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

在出生后大脑发育期间，新组装的神经回路通过加强突触连接的子集和同时消除其他突触连接来精炼。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，然后在出生后发育的后期由感觉经验驱动。感觉依赖性精炼的障碍被认为是导致一系列不同类型的神经发育障碍的原因，这与环境风险因素，如免疫挑战，对其病理生理的贡献是一致的。然而，旨在纠正这种损伤的治疗策略一直受到对分子和细胞机制的根本缺乏的了解，通过这些分子和细胞机制，感觉输入精炼了发育的回路。这项拟议研究的重点是更全面地了解感觉体验在发育过程中精炼突触连接的基本细胞和分子机制，并确定这些机制中的损伤可能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方法确定了Fn14基因，它是一种由兴奋性神经元中的视觉经验转录诱导的基因，编码一种细胞因子受体，这是发育中的大脑进行感觉依赖性精炼所必需的。该提案包含一项全面的培训和研究计划，旨在通过在短期内通过实验解决知识中的剩余差距，并通过促进建立一个创新的、多学科的研究计划，在长期内解决这些问题，从而建立在这些发现的基础上。在目标1中，申请者将学习并应用专门的急性切片电生理学技术来测试这样的假设，即Fn14的促炎细胞因子配体TWINE是必要的，并且足以通过小胶质细胞到神经元的信号轴来驱动感觉依赖性的细化。在目标2中，申请者将结合电生理学和生物信息学中新学的方法来确定在大脑发育异常的母体免疫激活(MIA)小鼠模型中，增强的TWAINE/Fn14信号是否有助于过度的突触细化。在目标3中，申请者将检验这样一个假设，即TWEEP/Fn14信号通过促进未成熟的突触脊椎向成熟脊椎的转化来介导功能细化。这些技术培训活动将得到几位非常成功的科学家的重点指导，他们致力于在哈佛医学院高度活跃和协作的培训环境中帮助申请者获得专业和智力技能。这些活动预计将有助于申请人成功地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.