Project 3: Microglia heterogeneity and function in interneuron development

摘要 神经回路需要准确放置正确数量的中间神经元(INS)。这一微妙的过程 在神经发育和神经精神疾病中脱轨。小胶质细胞，脑内的巨噬细胞， 影响大脑发育的多个方面，包括皮质的发生、迁移和成熟 中间神经元(CIN)。在这项提议之前的初步研究中，我们发现了不同的分子和 人类发育中的前脑小胶质细胞的细胞特性，我们发现特定的分子- 定义的亚型在大脑各区域的分布是不同的。此外，我们的结果表明，GPR56 表达定义了人小胶质细胞的一个子集，而小鼠小胶质细胞Gpr56的缺失导致了 特定脑区PV+中间神经元数量明显减少。然而，全面的 小胶质细胞转录和功能的异质性，特别是在人脑中，仍然难以捉摸。这个 拟议中的研究将建立人类出生后小胶质细胞的细胞和分子异质性 尾侧和内侧神经节突起，特别集中在小胶质细胞中的GPR56。我们假设 小胶质细胞GPR56促进中间神经元发育。为了检验这一假设和推论，我们将实施 以下三个目标：(1)定义小胶质细胞的形态、分布及其与神经细胞的相互作用 人类GES和Arc中的祖细胞和年轻神经元(一个独特的迁移性神经元簇 出生时在人侧脑室附近发现的中间神经元)；(2)小胶质细胞 在发育中的hMGE、hCGE和Arc中转录异质性；以及(3)研究细胞类型- 小胶质细胞特异性条件性基因敲除小胶质细胞GPR56在中间神经元发育中的特殊作用 老鼠模型。最有意义的是，我们的研究使用了人脑组织和 转基因小鼠模型，以利用可以在小鼠身上进行的许多操作，但始终 使我们的工作植根于我们试图理解的人类条件。这项拟议研究的成功将 开辟一条新的重要研究路线，研究自闭症等神经发育障碍的起源 和精神分裂症。鉴于aGPCRs作为药物靶点的地位，这一系列研究具有巨大的 翻译潜力。特别是，开始设计改变GPR56作用的药物是可行的 鉴于其晶体结构的发现。

Abstract Neural circuits require precise placement of correct numbers of interneurons (INs). This delicate process is derailed in neurodevelopmental and neuropsychiatric disease. Microglia, the brain resident macrophages, influence many aspects of brain development, including genesis, migration and maturation of cortical interneurons (cINs). In our preliminary study leading up to this proposal, we discovered diverse molecular and cellular properties of human microglia in the developing forebrain and we found that specific molecularly- defined subtypes are differentially distributed across brain regions. Furthermore, our results show that GPR56 expression defines a subset of human microglia and that deletion of murine microglial Gpr56 leads to a significant reduction in the numbers of PV+ interneurons in specific brain region. However, the full scope of microglia transcriptomic and functional heterogeneity, especially in the human brain, remains elusive. The proposed research will establish the postnatal cellular and molecular heterogeneity of microglia in the human caudal and medial ganglionic eminence with a specific focus on GPR56 in microglia. We hypothesize that microglial GPR56 promotes interneuron development. To test this and corollary hypotheses, we will carry out the following three aims: (1) Define microglia morphology, distribution, and their interactions with neural progenitors (NPCs) and young neurons in the human GEs and the Arc (a unique cluster of migratory interneurons found at birth in the vicinity of the human lateral ventricles); (2) Characterize microglial transcriptomic heterogeneity in the developing hMGE, hCGE and the Arc; and (3) Investigate the cell-type- specific function of microglial GPR56 in interneuron development using microglia-specific conditional knockout mouse model. Most meaningfully, we are conducting our studies using both human brain tissues and transgenic mouse models, to take advantage of the many manipulations that can be done in mice, but always grounding our work in the human conditions we seek to understand. The success of the proposed research will open a novel and important line of research into the origin of neurodevelopmental disorders, such as autism and schizophrenia. Given the status of aGPCRs as drug targets, this line of research carries tremendous translational potential. In particular, it is feasible to begin designing drugs that modify the action of GPR56 given the discovery of its crystal structure.