Identification of TMEM168 protein mutation in familial Brugada syndrome

• Project/Area Number: 18K08033
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 53020:Cardiology-related
• Research Institution: National Cardiovascular Center Research Institute (2019-2020); Shiga University of Medical Science (2018)
• Principal Investigator: Zankov Dimitar Petrov 国立研究開発法人国立循環器病研究センター, 研究所, 室長 (20631295)
• Co-Investigator(Kenkyū-buntansha): 扇田 久和 滋賀医科大学, 医学部, 教授 (50379236)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000); Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2018: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
• Keywords: Inherited arrhythmia / Brugada syndrome / Sodium channel / Ubiquitination / Brugada Syndrome / TMEM168 gene / TMEM168 / 不整脈 / 遺伝子解析

Outline of Final Research Achievements

Brugada syndrome (BrS) is an inherited channelopathy identified as a cause of sudden cardiac death. Only 10-15% of Japanese BrS patients are diagnosed genetically. We used whole-exome sequencing to investigate candidate mutations in a BrS family. A heterozygous R539Q mutation was detected in TMEM168 gene of symptomatic individuals. Endogenous and transfected in HL-1 cells TMEM168 wild-type (WT) and mutant showed nuclear membrane localization. A significant decrease in Nav1.5 protein and Na+ current was observed in HL-1 cells expressing mutant TMEM168. Ventricular tachyarrhythmias and conduction disorders were pharmacologically induced in the heterozygous Tmem168 knock-in mice, but not in WT mice. Nav1.5 protein and Na+ current were reduced in ventricular myocytes in Tmem168 knock-in hearts. The impairment was dependent on increased Nedd4-2 binding to Nav1.5 and subsequent ubiquitination. Our results show a link between TMEM168 R539Q mutation and arrhythmogenesis in a family with BrS.

Academic Significance and Societal Importance of the Research Achievements

This study identified novel genetic variant associated with Brugada Syndrome. TMEM168 protein carrying the mutation is localized in the nuclear membrane and so far has unknown function. The mechanism of modulation of Na+ channel is unusual and will contribute to understanding of arrythmogenesis.

Research Products

• [Journal Article] Identification of transmembrane protein 168 mutation in familial Brugada syndrome. (2020)
  • Author(s): Shimizu A, Zankov DP, Sato A, Komeno M, Toyoda F, Yamazaki S, Makita T, Noda T, Ikawa M, Asano Y, Miyashita Y, Takashima S, Morita H, Ishikawa T, Makita N, Hitosugi M, Matsuura H, Ohno S, Horie M, Ogita H.
  • Journal Title: FASEB Journal Volume: 34 Issue: 5 Pages: 6399-6417
  • DOI: 10.1096/fj.201902991r
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Mutant KCNJ3 and KCNJ5 potassium channels as novel molecular targets in bradyarrhythmias and atrial fibrillation. (2019)
  • Author(s): Yamada N, Asano Y, Fujita M, Yamazaki S, Inanobe A, Matsuura N, Kobayashi H, Ohno S, Ebana Y, Tsukamoto O, Ishino S, Takuwa A, Kioka H, Yamashita T, Hashimoto N, Zankov DP, Shimizu A, Asakura M, Asanuma H, Kato H, Nishida Y, Miyashita Y, Shinomiya H, Naiki N, Hayashi K, Makiyama T, Ogita H, et al.
  • Journal Title: Circulation Volume: In press Issue: 18 Pages: 2157-2169
  • DOI: 10.1161/circulationaha.118.036761
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Human-specific desmoglein 2 mutations in mice models of arrythmogenic right ventricular cardiomyopathy reproduce patients' phenotype (2021)
  • Author(s): D.P. Zankov & S. Ohno.
  • Organizer: European heart rhythm association congress, April 23-25
  • Int'l Joint Research
• [Presentation] A Novel TMEM168 Gene Mutation in Familial Brugada Syndrome Attenuates Na+ channel Function by Modulating Nav1.5 Expression (2019)
  • Author(s): Dimitar Petrov Zankov
  • Organizer: Japanese Circulation Society Meeting