Physiological and molecular mechanisms of impaired PV circuit homeostasis in Autism mouse models

项目总结 前馈中小白蛋白(PV)神经元功能减退和兴奋抑制比(E-I)升高 皮层回路可能导致自闭症谱系障碍的异常感觉处理，但起源 而光伏功能低下的分子机制，以及它超越前馈电路的普遍性，仍然存在 不清楚。在这里，我将检验这样一种假设，即光伏电路功能减退是由于体内平衡受损 PV回路的可塑性，正常情况下在感觉转移期间维持皮质兴奋性 输入。在L2/3的晶须初级躯体感觉皮层(S1)，PV环路的动态平衡由 短暂的胡须剥夺，降低了PV神经元的内在兴奋性，减少了前馈抑制。 在Aim 1.1中，我将使用PV细胞兴奋性的体外电生理测量来测试受损的PV 两种ASD小鼠模型(Fmr1-/y和Tsc2+/-)的电路内稳态。这些型号都有PV功能障碍，但 在几个分子和突触表型上的不同，使它们成为PV是否 功能减退可能是由共同的原因引起的。 以前的生理学研究主要集中在自下而上前馈回路的功能障碍 但最近在自闭症患者中的报告表明，感觉处理问题可能是由于 自上而下反馈通路的功能缺陷，导致过度依赖前馈输入。自上而下 通路为S1提供强大的输入，但尚不清楚反馈通路的生理学是否发生改变 在ASD小鼠模型中，以及它们的改变是否也可能是由于PV细胞内稳态的失败所致。在……里面 目标1.2和1.3，我将评估L2/3的S2-和S1输入的基线功能和动态平衡可塑性的变化 用光遗传学方法研究S1中的锥体细胞和PV细胞。 了解ASD中光伏回路稳态受损的分子机制可能 使治疗性干预能够恢复光伏电路功能。这些分子机制目前 未知。我将确定剥夺导致PV固有功能减弱的分子机制 兴奋性，光伏动态平衡的关键初始步骤。众所周知，这涉及到电压门控的增加 钾(Kv)通道电流。分子机制可能涉及活性依赖蛋白。 合成，据报道在Fmr1-/y和TSC2+/-小鼠中都是失调的，尽管可能相反 方向。一个可能调节光伏电路动态平衡的有希望的候选信号通路是活性- 转录因子Er81的依赖合成导致PV细胞Kv1.1表达增加。在目标2中，我 将使用新的特定于细胞的遗传策略来测试光伏电路稳态需要蛋白质的假设 体内合成，涉及ER81和增加的Kv1.1的活性依赖的合成--这是受损的 在ASD小鼠身上。我还将开发CRISPR工具来调节Kv1.1水平，以挽救ASD的PV动态平衡 小鼠，可能导致自闭症的治疗方法。

PROJECT SUMMARY Parvalbumin (PV) neuron hypofunction and increased excitation-inhibition (E-I) ratio in feedforward cortical circuits likely contribute to abnormal sensory processing in Autism Spectrum Disorders, but the origins and molecular mechanisms of PV hypofunction, and its generalizability beyond feedforward circuits, remain unclear. Here, I will test the hypothesis that PV circuit hypofunction arises because of impaired homeostatic plasticity of PV circuits, that normally acts to maintain cortical excitability during periods of shifting sensory input. In L2/3 of whisker primary somatosensory cortex (S1), PV circuit homeostasis is robustly engaged by brief whisker deprivation, which reduces intrinsic excitability of PV neurons, decreasing feedforward inhibition. In Aim 1.1, I will use in vitro electrophysiological measurements of PV cell excitability to test for impaired PV circuit homeostasis in two ASD mouse models (Fmr1-/y and Tsc2+/-). These models share PV hypofunction but differ in several molecular and synaptic phenotypes, making them a powerful test case for whether the PV hypofunction may arise from a common source. Previous physiological studies have primarily focused on dysfunction in bottom-up feedforward circuits in ASDs, but recent reports in people with ASDs suggest that sensory processing issues may result from a functional deficiency in top-down feedback pathways, resulting in overreliance on feedforward input. Top-down pathways provide strong input to S1, but it is unknown whether the physiology of feedback pathways is altered in ASD mouse models and whether their alteration may also result from a failure of homeostasis in PV cells. In Aims 1.2 & 1.3, I will assess changes in baseline function and homeostatic plasticity of S2->S1 inputs to L2/3 pyramidal and PV cells in S1 using optogenetics. Understanding the molecular mechanisms that underlie impaired PV circuit homeostasis in ASDs may enable therapeutic interventions to restore PV circuit function. These molecular mechanisms are currently unknown. I will identify the molecular mechanisms underlying deprivation-induced weakening of PV intrinsic excitability, the key initial step in PV homeostasis. This is known to involve an increase in voltage-gated potassium (Kv) channel currents. The molecular mechanisms likely involve activity-dependent protein synthesis, which is reportedly dysregulated in both the Fmr1-/y and Tsc2+/- mice, though potentially in opposite directions. A promising candidate signaling pathway that could mediate PV circuit homeostasis is activity- dependent synthesis of transcription factor ER81 leading to increased Kv1.1 expression in PV cells. In Aim 2, I will use novel cell-specific genetic strategies to test the hypothesis that PV circuit homeostasis requires protein synthesis in vivo and involves activity-dependent synthesis of ER81 and increased Kv1.1- and this is impaired in ASD mice. I will also develop CRISPR tools to modulate Kv1.1 levels to rescue PV homeostasis in ASD mice, potentially leading to therapeutic approaches for ASDs.