A SEL1L Mutation Links a Canine Progressive Early-Onset Cerebellar Ataxia to the Endoplasmic Reticulum–Associated Protein Degradation (ERAD) Machinery
(A) Normal cerebellar cortex in the ventrolateral parts of the cerebellum, with densely cellular granular cell layer (HE 100×). (B) Affected cerebellar cortex in the vermal region with marked loss of granular cells (HE 100×). (C) A higher magnification of unaffected cortex with viable Purkinje cells (PCs) and a normal granular cell density (HE 400×). (D) A higher magnification of affected cortex, with severe loss of PCs and linear reactive gliosis between the molecular and the granular layers (arrow) (HE 400×). (E) Degenerating, shrunken, eosinophilic PCs with margination of the nuclear chromatin (black arrow) or central chromatolysis of the cytoplasma (red arrow) (HE 400×). (F) PCs that show total loss of cytoplasmic basophilia (Nissl substance) and pyknotic or karyorhektic nuclei (arrows). Inset: viable PC with intact Nissl substance seen as basophilic cytoplasmic granulation (LFB-CEV, 400×). (G) Left: mild astrogliosis (arrows) within the granular cell layer and the white matter of the cerebellar folia. Right: unaffected part of same dog (IHC GFAP, 400×). (H) Left: secondary degeneration and myelinophagia in the affected cerebellar white matter. Right: unaffected parts of same dog (LFB-CEV, 400×). ML = molecular layer, PL = Purkinje cell layer, GL = granular cell layer, WM = white matter.