Mechanisms of Seizure Genesis in Human Hypothalamic Hamartomas

描述（由申请人提供）：下丘脑错构瘤（HH）是一种罕见的先天性人类大脑畸形，与弹性（或大笑）发作有关，在生命早期很难诊断，并且众所周知难以药物治疗。尽管越来越多的临床认识到这种情况，癫痫发生的机制在很大程度上是未知的。重要的是，癫痫发作已经被证明是由错构瘤本身引起的。在巴罗神经学研究所，在过去的几年里，我们已经治疗了100多名患有这种疾病的患者，构成了有史以来最大的单中心系列；我们目前是美国唯一的HH管理多学科项目，也是世界上最活跃的HH项目。因此，我们有独特的优势来研究HH的癫痫发生机制。所提出的研究的主要目的是利用细胞电生理、荧光成像、免疫细胞化学和基因表达技术的组合来确定手术切除的HH组织中癫痫发作的机制。我们的初步数据表明，HH组织包含两个不同的神经元群体；小的HH神经元表现出内在的类似起搏器的活动，而大的HH神经元是静止的。我们已经证明，当灌注gabaa受体激动剂muscimol时，大HH神经元亚群会去极化。基于这些有趣的发现，我们假设这种gabaa受体介导的去极化可能是阳离子-氯共转运体KCC2（相对于其表亲NKCC1）表达减少的结果，并且这种反应可能有助于癫痫发作的发生。具体来说，我们假设muscimol会增加细胞内钙水平，这一作用可以被NKCC1拮抗剂布美他胺阻断。此外，我们利用免疫细胞化学和单细胞RT-PCR表达技术推测HH组织中KCC2相对于NKCC1的表达会降低。虽然HH本身并不常见，估计患病率为5 -10万分之一，但它可能是皮质下癫痫的最佳人类模型，也是了解儿童灾难性癫痫后果的最有趣的模型之一。因此，对这种疾病的详细科学理解对于加快对发育性癫痫的转化研究具有重要的影响。公共卫生相关性：癫痫是一种常见的神经系统疾病，仅在美国就有300多万人患有该病，许多新诊断的患者是婴儿和儿童。为了开发更新、更有效的治疗方法，有必要了解癫痫在儿科人群中的发展情况。这项研究计划，虽然专注于一种罕见的脑肿瘤，导致不受控制的癫痫发作，可能提供新的见解，癫痫发作的传播和进展的机制。

DESCRIPTION (provided by applicant): The hypothalamic hamartoma (HH) is a rare congenital human brain malformation associated with gelastic (or laughing) seizures that are difficult to diagnosis early in life and are notoriously refractory to medical therapy. Despite increasing clinical recognition of this condition, the mechanisms of epileptogenesis are largely unknown. Importantly, seizures have previously been shown to originate from the hamartoma itself. At the Barrow Neurological Institute, we have treated over 100 patients with this condition over the past several years, constituting the largest single-center series ever; we are currently the only multidisciplinary program for HH management in the United States, and the most active HH program in the world. Thus, we are uniquely positioned to study the mechanisms of epileptogenesis in HH. The major goal of the proposed studies is to determine the mechanisms of seizure genesis in surgically resected HH tissue using a combination of cellular electrophysiological, fluorescence imaging, immunocytochemical and gene expression techniques. Our preliminary data demonstrate that HH tissue contains two distinct populations of neurons; small HH neurons exhibit intrinsic pacemaker-like activity, whereas large HH neurons are quiescent. We have demonstrated that a subpopulation of large HH neurons depolarize when perfused with the GABAA-receptor agonist muscimol. Based on these intriguing findings, we hypothesize that such GABAA-receptor mediated depolarization may be a consequence of decreased expression of the cation-chloride co-transporter KCC2 (relative to its cousin, NKCC1), and that such responses may contribute to seizure genesis. Specifically, we hypothesize that muscimol will increase intracellular calcium levels, an effect that can be blocked by the NKCC1 antagonist bumetanide. Further, we hypothesize that HH tissue will demonstrate decreased expression of KCC2 relative to NKCC1 using immunocytochemical and single-cell RT-PCR expression techniques. Although HH itself is uncommon with an estimated prevalence of 1 in 50,000-100,000 it is perhaps the best human model for subcortical epilepsy, and one of the most intriguing models for understanding the consequences of catastrophic epilepsy in childhood. As such, a detailed scientific understanding of this disorder has major ramifications for expediting translational research focused on the developmental epilepsies. PUBLIC HEALTH RELEVANCE: Epilepsy is a common neurological disorder that afflicts more than 3 million people in the United States alone, and many newly diagnosed patients are infants and children. There is a substantial need to understand how epilepsy develops in the pediatric population in order to develop newer, more effective treatments. This research proposal, while focused on a rare brain tumor that causes uncontrolled seizures, may provide novel insights into the mechanisms of seizure propagation and progression.