Development of a conditional inducible Huntington’s disease murine model to study complex pathogenic mechanisms

亨廷顿氏病（HD）是由一个异常的三核苷酸重复组成的单基因缺陷引起的 Huntingtin（HTT）。这种遗传缺陷引起了广泛的病理生理变化 导致一种多系统疾病，其最典型的特征是由其神经系统疾病引起的， 改变：神经精神疾病、运动缺陷和纹状体变性。然而，同样重要的是， 由影响其他器官、组织和细胞系统的损伤引起的疾病特征，包括 异常炎症反应、骨骼肌功能障碍、代谢改变和肝功能障碍。 考虑到这种全身性的参与，这些损伤可能与神经功能缺损协同作用，进一步改变 他们的病程。为了使HD发病机制的研究进一步复杂化，最近的研究表明， 致病性改变也是由早期神经发育期间发生的异步事件引起的， 出生后的成熟以及整个成年生活。这种复杂的相互作用，涉及多个细胞 变化，时间依赖性过程及其协调的相互作用，使得特别具有挑战性， 阐明主要的机械事件和过程，并作为必然结果，促进精确设计 药物干预。为了有效地剖析特定的主要病理生理机制，有必要 使用能够在HD靶向细胞中条件性诱导全长突变基因的遗传工具， 发病的时间和地点。为了实现这一目标，我们创建了一个 一种新的遗传模型，其人全长突变HTT转基因的表达被 HTT内含子1内存在loxP floxed STOP盒，iBACHD菌株。本R 03的总体目标 应用的目的是从遗传学上表征iBACHD菌株，并验证其用于更好地模拟HD， vivo. iBACHD模型的表征和验证将通过三个特定目标实现： (1)根据拷贝数和基因组位置表征转基因整合;（2） 图10示出了在施用后突变的人HTT的STOP盒功能完整性和表达模式的表征。 STOP盒的切除重组;和（3）iBACHD模型重现主要的 HD的特征：神经精神异常、运动缺陷和纹状体变性。这些研究 意义重大，因为它们将填补我们实验武器库中的一个关键空白，以剖析多个 系统紊乱我们的研究将产生一种高度创新的工具， 基于小鼠模型的机制研究现状，致病基因表达的多样性较低， 蛋白质产品

Huntington’s disease (HD) is caused by a single gene defect consisting of an aberrant trinucleotide repeat expansion in Huntingtin (HTT). This genetic defect gives rise to a broad array of pathophysiological alterations leading to a multi-system disease whose most characteristic traits are those resulting from its neurological alterations: neuropsychiatric disorders, motor deficits and striatal degeneration. However, no less important are those disease traits resulting from impairments affecting other organ, tissue and cellular systems, including aberrant inflammatory responses, skeletal muscle dysfunction, metabolic alterations, and liver dysfunction. Given this systemic involvement, these impairments likely synergize with neurological deficits, further altering their disease course. To further complicate the study of HD pathogenesis, recent investigations have shown that pathogenic alterations also result from asynchronous events taking place during early neural development, postnatal maturation as well as throughout adult life. This complex interplay, involving multiple cellular alterations, time-dependent processes and their concerted interactions, has made it particularly challenging to elucidate primary mechanistic events and processes and, as a corollary, to promote the design of precision medicine interventions. To effectively dissect specific primary pathophysiological mechanisms, it is necessary to employ a genetic tool with the ability to conditionally induce the full-length mutant gene in HD-targeted cells at the relevant times and places underlying disease pathogenesis. To accomplish this goal, we have created a novel genetic model whose expression of the human full-length mutant HTT transgene is abrogated by the presence of a loxP floxed STOP cassette within HTT intron 1, the iBACHD strain. The overall goal of this R03 application is to genetically characterize the iBACHD strain, and to validate its use for better modeling of HD in vivo. The characterization and validation of the iBACHD model will be achieved through three Specific Aims: (1) the characterization of transgene integration in term of copy number and genomic location; (2) the characterization of STOP cassette functional integrity and the pattern of expression of mutant human HTT after excisional recombination of the STOP cassette; and (3) ability of the iBACHD model to recapitulate the main hallmarks of HD: neuropsychiatric abnormalities, motoric deficits and striatal degeneration. These studies are significant as they will fill a critical gap in our experimental arsenal to dissect individual mechanisms of a multi- system disorder. Our studies will yield a highly innovative tool that would result in a departure from the status quo of mechanistic studies based on mouse models with less versatile expression of the pathogenic gene and protein product.