MUTANT MODELS TO STUDY HUNTINGTON'S DISEASE

亨廷顿氏病（HD）的表现与一种 基因中CAG三核苷酸重复扩增（编码多聚谷氨酰胺）（HD） 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 亨廷顿蛋白的正常功能从消融的结果， 小鼠中的关联基因（Hdh）。为了这个目的，我们已经扰乱了HDH 基因在胚胎干细胞（ES细胞）和获得广泛的嵌合小鼠 通过将定向克隆注射到宿主胚泡中。当嵌合体 传播的突变被确定，我们建议启动一个 杂合后代之间的育种计划，以获得纯合 突变体，并详细研究其无效表型。 与第一个目标相辅相成的第二个目标将 是一种有望模拟HD的小鼠模型的开发。这将是 再次使用基因靶向策略，通过替换一个区域， Hdh基因的同源片段与人HD基因的同源片段， 青少年HD患者的DNA，其含有高度扩增的CAG， 三胞胎（94 vs. 7在HDH）。这一现象的表型后果 小鼠中的替代突变，应该表现出显性， 与无效突变体不同;根据我们的工作， 假设，突变亨廷顿蛋白，含有扩展的多聚谷氨酰胺 伸展，通过正常途径保持活动，但也获得 与其他细胞效应物的新的异常相互作用。杂合 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， 详细的组织病理学和免疫化学分析该动物模型 应该是有价值的各种研究，包括潜在的 测试治疗方案。 我们提出的基因计划应该允许建立 定义的突变和它们的表型之间的因果关系 结果，并具有与人类相关的问题的优点 疾病将在体内和整个背景下解决， 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.