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

描述（由申请人提供）：突触缩放被认为在发育和活动依赖性可塑性期间维持网络的稳定性是重要的。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，表明缺乏稳态缩放。 因此，了解突触扩展对于了解神经元如何在正常和神经病理条件下传递信息并保持可塑性至关重要。由于发育和单眼剥夺，在大鼠视皮层中观察到突触缩放，这表明缩放在回路的活动依赖性细化中是重要的。然而，由于无法选择性地阻止缩放并保持其他形式的可塑性不变，研究受到限制，因此缩放在活动依赖性发育和可塑性中的确切作用仍然不清楚。在单个培养的皮层神经元中，可以用靶向AMPA受体亚基GluR 2的RNAi发夹阻断缩放，这表明GluR 2对缩放的表达至关重要。该提案将确定GluR 2是否也是响应于慢性活动增加而缩小规模所必需的，以及GluR 2亚基的哪个结构域是其在缩放中的调节作用所必需的。该提案还将解决是否可以用条件性GluR 2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动依赖性发育中的作用至关重要。这些问题将说服使用全细胞电压钳记录的微型兴奋性突触后电流（mEPSC）在培养的皮层细胞和急性切片含有层2/3初级视觉皮层。总之，本文提出的实验将（1）进一步表征培养的皮层细胞中突触缩放的分子调节，（2）开发一种在体内以高空间和时间分辨率选择性地阻断缩放的范例，并利用该范例，（3）描述突触缩放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，其特征在于兴奋和抑制平衡的扰动，这可能表明稳态缩放的缺陷。 这些研究将检查完整神经系统中突触缩放的机制和作用，这可能会提供对导致这些疾病的病理过程的见解。

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.