DNA Methylation Levels of the TBX5 Gene Promoter Are Associated with Congenital Septal Defects in Mexican Paediatric Patients

The TBX5 gene regulates morphological changes during heart development, and it has been associated with epigenetic abnormalities observed in congenital heart defects (CHD). The aim of this research was to evaluate the association between DNA methylation levels of the TBX5 gene promoter and congenital septal defects. DNA methylation levels of six CpG sites in the TBX5 gene promoter were evaluated using pyrosequencing analysis in 35 patients with congenital septal defects and 48 controls. Average methylation levels were higher in individuals with congenital septal defects than in the controls (p < 0.004). In five CpG sites, we also found higher methylation levels in patients than in the controls (p < 0.05). High methylation levels were associated with congenital septal defects (OR = 3.91; 95% CI = 1.02–14.8; p = 0.045). The analysis of Receiver Operating Characteristic (ROC) showed that the methylation levels of the TBX5 gene could be used as a risk marker for congenital septal defects (AUC = 0.68, 95% CI = 0.56–0.80; p = 0.004). Finally, an analysis of environmental factors indicated that maternal infections increased the risk (OR = 2.90; 95% CI = 1.01–8.33; p = 0.048) of congenital septal defects. Our data suggest that a high DNA methylation of the TBX5 gene could be associated with congenital septal defects.

Prenatal Diagnosis of Holt–Oram Syndrome With a Novel Mutation of TBX5 Gene: A Case Report

Background: Holt–Oram syndrome (HOS) is an autosomal dominant disorder caused by mutations of TBX5 gene.Case presentation: We report a fetus with HOS diagnosed sonographically at 23 weeks of gestation. The fetal parents are non-consanguineous. The fetus exhibited short radius and ulna, inability to supinate the hands, absence of the right thumb, and heart ventricular septal defect (VSD), while the fetal father exhibited VSD and short radius and ulna only. Fetal brother had cubitus valgus and thumb adduction, except for VSD, short radius and ulna. The pregnancy was terminated. Whole-exome sequencing (WES) revealed a novel mutation in the TBX5 (c.510+1G&gt;A) in the fetus inherited from the father. The variant (c.510+1G&gt;A) occurs at splice donor and may alter TBX5 gene function by impact on splicing. It was not previously reported in China.Conclusion: Our case reported a novel mutation in TBX5, which expanded the known genetic variants associated with HOS.

The Effect of Different Exercise Intensities on T-Box Transcription Factor 5 Gene Expression and Hypertrophy in the Heart Muscle of Male Rats

Background: Exercise is one of the methods affecting cardiovascular adaptation, but its cellular and molecular pathways and mechanisms are unknown. T-Box Transcription Factor 5 (TBX5) gene seems to be one of the factors involved in regulating cardiac hypertrophy. Objective: The aim of this study was to investigate the effect of an 8-week exercise program with different intensities on the expression of TBX5 gene in the heart of male Wistar rats. Methods: In this experimental study, 24 male adult Wistar rats were divided into three groups of High Intensity Training (HIT), Low Intensity Training and (LIT) and control. Training groups performed the exercise program for 8 weeks, 5 sessions per week. The exercise program for the HIT group consists of running on a treadmill with five 8-min intervals at 85-90% VO2 max intensity divided into 2-min intervals at 50-60% VO2 max intensity, while for the LIT group it was included five 8-min intervals with 50-60% VO2 max intensity divided into 2-min intervals with 45% -50% VO2 max intensity. The control group performed no exercise. The real-time Polymerase Chain Reaction (PCR) analysis was used to measure the expression level of TBX5 gene. The collected data were analyzed by one-way ANOVA and Tukey’s post hoc test. Findings: The heart weight (P≤0.001 and P=0.004), heart-weight to body-weight ratio (P≤0.0001 and P=0.001), and left ventricular wall thickness were significantly higher in the HIT and LIT groups than in the control group (P≤0.0001 and P=0.38 ). The left ventricular wall thickness in the HIT group was significantly higher than in the LIT group (P=0.001). The TBX5 expression in the two training groups were not significantly different from that of control group (P=0.11). Conclusion: It seems that more intensive exercise can have more significant effects on cardiac hypertrophy than less intensive exercise.

