A novel PRRX1 loss-of-function variation contributing to familial atrial fibrillation and congenital patent ductus arteriosus.

Atrial fibrillation (AF) represents the most common type of sustained cardiac arrhythmia in humans and confers a significantly increased risk for thromboembolic stroke, congestive heart failure and premature death. Aggregating evidence emphasizes the predominant genetic defects underpinning AF and an increasing number of deleterious variations in more than 50 genes have been involved in the pathogenesis of AF. Nevertheless, the genetic basis underlying AF remains incompletely understood. In the current research, by whole-exome sequencing and Sanger sequencing analysis in a family with autosomal-dominant AF and congenital patent ductus arteriosus (PDA), a novel heterozygous variation in the PRRX1 gene encoding a homeobox transcription factor critical for cardiovascular development, NM_022716.4:c.373G>T;p.(Glu125*), was identified to be in co-segregation with AF and PDA in the whole family. The truncating variation was not detected in 306 unrelated healthy individuals employed as controls. Quantitative biological measurements with a reporter gene analysis system revealed that the Glu125*-mutant PRRX1 protein failed to transactivate its downstream target genes SHOX2 and ISL1, two genes that have been causally linked to AF. Conclusively, the present study firstly links PRRX1 loss-of-function variation to AF and PDA, suggesting that AF and PDA share a common abnormal developmental basis in a proportion of cases.

Detection and functional characterization of a novel MEF2A variation responsible for familial dilated cardiomyopathy.

OBJECTIVES: Dilated cardiomyopathy (DCM) represents the most frequent form of cardiomyopathy, leading to heart failure, cardiac arrhythmias and death. Accumulating evidence convincingly demonstrates the crucial role of genetic defects in the pathogenesis of DCM, and over 100 culprit genes have been implicated with DCM. However, DCM is of substantial genetic heterogeneity, and the genetic determinants underpinning DCM remain largely elusive. METHODS: Whole-exome sequencing and bioinformatical analyses were implemented in a consanguineous Chinese family with DCM. A total of 380 clinically annotated control individuals and 166 more DCM index cases then underwent Sanger sequencing analysis for the identified genetic variation. The functional characteristics of the variant were delineated by utilizing a dual-luciferase assay system. RESULTS: A heterozygous variation in the MEF2A gene (encoding myocyte enhancer factor 2A, a transcription factor pivotal for embryonic cardiogenesis and postnatal cardiac adaptation), NM_001365204.1: c.718G>T; p. (Gly240*), was identified, and verified by Sanger sequencing to segregate with autosome-dominant DCM in the family with complete penetrance. The nonsense variation was neither detected in 760 control chromosomes nor found in 166 more DCM probands. Functional analyses revealed that the variant lost transactivation on the validated target genes MYH6 and FHL2, both causally linked to DCM. Furthermore, the variation nullified the synergistic activation between MEF2A and GATA4, another key transcription factor involved in DCM. CONCLUSIONS: The findings firstly indicate that MEF2A loss-of-function variation predisposes to DCM in humans, providing novel insight into the molecular mechanisms of DCM and suggesting potential implications for genetic testing and prognostic evaluation of DCM patients.

A novel TBX5 mutation predisposes to familial cardiac septal defects and atrial fibrillation as well as bicuspid aortic valve.

TBX5 has been linked to Holt-Oram syndrome, with congenital heart defect (CHD) and atrial fibrillation (AF) being two major cardiac phenotypes. However, the prevalence of a TBX5 variation in patients with CHD and AF remains obscure. In this research, by sequencing analysis of TBX5 in 178 index patients with both CHD and AF, a novel heterozygous variation, NM_000192.3: c.577G>T; p.(Gly193*), was identified in one index patient with CHD and AF as well as bicuspid aortic valve (BAV), with an allele frequency of approximately 0.28%. Genetic analysis of the proband's pedigree showed that the variation co-segregated with the diseases. The pathogenic variation was not detected in 292 unrelated healthy subjects. Functional analysis by using a dual-luciferase reporter assay system showed that the Gly193*-mutant TBX5 protein failed to transcriptionally activate its target genes MYH6 and NPPA. Moreover, the mutation nullified the synergistic transactivation between TBX5 and GATA4 as well as NKX2-5. Additionally, whole-exome sequencing analysis showed no other genes contributing to the diseases. This investigation firstly links a pathogenic variant in the TBX5 gene to familial CHD and AF as well as BAV, suggesting that CHD and AF as well as BAV share a common developmental basis in a subset of patients.

ISL1 loss-of-function mutation contributes to congenital heart defects.

