Auts2缺失导致孤独症样行为的脑区结构基础和分子机制

Autism is a complex genetic disease and is characterized by advanced brain dysfunction such as social deficit, cognitive impairment and stereotypic interests and behaviors. It is helpful to reveal the pathogenesis of autism by constructing genetically engineered animal models. Deletions or mutations of AUTS2 genomic sequences have been found in autistic patients. So far, AUTS2 has become an international important issue in autism research field, but it is unclear that whether the Auts2 deficient mice have autism-like behaviors or postnatal neural development abnormality. Our previous work indicated Auts2 conditional knockout mice showed autism-like behaviors and neural development deficits in prefrontal cortex and dentate gyrus. Based on systematic assessment of mice behaviors, we will detect neural proliferation, differentiation, migration, dendrite development and synaptic formation by using immunostaining, in utero electroporation and Golgi staining. Taking advantage of electrophysiological recording to study neuronal excitability, basal transmission, excitability/inhibition equilibrium and synaptic plasticity. At last we will explore the related molecular mechanism. This research will provide important clues to reveal the pathogenic mechanism of autistic susceptibility gene AUTS2.

孤独症是一种多基因复杂疾病，核心症状为社会交往及交流障碍、认知损害和刻板兴趣行为等脑高级功能障碍，建立基因工程动物模型有助于揭示孤独症的发病机制。既往研究发现孤独症患者存在AUTS2基因的缺失或突变。目前，AUTS2已是孤独症研究领域的国际热点，但Auts2缺陷小鼠是否有孤独症样行为表现以及Auts2对出生后小鼠神经系统发育的影响尚不清楚。课题组前期发现Auts2条件性敲除小鼠出现孤独症样行为以及前额叶皮层、海马齿状回神经发育异常表型。本项目将在系统评价小鼠行为学的基础上，采用免疫组化、子宫内电穿孔和Golgi染色等方法观察神经细胞增殖分化、神经元迁移、树突发育和突触形成等发育事件；利用电生理学记录手段明确神经元的兴奋性、基础突触传递、兴奋性/抑制性平衡和可塑性等特征；进而探索Auts2缺失影响神经发育和神经元活动的分子机理。本项目将为揭示孤独症易感基因AUTS2的致病机制提供重要线索。

Auts2基因在大脑发育过程中在前脑兴奋性神经元中高度表达。最近的遗传学和神经生物学研究报告了AUTS2基因变异可能导致包括孤独症在内的神经发育障碍。然而，有关Auts2导致孤独症相关特征如社会行为受损的神经环路基础和潜在的分子机制尚不明确。本项目中发现兴奋性神经元前体细胞或早期分裂后神经元中Auts2的敲除导致小鼠出生后海马齿状回（DG）发育异常和孤独症相关的行为特征。由于Auts2的缺失，在DG的分裂后颗粒细胞中会产生Ptgds的异位高表达，并通过非细胞自主方式抑制NSC/IPC从SPZ区向SGZ区的迁移，导致出生后早期DG中SGZ区形成障碍。进一步的分子生物学分析显示AUTS2与CTIP2结合通过招募NURD转录抑制复合物来抑制PTGDS转录。此外，我们还发现，海马DG-CA3神经环路在该敲除小鼠中受损。利用化学遗传学激活该神经环路可以部分恢复异常的社会认知行为。总之，我们的研究结果显示了AUTS2信号在出生后发育中的关键转录抑制作用，这对DG-CA3神经传递和社会行为至关重要，并为孤独症的病因提供了新的认识。