Molecular characterization of Hemimegalencephaly

描述(申请人提供)：半巨脑的分子特征摘要体细胞突变，即体内的一小部分细胞具有有害突变，在癌症中得到很好的认识，但直到最近才在神经疾病中被认识到。在祖细胞群体的体细胞突变的背景下，所有的子代细胞都继承了TE突变，并能够根据分化程序表达所产生的表型。我们最近在发育中的大脑中发现了第一个新生的体细胞突变，称为“半巨脑”(HME)，这是一种与大脑皮质发育畸形(MCD)相关的灾难性局灶性癫痫疾病。HME是最严重的MCD综合征之一，以两侧大脑半球大量错构瘤样过度生长为特征。大脑半球切除是难治性癫痫的一种常见治疗方法，允许对病变组织进行采样。通过比较病脑DNA和血液/唾液DNA，我们鉴定了mTOR途径中的PIK3CA、AKT3或MTOR的新的体细胞突变。在手术期间采集的不同大脑区域中，8-40%的已测序等位基因存在突变，一些突变存在于已知激活蛋白质的密码子中。然而，这项初步研究是基于有限的样本量。这项应用的目的是扩展我们的初步发现，并阐明HME的遗传、发育、信号和细胞生物学机制，特别是在哺乳动物皮质发育的背景下。我们将结合来自HME患者的下一代疾病大脑测序与先进的生物信息学、完整的临床相关神经解剖学和小鼠模型来帮助推进我们对这种重要疾病的机制的理解。我们将：1]在一个更大的回溯性和前瞻性收集的HME患者队列中检测从头开始的体细胞突变。[2]遗传病负担与临床、影像和组织病理学结果(表型)相关。3]测试这些从头开始的突变如何改变发育中的大脑皮层的祖细胞功能。实验的目标是确定这些基因的突变是如何导致皮质发育中断的，为什么这些病变是致痫的，以及改变批准的药物的用途是否可能使患者受益，并与其他局灶性发育不良和局灶性癫痫相关。

DESCRIPTION (provided by applicant): Molecular characterization of hemimegalencephaly Abstract Somatic mutations, in which a fraction of the cells in the body have a deleterious mutation, is well recognized in cancer but only recently appreciated in neurological disease. In the setting of a somatic mutation in a population of progenitor cells, all daughter cells inherit te mutation and are able to express the resultant phenotype as a function of the differentiation program. We recently identified the first de novo somatic mutations in the developing brain in the condition "hemimegalencephaly", (HME) a catastrophic focal epilepsy condition associated with a malformation of cerebral cortical development (MCD). HME is one of the most severe MCD syndromes, characterized by massive hamartomatous overgrowth of either of the two cerebral hemispheres. Cerebral hemispherectomy is a frequent treatment for the refractory epilepsy, allowing sampling of diseased tissue. By comparing DNA from diseased brain with DNA from blood/saliva, we identified de novo somatic mutations in PIK3CA, AKT3 or MTOR, part of the mTOR pathway. Mutations were present in 8-40% of sequenced alleles in various brain regions sampled during surgery, and some in codons known to activate the protein. However, the pilot study was based on a limited sample size. The goal of this application is to expand upon our initial findings, and elucidate the genetic, developmental, signaling and cell biological mechanisms of HME, particularly in the context of mammalian cortex development. We will combine next-generation sequencing of diseased brain from HME patients with advanced bioinformatics, complete clinical correlated neuroanatomy, and mouse modeling to help advance our understanding of the mechanism of this important disease. We will: 1] Test for de novo somatic mutations in a larger retrospectively and prospectively collected cohort of HME patients. 2] Correlate genetic disease burden with clinical, imaging, and histopathological findings (phenotype). 3] Test how these de novo mutations alter progenitor cell functions in the developing cerebral cortex. The goal of the experiments is to determine how mutations in these genes lead to disrupted cortical development, why these lesions are epileptogenic, and whether repurposing approved medications might benefit patients, with relevance to other focal dysplasias and focal epilepsies.