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Background: The zinc finger transcription factor CASZ1 plays a key role in cardiac development and postnatal adaptation, and in mice, deletion of the CASZ1 gene leads to dilated cardiomyopathy (DCM). However, in humans whether genetically defective CASZ1 contributes to DCM remains unclear. Methods: The coding exons and splicing junction sites of the CASZ1 gene were sequenced in 138 unrelated patients with idiopathic DCM. The available family members of the index patient harboring an identified CASZ1 mutation and 200 unrelated, ethnically matched healthy individuals used as controls were genotyped for CASZ1. The functional characteristics of the mutant CASZ1 were analyzed in contrast to its wild-type counterpart using a luciferase reporter assay system. Results: A novel heterozygous CASZ1 mutation, p.K351X, was identified in an index patient with DCM. Genetic analysis of the mutation carrier's family showed that the mutation co-segregated with DCM, which was transmitted in an autosomal dominant pattern with complete penetrance. The nonsense mutation, which was absent in 400 referential chromosomes, altered the amino acid that was highly conserved evolutionarily. Biological investigations revealed that the mutant CASZ1 had no transcriptional activity. Conclusions: The current study reveals CASZ1 as a new gene responsible for human DCM, which provides novel mechanistic insight and potential therapeutic target for CASZ1-associated DCM, implying potential implications in improved prophylactic and therapeutic strategies for DCM, the most common type of primary myocardial disease. [ABSTRACT FROM AUTHOR]

Background: The basic helix-loop-helix transcription factor HAND1 is essential for cardiac development and structural remodeling, and mutations in HAND1 have been causally linked to various congenital heart diseases. However, whether genetically compromised HAND1 predisposes to dilated cardiomyopathy (DCM) in humans remains unknown. Methods: The whole coding region and splicing junctions of the HAND1 gene were sequenced in 140 unrelated patients with idiopathic DCM. The available family members of the index patient carrying an identified mutation and 260 unrelated ethnically matched healthy individuals used as controls were genotyped for HAND1. The functional effect of the mutant HAND1 was characterized in contrast to its wild-type counterpart by using a dual-luciferase reporter assay system. Results: A novel heterozygous HAND1 mutation, p.R105X, was identified in a family with DCM transmitted as an autosomal dominant trait, which co-segregated with DCM in the family with complete penetrance. The nonsense mutation was absent in 520 control chromosomes. Functional analyses unveiled that the mutant HAND1 had no transcriptional activity. Furthermore, the mutation abolished the synergistic activation between HAND1 and GATA4, another crucial cardiac transcription factors that has been associated with various congenital cardiovascular malformations and DCM. Conclusions: This study firstly reports the association of HAND1 loss-of-function mutation with increased susceptibility to DCM in humans, which provides novel insight into the molecular mechanisms underpinning DCM. [ABSTRACT FROM AUTHOR]