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脑畸形，与早期难以诊断且难以药物治疗的痉挛性（或大笑）癫痫发作相关。尽管越来越多的临床认识这种情况下，癫痫发生的机制在很大程度上是未知的。重要的是，癫痫发作先前已被证明起源于错构瘤本身。在巴罗神经学研究所，我们在过去几年中治疗了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，我们处于独特的地位，以研究在HH癫痫发生的机制。提出的研究的主要目标是确定癫痫发作发生的机制，在手术切除HH组织使用细胞电生理，荧光成像，免疫细胞化学和基因表达技术的组合。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HH神经元表现出内在的起搏器样活动，而大HH神经元是静止的。我们已经证明，一个亚群的大HH神经元去甲氨蝶呤时，灌注GABAA受体激动剂蝇蕈醇。基于这些有趣的发现，我们推测，这种GABAA受体介导的去极化可能是阳离子-氯离子共转运蛋白KCC 2（相对于其表亲NKCC 1）表达减少的结果，并且这种反应可能有助于癫痫发作。具体来说，我们假设蝇蕈醇会增加细胞内钙水平，这种作用可以被NKCC 1拮抗剂布美他尼阻断。此外，我们假设，HH组织将表现出减少表达KCC 2相对于NKCC 1使用免疫细胞化学和单细胞RT-PCR表达技术。虽然HH本身并不常见，估计患病率为1/50，000 - 100，000，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模型之一。因此，对这种疾病的详细科学理解对于加快专注于发展性癫痫的转化研究具有重大影响。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多万人受到折磨，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，虽然集中在一种罕见的脑肿瘤，导致不受控制的癫痫发作，可能会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.