A Novel TBX1 Loss-of-Function Mutation Associated with Congenital Heart Disease.

Congenital heart disease (CHD) is the most prevalent type of birth defect in humans and is the leading non-infectious cause of infant death worldwide. There is a growing body of evidence demonstrating that genetic defects play an important role in the pathogenesis of CHD. However, CHD is a genetically heterogeneous disease and the genetic basis underpinning CHD in an overwhelming majority of patients remains unclear. In this study, the coding exons and splice junction sites of the TBX1 gene, which encodes a T-box homeodomain transcription factor essential for proper cardiovascular morphogenesis, were sequenced in 230 unrelated children with CHD. The available family members of the index patient carrying an identified mutation and 200 unrelated ethnically matched healthy individuals used as controls were subsequently genotyped for TBX1. The functional effect of the TBX1 mutation was predicted by online program MutationTaster and characterized by using a dual-luciferase reporter assay system. As a result, a novel heterozygous TBX1 mutation, p.Q277X, was identified in an index patient with double outlet right ventricle (DORV) and ventricular septal defect (VSD). Genetic analysis of the proband's available relatives showed that the mutation co-segregated with CHD transmitted in an autosomal dominant pattern with complete penetrance. The nonsense mutation, which was absent in 400 control chromosomes, altered the amino acid that was completely conserved evolutionarily across species and was predicted to be disease-causing by MutationTaster. Biochemical analysis revealed that Q277X-mutant TBX1 lost transcriptional activating function when compared with its wild-type counterpart. This study firstly associates TBX1 loss-of-function mutation with enhanced susceptibility to DORV and VSD in humans, which provides novel insight into the molecular mechanism underlying CHD and suggests potential implications for the development of new preventive and therapeutic strategies for CHD.

TBX20 loss-of-function mutation contributes to double outlet right ventricle.

Congenital heart disease (CHD), the most prevalent birth defect in humans worldwide, is still a leading non­infectious cause of infant morbidity and mortality. Increasing evidence demonstrates that genetic risk factors play a key role in the pathogenesis of CHD, and more than 50 genes have been linked to various types of CHD. Nevertheless, CHD is a heterogeneous disorder and the genetic components underpinning CHD in an overwhelming majority of cases remain unknown. In the present study, the entire coding exons and flanking introns of the TBX20 gene, which codes for a T-box transcription factor essential for the proper development of the heart, were sequenced in a cohort of 146 unrelated patients with CHD. The available relatives of the index patient harboring an identified mutation and 200 unrelated ethnically matched healthy individuals used as the controls were also genotyped for TBX20. The functional characteristics of the TBX20 mutation were assayed by using a dual-luciferase reporter assay system. As a result, a novel heterozygous TBX20 mutation, p.R143W, was identified in an index patient with double outlet right ventricle (DORV). Genetic analyses of the pedigree of the proband revealed that in the family, the mutation co-segregated with DORV transmitted in an autosomal dominant pattern with complete penetrance. The missense mutation was absent in 400 control chromosomes and the altered amino acid was completely conserved evolutionarily across species. Functional analysis revealed that mutant TBX20 had a significantly diminished transcriptional activity compared with its wild-type counterpart. To the best of our knowledge, this study is the first to report the association of TBX20 loss-of-function mutation with increased susceptibility to DORV in humans, which provides novel insight into the molecular mechanisms responsible for CHD, suggesting potential implications for the antenatal prophylaxis of CHD.

GATA5 loss-of-function mutation responsible for the congenital ventriculoseptal defect.

