NMDAR Mutations & Neurodevelopmental Disorder: from Mechanism to Targeted Therapy

摘要 N-甲基-D-天冬氨酸受体(NMDAR)是一种配体门控离子通道，介导慢反应 它是兴奋性突触后电流的组成部分，在正常脑功能中发挥着重要作用。遗传 编码谷氨酸亚基的GRIN基因变异与神经发育障碍有关， 包括癫痫脑病、自闭症和智力残疾，这些疾病会带来毁灭性的精神和心理障碍 对个人、他们的家庭和社会的经济后果。在第一份关于疾病的报告之后- 由于2010年导致了GRIN变异，大量的人类GRIN基因变异(&gt；300)已经被确定 在有各种神经问题的儿科患者中。我们在上一个资金周期中的研究表明， 类似的表型(即癫痫)可由功能获得(GOF)和功能丧失变异引起 (IOF)在同一基因中。我们的工作还揭示了不同的GRIN变体对 FDA批准的药物，三名无关患者对同一治疗有不同的反应 在“N of 1”试验中拥有相同的变种。拟议中的实验将提供第一个详细的评估 在不同的发展阶段跟踪LOF和GOF NMDAR的电路功能，并解决两者如何 对NMDAR的相反作用可能会产生类似的表型。这些研究将定义一个关键窗口 建立了哪些与异常活动相关的电路连接，并将为 通过建议新的治疗策略来缓解功能变化，从而使药物个性化。 具体目标1：新发现的与疾病相关的GRIN变体的功能评估和对 在普通人群中存在GRIN2A型变异。我们将分析所有新发布的功能属性 以及未发表的与疾病相关的GRIN变体在受体的未被研究的区域。我们会 确定健康个体蛋白质功能与等位基因频率的关系，并评估 不耐受基因的变异可以作为神经紊乱的危险因素的观点。 具体目标2：NMDAR活性丧失如何促进网络过度兴奋和诱发癫痫 表型？我们将在体内评估拥有两个LOF变体的敲除小鼠和GluN2A基因敲除小鼠 探讨NMDAR功能丧失是否会减少突触抑制并导致网络过度兴奋。 具体目标3：功能获得性GRIN变异相关的早发性癫痫的机制是什么？ 脑病？我们将使用三种Gof GRIN变体的活体敲打小鼠模型来确定 NMDAR功能增强是否会导致癫痫发作和早发性癫痫脑病。 具体目标4：如何才能最好地治疗GRIN/NMDAR通道病？我们将筛查~2,000名FDA- 批准的药物具有纠正GRIN变体引起的过度兴奋的能力。我们将评估以下行动： FDA批准的药物在转基因小鼠身上，以确定兴奋/抑制失衡是否可以恢复。

ABSTRACT N-methyl-D-aspartate receptors (NMDARs) are ligand-gated ion channels that mediate the slow component of excitatory post-synaptic currents and play important roles in normal brain function. Genetic variations in GRIN genes, which encode the GluN subunits, are linked to neurodevelopmental disorders, including epileptic encephalopathy, autism, and intellectual disability, which carry devastating mental and economic consequences for the individuals, their families, and society. Following the first report on disease- causing GRIN variants in 2010, a large number of human variants (>300) in GRIN genes have been identified in pediatric patients with various neurologic problems. Our studies in the previous funding cycle indicated that similar phenotypes (i.e. seizures) could result from both gain-of-function (GoF) and loss-of-function variants (LoF) in the same gene. Our work also revealed that different GRIN variants present differential sensitivity to FDA-approved drugs, and there are divergent responses to the same treatment among three unrelated patients hosting the same variant in “N of 1” trials. The proposed experiments will provide the first detailed evaluation of circuit function following LoF and GoF NMDAR at different developmental stages, and address how the two opposite effects on NMDARs might generate a similar phenotype. These studies will define a critical window in which circuit connections relevant for aberrant activity are established, and will advance opportunities for personalized medicine by suggesting new therapeutic strategies for mitigation of functional changes. Specific Aim 1: Functional assessment of newly identified disease-associated GRIN variants and evaluation of GRIN2A variants in the general population. We will analyze the functional properties of all newly published and unpublished disease-associated GRIN variants in the understudied regions of the receptors. We will determine the relationship between protein function and allelic frequency in healthy individuals, and evaluate the idea that variation of intolerant genes can act as risk factors for neurological disorders. Specific Aim 2: How does the loss of NMDAR activity promote network hyperexcitability and induce epileptic phenotypes? We will evaluate in vivo knockin mice hosting two LoF variants and GluN2A knockout mice to explore whether loss of NMDAR function reduces synaptic inhibition and leads to network hyperexcitability. Specific Aim 3: What is the mechanism of gain-of-function GRIN variant-associated early-onset epileptic encephalopathy? We will use in vivo knockin mouse models for three GoF GRIN variants to determine whether enhanced NMDAR function drives seizures and early-onset epileptic encephalopathy. Specific Aim 4: How can GRIN/NMDAR channelopathies best be treated? We will screen ~2,000 FDA- approved drugs for their ability to rectify GRIN variant-induced hyperexcitability. We will evaluate actions of FDA-approved drugs on transgenic mice to determine if the excitation/inhibition imbalance can be restored.