Characterization of the role of Fmr1 in oxytocin neuronal subtypes

修订后的 R01 申请重点阐明 Fmr1 基因在以自闭症谱系障碍 (ASD) 为特征的社交障碍发病机制中的细胞类型特异性功能；这是一个更大项目的第一步，旨在确定基于回路的方法，这些方法可以作为治疗自闭症谱系障碍的疗法。基于广泛的初步研究结果，我们的总体假设是，催产素（OT）神经元中 Fmr1 基因功能的丧失会导致通常促进社会奖励学习的机制的破坏，并且社会奖励学习关键期的关闭限制了成年期提供的治疗干预的效果。我们的假设是基于我们实验室的研究提出的，该研究表明，投射到伏隔核（NAc）的小细胞OT神经元中Fmr1的急性缺失重现了在组成型Fmr1 KO小鼠中观察到的社会奖励学习表型。此外，我们发现了社会奖励学习的一个新的关键时期，并确定了在成年期恢复社会奖励学习的操作。尽管我们有重要的初步发现，但 OT 神经元亚型在 ASD 相关表型中的重要性尚不清楚，而且只得到了最低限度的探索。基于我们的初步见解，我们建议解决有关 Fmr1 缺失的细胞、突触、回路和发育后果的一些悬而未决的问题，如下目标 1-4 中所述： 目标 1：确定 Fmr1 缺失对催产素 (OT) 神经元亚型的分子和细胞后果。在这里我们将 检验 Fmr1 基因缺失将选择性影响小细胞 OT 神经元的细胞特征的假设。目标 2：确定 Fmr1 缺失对 OT 依赖性突触可塑性的影响。在这里，我们将检验以下假设：删除 Fmr1 将导致伏隔核 (NAc) 中的 OT 突触可塑性受损。目标 3：确定 OT 神经元亚型的功能选择性。在这里，我们将检验这样的假设：在投射到 NAc 而不是 VTA 的 OT 神经元消融后，同伴社会奖励学习缺陷将是社会领域特定的。目标 4：确定社会奖赏学习关键期对脆性 X 细胞治疗方法的影响。在这里，我们将检验这样的假设：如果在该关键期结束之前或在成年期与重新开放社会奖赏学习关键期的操作结合进行治疗干预，则可以纠正 Fmr1 KO 小鼠的社会奖赏学习缺陷。此外，目标 1-4 中提出的研究将为功能基因组学提供几种新工具。这些工具将使我们能够执行复杂的分子、突触和电路水平的操作。我们希望所提出的实验能够为社会奖励行为背后的细胞类型特异性机制如何促进自闭症谱系障碍的社会缺陷的发病机制提供新的见解。

This revised R01 application focuses on elucidating the cell type specific functions of the Fmr1 gene in the pathogenesis of social impairments that characterize autism spectrum disorder (ASD); a first step in a larger project aimed at identifying circuit based approaches which could act as therapeutics for treating ASD. Based on extensive preliminary findings, our overall hypothesis is that the loss of Fmr1 gene function in oxytocin (OT) neurons leads to disruption of mechanisms that normally subserve social reward learning, and that closure of the social reward learning critical period limits the efficacy of therapeutic interventions delivered in adulthood. Our hypothesis was formulated based on research in our laboratory demonstrating that acute deletion of Fmr1 in parvocellular OT neurons projecting to the nucleus accumbens (NAc) recapitulates social reward learning phenotypes observed in constitutive Fmr1 KO mice. In addition, we have discovered a novel critical period for social reward learning, and identified manipulations to reinstate social reward learning in adulthood. Despite our important preliminary findings, the importance of subtypes of OT neurons in ASD relevant phenotypes is unknown and only minimally been explored. Building on our preliminary insights, we propose to address a number of outstanding questions concerning the cellular, synaptic, circuit, and developmental consequences of Fmr1 deletion, outlined below in Aims 1-4: Aim 1: To determine the molecular and cellular consequences of Fmr1 deletion in oxytocin (OT) neuronal subtypes. Here we will test the hypothesis that cellular characteristics of parvocellular OT neurons will be selectively impacted by deletion of the Fmr1 gene. Aim 2: To determine the consequences of Fmr1 deletion on OT dependent synaptic plasticity. Here we will test the hypothesis that deletion of Fmr1 will lead to an impairment of OT synaptic plasticity in the nucleus accumbens (NAc). Aim 3: To determine the functional selectivity of OT neuronal subtypes. Here we will test the hypothesis that peer-peer social reward learning deficits will be social domain specific following ablation of OT neurons projecting to the NAc, but not the VTA. Aim 4: To determine the impact of the critical period for social reward learning on the therapeutic approach to Fragile X. Here we will test the hypothesis that social reward learning deficits in Fmr1 KO mice can be corrected if therapeutic interventions are delivered either before the closure of this critical period, or in adulthood if given in conjunction with manipulations that reopen the social reward learning critical period. In addition, the studies proposed in Aims 1-4 will deliver several novel tools for functional genomics. These tools will allow us to perform sophisticated molecular, synaptic and circuit level manipulations. It is our hope that the proposed experiments will provide new insight into how cell type specific mechanisms underlying social reward behavior contribute to the pathogenesis of social deficits in ASD.