Chronic Axon Hypofunction in Maternal Immune Activation Models of Neurodevelopmental Disorders

新摘要： 怀孕期间的母体感染是神经发育障碍的一个既定风险因素，包括自闭症谱系障碍（ASD），但人们对免疫损伤如何改变发育中大脑的神经回路并因此损害行为知之甚少。免疫效应的一个潜在部位是内侧前额叶皮层（mPFC），它在神经发育改变的疾病中受损的高阶社会和认知功能中起着关键作用。通过探索性R21资助的支持，我们使用了母体免疫激活（MIA）的小鼠模型，并开发了一种基于硅探针的多通道记录系统，用于mPFC电路的高通量功能分析。使用这种方法，我们研究了mPFC的成年后代母亲暴露于病毒模拟聚肌苷酸：聚胞苷酸（聚（I：C）），并确定了一个意想不到的功能减退的输出纤维层5投射神经元的中央缺陷的mPFC。特别是，第5层轴突在长时间活动期间不太能够维持输出，并且它们的时间精度受损。mPFC的转录组学分析揭示了细胞粘附分子L1 cam的下调，这是一种假定的轴突兴奋性调节因子。在这里，拟议的工作将使用相同的小鼠MIA模型，以确定轴突功能减退对mPFC的特定长程靶点的功能影响，这些靶点介导ASD和相关疾病中的行为失调-中间背丘脑（MD），基底外侧杏仁核（BLA）和丘脑核（NAc）。本建议的目的1将测试是否直接招募和/或间接前馈抑制的主要细胞在这些皮层下区域受损的后代暴露于母体免疫激活（MIA）。第5层mPFC投射将特异性靶向病毒方法的光遗传学刺激。在目标2中，我们将用互补遗传（L1 cam拯救）或光遗传（SSFO驱动的增强兴奋性）方法来增加第5层输出，以确定这是否恢复了L5输出并拯救了ASD相关的缺陷。在目标3中，我们将在MIA模型和皮层区域中测试我们的发现的一般性。首先，我们将测试由脂多糖（LPS）诱导的MIA是否具有与poly（I：C）对mPFC轴突功能相似的作用。 接下来，我们将确定是否体感皮层，另一个皮质区域牵连ASD的行为，也显示特定的MIA诱导的变化，在第5层轴突功能，如可能预期的，如果孕中期MIA广泛影响第5层皮层神经元在其发展的关键步骤。拟议实验的结果既有助于解释ASD和其他神经发育障碍的发病机制，也有助于确定一种可以靶向恢复行为的分子途径。

New Summary: Maternal infection during pregnancy is an established risk factor for neurodevelopmental disorders, including Autism Spectrum Disorders (ASD), yet little is known about how immune insults alter neural circuitry in the developing brain and, as a result, impair behavior. One potential site for immune effects is the medial prefrontal cortex (mPFC), which plays a critical role in the higher-order social and cognitive functions compromised in disorders of altered neural development. Through the support of an exploratory R21 grant, we used a mouse model of Maternal Immune Activation (MIA) and developed a silicon probe-based multichannel recording system for high-throughput functional analysis of mPFC circuitry. Using this approach, we examined mPFC in adult offspring following maternal exposure to a viral mimetic polyinosinic:polycytidylic acid (poly(I:C)), and identified an unexpected hypofunction in the output fibers of layer 5 projection neurons as the central defect in the mPFC. In particular, layer 5 axons were less able to sustain output during prolonged activity, and their temporal precision was impaired. Transcriptomic profiling of the mPFC revealed a downregulation of the cell adhesion molecule L1cam, a putative regulator of axonal excitability. Here the proposed work will use the same mouse MIA model to determine the functional ramifications of axonal hypoactivity on specific long-range targets of the mPFC that mediate behaviors dysregulated in ASD and related disorders – mediodorsal thalamus (MD), basolateral amygdala (BLA), and nucleus accumbens (NAc). Aim 1 of this proposal will test whether direct recruitment and/or indirect feedforward inhibition of principal cells in these subcortical regions is impaired in offspring exposed to maternal immune activation (MIA). Layer 5 mPFC projections will be specifically targeted for optogenetic stimulation with viral approaches. In Aim 2, we will augment layer 5 output with complementary genetic (L1cam rescue) or optogenetic (SSFO-driven enhanced excitability) approaches to determine whether this restores L5 output and rescues ASD-related deficits. In Aim 3, we will test for generality of our findings in MIA models and cortical regions. First, we will test whether MIA induced by lipo-polysaccharide (LPS) has similar effects as poly(I:C) on mPFC axonal function. Next we will determine whether somatosensory cortex, another cortical region implicated in ASD behaviors, also shows specific MIA induced changes in layer 5 axonal function, as might be expected if midgestational MIA broadly affects layer 5 cortical neurons at a critical step in their development. The results of the proposed experiments could both help to explain pathogenesis of ASD and other neurodevelopmental disorders and identify a molecular pathway that could be targeted to restore behavior.