Niemann-Pick C Variant Detection by Altered Sphingolipid Trafficking and Correlation with Mutations within a Specific Domain of NPC1
AUTOR(ES)
Sun, Xiaofeng
FONTE
The American Society of Human Genetics
RESUMO
Niemann-Pick disease type C (NPC) is a fatal, autosomal recessive lipidosis characterized by lysosomal accumulation of unesterified cholesterol and multiple neurological symptoms, such as vertical supranuclear ophthalmoplegia, progressive ataxia, and dementia. More than 90% of cases of NPC are due to a defect in Niemann-Pick C1 (NPC1), a late endosomal, integral membrane protein that plays a role in cholesterol transport or homeostasis. Biochemical diagnosis of NPC has relied on the use of patient skin fibroblasts in an assay to demonstrate delayed low-density lipoprotein (LDL)–derived cholesterol esterification and a cytological technique—filipin staining—to demonstrate the intracellular accumulation of cholesterol. A small percentage of patients, referred to as “NPC variants,” present with clinical symptoms of NPC but show near-normal results of these biochemical tests, making laboratory confirmation of NPC disease problematic. Here, we demonstrate that NPC-variant fibroblast samples can be detected as sphingolipid storage disease cells, using a fluorescent sphingolipid analog, BODIPY-lactosylceramide. This lipid accumulated in endosomes/lysosomes in variant cells preincubated with LDL cholesterol but targeted to the Golgi complex in normal cells under these conditions. The reproducibility of this technique was validated in a blinded study. In addition, we performed mutation analysis of the NPC1 gene in NPC variant and “classical” NPC cell samples and found a high incidence of specific mutations within the cysteine-rich region of NPC1 in variants. We also found that 5 of the 12 variant cell samples had no apparent defect in NPC1 but were otherwise indistinguishable from other variant cells. This is a surprising result, since, in general, ∼90% of patients with NPC possess defects in NPC1. Our findings should be useful for the detection of NPC variants and also may provide significant new insight regarding NPC1 genotype/phenotype correlations.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1226123Documentos Relacionados
- Dynamic Movements of Organelles Containing Niemann-Pick C1 Protein: NPC1 Involvement in Late Endocytic EventsV⃞
- Niemann-Pick C1 Disease: Correlations between NPC1 Mutations, Levels of NPC1 Protein, and Phenotypes Emphasize the Functional Significance of the Putative Sterol-Sensing Domain and of the Cysteine-Rich Luminal Loop
- Distinct Niemann-Pick Disease Type C Clinical, Cytological, and Biochemical Phenotype in an Adult Patient With 1 Mutated, Overexpressed NPC1 Allele
- Cessation of rapid late endosomal tubulovesicular trafficking in Niemann–Pick type C1 disease
- Endocardial fibroelastosis and Niemann-Pick disease.