Ying-Jia Xu

A novel NKX2.5 loss-of-function mutation responsible for familial atrial fibrillation

Atrial fibrillation (AF) is the most commonly sustained cardiac arrhythmia, and confers a substantially increased risk of morbidity and mortality. Increasing evidence has indicated that hereditary defects are implicated in AF. However, AF is genetically heterogeneous and the genetic etiology of AF in a significant portion of patients remains unclear. In this study, the entire coding sequence and splice junctions of the GATA6 gene, which encodes a zinc-finger transcription factor crucial for cardiogenesis, were sequenced in 140 unrelated patients with lone AF. The available relatives of the index patient carrying an identified mutation and 200 unrelated ethnically-matched healthy individuals used as the controls were genotyped. The functional characteristics of the mutant GATA6 were assessed in contrast to its wild-type counterpart using a luciferase reporter assay system. As a result, a novel heterozygous GATA6 mutation, p.G469V, was identified in a family with AF inherited in an autosomal dominant pattern. The mutation was absent in the 200 control individuals and the altered amino acid was completely conserved across species. Functional analysis demonstrated that the GATA6 mutation was associated with a significantly decreased transcriptional activity. The findings provide novel insight into the molecular mechanism involved in the pathogenesis of AF, as well as insight into potential therapies for the prevention and treatment of AF.

Prevalence and spectrum of PITX2c mutations associated with familial atrial fibrillation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia seen in clinical practice, accounting for approximately one-third of hospitalizations for heart rhythm disorders. The prevalence of AF is estimated to be 1% in the general population and increases markedly with advancing age, rising from about 0.5% of people in their fifties to nearly 10% of the octogenarians (1) .A F is associated with substantial morbidity and mortality. It confers a 5-fold increased risk of stroke and a double risk of death (1). AF generally occurs secondary to various cardiac and systemic disorders, including hypertension, cor-

GATA5 loss-of-function mutations associated with congenital bicuspid aortic valve

Bicuspid aortic valve (BAV) is the most common form of congenital cardiovascular defect in humans worldwide and is responsible for substantial morbidity and mortality. Accumulating evidence has demonstated that genetic risk factors are involved in the pathogenesis of BAV. However, BAV is genetically heterogeneous and the genetic basis underlying BAV in a large number of patients remains unknown. In the present study, the coding regions and splice junction sites of the GATA5 gene, which codes for a zinc-finger transcription factor crucial for the normal development of the aortic valve, was sequenced initially in 110 unrelated patients with BAV. The available relatives of the mutation carriers and 200 unrelated healthy individuals used as controls were subsequently genotyped for GATA5. The functional effect of the mutations was characterized by using a luciferase reporter assay system. As a result, two novel heterozygous GATA5 mutations, p.Y16D and p.T252P, were identified in two families with autosomal dominant inheritance of BAV, respectively. The variations were absent in 400 control chromosomes and the altered amino acids were completely conserved evolutionarily. Functional assays revealed that the two GATA5 mutants were associated with significantly reduced transcriptional activity compared with their wild-type counterpart. To the best of our knowledge, this is the first study on the association of GATA5 loss-of-function mutations with enhanced susceptibility to BAV, providing novel insight into the molecular mechanism involved in human BAV and suggesting a potential role for the early prophylaxis and personalized treatment of this common congenital heart disease.

GATA4 loss-of-function mutations underlie familial tetralogy of fallot.

Tetralogy of Fallot (TOF) represents the most common form of cyanotic congenital heart disease and accounts for significant morbidity and mortality in humans. Emerging evidence has implicated genetic defects in the pathogenesis of TOF. However, TOF is genetically heterogeneous and the genetic basis for TOF in most patients remains unclear. In this study, the GATA4 gene were sequenced in 52 probands with familial TOF, and three novel heterozygous mutations, including A9P and L51V both located in the putative first transactivational domain and N285S in the C‐terminal zinc finger, were identified in three probands, respectively. Genetic analysis of the pedigrees demonstrated that in each family the mutation cosegregated with TOF with complete penetrance. The missense mutations were absent in 800 control chromosomes and the altered amino acids were highly conserved evolutionarily. Functional analysis showed that the GATA4 mutants were consistently associated with diminished DNA‐binding affinity and decreased transcriptional activity. Furthermore, the N285S mutation completely disrupted the physical interaction between GATA4 and TBX5. To our knowledge, this report associates GATA4 loss‐of‐function mutations with familial TOF for the first time, providing novel insight into the molecular mechanism involved in TOF and suggesting potential implications for the early prophylaxis and allele‐specific therapy of TOF.

