Role of histone deacetylases in the development of GABAergic interneuron connectivity and function

GABA能神经元是大脑中神经元群体的一个重要子集，它有力地控制着大脑回路的动力学。此外，它们通过调节几个过程，包括依赖经验的神经元连接，对大脑发育进行强有力的调控。到目前为止，大脑回路的复杂性和GABA能细胞群的非均质性使得研究这些神经元如何发育和形成突触连接变得非常困难。我们最近开发了标记和操作小白蛋白阳性GABA能细胞(PV细胞)的技术，这些细胞构成了最多类型的皮质GABA能神经元。PV细胞形成密集的轴突树枝状分支，支配数百个靶神经元，每个神经元在其胞体和近端树突上有多个簇状突触。光伏细胞突触的这种精确的亚细胞定位，再加上它们以极高的频率发射持续的短暂动作电位序列的惊人能力，使它们能够有力地控制目标细胞的输出，并影响大脑中的大型网络活动。我的长期目标是了解皮层光伏细胞连通性形成的潜在机制，以及它们如何调节年轻人和成年人大脑中依赖经验的皮质可塑性。 突触形成和加强的分子机制包括通过稳定的表观遗传修饰激活和抑制特定基因。染色质重塑，特别是通过组蛋白-尾部乙酰化，改变了紧密的染色质结构，改变了DNA对调控蛋白的可及性，正在成为调控基因表达的基本机制。特别是，组蛋白脱乙酰酶2(HDAC2)已被证明调节兴奋性突触的形成和可塑性。有趣的是，HDAC2与染色质的结合受到脑源性神经营养因子BDNF的强烈调控，BDNF是促进PV细胞突触形成的最强大的因素之一。在这里，我们建议使用单细胞遗传学、条件性基因敲除小鼠、高分辨率成像、小鼠行为测试、体外和体内电生理学的独特组合来研究HDAC2在光伏细胞电路发育中的作用。我们的工作假设是，HDAC2是光伏细胞回路出生后发育的关键分子决定因素，在没有HDAC2的情况下，光伏细胞的连接和功能仍然不成熟。 拟议的实验将阐明控制大脑皮层光伏细胞连通性发展的表观遗传学机制，进而阐明发育可塑性。所提出的方法的多学科核心以及体外和体内实验模型的使用将为HQP在研究生和本科生层面提供极好的培训机会。

GABAergic neurons form an important subset of the neuronal population in the brain, which powerfully control the dynamics of brain circuits. In addition, they strongly regulate brain development by modulating several processes including experience-dependent neuronal wiring. The complexity of brain circuitry and the non-homogeneity of the GABAergic cell population has so far made the study of how these neurons develop and form synaptic connections very difficult. We have recently developed techniques to label and manipulate parvalbumin positive GABAergic cells (PV cells), which constitute the most numerous types of cortical GABAergic neurons. PV cells form dense axonal arborisations that innervate hundreds of target neurons, each with multiple, clustered synapses onto their soma and proximal dendrites. Such precise subcellular location of PV cell synapses, in conjunction with their striking ability to fire sustained trains of brief action potentials at remarkably high frequency, allows them to powerfully control the output of their target cells and influence large network activities in the brain. My long-term goal is to understand the mechanisms underlying the formation of cortical PV cell connectivity and how they modulate experience-dependent cortical plasticity in the young and adult brain. Molecular mechanisms involved in synapse formation and strengthening include the activation and repression of specific genes by stable epigenetic modifications. Chromatin remodeling, especially through histone-tail acetylation, which alters the compact chromatin structure and changes the accessibility of DNA to regulatory proteins, is emerging as a fundamental mechanism for regulating gene expression. In particular, Histones Deacetylase 2 (HDAC2) has been shown to regulate excitatory synapse formation and plasticity. Interestingly, HDAC2 binding to chromatic is strongly regulated by the brain-derived neurotrophic factor BDNF, which is one of the most powerful factors promoting PV cell synapse formation. Here, we propose to use a unique combination of single-cell genetics, conditional knockout mice, high-resolution imaging, mouse behavioural testing, ex vivo and in vivo electrophysiology to investigate the role of HDAC2 in PV cell circuit development. Our working hypothesis is that HDAC2 is a critical molecular determinant of the postnatal development of PV cell circuits and that, in its absence, PV cell connectivity and function remain immature. The proposed experiments will shed light on the epigenetic mechanisms controlling the development of cortical PV cell connectivity and, in turn, developmental plasticity. The multidisciplinary core of the proposed approaches and the use of in vitro and in vivo experimental models will provide excellent training opportunities for HQPs at both the graduate and undergraduate levels.