Neurodegeneration in Niemann-Pick type C disease mice

Niemann-Pick disease type C (NP-C) is an inherited neurodegenerative disorder associated with intracellular cholesterol and glycolipid trafficking defects. Two separate genes, NPC1 and NPC2, have been linked to NP-C. NPC1 encodes a polytopic membrane-bound protein with a putative sterol-sensing domain. NPC2 has been recently identified as epididymal secretory glycoprotein 1. The NPC1 protein functions in the vesicular redistribution of endocytosed lysosomal cargo, but how its inactivation leads to neurodegeneration is not known. The neurological symptoms of NP-C typically appear after a period of normal early development and reflect progressive degeneration of widespread brain regions. Here we have delineated the pattern of neurodegeneration in NP-C mice, whose genetic defect has been shown to be an inactivating mutation of the mouse NPC1 gene. The results reveal a spatially and temporally specific pattern of degeneration of nerve fibers followed by degeneration of neuronal cell bodies beginning as early as day 9 and continuing throughout life. We have recently showed that in the primate brain, the NPC1 protein is localized predominantly within perisynaptic astrocytic processes. The present observations suggest that a functional disturbance in NPC1 could disrupt vesicular transport of cholesterol, glycolipids and possibly other endocytic cargo in glia, which is critical for maintaining the integrity of neurons.