Investigating Syngap1 as a regulator of striatal synaptic function

项目摘要 SYNGAP 1相关智力障碍是一种神经发育障碍，由以下基因突变引起： SYNGAP 1基因。SYNGAP 1编码SynGAP，这是一种在后- 兴奋性突触的突触密度在突触处，SynGAP的功能是抑制下游NMDAR 信号传导和AMPAR运输通过其抑制小GTP酶。SynGAP的易位 需要突触后密度以允许培养的神经元中的NMDAR依赖性长时程增强（LTP 神经元在缺乏SynGAP的情况下，NMDAR依赖的可塑性不受限制，导致改变 突触强度、脊柱结构和可塑性。虽然SynGAP的功能已经很好- 在皮质和海马中研究，纹状体也表现出高水平的SynGAP表达。 纹状体投射神经元是GABA能神经元，覆盖在密集的树突棘阵列中， 从大脑皮层接收兴奋性信息因此，SynGAP定位于在门控方面发挥关键作用 纹状体突触的传递和可塑性。尽管如此，SynGAP在纹状体神经元中的功能 尚未定义。重要的是，SYNGAP 1紊乱的几个主要症状可能与 涉及纹状体活动的改变，包括运动发育延迟、重复和限制性 行为和其他行为问题。 在这个项目中，我们将阐明SynGAP缺失对纹状体突触功能的影响， 并确定纹状体神经元SynGAP的缺失是否足以诱导行为改变 与SYNGAP 1紊乱有关。具体来说，我们将确定SynGAP的缺失如何影响纹状体 突触发育、传递和可塑性。此外，我们将使用成像方法， 研究SynGAP缺陷如何影响棘发生、棘数量和形态。以确定 无论Syngap 1从纹状体神经元的缺失是否足以改变疾病相关的行为，我们将 研究细胞类型特异性敲除小鼠中Syngap 1单倍不足如何影响运动功能， 习惯学习和行为灵活性。最后，我们将测试Syngap 1表达的恢复是否 选择性地在纹状体投射神经元中使用基因治疗可以改善突触和行为异常， 救援策略。总之，这项工作将1）进一步了解SynGAP在纹状体的功能， 突触，2）鉴定与SYNGAP 1病症的表现最相关的纹状体细胞类型， 和3）定义疾病相关表型发生和挽救的关键时期。

PROJECT SUMMARY SYNGAP1-related intellectual disability is a neurodevelopmental disorder caused by mutations in the SYNGAP1 gene. SYNGAP1 encodes SynGAP, which is a highly abundant protein in the post- synaptic density of excitatory synapses. At synapses, SynGAP functions to repress downstream NMDAR signaling and AMPAR trafficking through its inhibition of small GTPases. Translocation of SynGAP out of the post-synaptic density is required to allow NMDAR-dependent long-term potentiation (LTP) in cultured neurons. In the absence of SynGAP, NMDAR-dependent plasticity is unrestrained leading to alterations in synapse strength, spine structure, and plasticity. While the functions of SynGAP have been well- studied in the cortex and hippocampus, the striatum also exhibits high levels of SynGAP expression. Striatal projection neurons are GABA-ergic neurons covered in a dense array of dendritic spines, which receive excitatory inputs from the cortex. SynGAP is therefore positioned to play a key role in gating transmission and plasticity at striatal synapses. Despite this, SynGAP’s functions in striatal neurons have not yet been defined. Importantly, several of the major symptoms of SYNGAP1 disorder are likely to involve alterations in striatal activity including motor developmental delay, repetitive and restrictive behaviors, and other behavioral problems. In this project, we will elucidate the consequences of SynGAP loss on striatal synaptic function and determine whether loss of SynGAP from striatal neurons is sufficient to induce behavioral alterations relevant for SYNGAP1 disorder. Specifically, we will determine how loss of SynGAP impacts striatal synaptic development, transmission and plasticity. In addition, we will use imaging approaches to investigate how SynGAP deficiency affects spinogenesis, spine number and morphology. To determine whether deletion of Syngap1 from striatal neurons is sufficient to alter disease-relevant behaviors, we will investigate how haploinsufficiency of Syngap1 in cell type-specific knock-out mice affects motor function, habit learning, and behavioral flexibility. Finally, we will test whether restoration of Syngap1 expression selectively in striatal projection neurons can improve synaptic and behavioral abnormalities using genetic rescue strategies. Together, this work will 1) further our understanding of SynGAP’s functions at striatal synapses, 2) identify the striatal cell type(s) most relevant for the manifestations of SYNGAP1 disorder, and 3) define critical periods for the onset and rescue of disease-related phenotypes.