A homozygous DSC2 deletion associated with arrhythmogenic cardiomyopathy is caused by uniparental isodisomy

J Mol Cell Cardiol. 2020 Apr:141:17-29. doi: 10.1016/j.yjmcc.2020.03.006. Epub 2020 Mar 19.

Abstract

Aims: We aimed to unravel the genetic, molecular and cellular pathomechanisms of DSC2 truncation variants leading to arrhythmogenic cardiomyopathy (ACM).

Methods and results: We report a homozygous 4-bp DSC2 deletion variant c.1913_1916delAGAA, p.Q638LfsX647hom causing a frameshift carried by an ACM patient. Whole exome sequencing and comparative genomic hybridization analysis support a loss of heterozygosity in a large segment of chromosome 18 indicating segmental interstitial uniparental isodisomy (UPD). Ultrastructural analysis of the explanted myocardium from a mutation carrier using transmission electron microscopy revealed a partially widening of the intercalated disc. Using qRT-PCR we demonstrated that DSC2 mRNA expression was substantially decreased in the explanted myocardial tissue of the homozygous carrier compared to controls. Western blot analysis revealed absence of both full-length desmocollin-2 isoforms. Only a weak expression of the truncated form of desmocollin-2 was detectable. Immunohistochemistry showed that the truncated form of desmocollin-2 did not localize at the intercalated discs. In vitro, transfection experiments using induced pluripotent stem cell derived cardiomyocytes and HT-1080 cells demonstrated an obvious absence of the mutant truncated desmocollin-2 at the plasma membrane. Immunoprecipitation in combination with fluorescence measurements and Western blot analyses revealed an abnormal secretion of the truncated desmocollin-2.

Conclusion: In summary, we unraveled segmental UPD as the likely genetic reason for a small homozygous DSC2 deletion. We conclude that a combination of nonsense mediated mRNA decay and extracellular secretion is involved in DSC2 related ACM.

Keywords: Arrhythmogenic right ventricular cardiomyopathy; Cardiomyopathy; DSC2; Desmocollin-2; Desmosomes; Uniparental Isodisomy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arrhythmias, Cardiac / complications
  • Arrhythmias, Cardiac / genetics*
  • Base Sequence
  • Cardiomyopathies / complications
  • Cardiomyopathies / genetics*
  • Cell Line, Tumor
  • Desmocollins / chemistry
  • Desmocollins / genetics*
  • Desmocollins / metabolism
  • Female
  • Gene Deletion*
  • Homozygote
  • Humans
  • Male
  • Middle Aged
  • Mutation / genetics
  • Myocardium / pathology
  • Myocardium / ultrastructure
  • Myocytes, Cardiac / metabolism
  • Pedigree
  • Uniparental Disomy / genetics*

Substances

  • DSC2 protein, human
  • Desmocollins