Mechanisms of altered synaptic integration and plasticity underlying cellular and circuit dysfunction in genetic epilepsy disorders

项目摘要。突触整合和可塑性是信息传递的细胞机制， 认知、学习和记忆这些基本过程在癫痫中是如何被破坏的尚不清楚。 全身性癫痫伴热性惊厥+/Dravet综合征（GEFS+/DS）是一种癫痫病谱， 与SCN 1B基因突变有关的疾病，导致癫痫发作、神经发育迟缓和过早死亡。 为了开发GEFS+/DS癫痫发作/认知缺陷的治疗方法，迫切需要确定 SCN 1B突变破坏细胞水平信息处理和学习的机制。我们长久以来- 术语的目标是定义一般原则，将基因与破坏的突触整合和可塑性联系起来， 神经发育障碍我们的建议的总体目标是确定如何之间的相互作用syn- 突触、树突生理学和躯体生理学损害了Scn 1b敲除中的突触整合和可塑性， GEFS+/DS的KO小鼠模型。我们的中心假设是Scn 1b的丢失会使离子通道失调， 树突兴奋性，干扰整合和可塑性。为了验证这个假设，我们将完成三个目标： 目的1：探讨Scn 1b基因敲除神经元体细胞和树突细胞超兴奋的机制。 基于初步的数据，我们的假设是，树突和胞体的Scn 1b KO CA 1锥体神经元， 电子表现出内在的超兴奋性，部分原因是异常的HCN通道活性。我们将检验这一假设 用全细胞体细胞和树突记录、免疫组织化学和细胞形态学分析。 目的2：确定Scn 1b KO神经元突触整合改变的机制。基于我们 根据初步数据，我们的假设是Scn 1b的丢失从根本上改变了输入到输出的转换， 由于树突过度兴奋，时间和空间突触整合异常增强， 破坏了突触生理我们将使用全细胞记录来测试细胞的时间和空间特征， 输入/输出功能在Scn 1b KO神经元中响应于突触输入的自然模式而改变。 目的3：检验Scn 1b破坏改变突触学习规则和GABA门控的假设 决定了可塑性。根据我们的初步数据，我们的假设是， 由于抑制的兴奋、过度兴奋的内在因素之间的相互作用，LTP和LTD感应被重新塑造 性质，和异常门控的异常去极化抑制后的损失Scn 1b。我们将测试如何输入 在Scn 1b缺失后，诱发LTP和LTD转变的模式，以及抑制如何影响这种可塑性。 在成功完成拟议的研究后，我们将确定详细的机制， 神经元内在和突触生理学的变化及其相互作用重新塑造了神经元的细胞形式。 在GEFS+/DS的Scn 1b KO小鼠模型中的加工和学习。这一贡献将提供机械 遗传变化、主要神经生理学表型和神经元加工缺陷之间的联系， 在GEFS+/DS癫痫中癫痫发作和学习、记忆和认知障碍。

PROJECT SUMMARY. Synaptic integration and plasticity are the cellular mechanisms of information pro- cessing, learning, and memory. How these fundamental processes are disrupted in epilepsy is not understood. Generalized Epilepsy with Febrile Seizures Plus/Dravet syndrome (GEFS+/DS) is a spectrum of epilepsy disor- ders linked to mutations of the SCN1B gene which cause seizures, neurodevelopmental delays, and early death. To develop treatments for seizures/cognitive deficits of GEFS+/DS epilepsies, there is a critical need to identify mechanisms by which SCN1B mutations disrupt cellular-level information processing and learning. Our long- term goal is to define general principles linking genes to disrupted synaptic integration and plasticity in such neurodevelopmental disorders. The overall objective of our proposal is to define how the interplay between syn- apses, dendritic physiology, and somatic physiology impair synaptic integration and plasticity in the Scn1b knock- out (KO) mouse model of GEFS+/DS. Our central hypothesis is loss of Scn1b dysregulates ion channels and dendrite excitability, disturbing integration and plasticity. To test this hypothesis, we will complete three Aims: Aim 1: Determine the mechanisms of somatic and dendritic hyperexcitability in Scn1b KO neurons. Based on preliminary data, our hypothesis is that both dendrites and somata of Scn1b KO CA1 pyramidal neu- rons exhibit intrinsic hyperexcitability in part due to abnormal HCN channel activity. We will test this hypothesis with whole cell somatic and dendritic recordings, immunohistochemistry, and cell morphology analyses. Aim 2: Determine the mechanisms of altered synaptic integration in Scn1b KO neurons. Based on our preliminary data, our hypothesis is that loss of Scn1b fundamentally alters the translation of inputs into outputs, with both temporal and spatial synaptic integration abnormally enhanced due to dendritic hyperexcitability and disrupted synaptic physiology. We will use whole cell recordings to test how temporal and spatial features of input/output functions are altered in Scn1b KO neurons in response to naturalistic patterns of synaptic inputs. Aim 3: Test the hypothesis that Scn1b disruption alters synaptic learning rules and gating by GABA that dictate plasticity. Based on our preliminary data, our hypothesis is that synaptic learning rules governing LTP and LTD induction are re-shaped due to interplay between suppressed excitation, hyperexcitable intrinsic properties, and abnormal gating by aberrant depolarizing inhibition after loss of Scn1b. We will test how input patterns that evoke LTP and LTD shift after loss of Scn1b, and how inhibition influences this plasticity. Upon successful completion of the proposed research, we will have defined detailed mechanisms by which changes in neuron intrinsic and synaptic physiology and their interactions re-shape the cellular forms of neural processing and learning in the Scn1b KO mouse model of GEFS+/DS. This contribution will provide mechanistic links between genetic changes, primary neurophysiology phenotypes, and neuronal processing deficits underly- ing seizures and the learning, memory, and cognition impairments in GEFS+/DS epilepsies.