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）的额外副本的存在与唐氏综合症 (DS) 相关， 这是人类最常见的活产染色体改变。在美国，DS 有一个 DS 的发病率约为每 691 名新生儿中就有 1 人，并且 DS 患者表现出多种临床表型； 神经系统受累是负担最重的。如今，人类 21 三体仍然是主要的 发育迟缓和智力障碍的遗传原因几乎具有普遍的外显率。有效 针对此类临床表现的治疗将具有变革性，因为这些治疗可以深刻地 改善 DS 患者的生活质量。基于特定表型的普遍假设 DS 的增加受到人类 21 号染色体（Hsa21）上特定基因剂量增加的影响， 已经详细研究了特定的基因组片段，即人类片段三体性，以确定 基因型-表型关系，最终目标是识别剂量敏感的致病基因， 可以作为治疗靶点。然而，由于缺乏足够的支持，这些努力受到严重阻碍。 信息丰富的节段三体性病例数量。幸运的是，基于进化的更富有成果的替代方案 人类和老鼠之间的保护也一直在追求，这种方法使得遗传 解剖工作进展得更快。例如，小鼠 DYRK1A 基因直向同源物的分析 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 认知缺陷和直系同源 Hsa21 基因。为了进一步开展基因解剖工作，我们开发了 大量小鼠突变体在 Hsa21 直系同源区域携带不同的染色体重排。 在本申请的目标 1 中，我们将利用这些小鼠突变体并通过 CRISPR 开发新的突变体 - 介导的基因组工程，以加强我们识别新的剂量敏感致病基因的努力 DS 潜在的发育性认知缺陷，其人类直系同源物可以作为治疗靶点 与 DYRK1A 基因一起。除了通过增加基因剂量发挥作用外，人类 21 三体性可能还具有 影响表型的其他方式，例如通过改变核结构从而改变基因表达。在 本应用的目标 2，我们将使用小鼠模型来测试第二个假设。我们相信成功的 我们提出的项目将对 DS 的一般研究和 DS 相关的研究产生变革性的影响 尤其是发育性认知缺陷。

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.