Investigations of Neuronal Ensembles and Shank3-Homer Scaffolds on Reward and Social Behavior in a Shank3 model of Autism

建议书摘要 社交障碍是包括自闭症在内的几种神经精神障碍的特征 频谱障碍(ASD)。ASD社会缺陷的细胞、分子和回路机制主要是 未知，值得进一步研究。ASD最一致的病因学发现之一是完全性 缺失SHANK3基因，该基因编码神经元中的突触后支架蛋白。我们的实验室开发了 第一个Shank3通过删除外显子4-22(Shank3∆e4-22)来完成基因敲除模型。SHANK3∆e4-22小鼠表现出下降 伏隔核(NAC)的社交和奖赏行为以及对社交暗示的迟钝反应。 NAC是一个公认的社会行为监管者。然而，NAC内神经元的特征 在社会行为或社会群体中活跃的，没有很好的定义。~95%的NAC神经元是 中棘神经元(MSN)表达多巴胺受体d1(d1+)，它编码奖赏 强化，或D2(D2+)，编码厌恶反应。NAC MSN表达高水平的SHANK3，以及 SHANK3基因缺失导致D2+MSN功能发生深刻变化。总而言之，这表明了一种潜在的 Shank3∆e4-22小鼠社会行为缺陷的作用机制。 SHANK3支架HOMER1b/c和代谢型谷氨酸受体5(MGluR5)与突触后 密度(PSD)。NAC中的HOMER1b/c和mGluR5功能对调节社会和奖赏行为至关重要 WT小鼠的行为。为了研究SHANK3-Homer1b/c相互作用的作用，我们的实验室产生了第一个 SHANK3-HOMER1b/c突变小鼠，Shank3PL。自从加入江实验室以来，我收集了一些试点数据， Shank3PL小鼠显著减少了社交和寻求奖励的行为。飞行员数据还表明 Shank3PL小鼠降低了NAC PSD中HOMER1b/c的表达。 这项提案的具体目标是描绘SHANK3缺乏如何导致细胞和 使用我们的两个新的老鼠模型，导致异常电路和社会行为的分子故障： Shank3∆e4-22和Shank3PL。首先，我假设Shank3∆e4-22小鼠中的nac社会群体主要是 由D2+MSN组成，编码厌恶和消极社交；相反，我预测WT社交 合奏主要是D1+MSN，编码强化和积极的社会行为。第二，我 假设SHANK3-HOMER1B/C支架对社会和奖励行为至关重要。我们将测试这些 使用综合方法论的假设。 这项研究将首次在经过充分验证的遗传ASD模型中描述社会群体的特征，并 首次研究了SHANK3-HOMER1b/c支架对行为和NAC活性的影响。重要的是 这些研究可能导致确定新的治疗靶点，用于治疗社交和奖赏缺陷 自闭症和其他神经精神障碍。

PROPOSAL SUMMARY Deficits in social interaction are characteristic of several neuropsychiatric disorders, including Autism Spectrum Disorder (ASD). The cellular, molecular, and circuit mechanisms of social deficits in ASD are largely unknown and warrants further research. One of the most consistent etiological findings in ASD is a complete deletion of the SHANK3 gene, which encodes a postsynaptic scaffold protein in neurons. Our lab developed the first Shank3 complete knockout model by deleting exons 4-22 (Shank3∆e4-22). Shank3∆e4-22 mice show decreased social and reward-seeking behavior and blunted response of the Nucleus Accumbens (NAc) to social cues. The NAc is a well-established regulator of social behavior. Yet, the characteristics of neurons in the NAc that are active during social behavior, or social ensembles, are not well defined. ~95% of neurons in the NAc are medium-spiny neurons (MSNs) that express either dopamine receptor D1 (D1+), which encode reward reinforcement, or D2 (D2+), which encode aversive responses. NAc MSNs express high levels of SHANK3, and Shank3 deletion induces profound changes in D2+ MSN function. Taken together, this indicates a potential mechanism of action for social behavior deficits in Shank3∆e4-22 mice. SHANK3 scaffolds HOMER1b/c and metabotropic glutamate receptor 5 (mGluR5) to the postsynaptic density (PSD). HOMER1b/c and mGluR5 function in the NAc is crucial for regulating social and reward-seeking behaviors in WT mice. To study the role of SHANK3-HOMER1b/c interaction, our lab generated the first SHANK3-HOMER1b/c mutant mouse, Shank3PL. Since joining the Jiang lab, I have collected pilot data showing that Shank3PL mice have significantly decreased social and reward-seeking behavior. Pilot data also indicate Shank3PL mice have decreased HOMER1b/c expression in the PSD of the NAc. The specific objective of this proposal is to delineate how SHANK3 deficiency causes cellular and molecular malfunctions that underlie abnormal circuit and social behavior using our two novel mouse models: Shank3∆e4-22 and Shank3PL. First, I hypothesize that NAc social ensembles in Shank3∆e4-22 mice are primarily composed of D2+ MSNs and encode aversion and negative sociability; in contrast, I predict WT social ensembles are predominantly D1+ MSNs and encode reinforcement and positive social behavior. Second, I hypothesize that SHANK3-HOMER1b/c scaffolds are crucial for social and reward behavior. We will test these hypotheses using comprehensive methodologies. This study will be the first to characterize social ensembles in a well-validated genetic ASD model and the first to investigate the role of SHANK3-HOMER1b/c scaffolds on behaviors and NAc activity. Importantly, these studies may lead to the identification of novel therapeutic targets for treating social and reward deficits in ASD and other neuropsychiatric disorders.