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

描述（由申请人提供）：突触缩放被认为是在发育和活动依赖可塑性期间维持网络稳定性的重要因素。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，表明缺乏稳态标度。因此，理解突触尺度对于理解神经元如何在正常和神经病理条件下传递信息和保持可塑性至关重要。由于发育和单眼剥夺，在大鼠视觉皮层中观察到突触缩放，这表明缩放在活动依赖的回路优化中很重要。然而，由于无法有选择地阻断结垢并使其他形式的可塑性保持完整，研究受到限制，因此结垢在活动依赖性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，靶向AMPA受体亚基GluR2的RNAi发夹可以阻断鳞屑的表达，这表明GluR2对鳞屑的表达至关重要。该提案将确定GluR2是否对慢性高活性反应的缩小也是必要的，以及GluR2亚基的哪个结构域在其调节作用中是必需的。该提案还将探讨是否可以通过条件GluR2敲除小鼠模型在体内阻断结垢。能够在体内阻断结垢对于阐明结垢在活性依赖性发育中的作用至关重要。这些问题将在培养的皮质细胞和含有2/3层初级视觉皮层的急性切片中使用全细胞电压钳记录微型兴奋性突触后电流（mEPSCs）来解决。总之，本文提出的实验将(1)进一步表征培养皮层细胞中突触缩放的分子调控，(2)开发一种具有高时空分辨率的选择性阻断体内缩放的范式，并利用该范式(3)描述突触缩放在完整视觉皮层中经验依赖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、Rett综合征和自闭症，其特征是兴奋和抑制平衡受到干扰，这可能表明体内平衡失调。这些研究将探讨突触缩放在完整神经系统中的机制和作用，这可能为导致这些疾病的病理过程提供见解。

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.