DEGENERATION OF NEURONS AND GLIA IN THE NIEMANN^PICK C MOUSE IS UNRELATED TO THE LOW-DENSITY LIPOPROTEIN RECEPTOR D. C. GERMAN, a * E. M. QUINTERO, b C.-L. LIANG, a C. XIE c and J. M. DIETSCHY c a Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9070, USA b Department of Biomedical Sciences, Baylor College of Dentistry, Dallas, TX 75246, USA c Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9070, USA AbstractöThe BALB/c mouse model of Niemann^Pick type C disease exhibits similar neuropathological features to the human condition, including cerebral atrophy, demyelination of the corpus callosum, and degeneration of cerebellar Purkinje cells. The gene defect in Niemann^Pick C disease causes cholesterol to accumulate within the lysosomal compartment of neurons and glial cells. In order to determine whether cholesterol accumulation through the low-density lipoprotein receptor pathway plays an important role in the degenerative process, Niemann^Pick C mice were crossed with low-density lipoprotein receptor knockout mice. The purpose of the present study was to determine whether degeneration of neurons and glial cells is reduced in Niemann^Pick C animals lacking the low-density lipoprotein receptor. Using stereological counting methods, Purkinje cells were counted in the cerebellum and glial cell bodies were counted in the corpus callosum in mice at 3, 7.5 and 11 weeks of age. In the Niemann^Pick C animals, compared to wild-type control mice, there were 48% fewer glial cells at 3 weeks of age, and by 11 weeks of age there were 63% fewer glial cells. Purkinje cells were decreased in number by 13% at 3 weeks of age, and by 11 weeks of age there was a 96% loss. In the Niemann^Pick C animals lacking low-density lipoprotein receptors, there was no di¡erence in the magnitude of glial cell or Purkinje cell loss compared to the Niemann^Pick C animals. These data indicate that both neurons and glia are vulnerable to degeneration in the Niemann^Pick C mouse, but that blocking the accumulation of cholesterol through the low-density lipoprotein receptor pathway does not alter the degenerative phenotype of Niemann^Pick C disease. ß 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved. Key words: Purkinje cells, corpus callosum, glial cells, stereology. Niemann^Pick type C (NPC) disease is a fatal disorder that is characterized by progressive enlargement of inter- nal organs, and the onset of degenerative neurological disease often in late childhood (Brady, 1983). During the course of the disease dementia and ataxia are com- monly observed (Love et al., 1995; Pentchev et al., 1995). NPC disease is related to a defect in the intracellular tra¤cking of cholesterol (Blanchette-Mackie et al., 1988; Sokol et al., 1988). A mutant gene has been found to encode a 1278-amino acid protein, NPC1, that shares considerable homology to other proteins known to be important in regulating cholesterol balance across cells (e.g. sterol regulatory element-binding pro- tein and 3-hydroxy-3-methylglutaryl coenzyme A reduc- tase) (Carstea et al., 1997). Thus, in the liver and spleen of a¡ected children there is a signi¢cant accumulation of unesteri¢ed cholesterol and sphingomyelin. This accu- mulation occurs within the lysosomal compartment (Blanchette-Mackie et al., 1988; Sokol et al., 1988), explaining the increase in lysosomal structures within neurons along with di¡erent types of intracellular inclu- sion bodies (e.g. myelin ¢gures, multivesicular bodies) (Love et al., 1995; Pentchev et al., 1995). A mouse model for NPC disease has been identi¢ed. As in man, the NPC mouse has a gene mutation in NPC1 (Loftus et al., 1997), enlargement of the liver and spleen, liver function abnormalities, and exhibits progressive neurodegeneration (Pentchev et al., 1995). Every organ manifests the accumulation of unesteri¢ed cholesterol so that the whole-body pool of sterol increases almost three-fold by the time these animals are 11 weeks of age (Xie et al., 1999b). Even in the brains of newborn pups, there is an elevation in cholesterol content (Xie et al., 2000a). In the organs outside of the CNS, this cholesterol represents the sequestration of sterol in late endosomes and lysosomes that is derived from the uptake of chylomicron remnants and low-den- sity lipoproteins (LDL) utilizing LDL receptors (LDLR) and the clathrin-coated pit pathway (Xie et al., 1999a). 999 *Corresponding author. Tel. : +1-214-648-7385 ; fax : +1-214-648- 7397. E-mail address : dwight.german@utsouthwestern.edu (D. C. German). Abbreviations : ANOVA, analysis of variance ; apoE, apolipoprotein E; DAB, 3,3P-diaminobenzidine ; EDTA, ethylenediaminetetra- acetate; LDL, low-density lipoprotein; LDLR, low-density lipoprotein receptor ; NPC, Niemann^Pick C ; PBS, phosphate- bu¡ered saline; PBS-T, PBS with Triton X-100; PCR, polymer- ase chain reaction; SR-BI, scavenger receptor B-I. NSC 5075 21-8-01 www.elsevier.com/locate/neuroscience Neuroscience Vol. 105, No. 4, pp. 999^1005, 2001 ß 2001 IBRO. Published by Elsevier Science Ltd Printed in Great Britain. All rights reserved PII:S0306-4522(01)00230-5 0306-4522 / 01 $20.00+0.00