Bidirectional Tyrosine Kinase Signaling

描述（由申请人提供）：我们的项目以研究大脑为中心，这将帮助我们更好地理解在精神疾病中经常失控的神经网络是如何在发育过程中建立起来的。大脑皮层的正常功能主要取决于兴奋性神经元和抑制性神经元的精确平衡，它们共同控制着高阶大脑活动所必需的信息流和神经网络的同步。前脑gaba能抑制性中间神经元的紊乱会影响兴奋和抑制之间的微妙平衡，导致高兴奋性和神经精神疾病，如癫痫、自闭症、其他智力残疾、精神分裂症和情绪障碍。虽然这些情况彼此不同，但它们通常在前脑中间神经元的数量/分布/功能方面具有共同的干扰。这表明，在建立和维持正常大脑活动所必需的兴奋和抑制信号的稳态平衡中，相关机制发挥了作用，而中间神经元功能的破坏导致了失衡和病理后果。近年来，在鉴定人类精神疾病的基因方面取得了很大进展，其中包括高度保守的神经元EphB2受体酪氨酸激酶。敲除小鼠是一种特别有吸引力的动物模型，可以用来分析啮齿动物中这些基因的突变如何影响中间神经元的发育并导致精神类行为。尽管取得了这些进展，但我们对调节中间神经元迁移和整合到皮层网络的分子机制的了解仍然很初级。在我们正在进行的EphB受体及其跨膜ephrin-B配体的研究中，我们产生了新的条件脑特异性突变小鼠，并发现它们表现出癫痫发作和异常的高兴奋性自闭症样行为，这些行为与皮层和海马中有缺陷的中间神经元群有关。我们的新数据允许我们假设Eph/ephrin-B细胞间信号传导是正常兴奋/抑制（E/I）平衡所需的中间神经元的重要组成部分。为了进一步建立Eph/ephrin-B信号传导、中间神经元发育和E/I平衡之间的新联系，我们将确定gaba能细胞类型中ephrin-B的特异性缺失如何影响中间神经元向发育中的前脑和发达大脑中轴突/树突/突触形态的迁移。电生理和行为研究将评估抑制神经元中ephrin-B的缺失如何影响E/I平衡并导致异常的自闭症样行为。为了补充gaba能特异性条件敲除的分析，将研究细胞内ephrin-B突变体，以确定中间神经元中反向信号的作用。通过上述实验，我们将更好地了解ephrin-B蛋白如何参与调节皮质E/I平衡和功能，以防止异常精神类型行为的形成。

DESCRIPTION (provided by applicant): Our project is centered on studies of the brain that will help us better understand how neural networks that often go haywire in psychiatric disorders are built during development. Normal functioning of the cerebral cortex depends critically on the precise balance of excitatory neurons and inhibitory neurons, which together control the flow of information and synchronization of neural networks necessary for higher order brain activity. Disturbances in forebrain GABAergic inhibitory interneurons can affect the delicate balance between excitation and inhibition, leading to hyperexcitability and neuropsychiatric diseases such as epilepsy, autism, other intellectual disabilities, schizophrenia, and mood disorders. While these conditions are distinct from each other, they typically have in common disturbances in the number/distribution/function of forebrain interneurons. This suggests related mechanisms are in play to establish and maintain the homeostatic balance of excitatory and inhibitory signals necessary for normal brain activity and that disruption of interneuron function leads to imbalances with pathological consequences. Great progress has been made in recent years by the identification genes that contribute to psychiatric disorders in humans, including the highly conserved neuronal EphB2 receptor tyrosine kinase. Knockout mice are particularly attractive animal models to analyze how mutation of such genes in the rodent affects interneuron development and leads to psychiatric-type behaviors. Despite these advancements our knowledge of the molecular mechanisms that regulate interneuron migration and integration into the cortical network remains rudimentary. In our ongoing studies of the EphB receptors and their transmembrane ephrin-B ligands, we have generated new conditional brain-specific mutant mice and find they present with seizures and abnormal hyperexcitable autistic-like behaviors that are associated with defective interneuron populations in the cortex and hippocampus. Our new data allows us to hypothesize that Eph/ephrin-B cell-to-cell signaling is an essential component of interneurons required for normal excitatory/inhibitory (E/I) balance. To further build this new link between Eph/ephrin-B signaling, interneuron development, and E/I balance, we will determine how specific loss of ephrin-B's within the GABAergic cell type affects interneuron migration into the developing forebrain and axonal/dendritic/synaptic morphology in the developed brain. Electrophysiological and behavioral studies will assess how loss of ephrin-B in inhibitory neurons affects E/I balance and leads to abnormal autistic-like behaviors. To complement the analysis of GABAergic specific conditional knockouts, intracellular ephrin-B mutants will be studied to determine the role of reverse signaling in interneurons. Through the described experiments we will gain a better understanding of how the ephrin-B proteins participate in regulating cortical E/I balance and function to prevent formation of abnormal psychiatric-type behaviors.