Intercellular TWEAK/Fn14 Cytokine Signaling in Sensory-Dependent Circuit Refinement

在出生后的大脑发育过程中，新组装的神经回路通过加强一部分突触连接并同时消除其他突触连接而得到完善。这种突触细化的过程首先由生命早期内在产生的神经活动协调，然后由出生后发育后期的感觉经验驱动。感觉依赖性精细化的损伤被认为有助于神经发育障碍的异质阵列，与环境风险因素（如免疫挑战）对其病理生理学的贡献一致。然而，旨在纠正这种损伤的治疗策略受到了限制，因为对感觉输入改善发育回路的分子和细胞机制缺乏基本的了解。拟议研究的重点是获得对感觉经验在发育过程中改善突触连接的基本细胞和分子机制的更全面的理解，并确定这些机制中的损伤如何导致神经发育疾病。在初步研究中，申请人应用新开发的单细胞转录组学方法来鉴定Fn 14作为兴奋性神经元中由视觉体验转录诱导的基因，并编码发育中大脑中感觉依赖性细化所需的细胞因子受体。该提案包含一项全面的培训和研究计划，以这些调查结果为基础，在短期内通过实验解决知识方面的剩余差距，并促进建立一个创新的多学科研究计划，重点解决这些问题。在目标1中，申请人将学习并应用专门的急性切片电生理学技术来测试以下假设：TWEAK（Fn 14的促炎细胞因子配体）对于经由小胶质细胞至神经元信号传导轴驱动感觉依赖性细化是必要且足够的。在目标2中，申请人将联合收割机电生理学与生物信息学中新学到的方法相结合，以确定增强的TWEAK/Fn 14信号传导是否有助于异常脑发育的母体免疫激活（MIA）小鼠模型中的过度突触细化。在目的3中，申请人将测试TWEAK/Fn 14信号传导通过促进未成熟突触棘向成熟棘的转化来介导功能细化的假设。这些技术培训活动将得到来自几位非常成功的科学家的重点指导，这些科学家致力于帮助申请人在哈佛医学院充满活力和协作的培训环境中获得专业和智力技能。这些活动预计将有助于申请人成功过渡到学术机构的独立研究职位。

During postnatal brain development, newly assembled neural circuits are refined through the strengthening of a subset of synaptic connections and the concurrent elimination of others. This process of synaptic refinement is first coordinated by intrinsically generated neural activity early in life and then driven by sensory experience during a later phase of postnatal development. Impairments in sensory-dependent refinement are thought to contribute to a heterogeneous array of neurodevelopmental disorders, consistent with the contribution of environmental risk factors, such as immune challenge, to their pathophysiology. Yet, therapeutic strategies aimed at correcting such impairments have been limited by a fundamental lack of insight into the molecular and cellular mechanisms through which sensory input refines developing circuits. The key focus of the proposed research is to obtain a more comprehensive understanding of the basic cellular and molecular mechanisms by which sensory experience refines synaptic connections in the course of development, and to determine how impairments in these mechanisms may contribute to neurodevelopmental disease. In preliminary studies, the applicant applied newly developed single-cell transcriptomic methods to identify Fn14 as a gene that is transcriptionally induced by visual experience in excitatory neurons and encodes a cytokine receptor that is required for sensory-dependent refinement in the developing brain. This proposal contains a comprehensive training and research plan to build upon these findings by addressing the remaining gaps in knowledge experimentally in the short-term, and by facilitating the establishment of an innovative and multidisciplinary research program focused on addressing these questions in the long-term. In Aim 1, the applicant will learn and apply specialized acute slice electrophysiology techniques to test the hypothesis that TWEAK, the pro-inflammatory cytokine ligand of Fn14, is necessary and sufficient to drive sensory-dependent refinement via a microglia-to-neuron signaling axis. In Aim 2, the applicant will combine electrophysiology with newly learned methods in bioinformatics to determine whether heightened TWEAK/Fn14 signaling contributes to excessive synaptic refinement in the maternal immune activation (MIA) mouse model of aberrant brain development. In Aim 3, the applicant will test the hypothesis that TWEAK/Fn14 signaling mediates functional refinement by promoting the conversion of immature synaptic spines to mature spines. These technical training activities will be augmented by focused mentorship from several highly successful scientists who are committed to aiding in the applicant's acquisition of professional and intellectual skills in the highly energetic and collaborative training environment at Harvard Medical School. These activities are expected to facilitate the successful transition of the applicant into an independent research position at an academic institution.