A Recurrent Missense Variant in AP2M1 Impairs Clathrin-Mediated Endocytosis and Causes Developmental and Epileptic Encephalopathy
A Recurrent Missense Variant in AP2M1 Impairs Clathrin-Mediated Endocytosis and Causes Developmental and Epileptic Encephalopathy
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DOI：
10.1016/j.ajhg.2019.04.001
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发表时间：
2019-06-06
影响因子：
9.8
通讯作者：
White, Peter
中科院分区：
文献类型：
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作者：
Helbig, Ingo;Lopez-Hernandez, Tania;White, Peter
发育性脑病和癫痫性脑病 (DEE) 是具有很强遗传因素的异质性疾病，但在很大一部分个体中，其潜在的遗传病因学仍然未知。为了探索是否可以根据表型特征生成遗传病因学的统计支持，我们使用人类表型本体论 (HPO) 对 314 名 DEE 个体进行了全外显子组测序数据和表型相似性分析。我们在两个个体中发现了 AP2M1 中的从头 c.508C>T (p.Arg170Trp) 变异，其表型相似性高于偶然预期 (p = 0.003)，且表型与伴有肌阵挛失张力性癫痫发作的癫痫相关。随后，我们在接受诊断性全外显子组测序的 2,310 名个体队列中，在两名患有神经发育障碍和全身性癫痫的个体中发现了相同的从头变异。 AP2M1 编码接头蛋白复合物 2 (AP-2) 的 mu 亚基，该亚基参与网格蛋白介导的内吞作用 (CME) 和突触小泡再循环。蛋白质动力学建模表明 p.Arg170Trp 变体会损害 AP-2 复合物的构象激活和热力学熵。人类细胞中携带 p.Arg170Trp 变体的 mu 亚基和源自 AP-2 mu 条件敲除小鼠的星形胶质细胞的功能互补揭示了转铁蛋白的 CME 显着受损。相反，稳定性、表达水平、膜募集和定位并未受损，表明 AP-2 复合物的功能改变是潜在的疾病机制。我们确定 AP2M1 中的复发性致病性变异是导致具有独特表型特征的 DEE 的原因，并且我们将内吞作用早期步骤的功能障碍视为癫痫的一种疾病机制。
The developmental and epileptic encephalopathies (DEEs) are heterogeneous disorders with a strong genetic contribution, but the underlying genetic etiology remains unknown in a significant proportion of individuals. To explore whether statistical support for genetic etiologies can be generated on the basis of phenotypic features, we analyzed whole-exome sequencing data and phenotypic similarities by using Human Phenotype Ontology (HPO) in 314 individuals with DEEs. We identified a de novo c.508C>T (p.Arg170Trp) variant in AP2M1 in two individuals with a phenotypic similarity that was higher than expected by chance (p = 0.003) and a phenotype related to epilepsy with myoclonic-atonic seizures. We subsequently found the same de novo variant in two individuals with neurodevelopmental disorders and generalized epilepsy in a cohort of 2,310 individuals who underwent diagnostic whole-exome sequencing. AP2M1 encodes the mu-subunit of the adaptor protein complex 2 (AP-2), which is involved in clathrin-mediated endocytosis (CME) and synaptic vesicle recycling. Modeling of protein dynamics indicated that the p.Arg170Trp variant impairs the conformational activation and thermodynamic entropy of the AP-2 complex. Functional complementation of both the mu-subunit carrying the p.Arg170Trp variant in human cells and astrocytes derived from AP-2 mu conditional knockout mice revealed a significant impairment of CME of transferrin. In contrast, stability, expression levels, membrane recruitment, and localization were not impaired, suggesting a functional alteration of the AP-2 complex as the underlying disease mechanism. We establish a recurrent pathogenic variant in AP2M1 as a cause of DEEs with distinct phenotypic features, and we implicate dysfunction of the early steps of endocytosis as a disease mechanism in epilepsy.