Reversal of synaptic and behavioral deficits in a 16p11.2 duplication mouse model via restoration of the GABA synapse regulator Npas4

The human 16p11.2 gene locus is a hot spot for copy number variations, which predispose carriers to a range of neuropsychiatric phenotypes. Microduplications of 16p11.2 are associated with autism spectrum disorder (ASD), intellectual disability (ID), and schizophrenia (SZ). Despite the debilitating nature of 16p11.2 duplications, the underlying molecular mechanisms remain poorly understood. Here we performed a comprehensive behavioral characterization of 16p11.2 duplication mice (16p11.2dp/+) and identified social and cognitive deficits reminiscent of ASD and ID phenotypes. 16p11.2dp/+ mice did not exhibit the SZ-related sensorimotor gating deficits, psychostimulant-induced hypersensitivity, or motor impairment. Electrophysiological recordings of 16p11.2dp/+ mice found deficient GABAergic synaptic transmission and elevated neuronal excitability in the prefrontal cortex (PFC), a brain region critical for social and cognitive functions. RNA-sequencing identified genome-wide transcriptional aberrance in the PFC of 16p11.2dp/+ mice, including downregulation of the GABA synapse regulator Npas4. Restoring Npas4 expression in PFC of 16p11.2dp/+ mice ameliorated the social and cognitive deficits and reversed GABAergic synaptic impairment and neuronal hyperexcitability. These findings suggest that prefrontal cortical GABAergic synaptic circuitry and Npas4 are strongly implicated in 16p11.2 duplication pathology, and may represent potential targets for therapeutic intervention in ASD. This study was designed to characterize mice carrying 16p11.2 duplication behaviorally, biochemically, transcriptionally, and electrophysiologically. RNA-sequencing was performed in prefrontal cortex in order to characterize the transcriptional profile associated with this copy number variation. These animals were originally generated on a hybrid C57BL/6N:129Sv background before being backcrossed 10 generations onto C57BL/6 inbred strain and maintained on C57BL/6 genetic background.人类16p11.2基因座是拷贝数变异（copy number variation）的热点区域，此类变异会使携带者易罹患多种神经精神表型。16p11.2微重复（microduplication）与自闭症谱系障碍（autism spectrum disorder, ASD）、智力障碍（intellectual disability, ID）及精神分裂症（schizophrenia, SZ）相关。尽管16p11.2重复会引发严重功能障碍，但其潜在分子机制仍未被充分阐明。本研究对16p11.2重复小鼠（16p11.2dp/+）开展了全面的行为学表征，发现其存在与自闭症谱系障碍及智力障碍表型相似的社交与认知缺陷。16p11.2dp/+小鼠未表现出与精神分裂症相关的感觉运动门控（sensorimotor gating）缺陷、精神兴奋剂（psychostimulant）诱导的超敏反应或运动功能损伤。对16p11.2dp/+小鼠的电生理记录显示，其前额叶皮层（prefrontal cortex, PFC）中存在γ-氨基丁酸能（GABAergic）突触传递缺陷及神经元兴奋性升高，而前额叶皮层是调控社交与认知功能的关键脑区。RNA测序（RNA-sequencing）分析发现，16p11.2dp/+小鼠前额叶皮层存在全基因组范围的转录异常，包括γ-氨基丁酸突触调控因子Npas4的表达下调。在16p11.2dp/+小鼠的前额叶皮层中恢复Npas4的表达，可改善其社交与认知缺陷，并逆转γ-氨基丁酸能突触损伤及神经元过度兴奋。上述研究结果表明，前额叶皮层的γ-氨基丁酸能突触环路及Npas4与16p11.2重复的病理机制密切相关，或可成为自闭症谱系障碍治疗干预的潜在靶点。本研究旨在从行为学、生物化学、转录组学及电生理学层面，对携带16p11.2重复的小鼠开展系统表征。本研究通过对前额叶皮层进行RNA测序，以解析该拷贝数变异相关的转录组特征。该类小鼠最初构建于杂交C57BL/6N:129Sv遗传背景中，随后回交10代至C57BL/6近交系（inbred strain），并以C57BL/6遗传背景维持饲养。