The ventriculoseptal defect (VSD) is the most common form of congenital heart disease and a leading noninfectious cause of infant mortality. Growing evidence demonstrates that genetic defects are associated with congenital VSD. Nevertheless, VSD is genetically heterogeneous, and the molecular basis for VSD in an overwhelming majority of patients remains unknown. In this study, the whole coding region of GATA5, a gene encoding a zinc finger transcription factor crucial for normal cardiogenesis, was sequenced in 120 unrelated patients with VSD. The available relatives of the patient harboring the identified mutation and 200 unrelated individuals used as controls were subsequently genotyped. The causative potential of a sequence variation was evaluated by MutationTaster, and the functional effect of the mutation was characterized using a luciferase reporter assay system. As a result, a novel heterozygous GATA5 mutation, p.L199V, was identified in a patient with VSD, which was absent in 400 control chromosomes. Genetic analysis of the mutation carrier's available family members showed that the substitution co-segregated with VSD transmitted in an autosomal dominant pattern. The p.L199V variation was automatically predicted to be disease causing, and the functional analysis showed that the GATA5 p.L199V mutant protein was associated with significantly reduced transcriptional activation compared with its wild-type counterpart. To the best of the authors' knowledge, this is the first report on the link of functionally compromised GATA5 to human VSD, suggesting potential implications for the early prophylaxis and personalized treatment of VSD.

[Identification of novel mutations in GATA6 gene associated with tetralogy of Fallot].

OBJECTIVE: To identify the novel mutations in the GATA6 gene associated with tetralogy of Fallot (TOF). METHODS: The clinical data and blood samples from 120 unrelated Han Chinese TOF patients and 200 unrelated ethnically matched healthy controls were collected. The coding exons and flanking splice junctions of GATA6 gene were amplified by polymerase chain reaction and sequenced by the technique of di-deoxynucleotide chain termination. The acquired sequences were aligned with those derived from GenBank by the aid of program BLAST to identify the sequence variations. The software ClustalW was applied for the conservation analysis of altered amino acids. The pathogenic probability for each sequence variation was predicted automatically by software MutationTaster. RESULTS: Three novel heterozygous missense GATA6 mutations were identified in 3 TOF patients. Specifically, the triplet substitutions of CTC for CCC at codon 73, CGC for AGC at codon 364 and GGC for GCC at codon 591, predicting the transitions of proline into leucine at amino acid residue 73 (p.P73L), serine into arginine at amino acid residue 364 (p.S364R) and alanine into glycine at amino acid residue 591 (p.A591G), were detected. None of three mutations was observed in 200 healthy controls. A cross-species alignment of GATA6 encoded protein sequences showed that the mutated amino acids were highly conserved evolutionarily and all 3 mutations were predicted to be pathogenic. CONCLUSIONS: Novel mutations are identified in the GATA6 gene associated with TOF. Such a finding may contribute to an early prophylaxis and therapy of TOF.

A novel GATA6 mutation associated with congenital ventricular septal defect.

Ventricular septal defect (VSD) is the most common form of congenital cardiovascular malformation and an important contributor to the substantially increased morbidity and mortality in infants. Emerging evidence indicates the genetic basis for the pathogenesis of congenital VSD in a significant proportion of patients. However, congenital VSD is a genetically heterogeneous disease and the genetic defects responsible for VSD in the overwhelming majority of cases remain unclear. In this study, the entire coding region of the GATA6 gene, which encodes a zinc-finger transcription factor crucial to normal cardiogenesis, was sequenced in 130 unrelated patients with congenital VSD. The available relatives of the index patient carrying the identified mutation and 200 unrelated ethnically matched healthy individuals used as controls were subsequently 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 missense GATA6 mutation, p.G220S, was identified in a proband with VSD. The variation was absent in 400 control chromosomes and the altered amino acid was highly conserved evolutionarily across species. Genetic analysis of the family members of the mutation carrier showed that the substitution co-segregated with VSD was inherited as an autosomal dominant trait. Functional analysis demonstrated that the p.G220S mutation of GATA6 was associated with significantly decreased transcriptional activity. The findings provide novel insight into the molecular mechanism involved in VSD, implying the potential clinical implications in the gene-specific prophylaxis and therapy of this common developmental abnormality in neonates.