Naturally occurring G(M2) gangliosidosis in two Muntjak deer with pathological and biochemical features of human classical Tay-Sachs disease (type B G(M2) gangliosidosis)

Two juvenile sibling male Muntjak deer (Muntiacus muntjak) with histories o f depression, ataxia, circling and visual deficits were studied. Cerebrospi nal fluid analyses revealed vacuolated macrophages that contained long para llel needle-like intracytoplasmic inclusions. Light microscopically, nerve cell bodies throughout the brain, ganglion cells within the retina and neur ons in the myenteric plexuses were variably swollen and had pale granular t o finely vacuolated eosinophilic cytoplasm. Neuronal cytoplasm stained spec ifically with sudan black and Luxol-fast blue stains. Within the brain ther e were occasional axonal spheroids, foci of astrogliosis and scattered micr oglial cells with abundant pale foamy cytoplasm. Electron microscopy of the brain and retina revealed numerous neurons and ganglion cells, respectivel y, with multiple membrane-bound structures that contained compact electron- dense membranous whorls and fewer parallel membranous stacks. Thin layer ch romatography of total lipid extracts of the cerebral cortex of both cases r evealed massive accumulation of G(M2) ganglioside. Crude kidney extracts of the two affected deer were able to hydrolyze 4-methylumbelliferyl beta-Glc NAc, but not 4-methylumbelliferyl beta-GlcNAc-6-sulfate, indicating the def ect of beta-hexosaminidase A. Cellogel electrophoresis of the kidney extrac ts also revealed the deficiency of beta-hexosaminidase A in the two deer. I t is concluded that these two deer had the biochemical lesion identical to that of human type B G(M2) gangliosidosis (classical Tay-Sachs disease).