The Role of GluR2-dependent Synaptic Scaling in Development and Plasticity

描述(由申请人提供)：突触伸缩被认为在发育过程中维持网络的稳定性和活动依赖的可塑性方面很重要。在某些病理条件下，如癫痫，兴奋和抑制的平衡被极大地扰乱，表明缺乏动态平衡调节。因此，了解突触伸缩对于理解神经元在正常和神经病理条件下如何传递信息和保持可塑性至关重要。由于发育和单眼剥夺，在大鼠视皮层观察到突触伸缩，这表明伸缩在依赖活动的环路精炼中是重要的。然而，由于无法选择性地阻止伸缩并保持其他形式的可塑性不变，研究一直受到限制，因此，伸缩在依赖活动的发育和可塑性中的确切作用仍不清楚。在单个培养的皮质神经元中，通过针对AMPA受体亚单位GluR2的RNAi发夹可以阻止Scaling，这表明GluR2对Scaling的表达至关重要。这项提议将确定GluR2是否也是应对慢性活动增加而缩减规模所必需的，以及GluR2亚单位的哪个结构域是其在规模调整中所必需的。这项建议还将解决是否可以通过条件GluR2基因敲除小鼠模型在体内阻止伸缩。能够阻止体内的伸缩对于阐明伸缩在依赖活动的发育中的作用至关重要。这些问题将通过全细胞电压钳记录培养的皮质细胞和含有第2/3层初级视觉皮质的急性切片中的微型兴奋性突触后电流(MEPSCs)来解决。综上所述，本文提出的实验将(1)进一步表征培养的大脑皮层细胞突触伸缩的分子调控；(2)开发一种在体内以高空间和时间分辨率选择性阻断伸缩的范式；(3)描述突触伸缩在完整视皮层的经验依赖性发育和可塑性中的作用。公共卫生相关性：突触缩放被认为对维持神经网络的稳定性很重要。许多神经系统疾病，如癫痫、雷特综合征和自闭症，其特点是兴奋和抑制的平衡受到干扰，这可能暗示着自稳调节的缺陷。这些研究将考察突触伸缩在完整神经系统中的机制和作用，这可能有助于深入了解导致这些疾病的病理过程。

DESCRIPTION (provided by applicant): Synaptic scaling is thought to be important in maintaining the stability of networks during development and activity-dependent plasticity. Under certain pathological conditions, such as epilepsy, the balance of excitation and inhibition is greatly perturbed, suggesting a lack of homeostatic scaling. Therefore, understanding synaptic scaling is crucial for understanding how neurons transfer information and remain plastic under normal and neuropathological conditions. Synaptic scaling has been observed in rat visual cortex as a result of development and monocular deprivation, suggesting that scaling is important in the activity-dependent refinement of circuits. However, studies have been limited by the inability to selectively block scaling and leave other forms of plasticity intact, and so the precise role of scaling in activity-dependent development and plasticity remains unclear. Scaling can be blocked in single cultured cortical neurons with an RNAi hairpin that targets the AMPA receptor subunit, GluR2, suggesting that GluR2 is critical for expression of scaling. This proposal will determine if GluR2 is also essential for scaling down in response to chronic heightened activity and which domain of the GluR2 subunit is required for its regulatory role in scaling. This proposal will also address whether scaling can be blocked in vivo with a conditional GluR2 knockout mouse model. Being able to block scaling in vivo is critical for elucidating the role of scaling in activity-dependent development. These questions will be persued using whole-cell voltage-clamp recordings of miniature excitatory postsynaptic currents (mEPSCs) in cultured cortical cells and acute slices containing layer 2/3 primary visual cortex. Together, the experiments proposed here will (1) further characterize the molecular regulation of synaptic scaling in cultured cortical cells, (2) develop a paradigm for selectively blocking scaling with high spatial and temporal resolution in vivo, and with this paradigm, (3) describe the role of synaptic scaling in experience-dependent development and plasticity in intact visual cortex. PUBLIC HEALTH RELEVANCE: Synaptic scaling is thought to be important in maintaining the stability of neural networks. Many neurological disorders, such as epilepsy, Rett Syndrome, and autism, are characterized by a perturbation in the balance of excitation and inhibtion, perhaps suggesting a deficit in homeostasic scaling. These studies will examine the mechanism and role of synaptic scaling in the intact nervous system, which may provide insight into the pathological processes that result in these disorders.