Ribeiro I, Marcão A, Amaral O, Sá Miranda M C, Vanier M T, Millat G
Genetic Neurobiology, IBMC University of Porto, 4150-180 Porto, Portugal.
Hum Genet. 2001 Jul;109(1):24-32. doi: 10.1007/s004390100531.
Niemann-Pick type C disease (NPC) is a rare neurodegenerative disorder characterised by lysosomal/late endosomal accumulation of endocytosed unesterified cholesterol and delayed induction of cholesterol homeostatic reactions. The large majority of mutations in the NPC1 gene described thus far have been associated with severe cellular cholesterol trafficking impairment (classic biochemical phenotype, present in about 85% of NPC patients). In our population of 13 unrelated NP-C1 patients, among which 12 were of Portuguese extraction, we observed an unusually large proportion of families presenting mild alterations of intracellular cholesterol transport (variant biochemical phenotype), without strict correlation between the biochemical phenotype and the clinical expression of the disease. Mutational studies were carried out to compare molecular lesions associated with severe and mild cholesterol traffic impairment. Levels of NPC1 protein were studied by Western blot in cultured fibroblasts of four patients with homozygous mutant alleles. Ten novel mutations were identified (Q92R, C177Y, R518W, W942C, R978C, A1035V, 2129delA, 3662delT, IVS23+1 G>A and IVS16-82 G>A). The mutational profile appeared to be correlated with the biochemical phenotype. Splicing mutations, I1061T and A1035V, corresponded to "classic" alleles, while three missense mutations, C177Y, R978C and P1007A, could be defined as "variant" alleles. All "variant" mutations described so far appear to be clustered within the cysteine-rich luminal loop between TM 8 and 9, with the remarkable exception of C177Y. The latter mutant allele, at variance with P1007A, was correlated to a decreased level of NPC1 protein and a severe course of the disease, and disclosed a new location for "variant" mutations, the luminal loop located at the N-terminal end of the protein.
尼曼-匹克C型病（NPC）是一种罕见的神经退行性疾病，其特征是内吞的未酯化胆固醇在溶酶体/晚期内体中积累，以及胆固醇稳态反应的诱导延迟。迄今为止描述的NPC1基因中的绝大多数突变都与严重的细胞胆固醇转运受损有关（经典生化表型，约85%的NPC患者中存在）。在我们的13例无亲缘关系的NP-C1患者群体中，其中12例为葡萄牙裔，我们观察到异常大比例的家族呈现细胞内胆固醇转运的轻度改变（变异生化表型），疾病的生化表型与临床表达之间没有严格的相关性。进行了突变研究以比较与严重和轻度胆固醇转运受损相关的分子损伤。通过蛋白质印迹法研究了四名纯合突变等位基因患者培养的成纤维细胞中NPC1蛋白的水平。鉴定出了10个新突变（Q92R、C177Y、R518W、W942C、R978C、A1035V、2129delA、3662delT、IVS23+1 G>A和IVS16-82 G>A）。突变谱似乎与生化表型相关。剪接突变I1061T和A1035V对应于“经典”等位基因，而三个错义突变C177Y、R978C和P1007A可被定义为“变异”等位基因。迄今为止描述的所有“变异”突变似乎都聚集在跨膜区8和9之间富含半胱氨酸的腔内环内，C177Y是一个显著的例外。与P1007A不同，后一种突变等位基因与NPC1蛋白水平降低和疾病的严重病程相关，并揭示了“变异”突变的一个新位置，即位于蛋白质N末端的腔内环。