A novel GATA5 loss-of-function mutation underlies lone atrial fibrillation

Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is associated with significantly increased morbidity and mortality. Cumulative evidence highlights the importance of genetic defects in the pathogenesis of AF. However, AF is of remarkable heterogeneity and the genetic determinants of AF in a vast majority of patients remain illusive. In this study, the coding exons and splice junctions of the GATA5 gene, which encodes a zinc-finger transcription factor essential for normal cardiogenesis, were sequenced in 118 unrelated patients with lone AF. The available relatives of the index patient carrying an identified mutation and 200 unrelated ethnically-matched healthy individuals used as controls were genotyped. The functional effect of the mutant GATA5 was characterized in contrast to its wild-type counterpart using a luciferase reporter assay system. As a result, a novel heterozygous GATA5 mutation, p.W200G, was identified in a family with AF inherited as an autosomal dominant trait. The mutation was absent in 200 control individuals and the altered amino acid was completely conserved evolutionarily across species. Functional analysis showed that the mutation of GATA5 was associated with a significantly decreased transcriptional activity. These findings provide novel insight into the molecular mechanism involved in AF, suggesting potential implications for the early prophylaxis and gene-specific therapy of AF.

A Novel NKX2.5 Loss-of-Function Mutation Associated With Congenital Bicuspid Aortic Valve

Bicuspid aortic valve (BAV) is the most common form of congenital cardiovascular defect in humans and is associated with substantial morbidity and mortality. Emerging evidence demonstrates that genetic risk factors play an important role in the pathogenesis of BAV. However, BAV is a genetically heterogenous disorder, and the genetic defects underpinning BAV in most patients remain to be identified. In the present study, the coding exons and flanking introns of the NKX2.5 gene, which encodes a homeodomain-containing transcription factor essential for the normal development of the aortic valve, were sequenced in 142 unrelated patients with BAV. The available relatives of the mutation carrier and 200 unrelated healthy subjects used as controls were also genotyped for NKX2.5. The functional characteristics of the mutation were delineated by using a dual-luciferase reporter assay system. As a result, a novel heterozygous NKX2.5 mutation, p.K192X, was identified in a family with BAV transmitted in an autosomal dominant pattern. The nonsense mutation was absent in 400 control chromosomes. Functional analyses revealed that the mutant NKX2.5 had no transcriptional activity compared with its wild-type counterpart. Furthermore, the mutation abolished the synergistic transcriptional activation between NKX2.5 and GATA5, another transcription factor crucial for the aortic valvular morphogenesis. In conclusion, this study is the first to link an NKX2.5 loss-of-function mutation to enhanced susceptibility to human BAV, providing novel insight into the molecular mechanism of BAV and suggesting potential implications for genetic counseling and clinical care of families presenting with BAV.

GATA6 loss-of-function mutation in atrial fibrillation

Atrial fibrillation (AF) is the most common type of sustained cardiac arrhythmia and is associated with substantial morbidity and mortality. Increasing evidence demonstrates that hereditary defects are involved in the pathogenesis of AF. However, AF is of remarkable genetic heterogeneity, and the heritable components responsible for AF in the majority of patients remain unclear. In this study, the entire coding region of the GATA6 gene, which encodes a zinc-finger transcription factor crucial for cardiogenesis, was sequenced in 138 unrelated patients with lone AF, and a novel heterozygous GATA6 mutation, c.704A > C equivalent to p.Y235S, was identified in a patient. The detected substitution, which altered the amino acid highly conserved evolutionarily across species, was absent in 200 unrelated ethnically matched healthy individuals, and was predicted to be disease-causing by MutationTaster. Genetic analysis of the available relatives of the mutation carrier showed that in the family the variation co-segregated with the disease transmitted as an autosomal dominant trait, with complete penetrance. The functional analysis performed using a luciferase reporter assay system revealed that the mutant GATA6 protein resulted in significantly decreased transcriptional activity compared with its wild-type counterpart. These findings provide novel insight into the molecular pathophysiology implicated in AF, suggesting the potential implications in the prophylactic strategy and effective therapy for this common arrhythmia.

