Maladaptive Compensatory Plasticity in Developing Cortical Circuits

包括自闭症谱系障碍和智力障碍在内的发育障碍可导致 大脑皮层活动减少。矛盾的是，这些疾病也大大增加了罹患癌症的风险。 癫痫发作。多种动态平衡可塑性机制可以通过增加 兴奋性突触传递和细胞兴奋性，和/或通过减少抑制性突触传递。 但这些通常有益的机制可能会产生不适应的影响，特别是当活动减少时 持续时间长，发生得早，处于电路形成的关键时期。例如，体内的活动阻断在 大鼠或小鼠的新皮质，可诱导癫痫发作，但只有在发作较早且持续时间较长的情况下。在这里我们 探讨培养的新皮质细胞发生不适应性代偿性可塑性(MCP)的机制 切片。活动阻止会在后续同步的活动中产生持续的质的变化 在长时间的剥夺之后，当活动恢复时。伴随着这一变化的是 在兴奋和抑制之间取得平衡。生理和影像研究符合戏剧性的 突触连接性的改变。目标1将确定MCP的关键生理特征，将其分开 来自正常的体内平衡可塑性。通过阻断单个神经元的活动，并通过改变时间和 活动封锁的持续时间，我们将区分细胞自治和网络影响，并确定 对MCP的持久影响至关重要。使用突触成像技术和配对记录，我们要求 MCP的诱导是否会改变功能性兴奋性和抑制性突触的数量。 AIMS 2发展了内稳态可塑性的推/拉转录调控的新概念。我们 识别一对密切相关的转录因子(TF)，它们被有效地、渐进地上调 在封锁活动期间。有趣的是，这些TF是反对补偿性可塑性的途径的一部分， 因为当补偿反应被击倒时，它们被夸大了。基于CRISPR的操作将 用于选择性地改变特定细胞类型中的转铁蛋白表达。RNAseq将用于识别候选人 目标，染色质分析将区分直接和间接目标。最后，我们将启动体内研究 为了更直接地测试稳态可塑性及其转录调控在听源性癫痫发作中的作用。 总之，这些研究可能会确定减轻正常适应不良后果的新策略 有益的可塑性机制。

Developmental disorders including Autism Spectrum Disorders and Intellectual Disability can lead to reduced cortical activity. Paradoxically, these same disorders also greatly increase the risk for developing seizures. Multiple homeostatic plasticity mechanisms can compensate for reduced activity by increasing excitatory synaptic transmission and cellular excitability, and/or by decreasing inhibitory synaptic transmission. But these normally beneficial mechanisms can have maladaptive effects, especially when reduced activity is prolonged and occurs early, during a critical period of circuit formation. For example, activity blockade in vivo in rat or mouse neocortex, induces seizures, but only if it occurs early and for a prolonged period. Here we explore the mechanisms underlying this Maladaptive Compensatory Plasticity (MCP) in cultured neocortical slices. Activity blockade produces a qualitative change in subsequent synchronized activity that persists following prolonged deprivation when activity is restored. This is accompanied by a dramatic shift in the balance between excitation and inhibition. Physiological and imaging studies are consistent with a dramatic change in synaptic connectivity. Aim 1 will identify the critical physiological features of MCP, that separate it from normal homeostatic plasticity. By blocking activity in single neurons, and by varying the timing and duration of activity blockade, we will distinguish cell autonomous from network effects, and determine which are critical for persistent effects of MCP. Using synapse imaging techniques and paired recording, we ask whether induction of MCP alters the number of functional excitatory and inhibitory synapses. Aims 2 develops the novel idea of push/pull transcriptional regulation of homeostatic plasticity. We identify a pair of closely related transcription factors (TFs) that are potently and progressively upregulated during blockade of activity. Intriguingly, these TFs are part of a pathway that opposes compensatory plasticity, since compensatory responses are exaggerated when they are knocked out. CRISPR-based manipulations will be used to alter TF expression selectively in specific cell types. RNAseq will be used to identify candidate targets, and chromatin assays will distinguish direct and indirect targets. Finally, we will initiate in vivo studies to more directly test the role of homeostatic plasticity and its transcriptional regulation in audiogenic seizures. Together these studies may identify new strategies for mitigating maladaptive consequences of normally beneficial plasticity mechanisms.