Congenital heart defect (CHD) is the most common form of birth deformity and is responsible for substantial morbidity and mortality in humans. Increasing evidence has convincingly demonstrated that genetic defects play a pivotal role in the pathogenesis of CHD. However, CHD is a genetically heterogeneous disorder and the genetic basis underpinning CHD in the vast majority of cases remains elusive. This study was sought to identify the pathogenic mutation in the ISL1 gene contributing to CHD. A cohort of 210 unrelated patients with CHD and a total of 256 unrelated healthy individuals used as controls were registered. The coding exons and splicing boundaries of ISL1 were sequenced in all study subjects. The functional effect of an identified ISL1 mutation was evaluated using a dual-luciferase reporter assay system. A novel heterozygous ISL1 mutation, c.409G > T or p.E137X, was identified in an index patient with congenital patent ductus arteriosus and ventricular septal defect. Analysis of the proband's pedigree revealed that the mutation co-segregated with CHD, which was transmitted in the family in an autosomal dominant pattern with complete penetrance. The nonsense mutation was absent in 512 control chromosomes. Functional analysis unveiled that the mutant ISL1 protein failed to transactivate the promoter of MEF2C, alone or in synergy with TBX20. This study firstly implicates ISL1 loss-of-function mutation with CHD in humans, which provides novel insight into the molecular mechanism of CHD, implying potential implications for genetic counseling and individually tailored treatment of CHD patients.

A New ISL1 Loss-of-Function Mutation Predisposes to Congenital Double Outlet Right Ventricle.

Occurring in about 1% of all live births, congenital heart defects (CHDs) represent the most frequent type of developmental abnormality and account for remarkably increased infant morbidity and mortality. Aggregating studies demonstrate that genetic components have a key role in the occurrence of CHDs. Nevertheless, due to pronounced genetic heterogeneity, the genetic causes of CHDs remain unclear in most patients. In this research, 114 unrelated patients affected with CHDs and 218 unrelated individuals without CHDs served as controls were recruited. The coding regions and splicing donors/acceptors of the ISL1 gene, which codes for a transcription factor required for proper cardiovascular development, were screened for mutations by sequencing in all study participants. The functional characteristics of an identified ISL1 mutation were delineated with a dual-luciferase reporter assay system. As a result, a new heterozygous ISL1 mutation, NM_002202.2: c.225C>G; p. (Tyr75*), was discovered in an index patient with double outlet right ventricle and ventricular septal defect. Analysis of the proband's family unveiled that the mutation co-segregated with the CHD phenotype. The nonsense mutation was absent in the 436 control chromosomes. Biological analysis showed that the mutant ISL1 protein had no transcriptional activity. Furthermore, the mutation nullified the synergistic activation between ISL1 and TBX20, another CHD-associated transcription factor. This research for the first time links an ISL1 loss-of-function mutation to double outlet right ventricle in humans, which adds insight to the molecular pathogenesis underpinning CHDs, suggesting potential implications for timely personalized management of CHD patients.

MEF2C loss-of-function mutation associated with familial dilated cardiomyopathy.

BACKGROUND: The MADS-box transcription factor myocyte enhancer factor 2C (MEF2C) is required for the cardiac development and postnatal adaptation and in mice-targeted disruption of the MEF2C gene results in dilated cardiomyopathy (DCM). However, in humans, the association of MEF2C variation with DCM remains to be investigated. METHODS: The coding regions and splicing boundaries of the MEF2C gene were sequenced in 172 unrelated patients with idiopathic DCM. The available close relatives of the index patient harboring an identified MEF2C mutation and 300 unrelated, ethnically matched healthy individuals used as controls were genotyped for MEF2C. The functional effect of the mutant MEF2C protein was characterized in contrast to its wild-type counterpart by using a dual-luciferase reporter assay system. RESULTS: A novel heterozygous MEF2C mutation, p.Y157X, was detected in an index patient with adult-onset DCM. Genetic screen of the mutation carrier's family members revealed that the mutation co-segregated with DCM, which was transmitted as an autosomal dominant trait with complete penetrance. The non-sense mutation was absent in 300 control individuals. Functional analyses unveiled that the mutant MEF2C protein had no transcriptional activity. Furthermore, the mutation abolished the synergistic transactivation between MEF2C and GATA4 as well as HAND1, two other transcription factors that have been associated with DCM. CONCLUSIONS: This study indicates MEF2C as a new gene responsible for human DCM, which provides novel insight into the mechanism underpinning DCM, suggesting potential implications for development of innovative prophylactic and therapeutic strategies for DCM, the most prevalent form of primary myocardial disease.

A SHOX2 loss-of-function mutation underlying familial atrial fibrillation.

