Transgenic Mouse Models of Huntington's Disease

描述（由申请人提供）：本提案将使用四种不同的小鼠模型来检查在亨廷顿病（HD）中检测到的功能障碍的细胞机制。HD中的致死突变在蛋白亨廷顿内产生扩展的三核苷酸（GAG）重复。它通过一种未知的机制引起选择性神经变性，特别是在纹状体和皮质。我们将检查的每种HD模型都表现出由独特的转基因构建体或“敲入”GAG重复长度产生的不同表型。通过评估多个模型，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，我们发现了两种模型中几种常见的细胞缺陷。这些是纹状体中N-甲基-D-天冬氨酸（NMDA）受体的反应性增强，与Ca 2+通量增加、K+电导显著降低和皮质纹状体突触反应变化相关。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型多刺神经元易受兴奋性毒性损伤。使用生理学方法，我们将研究关于HD功能障碍的细胞机制的四个假设：1）离子型谷氨酸受体功能的改变以及对纹状体神经元的诱发和自发兴奋性突触输入的改变2）离子型谷氨酸受体功能的代谢型谷氨酸和多巴胺能受体调节的改变，3）K+电导的改变; 4）Ca ~（2+）电导的改变。将使用出现症状前或明显运动体征后的动物，研究变化的确切发作与行为缺陷表达的关系。我们将研究纹状体和皮质纹状体神经元，在切片制备或急性分离的细胞中可视化，通过电流和电压钳分析来表征基本功能。由于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阐明HD中细胞功能障碍的见解与理解其他GAG重复障碍和与蛋白质聚集病理学相关的神经系统疾病（如阿尔茨海默氏症和帕金森氏症）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.