Inhibitors of Synaptogenesis and Mental Health

越来越多的证据表明，许多神经精神障碍与发育有关 基因基础。大量的等位基因变异已经被发现与精神疾病有关。 虽然基因发现是关键的第一步，但下一个主要挑战是定义生化 疾病等位基因改变的途径，并对这些功能障碍如何产生更细微的理解 通路扰乱了与疾病症状相关的大脑功能。令人感兴趣的是，基因成员的突变 信号素(SEMA)家族轴突引导分子及其受体PLEXINS(PLXN)携带 精神疾病的遗传风险各不相同。SEMA5A及其受体PLXNA2的等位基因变异与 情绪障碍会导致基因表达减少。来探索如何减少的潜在生物学 SEMA5A/PLXNA2的表达可能与精神疾病有关，我们使用PlxNA2转基因小鼠作为 实验系统。对Sema5a和PlxNa2突变小鼠的形态研究发现 解剖学表型：早期出生的齿状颗粒细胞(GC)前体细胞迁移缺陷 成年大鼠海马齿状回初级神经上皮细胞和脊髓突触密度的增加 DG。成年Plxna2小鼠在情景记忆中表现出基因剂量和性别特异性的行为缺陷， 感觉运动门控和社交能力；在精神障碍中常见的特征包括 精神分裂症。为了更深入地了解PlxNA2缺陷如何影响行为表型， 我们使用基因编辑来破坏PlxnA2细胞质区域的GTP酶激活蛋白(GAP)结构域。 PlxnA2-GAP酶活性丧失损害RAP1-GTP酶依赖的GC前体迁移并导致 成熟GC中的额外脊椎突触。此外，PlxnA2-GAP缺陷扰乱了情景记忆 和感觉运动门控。进一步探讨Sema5A/PlxnA2-GAP/Rap1信号受损是如何导致 行为缺陷，我们使用了基于蛋白质组学的方法，并鉴定了新的PlxnA2相互作用蛋白。在……里面 在目前的应用中，我们提出了一个多学科的方法，包括最近发展起来的生化 工具、电生理技术、条件性基因消融和小鼠行为。特定的目标1是 针对调节Sema5A-PlxnA2信号的新机制的特征，包括 鸟嘌呤核苷酸交换因子(GEF)，拮抗PlxnA2-GAP活性。特定的AIM 2构建于 我们观察到前脑特异性消融PlxNA2模拟了在PlxNA2中观察到的行为缺陷 生殖系缺失小鼠。我们采用老鼠遗传方法来识别易受攻击的发育时期。 以及与PlxNA2-/-和PlxNA2-GAP缺陷小鼠的行为受损有关的神经底物。 基因研究将得到电生理记录、组织学分析和高密度脂蛋白的补充。 分辨率磁共振成像。研究的目的是确定PlxNA2-GAP的地点和时间 在大脑发育过程中，功能是必需的，以确保成年后的正常行为。

Mounting evidence suggests that many neuropsychiatric disorders have a developmental origin with a strong genetic underpinning. A large number of allelic variants has been identified that associate with mental illness. While genetic discoveries are a crucial first step, the next major challenge is to define the biochemical pathways altered by disease alleles and to develop a more nuanced understanding of how these dysfunctional pathways disrupt brain function relevant to disease symptomatology. Of interest, mutations in members of the SEMAPHORIN (SEMA) family of axon guidance molecules, and their receptors, the PLEXINS (PLXN) carry varying genetic risks for mental illness. Allelic variants of SEMA5A and its receptor PLXNA2 associated with mood disorders cause reduced gene expression. To explore the underlying biology of how reduced SEMA5A/PLXNA2 expression may contribute to mental illness, we use Plxna2 transgenic mice as an experimental system. Morphological studies with Sema5a and Plxna2 mutant mice identified distinct anatomical phenotypes: defects in migration of early-born dentate granule cells (GCs) progenitors from the primary neuroepithelium to the dentate gyrus (DG) and an increase in spine synapse density in mature GCs in the DG. Adult Plxna2 mice exhibit gene-dosage and sex-specific behavioral defects in episodic memory, sensorimotor gating, and sociability; traits commonly observed in psychiatric disorders including Schizophrenia. For a deeper understanding of how Plxna2 deficiency may contribute to behavioral phenotypes, we used gene editing to disrupt the GTPase-activating protein (GAP) domain in the PlxnA2 cytoplasmic region. Loss of PlxnA2-GAP enzymatic activity impairs Rap1-GTPase dependent GC progenitor migration and leads to supernumerary spine synapses in mature GC. Moreover, PlxnA2-GAP deficiency disrupts episodic memory and sensorimotor gating. To probe deeper into how impaired Sema5A/PlxnA2-GAP/Rap1 signaling leads to behavioral defects, we used a proteomics-based approach and identified novel PlxnA2 interacting proteins. In the current application we propose a multidisciplinary approach comprised of recently developed biochemical tools, electrophysiological techniques, conditional gene ablation and mouse behavior. SPECIFIC AIM 1 is aimed at the characterization of novel mechanisms that regulate Sema5A-PlxnA2 signaling, including the guanine nucleotide exchange factors (GEFs) that antagonize PlxnA2-GAP activity. SPECIFIC AIM 2 builds on our observation that forebrain specific ablation of Plxna2 mimics behavioral defects observed in Plxna2 germline null mice. We pursue a mouse genetic approach to identify developmental epochs of vulnerability and the neural substrate associated with impaired behaviors in Plxna2-/- and Plxna2-GAP deficient mice. Genetic studies will be complemented by electrophysiological recordings, histological analyses and high- resolution magnetic resonance imaging. Studies are aimed at determining where and when Plxna2-GAP function is required during brain development to ensure normal behavior in adulthood.