Atrial fibrillation (AF), as the most common sustained cardiac arrhythmia, is associated with substantially increased morbidity and mortality. Aggregating evidence demonstrates that genetic defects play a crucial role in the pathogenesis of AF, especially in familial AF. Nevertheless, AF is of pronounced genetic heterogeneity, and in an overwhelming majority of cases the genetic determinants underlying AF remain elusive. In the current study, 162 unrelated patients with familial AF and 238 unrelated healthy individuals served as controls were recruited. The coding exons and splicing junction sites of the SHOX2 gene, which encodes a homeobox-containing transcription factor essential for proper development and function of the cardiac conduction system, were sequenced in all study participants. The functional effect of the mutant SHOX2 protein was characterized with a dual-luciferase reporter assay system. As a result, a novel heterozygous SHOX2 mutation, c.580C>T or p.R194X, was identified in an index patient, which was absent from the 476 control chromosomes. Genetic analysis of the proband's pedigree revealed that the nonsense mutation co-segregated with AF in the family with complete penetrance. Functional assays demonstrated that the mutant SHOX2 protein had no transcriptional activity compared with its wild-type counterpart. In conclusion, this is the first report on the association of SHOX2 loss-of-function mutation with enhanced susceptibility to familial AF, which provides novel insight into the molecular mechanism underpinning AF, suggesting potential implications for genetic counseling and individualized management of AF patients.

ZBTB17 loss-of-function mutation contributes to familial dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is a common primary myocardial disease leading to congestive heart failure, arrhythmia and sudden cardiac death. Increasing studies demonstrate substantial genetic determinants for DCM. Nevertheless, DCM is of substantial genetic heterogeneity, and the genetic basis for DCM in most patients remains unclear. The present study was sought to investigate the association of a genetic variant in the ZBTB17 gene with DCM. A cohort of 158 unrelated patients with idiopathic DCM and a total of 230 unrelated, ethnically matched healthy individuals used as controls were recruited. The coding exons and splicing boundaries of ZBTB17 were sequenced in all study participants. The functional effect of the mutant ZBTB17 was characterized by a dual-luciferase reporter assay system. A novel heterozygous ZBTB17 mutation, p.E243X, was discovered in an index patient. Genetic scan of the mutation carrier's available relatives showed that the mutation was present in all affected family members but absent in unaffected family members. Analysis of the proband's pedigree revealed that the mutation co-segregated with DCM, which was transmitted in an autosomal dominant pattern with complete penetrance. The nonsense mutation was absent in the 460 control chromosomes. Functional assays demonstrated that the truncated ZBTB17 protein had no transcriptional activity as compared with its wild-type counterpart. This study firstly associates ZBTB17 loss-of-function mutation with enhanced susceptibility to DCM in humans, which provides novel insight into the molecular mechanism underpinning DCM, implying potential implications for genetic counseling and personalized management of DCM.

CASZ1 loss-of-function mutation contributes to familial dilated cardiomyopathy.

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.

MEF2C loss-of-function mutation contributes to congenital heart defects.

Congenital heart disease (CHD) is the most common type of developmental abnormality in humans, and is a leading cause for substantially increased morbidity and mortality in affected individuals. Increasing studies demonstrates a pivotal role of genetic defects in the pathogenesis of CHD, and presently mutations in more than 60 genes have been associated with CHD. Nevertheless, CHD is of pronounced genetic heterogeneity, and the genetic basis underpinning CHD in a large proportion of patients remains unclear. In the present study, the whole coding exons and splicing donors/acceptors of the MEF2C gene, which codes for a transcription factor essential for normal cardiovascular development, were sequenced in 200 unrelated patients affected with CHD, and a novel heterozygous missense mutation, p.L38P, was identified in an index patient with patent ductus arteriosus (PDA) and ventricular septal defect (VSD). Genetic scan of the mutation carrier's family members available showed that the mutation was present in all affected family members but absent in unaffected family members. Analysis of the proband's pedigree revealed that the mutation co-segregated with PDA, which was transmitted as an autosomal dominant trait with complete penetrance. The mutation changed the amino acid that was completely conserved evolutionarily, and did not exist in 300 unrelated, ethnically-matched healthy individuals used as controls. Functional deciphers by using a dual-luciferase reporter assay system unveiled that the mutant MEF2C protein had a significantly reduced transcriptional activity. Furthermore, the mutation significantly diminished the synergistic activation between MEF2C and GATA4, another cardiac core transcription factor that has been causally linked to CHD. In conclusion, this is the first report on the association of a MEF2C loss-of-function mutation with an increased vulnerability to CHD in humans, which provides novel insight into the molecular mechanisms underlying CHD, implying potential implications for early diagnosis and timely prophylaxis of CHD.