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Loss of desmoplakin isoform I causes early onset cardiomyopathy and heart failure in a Naxos-like syndrome
  1. A Uzumcu1,
  2. E E Norgett2,
  3. A Dindar3,
  4. O Uyguner1,
  5. K Nisli3,
  6. H Kayserili1,
  7. S E Sahin1,
  8. E Dupont4,
  9. N J Severs4,
  10. I M Leigh2,
  11. M Yuksel-Apak1,
  12. D P Kelsell2,
  13. B Wollnik1,5
  1. 1Division of Medical Genetics, Child Health Institute, Istanbul University, Istanbul, Turkey
  2. 2Centre for Cutaneous Research, Institute of Cell and Molecular Science, Barts and The London, Queen Mary’s School of Medicine and Dentistry, University of London, London, UK
  3. 3Department of Pediatric Cardiology, Istanbul Medical Faculty, Istanbul, Turkey
  4. 4NHLI, Imperial College London, London, UK
  5. 5Center for Molecular Medicine Cologne (CMMC) and Institute of Human Genetics, University of Cologne, Cologne, Germany
  1. Correspondence to:
 Dr B Wollnik
 Center for Molecular Medicine Cologne (CMMC), Institute of Human Genetics, Kerpener Str. 34, 50931 Cologne, Germany; bwollnik{at}uni-koeln.de

Abstract

Background: Desmosomes are cellular junctions important for intercellular adhesion and anchoring the intermediate filament (IF) cytoskeleton to the cell membrane. Desmoplakin (DSP) is the most abundant desmosomal protein with 2 isoforms produced by alternative splicing.

Methods: We describe a patient with a recessively inherited arrhythmogenic dilated cardiomyopathy with left and right ventricular involvement, epidermolytic palmoplantar keratoderma, and woolly hair. The patient showed a severe heart phenotype with an early onset and rapid progression to heart failure at 4 years of age.

Results: A homozygous nonsense mutation, R1267X, was found in exon 23 of the desmoplakin gene, which results in an isoform specific truncation of the larger DSPI isoform. The loss of most of the DSPI specific rod domain and C-terminal area was confirmed by Western blotting and immunofluorescence. We further showed that the truncated DSPI transcript is unstable, leading to a loss of DSPI. DSPI is reported to be an obligate constituent of desmosomes and the only isoform present in cardiac tissue. To address this, we reviewed the expression of DSP isoforms in the heart. Our data suggest that DSPI is the major cardiac isoform but we also show that specific compartments of the heart have detectable DSPII expression.

Conclusions: This is the first description of a phenotype caused by a mutation affecting only one DSP isoform. Our findings emphasise the importance of desmoplakin and desmosomes in epidermal and cardiac function and additionally highlight the possibility that the different isoforms of desmoplakin may have distinct functional properties within the desmosome.

  • ARVC, arrhythmogenic right ventricular cardiomyopathy
  • DP, desmoplakin
  • EPPK, mild epidermolytic palmoplantar keratoderma
  • IF, intermediate filament
  • PPK, palmoplantar keratoderma
  • SPPK, striate palmoplantar keratoderma
  • desmosomes
  • desmoplakin
  • isoforms
  • mutation

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Footnotes

  • The first two authors contributed equally to this work.

  • Competing interests: there are no competing interests.

  • Written consent was given by the parents of the patient for the publication of the images of the patient.

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