Seizure generation and network excitability in Arx related Infantile Spasms

描述（由申请人提供）：在婴儿期癫痫发作和智力残疾儿童的发病机制方面存在广泛的知识空白。 痉挛综合征（ISS），早期癫痫性脑病之一。婴儿痉挛是一种影响1：2000活产的恶性疾病，导致大多数儿童出现耐药性癫痫发作和严重的发育障碍。婴儿痉挛综合征由癫痫性痉挛、高度心律失常的EEG模式和发育停滞组成。这种情况给家庭造成无数困难，给儿童造成终身残疾。目前，没有真正特异性治疗ISS或任何早期癫痫性脑病。因此，迫切需要进一步研究这些条件的机制。我们建议阐明婴儿痉挛症的一种模型的机制。我们的模型是一种在Arx基因（Arx（GCG）7/Y）中具有多聚丙氨酸扩增突变的转基因小鼠，是患有ARX相关ISS的儿童中最常见的突变，并重现了许多临床观察到的癫痫发作和行为表型。这是唯一一个模仿人类侮辱的模型。提出的研究验证了我们的假设，即发育过程中Arx的变化改变了中间神经元的发育和功能，导致过度兴奋的局部网络和癫痫发作，这些网络和癫痫发作随着小鼠的发育而变化。 我们的初步数据表明，在DG和CA 3的过度兴奋，并对CA 1锥体细胞的抑制损失。为了扩展这些发现并阐明婴儿痉挛症的机制，提出了三个系列的实验。首先，将使用婴儿和年轻成年Arx（GCG）7/Y小鼠的电压敏感染料（VSD）成像和多电极记录（MEA）在不同年龄确定局部网络功能障碍。由于我们的初步数据建立了海马DG和CA 3区域的活性增加，我们将尝试通过将GABA激动剂直接应用于CA 3和DG来局部挽救表型。接下来，我们将通过膜片钳记录锥体细胞和中间神经元并量化Arx（GCG）7/Y和对照小鼠之间的基线和诱发活动的变化来确定Aim 1中发现的网络变化背后的机制。最后，我们将通过研究Arx（GCG）7/Y和对照小鼠的丘脑皮质回路来确定海马体外是否存在局部网络变化。指导所提出的实验的基本原理是通过定义在ISS的定义模型中产生癫痫发作所涉及的机制，可以开发针对这些机制的特定疗法。因此，从拟议的研究中获得的知识将成为为这些破坏性疾病设计新疗法的转化研究的基础。

DESCRIPTION (provided by applicant): There is an extensive gap in the knowledge of the mechanisms involved in generating seizures and intellectual disabilities in children with infantile spasms syndrome (ISS), one of the early epileptic encephalopathies. Infantile spasms, a malignant disorder affecting 1:2000 live births, results in the majority of children developing medication resistant seizures and severe developmental disabilities. Infantile spasms syndrome consists of epileptic spasms, an EEG pattern of hypsarrhythmia and developmental stagnation. This condition results in innumerable hardships to the families and life long disabilities to the child. Currently, there is no treatment truly specific for ISS or any early epileptic encephalopathies. Consequently, there is a pressing need for further research into the mechanisms of these conditions. We are proposing to elucidate the mechanisms of one model of infantile spasms. Our model, a transgenic mouse with a polyalanine expansion mutation in the Arx gene (Arx(GCG)7/Y), is the most common mutation in children with ARX related ISS and recapitulates much of the clinically observed seizure and behavioral phenotype. This is the only model that mimics a known human insult. The studies proposed test our hypothesis that changes in Arx during development alter both interneuron development and function resulting in hyperexcitable local networks and seizures that change as the mouse develops. Our preliminary data demonstrates hyperexcitability in the DG and CA3, and loss of inhibition onto CA1 pyramidal cells. To extend these findings and elucidate the mechanisms of infantile spasms, three series of experiments are proposed. First local network dysfunction will be determined at different ages using voltage sensitive dye (VSD) imaging and multielectrode recordings (MEA) of infantile and young adult Arx(GCG)7/Y mice. As our preliminary data establishes increased activity in the DG and CA3 regions of the hippocampus, we will attempt to locally rescue the phenotype by application of GABA agonists directly into CA3 and the DG. Next, we will determine the mechanisms behind the network changes found in Aim 1 by patch clamp recording both pyramidal cells and interneurons and quantifying the alterations in baseline and evoked activity between the Arx(GCG)7/Y and control mice. Finally, we will determine if there are local network changes outside the hippocampus by studying the thalamocortical circuitry in the Arx(GCG)7/Y and control mice. The rationale guiding the proposed experiments is by defining the mechanisms involved in generating seizures in a defined model of ISS, specific therapies can be developed to target these mechanisms. Hence, the knowledge obtained from the proposed studies will be the foundation for the translational studies that design novel therapeutics for these devastating conditions.