Developmental cerebellar deficits caused by Chd8 haploinsufficiency

摘要 小脑(CB)在本体感觉和精细运动控制中的作用是公认的，但更多的是 最近的研究也强烈地表明，这种结构与语言等高级认知功能有关， 认知加工和情感调节。尽管这些小脑功能之间的紧密联系 以及神经发育障碍(NDDS)，如自闭症谱系障碍(ASD)和智力障碍 残疾(ID)，在NDD研究中，CB的非运动贡献的作用经常被忽视 尤其是在这些疾病的动物模型中，与大脑等结构相比，研究不足 大脑皮质和海马体。随着人们逐渐认识到CB在更高层次上发挥着关键作用 大脑功能和小脑功能紊乱可导致ASD和NDD相关表型 这是关注新城疫动物模型中CB功能障碍的强有力的理由。染色质中的从头突变- 重塑因子CHD8(Chromodomain-helicase DNA-bindingProtein 8)已成为一种重要的遗传物质 原因因素与ASD密切相关，更普遍地与NDDS有关。怀有新希望的个人 CHD8杂合突变通常具有ASD、认知障碍和 巨头畸形，与其他表型也出现在一些患者。多个鼠标CHD8型号已经推出 发表(包括我们的小组)，杂合突变体表现出相关的表型，包括 大头畸形和行为缺陷。迄今为止，与CHD8突变相关的动物病理模型 主要集中在前脑，特别是大脑皮层。在已发表的和初步的研究中，我们 确定了小脑深部核团的结构改变和小脑解剖改变的证据 CHD8杂合突变小鼠的生理学研究。我们假设CHD8对小脑的影响 突变导致了更高层次的认知和行为病理。在这里，我们提出了初步的工作 为了测试这一模型，定义CHD8单倍体功能不全对小脑结构和 跨解剖、基因组和电生理维度的功能。在目标1中，我们将测试CB 在构型和细胞特性方面对CHD8单倍体不足的敏感性。在目标2中，我们将测试 小脑神经元在电生理、转录和形态水平上的表型。这些 实验将建立杂合子CHD8突变对小鼠CB的影响，联系神经解剖学， 神经功能和信号传递。这些研究将为未来的工作提供关键证据，以确定具体的 CB中与CHD8杂合消融相关的表型及其与建立电路水平的关系 了解CHD8突变如何影响CB内部以及CB与其他 结构。如果成功，这项工作将带来研究NDDS小脑功能障碍的新途径 通过将一个高度可信和最优先的基因与CB中的细胞、分子和结构缺陷联系起来，ASD。

SUMMARY The role of the cerebellum (CB) in proprioception and fine motor control is well-established, however more recent studies also strongly implicate this structure in higher order cognitive functions such as language, cognitive processing and affective regulation. Despite the tight relationship between these cerebellar functions and Neurodevelopmental Disorders (NDDs) such as Autism Spectrum Disorder (ASD) and Intellectual Disability (ID), the role of non-motor contributions of the CB is often overlooked in NDD research and especially understudied in animal models of these disorders compared to structures such as the cerebral cortex and hippocampus. With the emerging understanding that the CB plays a critical role in higher order brain function and that perturbed cerebellar functioning can lead to ASD and NDD relevant phenotypes, there is strong justification for focus on CB dysfunction in NDD animal models. De novo mutations in the chromatin- remodeling factor CHD8 (Chromodomain-Helicase DNA-binding protein 8) have emerged as a key genetic causal factor strongly associated with ASD and more generally with NDDs. Individuals harboring de novo heterozygous mutations in CHD8 typically present with hallmarks of ASD, cognitive disability, and macrocephaly, with other phenotypes also present in some patients. Multiple mouse Chd8 models have been published (including by our group), with heterozygous mutants exhibiting relevant phenotypes including macrocephaly and behavioral deficits. To date, animal models of pathology associated with CHD8 mutation have focused on the forebrain, and in particular the cerebral cortex. In published and preliminary studies, we identified altered structure of the deep cerebellar nuclei and evidence of altered cerebellar anatomy and physiology in mice harboring heterozygous Chd8 mutation. We hypothesize that cerebellar impact of Chd8 mutation contributes to higher order cognitive and behavioral pathology. Here, we propose initial work towards testing this model, defining the impact of Chd8 haploinsufficiency on cerebellar structure and function across anatomical, genomic, and electrophysiological dimensions. In Aim 1, we will test CB sensitivity to Chd8 haploinsufficiency with regard to patterning and cell identity. In Aim 2, we will test for phenotypes at the electrophysiological, transcriptomic and morphologic level in cerebellar neurons. These experiments will establish impacts of heterozygous Chd8 mutation on the mouse CB, linking neuroanatomy, neuronal function, and signaling. These studies will provide critical evidence for future work defining specific phenotypes associated with heterozygous Chd8 ablation in the CB and towards building a circuit level understanding of how Chd8 mutations impact connectivity within the CB and between the CB and other structures. If successful, this work will lead to new avenues of research on cerebellar dysfunction in NDDs and ASD by linking a high confidence and top priority gene with cellular, molecular, and structural deficits in the CB.