Neurodevelopmental disorder-associated Rho regulators in neocortical development

摘要 新皮质是一种对所有高级功能至关重要的大脑结构，它的正常发育和功能依赖于 新皮质锥体(NP)神经元从出生地到终末的严格控制的迁移 在发育中的新皮质中的位置。一旦神经元到达目的地，它们就会进一步成熟和建立 功能连接。值得注意的是，NP神经元的迁移缺陷与神经发育有关 认知障碍(NDDS)和癫痫，强调这一过程在新皮质的重要性 发展和功能。然而，控制NP神经元迁移和相关的分子机制 人们对脑部疾病的了解仍然很少。我们最近发现，包含Rho-Gap的多域 寡胺-1(OPHN1)在发育中的新皮质中的NP神经元中显著表达，重要的是， 它在新生NP神经元在体内的正确迁移和随后的定位中起着关键作用。值得注意的是， OPHN1的突变会导致一种综合征形式的智力残疾。除了学习障碍，受影响的 个人通常表现为癫痫发作和行为/感觉缺陷。这些发现提供了一种独特的 研究控制NP神经元迁移的机制以及这种放松管制如何起作用的切入点 常见的脑部疾病。本申请旨在定义OPHN1管理的基本机制 NP神经元迁移，以阐明OPHN1是如何在这些神经元中调节的，并表征其丢失的特征 在胚胎发育过程中影响出生后/成年小鼠新皮质的细胞结构/功能，并 这种动物的行为。为此，目标1将定义和描述细胞过程和效应器 OPHN1侵袭的路径。我们的初步数据表明，OPHN1通过依赖RhoA发挥作用 和RhoA不依赖的通路，每一个都影响NP神经元迁移的不同细胞方面。因此， 我们将描绘涉及的RhoA效应途径(S)，并确定新的分子相互作用 利用创新的遗传、分子和细胞工具，OPHN1的S对NP神经元迁移产生了影响。目标2将 研究NP神经元中OPHN1功能的调节机制，尤其是BDNF 受体酪氨酸激酶TrkB，我们推测它是OPHN1在NP神经元迁移中的关键调节因子 使蛋白质磷酸化，从而激活蛋白质。为了测试这一点，我们将使用分子/细胞工具和 阐明BDNF/TrkB信号调节OPHN1的方式并解决其功能的遗传策略 对NP神经元迁移的重要性。目标3将应用形态测量和电生理技术 观察幼年和成年NEX大鼠新皮质内NP神经元的形态和神经元/网络活动。 Ophn1cKO小鼠在有丝分裂后NP神经元中缺乏OPHN1。此外，我们将研究NEX的行为- Ophn1cKO小鼠，除癫痫外，特别关注基于感觉和社会/行为的反应 敏感度。总之，我们的研究将为控制NP神经元的机制提供新的见解 迁移，并阐明了有助于认知和癫痫的NDDS的病理机制。

ABSTRACT Proper development and function of the neocortex, a brain structure critical for all higher-order functions, relies on the tightly controlled migration of neocortical pyramidal (NP) neurons from their place of birth to their final position in the developing neocortex. Once neurons reach their destination, they further mature and establish functional connections. Significantly, defects in the migration of NP neurons are linked to neurodevelopmental disorders (NDDs) of cognition and epilepsy, highlighting the importance of this process in neocortical development and function. Yet, the molecular mechanisms that govern NP neuron migration and associated brain disorders remain poorly understood. We recently uncovered that the multi-domain containing Rho-GAP oligophrenin-1 (OPHN1) is prominently expressed in NP neurons in the developing neocortex, and, importantly, that it plays a key role in the proper migration and consequent positioning of newborn NP neurons in vivo. Notably, mutations in OPHN1 cause a syndromic form of intellectual disability. Besides learning disabilities, affected individuals typically exhibit epileptic seizures and behavioral/sensory deficits. These findings provide a unique entry point for studying the mechanisms that control NP neuron migration and how such deregulation contributes to common brain disorders. This application aims to define the underlying mechanisms by which OPHN1 governs NP neuron migration, to elucidate how OPHN1 is regulated in such neurons, and to characterize how its loss during embryonic development affects the cytoarchitecture/function of the postnatal/adult mouse neocortex and the behavior of such animals. To this end, Aim 1 will define and characterize the cellular processes and effector pathways OPHN1 impinges on. Our preliminary data suggest that OPHN1 exerts its effects via RhoA-dependent and RhoA-independent pathways, each influencing distinct cellular aspects of NP neuron migration. Therefore, we will delineate the RhoA effector pathway(s) involved and identify novel molecular interactions that mediate OPHN1’s effects on NP neuron migration, using innovative genetic, molecular and cellular tools. Aim 2 will investigate the mechanisms that regulate OPHN1 function in NP neurons, with a particular focus on the BDNF receptor tyrosine kinase TrkB, which we posit to act as key regulator of OPHN1 in NP neuron migration by phosphorylating and consequently activating the protein. To test this, we will employ molecular/cellular tools and genetic strategies to illuminate the mode of OPHN1 regulation by BDNF/TrkB signaling and address its functional importance for NP neuron migration. Aim 3 will apply morphometric and electrophysiological techniques to examine the morphology of NP neurons and neuronal/network activity in neocortices of juvenile/adult NEX- Ophn1cKO mice lacking OPHN1 in postmitotic NP neurons. Furthermore, we will examine the behavior of NEX- Ophn1cKO mice, with a particular focus on sensory-based and social/behavioral responses in addition to seizure susceptibility. Together, our studies will provide novel insight into the mechanisms governing NP neuron migration and shed light on the pathomechanisms contributing to NDDs of cognition and epilepsy.