GATA5 loss-of-Function Mutations Underlie Tetralogy of Fallot

Tetraology of Fallot (TOF) is the most common form of cyanotic congenital heart disease and is a major cause of significant morbidity and mortality. Emerging evidence demonstrates that genetic risk factors are involved in the pathogenesis of TOF. However, TOF is genetically heterogeneous and the genetic defects responsible for TOF remain largely unclear. In the present study, the whole coding region of the GATA5 gene, which encodes a zinc-finger transcription factor essential for cardiogenesis, was sequenced in 130 unrelated patients with TOF. The relatives of the index patients harboring the identified mutations and 200 unrelated control individuals were subsequently genotyped. The functional characteristics of the mutations were analyzed using a luciferase reporter assay system. As a result, 2 novel heterozygous GATA5 mutations, p.R187G and p.H207R, were identified in 2 families with autosomal dominantly inherited TOF, respectively. The variations were absent in 400 control alleles and the altered amino acids were completely conserved evolutionarily. Functional analysis showed that the GATA5 mutants were associated with significantly decreased transcriptional activation compared with their wild-type counterpart. To our knowledge, this is the first report on the association of GATA5 loss-of-function mutations with TOF, suggesting potential implications for the early prophylaxis and allele-specific therapy of human TOF.

GATA4 loss-of-function mutation underlies familial dilated cardiomyopathy

The cardiac transcription factor GATA4 is essential for cardiac development, and mutations in this gene have been implicated in a wide variety of congenital heart diseases in both animal models and humans. However, whether mutated GATA4 predisposes to dilated cardiomyopathy (DCM) remains unknown. In this study, the whole coding region and splice junction sites of the GATA4 gene was sequenced in 110 unrelated patients with idiopathic DCM. The available relatives of the index patient harboring an identified mutation and 200 unrelated ethnically matched healthy individuals used as controls were genotyped. The functional effect of the mutant GATA4 was characterized in contrast to its wild-type counterpart using a luciferase reporter assay system. As a result, a novel heterozygous GATA4 mutation, p.C271S, was identified in a family with DCM inherited as an autosomal dominant trait, which co-segregated with DCM in the family with complete penetrance. The missense mutation was absent in 400 control chromosomes and the altered amino acid was completely conserved evolutionarily among species. Functional analysis demonstrated that the GATA4 mutant was associated with significantly decreased transcriptional activity and remarkably reduced synergistic activation between GATA4 and NKX2-5, another transcription factor crucial for cardiogenesis. The findings provide novel insight into the molecular mechanisms involved in the pathogenesis of DCM, suggesting the potential implications in the prenatal diagnosis and gene-specific treatment for this common form of myocardial disorder.

Prevalence and spectrum of GATA5 mutations associated with congenital heart disease

Congenital heart disease (CHD) is the most common form of birth defect and is the leading noninfectious cause of infant death. A growing body of evidence demonstrates that genetic risk factors are involved in the pathogenesis of CHD. However, CHD is a genetically heterogeneous disease and the genetic defects underlying CHD in an overwhelming majority of patients remain unclear. In this study, the whole coding region and splice junction sites of the PITX2c gene, which encodes variant 3 of paired-like homeodomain transcription factor 2 crucial for normal cardiovascular morphogenesis, were sequenced in 382 unrelated patients with CHD, and 2 novel heterozygous mutations, p.W147X and p.N153D, were identified in 2 unrelated patients with CHD, respectively, including a 1-year-old male patient with double outlet right ventricle in combination with ventricular septal defect and a 4-year-old female patient with ventricular septal defect. The mutations were absent in 400 control chromosomes and were both predicted t...