Background Dilated cardiomyopathy (DCM) is a primary myocardial disease leading to contractile dysfunction, progressive heart failure and excessive risk of sudden cardiac death. Around half of DCM cases are idiopathic, and genetic factors seem to play an important role.
Aim We investigated a possible genetic cause of DCM in two consanguineous children from a Bedouin family.
Methods and results Using exome sequencing and searching for rare homozygous variations, we identified a nucleotide change in the donor splice consensus sequence of exon 7 in CAP2 as the causative mutation. Using patient-derived fibroblasts, we demonstrated that the mutation causes skipping of exons 6 and 7. The resulting protein is missing 64 amino acids in its N-CAP domain that should prevent its correct folding. CAP2 protein level was markedly reduced without notable compensation by the homolog CAP1. However, β-actin mRNA was elevated as demonstrated by real-time qPCR. In agreement with the essential role of CAP2 in actin filament polymerization, we demonstrate that the mutation affects the kinetics of repolymerization of actin in patient fibroblasts.
Conclusions This is the first report of a recessive deleterious mutation in CAP2 and its association with DCM in humans. The clinical phenotype recapitulates the damaging effects on the heart observed in Cap2 knockout mice including DCM and cardiac conduction disease, but not the other effects on growth, viability, wound healing and eye development. Our data underscore the importance of the proper kinetics of actin polymerization for normal function of the human heart.
- dilated cardiomyopathy
- splice mutation
- actin polymerization
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LA and AL contributed equally.
Contributors LA: performed the genetic analyses. AL: performed the clinical evaluation and treatment and recruited the family. SE: helped in drafting the MS. HK: participated in the recruitment and clinical evaluation of the family. LS: participated in the recruitment and clinical evaluation of the family. RZ: analysed the effect of mutation on the structure of the protein. YE: critically revised the MS and performed the statistical analysis. RP: designed the genetics and molecular biology analyses, coordinated the research and drafted the main text of the MS.
Funding This work was partly supported by an internal grant from Ben-Gurion University of the Negev, Faculty of Health Sciences.
Competing interests None declared.
Patient consent Not required.
Ethics approval This study was approved by Soroka University Medical Center Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
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