DiProspero Nicholas A, Chen Er-Yun, Charles Vinod, Plomann Markus, Kordower Jeffrey H, Tagle Danilo A
Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, NIH, 9000 Rockville Pike, Bethesda, MD 20892, USA.
J Neurocytol. 2004 Sep;33(5):517-33. doi: 10.1007/s11068-004-0514-8.
Huntington's disease (HD) is caused by a polyglutamine repeat expansion in the N-terminus of the huntingtin protein. Huntingtin is normally present in the cytoplasm where it may interact with structural and synaptic elements. The mechanism of HD pathogenesis remains unknown but studies indicate a toxic gain-of-function possibly through aberrant protein interactions. To investigate whether early degenerative changes in HD involve alterations of cytoskeletal and vesicular components, we examined early cellular changes in the frontal cortex of HD presymptomatic (PS), early pathological grade (grade 1) and late-stage (grade 3 and 4) patients as compared to age-matched controls. Morphologic analysis using silver impregnation revealed a progressive decrease in neuronal fiber density and organization in pyramidal cell layers beginning in presymptomatic HD cases. Immunocytochemical analyses for the cytoskeletal markers alpha -tubulin, microtubule-associated protein 2, and phosphorylated neurofilament demonstrated a concomitant loss of staining in early grade cases. Immunoblotting for synaptic proteins revealed a reduction in complexin 2, which was marked in some grade 1 HD cases and significantly reduced in all late stage cases. Interestingly, we demonstrate that two synaptic proteins, dynamin and PACSIN 1, which were unchanged by immunoblotting, showed a striking loss by immunocytochemistry beginning in early stage HD tissue suggesting abnormal distribution of these proteins. We propose that mutant huntingtin affects proteins involved in synaptic function and cytoskeletal integrity before symptoms develop which may influence early disease onset and/or progression.
亨廷顿舞蹈症（HD）由亨廷顿蛋白N端的多聚谷氨酰胺重复序列扩增引起。亨廷顿蛋白通常存在于细胞质中，可能与结构和突触成分相互作用。HD发病机制尚不清楚，但研究表明可能通过异常的蛋白质相互作用产生毒性功能获得。为了研究HD早期的退行性变化是否涉及细胞骨架和囊泡成分的改变，我们检查了HD症状前（PS）、早期病理分级（1级）和晚期（3级和4级）患者额叶皮质的早期细胞变化，并与年龄匹配的对照组进行比较。使用银浸染的形态学分析显示，从症状前HD病例开始，锥体细胞层的神经元纤维密度和组织逐渐降低。对细胞骨架标记物α-微管蛋白、微管相关蛋白2和磷酸化神经丝进行免疫细胞化学分析，结果显示早期分级病例中染色同时缺失。对突触蛋白进行免疫印迹分析显示，结合蛋白2减少，在一些1级HD病例中明显减少，在所有晚期病例中显著降低。有趣的是，我们发现两种突触蛋白，发动蛋白和PACSIN 1，免疫印迹未显示变化，但从HD早期组织开始，免疫细胞化学显示其显著缺失，表明这些蛋白分布异常。我们提出，突变的亨廷顿蛋白在症状出现之前就会影响参与突触功能和细胞骨架完整性的蛋白质，这可能会影响疾病的早期发作和/或进展。
