Identification of microglia-specific molecules that dictate microglial responses to neural activity and function at developing and refining neural circuits

小胶质细胞，一个相对研究不足的居民中枢神经系统免疫细胞群体，几十年来一直被认为是在健康的脑实质功能静止。然而，最近，小胶质细胞显示出动态调节其精细过程的运动性，增加与不太活跃的突触的接触频率，并最终通过吞噬吞噬来修剪这些突触，以响应神经活动的改变。这些有趣的发现首次表明了小胶质细胞在发育中的大脑中形成和完善神经回路的重要生理功能。然而，这些反应的分子机制和功能后果是完全未知的，活动依赖性突触重塑的机制，一般来说，仍然很难定义。该提案描述了一种结合体外和体内模型的多维方法，以解开小胶质细胞依赖性突触可塑性的分子机制，并评估健康大脑中神经回路的发育和完善的结构和功能后果。我们研究的一个主要内容将是消融与细胞运动、细胞骨架重排和吞噬细胞吞噬有关的小胶质细胞特异性基因，并评估这些分子如何调节小胶质细胞功能以响应神经活动。受神经活性调节的小胶质细胞特异性感兴趣基因（GOI）最初将通过小胶质细胞的比较转录谱来鉴定，所述小胶质细胞来源于在正常光/暗循环中在对照条件下圈养的小鼠，或来自在黑暗中饲养以抑制初级视觉皮层区域V1中的神经活性的小鼠。或者，公众可访问的基因表达谱，从密切的个体发育亲属，如组织驻留的巨噬细胞外的大脑，将被用来识别基因，特别是由神经活动调节。此外，我们将评估小胶质细胞的基因消融和小胶质细胞特异性GOI的缺失如何影响结构和功能神经回路的发展和完善。这项拟议中的研究将是第一个定义受神经活动调控的小胶质细胞特异性基因的研究，并将开发和推进遗传操纵小胶质细胞的新技术。此外，这些实验将确定令人兴奋的新的小胶质细胞靶点，这些靶点决定突触重塑，从而在多种情况下控制结构和功能神经回路的发展和完善，包括发育和疾病。

Microglia, a relatively understudied resident CNS immune cell population, have for decades been regarded as functionally quiescent in the healthy brain parenchyma. However, recently, microglia were shown to dynamically modulate the motility of their fine processes, increase the contact frequency with less active synapses and ultimately prune these synapses by phagocytic engulfment in response to alterations in neural activity. These intriguing findings first indicated important physiological functions of microglia for the formation and refinement of neural circuits in the developing brain. However, the molecular mechanisms and functional consequences underlying these responses are completely unknown and mechanisms underlying activity-dependent synapse remodeling, in general, remain poorly defined. This proposal describes a multi-dimensional approach combining in vitro and in vivo models to unravel the molecular mechanisms of microglia-dependent synaptic plasticity and to assess the structural and functional consequences on the development and refinement of neural circuits in the healthy brain. One main element of our studies will be the ablation of microglia-specific genes implicated in cell motility, cytoskeletal rearrangements and phagocytic engulfment and the assessment of how these molecules regulate microglial functions in response to neural activity. Microglia-specific genes of interest (GOIs) that are regulated by neural activity will initially be identified by comparative transcriptional profiling of microglia either derived from mice housed under control conditions in a normal light/dark cycle, or from mice reared in the dark to dampen neural activity in the primary visual cortex area V1. Alternatively, public accessible gene expression profiles from close ontogenetic relatives, such as tissue-resident macrophages outside the brain, will be used to identify genes that are specifically regulated by neural activity. Furthermore, we will assess how genetic ablation of microglia and deletion of microglia-specific GOIs affect the development and refinement of structural and functional neural circuits in general. The proposed study will be the first to define microglia-specific genes that are regulated by neural activity and will develop and advance new technologies to genetically manipulate microglia. Moreover, these experiments will identify exciting new microglial targets that dictate synapse remodeling, and thereby control the development and refinement of structural and functional neural circuits in multiple contexts, including development and disease.