Sex-specific mechanisms of cortical circuit dysfunction in a mouse ASD model

虽然ASD更多地诊断为男性，但ASD的行为表现以及神经解剖学表现， 与ASD相关的变化和脑功能障碍在男性和女性之间存在差异。很少有人知道， ASD基因如何影响女性大脑雌激素通过膜结合雌激素受体α（ERα）发挥作用， 在雌性神经元中选择性地与Gq偶联的第1组mGluRs、mGluR 1和mGluR 5相互作用并激活它们 在不同的大脑区域调节信号，神经生理学和行为。mGluRs功能改变， 主要是mGluR 5，与ASD小鼠模型的病理生理学密切相关，最明显的是脆性X染色体 综合征，但许多其他人，和mGluR 5拮抗剂是在FXS儿童的临床试验。我们是第一个 在FXS小鼠模型Fmr 1 KO中发现mGluR 5功能过度活跃，并显示了来自 异常的mGluR 5复合物; mGluR 5与其突触后支架蛋白Homer分离， 反过来，导致组成型mGluR 5活性，下游效应子的异常信号传导和疾病相关性 表型，如电路过度兴奋。尽管mGluR 5在ASD病理生理学中的证据， 已知雌激素对mGluR 1/5的性别依赖性调节，但对ASD相关基因如何与 雌激素影响mGluR 1/5的功能和ASD相关的神经生理学和行为的后果。 我们发现了一种性别特异性的、mGluR 5依赖性的感觉新皮质回路功能障碍， 由Pten（磷酸酶和张力蛋白同源物， 染色体10），PI 3 K/mTORC 1途径的抑制因子。具体来说，我们观察到超兴奋性 新皮层回路振荡，称为UP状态，在两种不同的PTEN缺失模型的雌性中;胚胎， 海马和第5层新皮层神经元中Pten敲除，以及种系Pten杂合小鼠 （Pten-het），其是人类中Pten相关ASD的遗传有效模型。超激发UP状态， 雌性Pten模型通过mGluR 5或ERα的急性拮抗作用得到纠正，表明mGluR 5- ERα信号转导。增强mGluR 5-ERα活性的候选分子底物是观察到的mGluR 5-ERα活性的增加。 雌性Pten-het皮质中mGluR 5-ERα和mGluR 5-Homer复合物减少。我们假设 在Pten缺失的雌性神经元中，mGluR 5与ER α和Homer相互作用的不平衡导致 增强mGluR 5信号对雌激素的反应，作用于ERα，以及组成性活性 mGluR 5导致过度兴奋的皮层振荡和ASD相关行为。我们建议 目的1：确定Pten和ERα的性别依赖性相互作用， 皮质回路功能障碍和mGluR 5复合物调节。目的2：检查mGluR 5的性别特异性作用 和ERα对Pten缺失的第5层神经元的内在和突触特性的影响。目的3：确定性别特异性， Pten缺失模型中EEG的mGluR 5和ERα依赖性体内皮质振荡。目标4。确定 女性特异性Pten依赖性皮质回路过度兴奋在ASD相关行为中的作用。

Although ASD is more diagnosed in males, the behavioral manifestations of ASD, as well as the neuroanatomical changes and brain dysfunction associated with ASD, differ between males and females. There is little known of how ASD genes impact the female brain. Estrogen, acting through membrane bound estrogen receptor α (ERα), interacts with and activates Gq-coupled Group 1 mGluRs, mGluR1 and mGluR5, selectively in female neurons in diverse brain regions to regulate signaling, neurophysiology, and behavior. Altered functioning of mGluRs, primarily mGluR5, is strongly implicated in the pathophysiology of ASD mouse models, most notably Fragile X Syndrome, but many others, and mGluR5 antagonists are in clinical trials of FXS children. We were the first to discover hyperactivity of mGluR5 function in the FXS mouse model, Fmr1 KO, and show this results from an abnormal mGluR5 complex; mGluR5 is dissociated from its postsynaptic scaffolding protein, Homer, which, in turn, leads to constitutive mGluR5 activity, abnormal signaling to downstream effectors and disease relevant phenotypes, such as circuit hyperexcitability. Despite the evidence for mGluR5 in ASD pathophysiology, the known sex-dependent regulation of mGluR1/5 by estrogen, little is known of how ASD-linked genes interact with estrogen to affect mGluR1/5 function and the consequences on ASD-relevant neurophysiology and behavior. We have discovered a sex-specific, mGluR5 -dependent dysfunction of sensory neocortical circuits in a mouse model of ASD that results from deletion of Pten (Phosphatase and tensin homolog deleted on chromosome 10), a suppressor of the PI3K/mTORC1 pathway. Specifically, we observe hyperexcitable neocortical circuit oscillations, termed UP states, in females of two distinct PTEN deletion models; an embryonic, knockout of Pten in hippocampus and layer 5 neocortical neurons, and a germline Pten heterozygous mouse (Pten-het), which is a genetically valid model for Pten-related ASD in humans. Hyperexcitable UP states in female Pten models are corrected by acute antagonism of mGluR5 or ERα, indicative of hyperactive mGluR5- ERα signaling. A candidate molecular substrate for enhanced mGluR5-ERα activity is the observed increase in mGluR5-ERα, and decreased mGluR5-Homer, complexes in female Pten-het cortex. We hypothesize that an imbalance in mGluR5 interactions with ERa and Homer in Pten deleted female neurons results in enhanced mGluR5-signaling in response to estrogen, acting on ERα, as well as constitutively active mGluR5 which leads to hyperexcitable cortical oscillations and ASD-relevant behaviors. We propose the following aims to test this hypothesis: Aim 1: Determine the sex-dependent interactions of Pten and ERα in cortical circuit dysfunction and mGluR5 complex regulation. Aim 2: Examine the sex-specific effects of mGluR5 and ERα on intrinsic and synaptic properties of Pten-deleted layer 5 neurons. Aim 3: Determine the sex-specific, mGluR5- and ERα-dependent in vivo cortical oscillations with EEG in Pten deletion models. Aim 4. Determine the role of female-specific, Pten-dependent cortical circuit hyperexcitability in ASD-relevant behaviors.