Generation and analysis of new mouse models to determine novel therapeutic targets for Down syndrome-associated cognitive deficits

摘要 人类21号染色体（21三体）的额外拷贝的存在与唐氏综合征（DS）有关， 这是人类最常见的活产染色体变异。在美国，DS有一个 发病率约为1/691新生儿，DS个体表现出多种临床表型; 神经系统受累是最繁重的。今天，人类21三体仍然是一个领先的 发育迟缓和智力残疾的遗传原因，几乎普遍的智力障碍。有效 这种临床表现的治疗将是变革性的，因为这些治疗可以深刻地 改善DS患者的生活质量。基于流行的假设，特定的表型 的DS受人类21号染色体（Hsa21）上特定基因剂量增加的影响， 特定的基因组片段，即，人类节段性三体，已经被详细研究以建立 基因型-表型关系，最终目标是鉴定剂量敏感的致病基因， 可以作为治疗靶点。然而，由于缺乏足够的人力资源， 提供信息的节段性三体病例数。幸运的是，一个更富有成效的替代方案， 人类和小鼠之间的保护也一直在进行，这种方法使遗传 解剖工作进展得更快。例如，小鼠中DYRK1A基因直系同源物的分析 证明该基因是DS相关发育性认知缺陷的致病决定因素; 随后，这些结果成为唯一成功的涉及发育的临床试验的基础。 认知缺陷和正向Hsa21基因。为了进一步进行基因解剖，我们开发了一种 大量小鼠突变体在Hsa21正向区携带不同的染色体重排。 在本申请的目的1中，我们将利用这些小鼠突变体并通过使用CRISPR-1来开发新的突变体。 介导的基因组工程，以加强我们的努力，以确定新的剂量敏感的致病基因 DS的潜在发育认知缺陷，其人类直系同源物可作为治疗靶点 沿着DYRK1A基因。除了通过基因剂量增加起作用外，人类21三体可能具有 影响表型的其他方式，如通过改变核结构，从而改变基因表达。在 本申请的目的2，我们将通过使用小鼠模型来测试第二个假设。我们相信， 我们建议的项目将对DS的研究产生变革性的影响， 尤其是发展性认知缺陷

ABSTRACT The presence of an extra copy of human chromosome 21 (trisomy 21) is associated with Down syndrome (DS), and this is the most common live-born chromosomal alteration in humans. In the United States, DS has an incidence rate of approximately 1 in 691 newborns, and individuals with DS exhibit many clinical phenotypes; nervous system involvement is among the most burdensome. Today, human trisomy 21 remains a leading genetic cause of developmental delays and intellectual disabilities with near universal penetrance. Effective treatments for such clinical manifestations would be transformative because these treatments could profoundly improve the quality of life for individuals with DS. Based on the prevailing hypothesis that particular phenotypes of DS are affected by the dosage increase of specific genes on human chromosome 21 (Hsa21), triplications of particular genomic segments, i.e., human segmental trisomies, have been studied in detail to establish genotype–phenotype relationships with the ultimate goal of identifying dosage sensitive causative genes that can serve as therapeutic targets. However, such efforts have been severely hampered by the lack of an adequate number of informative segmental trisomy cases. Fortunately, amore fruitful alternative based on the evolutionary conservation between humans and mice has also been pursued, and this approach has allowed the genetic dissection efforts to advance much more rapidly. For example, analyses of the DYRK1A gene ortholog in mice demonstrated that this gene is a causative determinant for DS-associated developmental cognitive deficits; subsequently, these results served as the basis for the only successful clinical trials involving developmental cognitive deficits and orthologous Hsa21 genes. To further the genetic dissection efforts, we have developed a large number of mouse mutants carrying different chromosomal rearrangements in Hsa21 orthologous regions. In Aim 1 of this application, we will utilize these mouse mutants and develop new mutants by using CRISPR - mediated genome engineering to enhance our efforts to identify novel dosage sensitive causative genes underlying developmental cognitive deficits in DS, whose human orthologs can serve as therapeutic targets along with the DYRK1A gene. Besides acting through a gene dosage increase, human trisomy 21 may have other ways of influencing phenotypes, such as by altering the nuclear architecture and thus gene expression. In Aim 2 of this application, we will test this second hypothesis by using mouse models. We believe the success of our proposed project will have a transformative impact on research on DS in general and on DS-associated developmental cognitive deficits in particular.