Transgenic Mouse Models of Huntington's Disease

描述（由申请人提供）：该提案将使用四种不同的小鼠模型研究亨廷顿舞蹈病（HD）中检测到的功能障碍的细胞机制。HD的致命突变在蛋白质亨廷顿蛋白中产生扩增的三核苷酸（GAG）重复。它引起选择性神经变性，尤其是纹状体和皮层，机制不明。我们将研究的每种HD模型都表现出由独特的转基因结构或“敲入”GAG重复长度产生的不同表型。通过评估多种模型，我们将能够更详细地检查功能障碍，并了解HD和模型共同的生理变化的特异性和顺序。基于我们的初步研究，我们在两种模型中发现了几种常见的细胞缺陷。纹状体中n -甲基- d -天冬氨酸（NMDA）受体的反应性增强与Ca2+通量增加有关，K+电导显着减少，皮质纹状体突触反应发生变化。第三个模型也显示了对NMDA的增强反应。其中一些变化可能使纹状体中等棘神经元易受兴奋性毒性损伤。利用生理学方法，我们将研究关于HD功能障碍的细胞机制的四种假设：1)嗜离子性谷氨酸受体功能的改变和纹状体神经元诱发和自发兴奋性突触输入的变化2)代谢性谷氨酸和多巴胺能受体调节嗜离子性谷氨酸受体功能的改变3)K+电导的改变和4)Ca2+电导的改变。将通过使用症状前或明显运动体征发展后的动物来研究变化的确切开始与行为缺陷表达的关系。我们将检查纹状体和皮质纹状体神经元，在切片准备或急性解离细胞中可视化，通过电流和电压钳分析来表征基本功能。因为HD破坏了许多不同的能力——智力、身体和情感——从这项研究中获得的见解阐明了HD的细胞功能障碍，这与理解其他GAG重复疾病和与蛋白质聚集病理相关的神经系统疾病（如阿尔茨海默病和帕金森病）有关。

DESCRIPTION (provided by applicant): This proposal will examine cellular mechanisms underlying the dysfunctions detected in Huntington's disease (HD) using four different murine models. The lethal mutation in HD produces an expanded trinucleotide (GAG) repeat within the protein huntingtin. It causes selective neurodegeneration especially in the striatum and cortex, by an unidentified mechanism. Each of the HD models we will examine exhibits a different phenotype produced by unique transgene constructs or 'knocked-in" GAG repeat lengths. By evaluating multiple models we will be able to examine the dysfunctions in more detail and understand the specificity and sequence of physiological changes common to HD and the models. Based on our preliminary studies, we have uncovered several common cellular deficits in two models. These are enhanced responsiveness of N-methyl-D-aspartate (NMDA) receptors in the striatum associated with increased Ca2+ flux, a marked decrease in K+ conductances and a change in the corticostriatal synaptic response. A third model also displays the enhanced response to NMDA. Some of these changes potentially predispose striatal medium-sized spiny neurons to excitotoxic damage. Using a physiological approach, we will examine four hypotheses concerning the cellular mechanisms of dysfunction in HD: 1) alterations in ionotropic glutamate receptor function and changes in evoked and spontaneous excitatory synaptic inputs to striatal neurons 2) alterations in metabotropic glutamate and dopaminergic receptor modulation of ionotropic glutamate receptor function, 3) alterations in K+ conductances and 4) alterations in Ca2+ conductances. The precise onset of changes will be investigated in relationship to the expression of behavioral deficits by using animals that are presymptomatic or after development of overt motor signs. We will examine striatal and corticostriatal neurons, visualized in the slice preparation or acutely dissociated cells, to characterize basic functions by current- and voltage-clamp analyses. Because HD destroys so many different capabilities - intellectual, physical and emotional - the insights gained from this research elucidating the cellular malfunctions in HD are relevant to understanding other GAG repeat disorders and neurological diseases associated with protein aggregate pathologies like Alzheimer's and Parkinson's disease.