Department of Epilepsy Genetics and Personalized Medicine (member of ERN EpiCARE), Danish Epilepsy Centre, Dianalund, Denmark.
Department of Biomedical, Metabolic, and Neural Science, University of Modena and Reggio Emilia, Modena, Italy.
Ann Neurol. 2023 Aug;94(2):332-349. doi: 10.1002/ana.26662. Epub 2023 May 22.
Pathogenic variants in KCNT2 are rare causes of developmental epileptic encephalopathy (DEE). We herein describe the phenotypic and genetic features of patients with KCNT2-related DEE, and the in vitro functional and pharmacological properties of KCNT2 channels carrying 14 novel or previously untested variants.
Twenty-five patients harboring KCNT2 variants were investigated: 12 were identified through an international collaborative network, 13 were retrieved from the literature. Clinical data were collected and included in a standardized phenotyping sheet. Novel variants were detected using exome sequencing and classified using ACMG criteria. Functional and pharmacological studies were performed by whole-cell electrophysiology in HEK-293 and SH-SY5Y cells.
The phenotypic spectrum encompassed: (a) intellectual disability/developmental delay (21/22 individuals with available information), ranging from mild to severe/profound; (b) epilepsy (15/25); (c) neurological impairment, with altered muscle tone (14/22); (d) dysmorphisms (13/20). Nineteen pathogenic KCNT2 variants were found (9 new, 10 reported previously): 16 missense, 1 in-frame deletion of a single amino acid, 1 nonsense, and 1 frameshift. Among tested variants, 8 showed gain-of-function (GoF), and 6 loss-of-function (LoF) features when expressed heterologously in vitro. Quinidine and fluoxetine blocked all GoF variants, whereas loxapine and riluzole activated some LoF variants while blocking others.
We expanded the phenotypic and genotypic spectrum of KCNT2-related disorders, highlighting novel genotype-phenotype associations. Pathogenic KCNT2 variants cause GoF or LoF in vitro phenotypes, and each shows a unique pharmacological profile, suggesting the need for in vitro functional and pharmacological investigation to enable targeted therapies based on the molecular phenotype. ANN NEUROL 2023;94:332-349.
KCNT2 中的致病性变异是发育性癫痫性脑病（DEE）的罕见病因。本文描述了 KCNT2 相关 DEE 患者的表型和遗传特征，以及携带 14 种新的或以前未测试的变异的 KCNT2 通道的体外功能和药理学特性。
对 25 名携带 KCNT2 变异的患者进行了研究：12 名通过国际合作网络确定，13 名从文献中检索。收集临床数据并包含在标准化表型表中。使用外显子组测序检测新变体，并使用 ACMG 标准进行分类。通过在 HEK-293 和 SH-SY5Y 细胞中的全细胞电生理学进行功能和药理学研究。
表型谱包括：（a）智力障碍/发育迟缓（22 名有可用信息的个体中的 21 名），从轻度到重度/重度；（b）癫痫（25 名中的 15 名）；（c）神经功能障碍，伴有肌肉张力改变（22 名中的 14 名）；（d）发育异常（20 名中的 13 名）。发现 19 种致病性 KCNT2 变异（9 种新变异，10 种先前报道的变异）：16 种错义，1 种单个氨基酸的框内缺失，1 种无义，1 种移码。在测试的变体中，当在体外异源表达时，8 种表现出获得功能（GoF），6 种表现出功能丧失（LoF）特征。奎尼丁和氟西汀阻断所有 GoF 变体，而洛沙平利鲁唑激活一些 LoF 变体，同时阻断其他变体。
我们扩展了 KCNT2 相关疾病的表型和基因型谱，强调了新的基因型-表型关联。致病性 KCNT2 变异在体外表现出 GoF 或 LoF 表型，并且每种表型都具有独特的药理学特征，表明需要进行体外功能和药理学研究，以便根据分子表型进行靶向治疗。ANN NEUROL 2023；94:332-349。
