NL3 R451C KI自闭症模型小鼠社交障碍的分子和细胞机制及其治疗干预

Autism spectrum disorders are deemed to result from dysfunction of specific neural circuits caused by deficits in synaptic transmission. Neuroligins (NLs) are cell-adhesion molecules that act as postsynaptic ligands for presynaptic neurexins, contributing to synaptogenesis and synaptic transmission. NLs are expressed as four principal isoforms and a mutation of NL3, R451C, is associated with autism. Knock-in (KI) mice with the mutation exhibit autistic behavioral abnormalities, including deficits in social novelty behavior. Our article recently published on Neuron reports that the abnormalities of PV interneurons and gamma oscillation in the medial prefrontal cortex (mPFC) are the cause of behavioral defects of KI mice. Our previous study also found that NMDARs function of pyramidal neurons in the mPFC was decreased and the D-cycloserine (DCS), a partial agonist of NMDARs, could rescue social behavioral deficits in KI mice. However, its cellular and molecular mechanisms remain to be further elucidated. In this research, we aim to identify the key role of NMDARs in the molecular pathology of KI mice, to elucidate its molecular and cellular mechanisms in different subtypes of neurons of local neural circuits, and to systematically study the synaptic and cellular basis of DCS for improving social defects, which will help us understand the pathogenesis of social deficits in autism and propose new therapeutic targets.

自闭症谱系障碍被认为是由突触功能缺陷导致特定神经环路功能紊乱引起。神经连接蛋白（NL）属于细胞粘附分子，是突触前Neurexin的突触后配体，与突触发生和传递密切相关。NL有四种主要亚型，NL3的R451C点突变与自闭症相关，该点突变的基因敲入（KI）小鼠也表现出自闭症样行为，包括社交趋新缺陷。最近我们在Neuron上报道该KI小鼠前额叶皮层（mPFC）的PV中间神经元和场电位gamma振荡功能障碍是社交缺陷的原因。我们前期研究还发现该KI小鼠mPFC中锥体神经元的NMDA受体功能下降、部分激动剂D-环丝氨酸（DCS）可拯救小鼠社交缺陷，但分子细胞机制尚不清楚。本项目拟明确NMDA受体在该KI小鼠分子病理学中的关键作用，在神经元亚型和局部环路功能水平阐明其分子细胞机制，并系统研究DCS改善社交缺陷的突触和细胞基础，这将有助于深入认识自闭症社交缺陷的发病机制并提出新的治疗靶点。

突触后细胞粘附分子neuroligin（NL）的突变与自闭症谱系障碍（autism spectrum disorders，ASDs）息息相关。NL3 R451C位点突变是在一个瑞典家庭的两兄弟中发现的，其位点敲入（knock-in，KI）模型小鼠是表现出社交缺陷。我们已发表的论文报道了，在NL3 R451C KI小鼠内侧前额叶皮层（medial prefrontal cortex，mPFC）中，小清蛋白（parvalbumin，PV）阳性中间神经元兴奋性受损和伽马振荡功能障碍导致其出现社交驱新缺陷。然而，潜在的分子细胞机制仍不清楚。在本研究中，我们发现NL3 R451C KI小鼠mPFC中锥体神经元和PV阳性中间神经元的N-甲基-D-天冬氨酸（N-methyl-D-aspartate，NMDA）受体功能减弱。在突触后致密区发现GluN1亚基表达分布减少。腹腔注射NMDA受体部分激动剂D-环丝氨酸（D-cycloserine，DCS），可恢复KI小鼠mPFC的NMDA受体功能，并挽救了KI小鼠的社交驱新缺陷。敲除mPFC中PV阳性中间神经元的GluN1亚基会导致这些神经元的内在兴奋性降低。总之，我们的研究结果表明，mPFC中NMDA受体功能障碍导致PV阳性中间神经元的兴奋性降低，并最终导致KI小鼠社交缺陷的发展。此项研究有利于自闭症谱系障碍患者社交行为方面的治疗。