Amygdala hyper-connectivity in a mouse model of unpredictable early life stress

摘要 儿童期虐待会以剂量依赖性方式增加焦虑和其他精神病理学的风险 方式生命早期的多种不良事件协同作用影响焦虑的机制很差 在人类中理解，并且很少努力在早期生活压力的动物模型中澄清这个问题 （ELS）。我们最近发现，暴露于UPS，这是一个复杂的和不可预测的小鼠模型的ELS， 导致焦虑的强烈增加，这在暴露于简单且可预测的 ELS称为有限寝具（LB）。有趣的是，暴露于LB或UPS并不影响焦虑样 雌性小鼠的行为。由于杏仁核与额叶边缘脑区的连接， 海马（HPC）和前额叶皮层（PFC）在焦虑样行为中起重要作用， 暴露于童年虐待会导致我们使用的这些大脑区域之间的异常连接 静息状态fMRI（rsfMRI），比较UPS和对照组中杏仁核与HPC和PFC的连接 雄性老鼠我们发现杏仁核和前额叶皮质之间以及杏仁核之间的连接性增加 以及UPS男性的HPC。重要的是，这些连接的强度与焦虑高度相关- 比如行为在这个应用程序中，我们假设杏仁核与PFC和HPC的连接 在围产期经历小胶质细胞介导的修剪。在男性中，更严重的ELS形式，如 UPS导致出生后小胶质细胞中主调节因子PU.1的表达更大程度地减少。这 turn会导致调节焦虑的额-边缘连接的完善受到剂量依赖性损害。 暴露于LB或UPS对女性的PU.1水平和小胶质细胞功能没有影响。因此，女性 当暴露于LB或UPS时，表现出正常的杏仁核连接和焦虑。目标1中的工作将使用rsfMRI 和高分辨率DTI来测试不同类型的ELS（UPS和LB）如何与性别相互作用以改变额边缘系统 连通性。在aim 2中，我们将使用光遗传学和化学遗传学病毒来标记和操纵基底外侧 杏仁核（BLA）投射到PFC和HPC。这种方法将使我们能够精确地绘制出 这些投射决定了它们对焦虑的贡献，并评估了它们诱导c-fos激活的能力， 来改变BOLD信号。目标3中提出的研究将使用rsfMRI和高分辨率DTI， 表征PU.1-hets小鼠中的功能和结构连接性。这种方法的优势在于 我们团队的各种专业知识。这种多学科的努力使我们能够使用小胶质细胞特异性遗传学 操作，使用光遗传学和化学遗传学工具严格测试因果关系，并利用人类成像 评估ELS小鼠模型中大脑连接的工具。

Abstract Childhood maltreatment increases the risk for anxiety and other psychopathologies in a dose-dependent manner. The mechanisms by which multiple adverse events early in life synergize to affect anxiety is poorly understood in humans and little effort has been made to clarify this issue in animal models of early life stress (ELS). We recently showed that exposure to UPS, which is a complex and unpredictable mouse model of ELS, leads to robust increase in anxiety that was not seen in mice exposed to a simple and predictable paradigm of ELS known as the limited bedding (LB). Interestingly, exposure to LB or UPS did not affect anxiety-like behavior in female mice. Since amygdala connectivity with fronto-limbic brain regions such as the hippocampus (HPC) and the prefrontal cortex (PFC) play an important role in anxiety-like behavior and exposure to childhood maltreatment leads to abnormal connectivity between these brain regions we used resting state fMRI (rsfMRI) to compare amygdala connectivity with the HPC and the PFC in UPS and control male mice. We found increased connectivity between the amygdala and the PFC and between the amygdala and the HPC in UPS males. Importantly, the strength of theses connections was highly correlated with anxiety- like behavior. In this application we hypothesize that amygdala connectivity with the PFC and the HPC undergo microglial-mediated pruning during the perinatal period. In males, more severe forms of ELS, such as UPS, lead to greater reduction in the expression of the master regulator PU.1 in postnatal microglia. This in turn causes a dose-dependent impairment in the refinement of fronto-limbic connections that regulate anxiety. Exposure to LB or UPS has no effect on PU.1 levels and microglial function in females. As a result, females show normal amygdala connectivity and anxiety when exposed to LB or UPS. Work in aim 1 will use rsfMRI and high resolution DTI to test how different types of ELS (UPS and LB) interact with sex to alter fronto-limbic connectivity. In aim 2 we will use optogenetics and chemogenetics viruses to label and manipulate basolateral amygdala (BLA) projections to the PFC and HPC. This approach will allow us to precisely map the size of these projections, determine their contribution to anxiety, and assess their ability to induce c-fos activation and to alter BOLD signal using fMRI. Studies proposed in aim 3 will use rsfMRI and high resolution DTI to characterize functional and structural connectivity in PU.1-hets mice. The strength of this approach lies in the diverse expertise of our team. This multidisciplinary effort allows us to use microglial specific genetic manipulations, rigorously test causality using optogenetic and chemogenetic tools, and utilize human imaging tools to assess brain connectivity in a mouse model of ELS.