Abstract

Aims

In long QT syndrome (LQTS) patients, modifier genes modulate the arrhythmic risk associated with a disease-causing mutation. Their recognition can improve risk stratification and clinical management, but their discovery represents a challenge. We tested whether a cellular-driven approach could help to identify new modifier genes and especially their mechanism of action.

Methods and results

We generated human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) from two patients carrying the same KCNQ1-Y111C mutation, but presenting opposite clinical phenotypes. We showed that the phenotype of the iPSC-CMs derived from the symptomatic patient is due to impaired trafficking and increased degradation of the mutant KCNQ1 and wild-type human ether-a-go-go-related gene. In the iPSC-CMs of the asymptomatic (AS) patient, the activity of an E3 ubiquitin-protein ligase (Nedd4L) involved in channel protein degradation was reduced and resulted in a decreased arrhythmogenic substrate. Two single-nucleotide variants (SNVs) on the Myotubularin-related protein 4 (MTMR4) gene, an interactor of Nedd4L, were identified by whole-exome sequencing as potential contributors to decreased Nedd4L activity. Correction of these SNVs by CRISPR/Cas9 unmasked the LQTS phenotype in AS cells. Importantly, the same MTMR4 variants were present in 77% of AS Y111C mutation carriers of a separate cohort. Thus, genetically mediated interference with Nedd4L activation seems associated with protective effects.

Conclusion

Our finding represents the first demonstration of the cellular mechanism of action of a protective modifier gene in LQTS. It provides new clues for advanced risk stratification and paves the way for the design of new therapies targeting this specific molecular pathway.

中文翻译：

---

MTMR4 SNV 调节先天性长 QT 综合征的离子通道降解和临床严重程度：对保护性修饰基因作用机制的见解

摘要

宗旨

在长 QT 综合征 (LQTS) 患者中，修饰基因调节与致病突变相关的心律失常风险。他们的认识可以改善风险分层和临床管理，但他们的发现是一个挑战。我们测试了细胞驱动的方法是否有助于识别新的修饰基因，尤其是它们的作用机制。

方法和结果

我们从携带相同KCNQ1 -Y111C 突变但呈现相反临床表型的两名患者中生成了人类诱导的多能干细胞衍生心肌细胞 (iPSC-CM) 。我们表明，来自有症状患者的 iPSC-CM 的表型是由于运输受损和突变 KCNQ1 和野生型人类 ether-a-go-go 相关基因的降解增加。在无症状 (AS) 患者的 iPSC-CM 中，参与通道蛋白降解的 E3 泛素蛋白连接酶 (Nedd4L) 的活性降低，导致致心律失常底物减少。肌管蛋白相关蛋白 4 ( MTMR4 ) 上的两个单核苷酸变异 (SNV)) 基因，Nedd4L 的相互作用因子，通过全外显子组测序被鉴定为降低 Nedd4L 活性的潜在贡献者。通过 CRISPR/Cas9 校正这些 SNV 揭示了 AS 细胞中的 LQTS 表型。重要的是，在单独队列的 77% 的 AS Y111C 突变携带者中存在相同的MTMR4变体。因此，对 Nedd4L 激活的遗传介导的干扰似乎与保护作用有关。

结论

我们的发现首次证明了 LQTS 中保护性修饰基因的细胞作用机制。它为高级风险分层提供了新线索，并为设计针对这一特定分子途径的新疗法铺平了道路。