MUTANT MODELS TO STUDY HUNTINGTON'S DISEASE

亨廷顿病(HD)的表现与 CAG三核苷酸重复扩增(编码聚谷氨酰胺)在一个基因(HD)中 位于染色体4p16.3，编码一种蛋白质(亨廷顿蛋白) 未知函数。我们的目标之一是提供有关 从消融结果判断亨廷顿蛋白的正常功能 小鼠的同源基因(Hdh)。为此，我们扰乱了HDH 基因在胚胎干细胞中的表达并获得广泛嵌合的小鼠 通过将目标克隆注射到宿主胚泡中。当嵌合体 传播突变的情况下，我们建议启动一个 杂合子后代之间的育种计划，以获得纯合子 并对其无效表型进行了详细研究。 将同时追求的第二个目标，以补充第一个意愿 是一种有望模拟HD的老鼠模型的开发。这将是 再次使用基因打靶策略，通过替换一个区域来完成 Hdh基因与克隆的人hD基因同源片段的比较 青少年HD患者的DNA中含有高度扩增的CAG 三胞胎(94对7)。这种现象的表型后果 小鼠的替换突变应该是显性的，这是可以预料的。 与零突变体不同；根据我们的工作 假设，突变的亨廷顿蛋白含有一种扩展的聚谷氨酰胺 伸展，通过正常的途径保持活动，但也获得 与其他细胞效应器的新的、不正常的相互作用。杂合子 携带这种“显性”突变的纯合子小鼠将被研究 广泛用于表型表现，使用各种测试 可以评估运动、认知和行为异常，还可以通过 详细的组织病理学和免疫化学分析。这个动物模型 应该对各种研究有价值，包括潜在的 治疗方案的测试。 我们提出的遗传计划应该允许建立 已定义突变与其表型之间的因果关系 结果，并具有与人类相关的问题的优势 疾病将在活体内和在整个 发展模式生物。

The manifestation of Huntington's disease (HD) has been correlated with a CAG trinucleotide repeat expansion (encoding polyglutamine) in a gene (HD) residing on chromosome 4p16.3 that encodes a protein (huntingtin) of unknown function. One of our aims is to contribute information pertaining to the normal function of huntingtin from the results of ablation of the cognate gene (Hdh) in mice. For this purpose, we have disrupted the Hdh gene in embryonic stem (ES) cells and obtained extensively chimeric mice by injecting targeted clones into host blastocysts. When chimeras transmitting the mutation are identified, we propose to initiate a breeding program between heterozygous offspring, to obtain homozygous mutants and study in detail their null phenotype. A second aim that will be pursued in parallel to complement the first will be the development of a mouse model hopefully simulating HD. This will be accomplished using again a gene targeting strategy, by replacing a region of the Hdh gene with the homologous segment of a human HD gene cloned from the DNA of a juvenile HD patient, which contains highly expanded CAG triplets (94 vs. 7 in Hdh). The phenotypic consequences of this replacement mutation in mice, which should exhibit dominance, are expected to be different than those in null mutants; according to our working hypothesis, the mutant huntingtin, containing an expanded polyglutamine stretch, maintains activity through a normal pathway, but also acquires novel, abnormal interactions with other cellular effectors. Heterozygous and homozygous mice carrying this "dominant" mutation will be studied extensively for phenotypic manifestations, using a variety of tests that can assess movement, cognitive and behavioral abnormalities, and also by detailed histopathological and immunochemical analyses. This animal model should be valuable for a variety of studies, including the potential testing of therapeutic regimes. The genetic program that we propose should allow the establishment of causal relationships between defined mutations and their phenotypic consequences, and has the advantage that questions pertinent to a human disease will be addressed in vivo and in the context of the entire developing model organism.