Neurons in Niemann-Pick Disease Type C Accumulate Gangliosides as Well as Unesterified Cholesterol and Undergo Dendritic and Axonal Alterations

Abstract

Niemann-Pick disease type C (NPC) is a lethal neurologic storage disorder of children most often caused by a defect in the protein NPC1. To better understand the disease we thoroughly characterized the cellular and morphological alterations occurring in murine, feline, and human NPC. Using immunocytochemistry and filipin histochemistry we show that both gangliosides and unesterified cholesterol are differentially stored in neurons of the cerebral cortex, cerebellum, and hippocampus, as well as in liver. Double fluorescence labeling revealed that GM2 ganglioside and unesterified cholesterol were partially co-localized in vesicular structures, and triple fluorescence labeling utilizing a LAMP-1 antibody identified many of these organelles as part of the late endosomal/lysosomal pathway. These observations, coupled with the proposed role of NPC1 in intracellular cholesterol movement, suggest that GM3 and GM2 gangliosides as well as unesterified cholesterol may be retrogradely cleared from late endosomes/lysosomes by an NPC1-dependent mechanism. Cellular consequences of the NPC metabolic defect as shown by parvalbumin immunocytochemistry and rapid Golgi staining, respectively, revealed characteristic axonal spheroids on GABAergic neurons and ectopic dendritogenesis that followed a species-specific gradient of: mouse < feline < human. These studies suggest that the homeostatic regulation of gangliosides and cholesterol in neurons is mediated by NPC1 and that perturbations in this mechanism cause a complex neuronal storage disorder.

Lysosomal accumulation of SCMAS (subunit c of mitochondrial ATP synthase) in neurons of the mouse model of mucopolysaccharidosis III B

“…Sections, 40 μm thick, were cut sagittally on vibratome VT1000S (Leica Microsystems, Bannockburn, IL). Glycosaminoglycan was detected by the Muller-Mowry colloidal iron stain [29] and unesterified cholesterol by binding of the fluorescent reagent, filipin [30].…”

Targeted Mutation of the MLN64 START Domain Causes Only Modest Alterations in Cellular Sterol Metabolism

“…Brain tissue was stained with filipin and an anti-GM3 ganglioside antibody as described by Zervas et al (32). Mouse embryonic fibroblasts were grown on Nunc LabTek two-chambered glass slides.…”

Longitudinal Changes in White Matter Fractional Anisotropy in Adult-Onset Niemann-Pick Disease Type C Patients Treated with Miglustat

“…Axonal structure is known to be altered in NPC and can include axonal swelling, spheroid formation and abnormal axonal branching and growth of collaterals (March et al 1997;Sarna et al 2003;Zervas et al 2001). Such disruptions to healthy axonal growth may reflect the abnormal transport of cholesterol and other lipid products to distal axons.…”

“…The accumulation of lipids in neurons results in changes to dendritic and axonal morphology (Zervas et al 2001). Axonal transport mechanisms are also altered, and hyperphosphorylated tau accumulates within neurons (Suzuki et al 1995).…”

“…This reduces glycolipid storage in neurons and has been shown in a controlled clinical trial of juvenile, adolescent and adult-onset NPC to slow disease course (Patterson et al 2007). Feline models of NPC have found increased purkinje cell survival in the cerebella of treated cats (Stein et al 2012;Zervas et al 2001).…”