, and K applies to A, D, and J, respectively).