Park Walter D, O'Brien John F, Lundquist Patrick A, Kraft Daniel L, Vockley Cate Walsh, Karnes Pamela S, Patterson Marc C, Snow Karen
Division of Laboratory Genetics, Department of Laboratory Medicine and Pathology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
Hum Mutat. 2003 Oct;22(4):313-25. doi: 10.1002/humu.10255.
The two known complementation groups of Niemann-Pick Type C disease, NPC1 and NPC2, result from non-allelic protein defects. Both the NPC1 and NPC2 (HE1) gene products are intimately involved in cholesterol and glycolipid trafficking and/or transport. We describe mutation analysis on samples from 143 unrelated affected NPC patients using conformation sensitive gel electrophoresis and DNA sequencing as the primary mutation screening methods for NPC1 and NPC2, respectively. These methods are robust, sensitive, and do not require any specialized laboratory equipment. Analyses identified two NPC1 mutations for 115 (80.4%) patients, one NPC1 mutation for 10 (7.0%) patients, two NPC2 mutations for five (3.5%) patients, one NPC2 mutation for one (0.7%) patient, and no mutations for 12 (8.4%) patients. Thus, mutations were identified on 251 of 286 (88%) disease alleles, including 121 different mutations (114 in NPC1 and seven in NPC2), 58 of which are previously unreported. The most common NPC1 mutation, I1061T, was detected on 18% of NPC alleles. Other NPC1 mutations were mostly private, missense mutations located throughout the gene with clustering in the cysteine-rich luminal domain. Correlation with biochemical data suggests classification of several mutations as severe and others as moderate or variable. The region between amino acids 1038 and 1253, which shares 35% identity with Patched 1, appears to be a hot spot for mutations. Additionally, a high percentage of mutations were located at amino acids identical to the NPC1 homolog, NPC1L1. Biochemical complementation analysis of cases negative for mutations revealed a high percentage of equivocal results where the complementation group appeared to be non-NPC1 and non-NPC2. This raises the possibilities of an additional NPC complementation group(s) or non-specificity of the biochemical testing for NPC. These caveats must be considered when offering mutation testing as a clinical service.
尼曼-匹克C型病已知的两个互补群，NPC1和NPC2，是由非等位基因蛋白缺陷导致的。NPC1和NPC2（HE1）基因产物都与胆固醇和糖脂的运输及转运密切相关。我们分别使用构象敏感凝胶电泳和DNA测序作为NPC1和NPC2的主要突变筛查方法，对143例无亲缘关系的NPC患者样本进行了突变分析。这些方法可靠、灵敏，且不需要任何专门的实验室设备。分析发现，115例（80.4%）患者有两个NPC1突变，10例（7.0%）患者有一个NPC1突变，5例（3.5%）患者有两个NPC2突变，1例（0.7%）患者有一个NPC2突变，12例（8.4%）患者未发现突变。因此，在286个疾病等位基因中的251个（88%）上鉴定出了突变，包括121种不同的突变（NPC1中有114种，NPC2中有7种），其中58种是以前未报道过的。最常见的NPC1突变I1061T在18%的NPC等位基因上被检测到。其他NPC1突变大多是私有的错义突变，分布在整个基因中，在富含半胱氨酸的腔内结构域有聚集现象。与生化数据的相关性表明，一些突变可分类为严重突变，另一些则为中度或可变突变。氨基酸1038至1253之间的区域与Patched 1有35%的同源性，似乎是一个突变热点。此外，高比例的突变位于与NPC1同源物NPC1L1相同的氨基酸位置。对突变阴性病例的生化互补分析显示，相当一部分结果不明确，其中互补群似乎既不是NPC1也不是NPC2。这增加了存在额外的NPC互补群或NPC生化检测不特异的可能性。在将突变检测作为临床服务提供时，必须考虑这些注意事项。
