NEUROPATHOLOGY AND PATHOGENESIS OF HUNTINGTON' DISEASE

描述：(逐字摘自申请者的摘要)这是一场竞争 继续NS 28721。在即将到来的5年项目中，申请者将 检验亨廷顿病(HD)是由AMPA引起的假设 受体(AMPAR)介导的兴奋毒性。他提出HD基因缺陷 通过以下方式导致选择性纹状体神经元死亡：1)AMPAR和 纹状体投射神经元和副蛋白能神经元的皮质传入 HD的中间神经元。2)在纹状体中含有AMPAR的GluR2占优势 投射到苍白球内侧节的神经元所占比例较小 HD的脆弱性和3)HD突变减少了II组的数量 皮质纹状体终末上的mGluRs，从而增加皮质的激活和 纹状体神经元的兴奋性毒性。 主要假设基于以下观察结果： A.HD基因产物在大脑中广泛表达，而神经元 在HD中被杀的人定位于纹状体 B.与HD蛋白相互作用的任何细胞类型的特定蛋白都不是特定的 到脆弱的纹状体神经元。 C.在一种特定类型的纹状体神经元中，亨廷顿蛋白的水平似乎不会 与脆弱性相关。 D.提示在HD转基因小鼠(Bates R6/2)中，第二组mGluRs SEPSP频率被下调，sEPSP频率增加。 E.HD病理可通过3-NP和喹啉酸注射复制 死亡的神经元有丰富的皮质输入。 G.死亡的神经元富含AMPAR，其中一些似乎比 缺乏GluR2(GluR2假说)。 从这些观察中，申请人得出结论：HD突变可能会导致 皮质纹状体神经元破坏纹状体神经元，而不是破坏纹状体神经元 易受攻击。“ 这些假设将在5个具体目标中得到检验： 目的1：应用单细胞RT-PCR、免疫沉淀和免疫组织化学标记 表征目前存在的AMPA受体的丰度和亚基组成 HD易感和抗HD纹状体中间神经元和投射神经元的研究 老鼠的类型。 目的2：描述纹状体中间神经元和投射的差异 AMPAR中的神经元介导对皮质和亚单位的突触反应 依赖AMPA的生理(钙通透性、整流和脱敏) 在大鼠身上 目的3：从药理学角度研究AMPAR和AMPAR的作用 选择性死亡中mGluR2/3调节的皮质纹状体谷氨酸释放 慢性给予HD模型3NP大鼠纹状体神经元的变化。 目的4：应用原位杂交组织化学、光镜和免疫组织化学方法检测 在猴纹状体神经元和HD纹状体中是否有分布 HD易损性和HD抗性纹状体神经元中的Ampar亚单位是一致的 它们在选择性神经退行性变中的假想作用。 目的5：应用原位杂交组织化学、光镜和电镜免疫组织化学方法检测 在HD转基因大鼠模型和人类HD标本中，无论HD 突变降低皮质纹状体神经元及其纹状体内mGluR2/3 终点站。

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.