MTMR4 SNVs modulate ion channel degradation and clinical severity in congenital long QT syndrome: insights in the mechanism of action of protective modifier genes

Yee Ki Lee, Luca Sala, Manuela Mura, Marcella Rocchetti, Matteo Pedrazzini, Xinru Ran, Timothy S.H. Mak, Lia Crotti, Pak C. Sham, Eleonora Torre, Antonio Zaza, Peter J. Schwartz, Hung Fat Tse, Massimiliano Gnecchi

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish
Pages (from-to)767-779
Number of pages13
JournalCardiovascular Research
Volume117
Issue number3
DOIs
Publication statusPublished - Feb 22 2021

Keywords

  • Arrhythmias
  • Induced pluripotent stem cells
  • Long QT syndrome
  • MTMR4
  • Nedd4L
  • Variants

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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