NEUROPATHOLOGY AND PATHOGENESIS OF HUNTINGTON' DISEASE

描述：（来自申请人摘要的逐字逐句）这是一个竞争性的 NS 28721的延续。在这个为期5年的项目中，申请人将 检验亨廷顿病（HD）是由AMPA引起的假设 受体（AMPAR）介导的兴奋性毒性。他提出HD基因缺陷 导致选择性纹状体神经元死亡，通过1）富集AMPAR， 纹状体投射神经元和小清蛋白能的皮质输入 HD中的中间神经元。2)纹状体中含有AMPAR的GluR 2的优势 投射到苍白球内段的神经元负责它们的小 HD的脆弱性和3）HD突变减少了II组的数量 皮质纹状体末梢上的mGluRs，从而增加皮质激活， 纹状体神经元的兴奋性毒性。 主要假设基于以下观察： a. HD基因产物在大脑中广泛表达，而神经元 在HD中死亡的细胞定位于纹状体 B.与HD蛋白相互作用的细胞类型特异性蛋白质都不是特异性的 脆弱的纹状体神经元 C.在特定类型的纹状体神经元中，亨廷顿蛋白的水平似乎并不影响 与脆弱性相关。 D.提示在HD转基因小鼠（Bates R6/2）中，II组mGluRs 下调，sEPSP频率增加。 e. HD病理学可通过3-NP和喹啉酸给药再现 F.死亡的神经元富含皮层输入。 G.死亡的神经元富含AMPAR，其中一些似乎更 GluR 2假说（GluR 2 hypothesis） 从这些观察结果中，申请人得出结论“HD突变可能导致 皮质纹状体神经元的破坏性，而不是使纹状体神经元 脆弱" 这些假设将在5个特定目标中进行检验： 目的1：应用单细胞RT-PCR、免疫沉淀、LM和EM免疫标记技术 为了表征存在的AMPA受体的丰度和亚基组成， 对HD易感和HD抵抗纹状体中间神经元和投射神经元的影响 老鼠的类型 目的2：描述纹状体中间神经元和投射之间的差异 AMPAR神经元介导对皮层输入的突触反应， 依赖AMPA生理学（Ca渗透性、整流和脱敏） 大鼠 目的3：从药理学上表征AMPAR的作用， 选择性死亡中mGluR 2/3调节的皮质纹状体谷氨酸释放 的纹状体神经元在大鼠长期给予3 NP，HD模型。 目的4：应用原位杂交组织化学、光镜和电镜免疫组化技术， 在猴纹状体神经元和HD纹状体中， HD易感和HD抗性纹状体神经元中的AMPAR亚基是一致的 在选择性神经退化中的假设作用。 目的5：应用原位杂交组织化学、光镜和电镜免疫组化技术， 在HD的转基因大鼠模型和人类HD样本中，无论HD是否 突变降低皮质纹状体神经元及其纹状体内的mGluR 2/3 terminals.

DESCRIPTION: (Verbatim from the Applicant's Abstract) This is a competing continuation of NS 28721. In this upcoming 5-year project, the applicant will examine the hypothesis that Huntington's disease (HD) is caused by AMPA receptor (AMPAR)-mediated excitotoxicity. He proposes that the HD gene defect leads to selective striatal neuronal death by 1) enrichment in AMPARs and cortical inputs in striatal projection neurons and parvalbuminergic interneurons in HD. 2) A preponderance of GluR2 containing AMPARs in striatal neurons projecting to the internal pallidal segment accounts for their lesser vulnerability in HD and 3) The HD mutation decreases the numbers of group II mGluRs on corticostriatal terminals, thereby increasing cortical activation and excitotoxicity of striatal neurons. The main hypotheses are based on the following observations: a. The HD gene product is widely expressed in the brain, whereas the neurons killed in HD are localized to the striatum b. No cell-type specific proteins that interact with HD proteins are specific to vulnerable striatal neurons. c. The level of huntingtin in a given type of striatal neuron does not seem to correlate with vulnerability. d. There is suggestion that in HD transgenic mice (Bates R6/2), group II mGluRs are downregulated and that sEPSP frequency is increased. e. HD pathology can be reproduced by 3-NP and by quinolinic acid administration f. Neurons that die are rich in cortical input. g. Neurons that die are rich in AMPARs, some of which appear to be more deficient in GluR2 (the GluR2 hypothesis). From these observations, the applicant concludes "the HD mutation may render corticostriatal neurons destructive rather than render striatal neurons vulnerable." These hypotheses will be tested in 5 Specific Aims: Aim 1: Use single cell RT-PCR, immunoprecipitation and LM and EM immunolabeling to characterize the abundance and subunit composition of AMPA receptors present on HD-vulnerable and HD-resistant striatal interneuron and projection neuron types in rats. Aim 2: Characterize differences between striatal interneurons and projection neurons in AMPAR mediated synaptic responses to cortical input and in subunit dependent AMPA physiology (Ca permeability, rectification and desensitization) in rats Aim 3: Pharmacologically characterize the role of AMPARs and mGluR2/3-regulatable corticostriatal glutamate release in the selective death of striatal neurons in rats chronically administered 3NP, a model of HD. Aim 4: Use in-situ hybridization histochemistry, LM and EM immuno to determine in striatal neurons in monkey and in HD striatum whether the distribution of AMPAR subunits in HD vulnerable and HD resistant striatal neurons is consistent with their hypothesized role in selective neurodegeneration. Aim 5: Use in-situ hybridization histochemistry, LM and EM immuno to determine in a transgenic rat model of HD and in human HD specimens whether or not the HD mutation decreases mGluR2/3 in corticostriatal neurons and their intrastriatal terminals.