Development of aberrant cortical interneuron circuitry in genetic mouse models of absence epilepsy

摘要 在美国，癫痫影响超过200万人，导致显著的发病率，给社会带来高成本。 虽然已经研究了患者和动物模型中癫痫发作的行为和电生理相关性， 经过世纪，潜在的电路异常仍在被阐明。广义棘波（SW）缺失sei- 癫痫是儿童中最常见的癫痫病，被认为完全是遗传性的。虽然超过20 基因在SW癫痫中被发现和研究，但仍不清楚每个遗传病变如何损害正常的电路发展。 并最终导致易损伤的皮层回路。由于SW癫痫发作表型可能非常相似， 尽管有不同的遗传病因，但可能存在一种典型的回路缺陷，这种缺陷是癫痫发作的基础 格局最近，随着我们开始了解细胞水平上皮层微电路的布线原理， 类型，它已经成为可能问这些典型的网络中断可能是如何启动癫痫发作负责 活动和损害认知功能的SW癫痫，是否致病电路的变化重叠，尽管dis- 分离的分子病变，以及如何从遗传的分子缺陷中出现一个易于癫痫发作的回路，以促进癫痫发作- 设定在可预测的发育时间点。这些信息不仅表明了新的和广泛适用的治疗方法， tic目标，而且还导致对不同细胞类型和特定连接的功能作用的有价值的见解 正常大脑的原则。为了回答这些重要的问题，我们正在利用三种小鼠模型， 感觉癫痫，观星者，蹒跚和Gabrg 2突变小鼠，这些小鼠在三个不相关的基因中携带突变，但共享 相同的SW表型，并提出了一个全面的微电路比较不同的基因型之间的水平 细胞类型和它们之间的联系。我们对整列的躯体进行了大规模的电路分析- 感觉皮层（S1）在三个模型中沿着癫痫发作的发展，通过利用高通量的多修补方法 (up第12章我们最近开发的我们将测量S1内不同细胞类型的多种神经元特征， 癫痫回路，重点是皮层GABA能中间神经元的主要群体的连接和形态。 同时，将对WT同窝仔进行相同的分析作为对照，以揭示细胞类型特异性连接 作为基因型和发育阶段的函数而变化。这些全面、动态的比较，基于 用灵敏的、最先进的方法进行大规模电路分析，将揭示异常微电路的全部范围 与癫痫发作密切相关的结构和功能。我们的初步数据揭示了几种联系 这些模型的缺陷。最令人惊讶的是，表达生长抑素的刻板连接和形态学 Martinotti细胞被严重破坏，这种破坏似乎只出现在癫痫发作后，并被共享。 模型，表明共同的电路缺陷的基础缺席癫痫。潜在的致病电路机制将 通过网络建模和体内化学遗传学测定进一步测试。识别致病性电路缺陷基因- 在遗传异质性，但高度刻板的SW癫痫发作将指导该领域的发展， 创新的，广泛适用的电路为基础的干预失神癫痫及其相关的合并症。

Abstract Epilepsy affects over 2 million of people in the United States, causing significant morbidity with a high cost to society. While the behavioral and electrophysiological correlates of seizures in patients and animal models have been studied for over a century, the underlying circuit abnormalities are still being elucidated. Generalized spike-wave (SW) absence sei- zures are the most common seizure disorder in children and thought to be exclusively of genetic origin. While over 20 genes are discovered and studied in SW epilepsies, it is still unclear how each genetic lesion impairs normal circuit devel- opment and ultimately results in a seizure-prone cortical circuit. Since the SW seizure phenotype can be very similar de- spite disparate genetic etiologies, a stereotypical circuit deficit may exist which underlies the expression of this seizure pattern. More recently, as we have begun to understand the wiring principles of cortical microcircuits at the level of cell types, it has become possible to ask how disruption of these canonical networks may be responsible for initiating seizure activity and impairing cognitive functions in SW epilepsies, whether the pathogenic circuit changes overlap despite dis- parate molecular lesions, and how a seizure-prone circuit emerges from inherited molecular defects to favor seizure on- set at predictable developmental time-points. This information not only suggests novel and broadly-applicable therapeu- tic targets, but also leads to valuable insights into the functional roles of distinct cell types and specific connectivity principles in normal brain. To answer these important questions, we are taking advantage of three mouse models of ab- sence epilepsy, stargazer, tottering and Gabrg2 mutant mice, which harbor mutations in three unrelated genes but share the same SW phenotype, and propose a comprehensive microcircuit comparison among distinct genotypes at the level of cell types and their connections. We perform a large-scale circuit analysis across a whole column of the somatosen- sory cortex (S1) in three models along the seizure development, by leveraging a high-throughput multi-patching method (up to 12-patch) we recently developed. We will measure multiple neuronal features of distinct cell types within the S1 epileptic circuit, with an emphasis on connectivity and morphology of major groups of cortical GABAergic interneurons. In parallel, the same analysis will be performed on WT littermates as controls to reveal cell type-specific connectivity changes as a function of the genotype and developmental stage. These comprehensive, dynamic comparisons, based on large-scale circuit analyses with sensitive, state-of-the-art methods, will reveal the full extent of abnormal microcircuit structure and functions that are closely associated with seizure onset. Our preliminary data uncover several connectivity defects in these models. The most striking is that stereotypical connectivity and morphology of somatostatin-expressing Martinotti cells are severely disrupted, and this disruption appears to emerge only after seizure onset and is shared by models, suggesting a common circuit deficit underlying absence epilepsy. The potential causative circuit mechanisms will be further tested via network modeling and an in vivo chemogenetic assay. Identification of causative circuit deficits gen- eralized across genetically heterogeneous, yet highly stereotyped SW seizures will direct the field toward the develop- ment of innovative, broadly applicable circuit-based interventions for absence epilepsy and its related comorbidities.