Developmental cerebellar deficits caused by Chd8 haploinsufficiency

总结 小脑（CB）在本体感觉和精细运动控制中的作用是公认的，然而， 最近的研究也强烈地暗示了这种结构在高级认知功能如语言中， 认知加工和情感调节。尽管这些小脑功能之间的紧密联系 和神经发育障碍（NDD），如自闭症谱系障碍（ASD）和智力障碍（AD）。 残疾（ID），CB的非运动贡献的作用在NDD研究中经常被忽视， 特别是在这些疾病的动物模型中， 皮质和海马体。随着人们逐渐认识到CB在高阶中起着关键作用， 脑功能和小脑功能紊乱可导致ASD和NDD相关表型， 是关注NDD动物模型中CB功能障碍的有力理由。染色质的新生突变- 重塑因子CHD 8（染色体结构域解旋酶DNA结合蛋白8）已成为一种关键的遗传 与ASD和更普遍的NDD密切相关的因果因素。重新犯罪的个人 CHD 8中的杂合突变通常表现为ASD、认知障碍和 在一些患者中还存在其他表型。多个小鼠Chd 8模型已被 已发表（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CHD 8突变相关的病理学的动物模型 主要集中在前脑，特别是大脑皮层。在已发表和初步研究中，我们 确定了小脑深部核团结构的改变和小脑解剖结构改变的证据， 在携带杂合Chd 8突变的小鼠中的生理学。我们假设Chd 8对小脑的影响 突变导致更高级的认知和行为病理学。在这里，我们提出初步工作， 为了测试这个模型，定义Chd 8单倍不足对小脑结构的影响， 在解剖学、基因组学和电生理学维度上发挥作用。在目标1中，我们将测试CB 在模式和细胞身份方面对Chd 8单倍不足敏感。在目标2中，我们将测试 在小脑神经元的电生理，转录组和形态学水平的表型。这些 实验将确定杂合Chd 8突变对小鼠CB的影响，将神经解剖学， 神经元功能和信号传导。这些研究将为未来的工作提供关键证据， 与CB中杂合子Chd 8消融相关的表型，并朝向建立回路水平 了解Chd 8突变如何影响CB内以及CB与其他组织之间的连接 结构.如果成功的话，这项工作将为NDD小脑功能障碍的研究开辟新的途径， ASD通过将高置信度和最高优先级基因与CB中的细胞、分子和结构缺陷联系起来。

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.