Contribution of GABA-A receptor subunit deletions to Angelman syndrome pathophysiology

项目概要 染色体 15q11-q13 缺失的个体患有天使综合征 (AS)，这是一种神经遗传病 以智力障碍、运动性共济失调、失语和癫痫发作为特征的发育障碍。的 负责 AS 的特定基因编码泛素蛋白连接酶 UBE3A，尽管 AS 中的其他基因 区域也被删除。 AS 也可能是由于 UBE3A 的功能缺失突变导致的，而 UBE3A 的功能突变可以避免其他突变 基因位于该区域。 UBE3A 突变 AS 患者通常具有较温和的表型，尤其是 关于癫痫和惊厥。这表明除了 UBE3A 之外，该区域其他基因的丢失， 可能导致缺失 AS 患者出现严重癫痫表型。特别是基因簇 编码三个 GABAA 受体亚基的基因位于 AS 中通常缺失的区域内。表达减少 这些亚基的一部分与多种人类神经发育障碍有关，例如 Angelman 综合征、某些综合征形式的癫痫和自闭症。我们假设 GABRB3 的半合子缺失， GABRA5 和/或 GABRG3 与 UBE3A 表达缺失相结合，会导致神经元过度兴奋并 人类 AS 个体的癫痫易感性增强。我们将通过比较来检验这个假设 来自突变和缺失 AS 患者的 AS 神经元的生理表型。我们将使用反义 寡核苷酸方法来确定是否敲低这些 GABA 受体亚基的表达 UBE3A 缺陷系将赋予 AS 缺失患者的神经元兴奋性增加。 这些研究将揭示导致 AS 癫痫发作的细胞机制，并确定治疗的靶点 新疗法的开发。

PROJECT SUMMARY Individuals with a deletion of chromosome 15q11-q13 suffer from Angelman syndrome (AS), a neurogenetic developmental disorder characterized by intellectual disability, motor ataxia, absent speech, and seizures. The specific gene that is responsible for AS encodes the ubiquitin protein ligase UBE3A, although other genes in the region are also deleted. AS can also result from loss of function mutations of UBE3A, which spares the other genes located in the region. UBE3A mutation AS patients typically have a milder phenotype, especially with regard to epilepsy and seizures. This suggests that the loss of other genes in the region, in addition to UBE3A, likely contribute to the severe epilepsy phenotype in deletion AS patients. In particular, a cluster of genes encoding three GABAA receptor subunits is located within the region typically deleted in AS. Reduced expression of these subunits has been implicated in several human neurodevelopmental disorders such as Angelman syndrome, certain syndromic forms of epilepsy, and autism. We hypothesize that hemizygous loss of GABRB3, GABRA5, and/or GABRG3, in conjunction with loss of UBE3A expression, causes neuronal hyperexcitability and enhanced seizure susceptibility in human AS individuals. We will test this hypothesis by comparing the physiological phenotype of AS neurons derived from mutation and deletion AS patients. We will use antisense oligonucleotide approaches to determine if knocking down expression of these GABA receptor subunits in a UBE3A deficient line will confer the increased excitability seen in neurons derived from AS deletion patients. These studies will shed light on the cellular mechanisms responsible for seizures in AS and identify targets for development of novel therapeutics.