Identification of Deleterious Single Nucleotide Polymorphism (SNP)s in the Human TBX5 Gene & Prediction of Their Structural & Functional Consequences: An In Silico approach

ABSTRACTT-box transcription factor 5 (TBX5) gene encodes the transcription factor TBX5 which plays a crucial role in the development of the heart and upper limbs. Alternative splicing resulting in several isoforms regulate the functions of this gene during the developmental process. Damaging single nucleotide variants in this gene alter the structure and disturb the functions of TBX5 and ultimately cause Holt-Oram Syndrome (HOS), an autosomal dominant disease where various congenital malformations of the heart (with or without conduction defects), upper limbs and shoulder girdles are observed. Besides HOS, TBX5 single nucleotide variants can also be associated with Dilated Cardiomyopathy, Atrial Fibrillation, and Tetralogy of Fallot without skeletal deformity.By exploiting available Single Nucleotide Polymorphism information in dbSNP, this study was designed to identify in silico the deleterious TBX5 SNPs, and predict their structural and functional consequences, and alteration of biochemical properties on the candidate protein. For this purpose, various reliable in silico analysis tools such as PROVEAN, SIFT, PolyPhen-2, MutPred2, PredictSNP1, PredictSNP2, MetaLR, MetaSVM, REVEL, ConSurf, NetsurfP-2.0, iStable 2.0, Missense3D, UTRdb, MirSNP, and Human Splicing Finder (HSF) have been used. 58 missense substitutions were found damaging by both sequence homology-based tools SIFT (Sorting Intolerant from Tolerant) and PROVEAN (Protein Variation Effect Analyzer), and structure homology-based tool PolyPhen-2 (Polymorphism Phenotyping-2). Among these 58 substitutions, 13 are already annotated as Pathogenic/Likely Pathogenic in ClinVar database, and so they were excluded. Then, the rest 45 high confidence substitutions were further scrutinized by various disease association predicting meta servers. Next, conservation profile of the native amino acid residues, their surface & solvent accessibility, and stability and structural integrity of the protein upon mutation were assessed. Analysis of 1 stop loss SNP, and 2 nonsense SNPs were done by PredictSNP2. Analysis of SNPs in the UTR region were done using UTRdb and MirSNP, and splice site SNPs were evaluated by Human Splicing Finder (HSF). This study provides a comprehensive list of most deleterious SNPs onTBX5 gene. The results from this study can help in early diagnosis of HOS and in relevant genetic counseling.

Identification and functional analysis of genetic variants in TBX5 gene promoter in patients with acute myocardial infarction

Background Coronary artery disease (CAD), including acute myocardial infarction (AMI), is a common complex disease. Although a great number of genetic loci and variants for CAD have been identified, genetic causes and underlying mechanisms remain largely unclear. Epidemiological studies have revealed that CAD incidence is strikingly higher in patients with congenital heart disease than that in normal population. T-box transcription factors play critical roles in embryonic development. In particular, TBX5 as a dosage-sensitive regulator is required for cardiac development and function. Thus, dysregulated TBX5 gene expression may be involved in CAD development. Methods TBX5 gene promoter was genetically and functionally analysed in large groups of AMI patients (n = 432) and ethnic-matched healthy controls (n = 448). Results Six novel heterozygous DNA sequence variants (DSVs) in the TBX5 gene promoter (g.4100A > G, g.4194G > A, g.4260 T > C, g.4367C > A, g.4581A > G and g.5004G > T) were found in AMI patients, but in none of controls. These DSVs significantly changed the activity of TBX5 gene promoter in cultured cells (P < 0.05). Furthermore, three of the DSVs (g.4100A > G, g.4260 T > C and g.4581A > G) evidently modified the binding sites of unknown transcription factors. Conclusions The DSVs identified in AMI patients may alter TBX5 gene promoter activity and change TBX5 level, contributing to AMI development as a rare risk factor.

Holt-Oram Syndrome: A Variety of Heart-Hand Syndrome

Holt-Oram syndrome (HOS) is a heart-upper limb malformation complex , is a rare autosomal dominant disorder, caused by a mutation in the TBX5 gene located on chromosome 12 and near complete penetrance but variable expression. Holt and Oram first described this syndrome in 1960. Approximately 40% of cases represent new mutations. The syndrome is associated with defective development of cardiac structures that results in atrial septal defect(ASD), most commonly the secundum type; heart block of varying degree or both.The syndrome is characterized by cardiac malformations and aplasia or hypoplasia of the thumb. The incidence of HOS is estimated at 1:100,000 live births. In the literature, it is also known as atriodigital syndrome, heart-hand syndrome, upper limb-cardiovascular syndrome, cardiac-limb syndrome, or cardiomelic syndrome. Herein, we report a 45-year-old female case of HOS presenting a large ostium secundum type ASD along with congenitally fusion of carpal bones in both hands and absence of right first metacarpal bone with triphalagial thumb where as hypoplastic proximal phalange. In left hand, hypoplastic first metacarpal bone and hypoplastic thumb with syndactyly of both thumb with index finger.University Heart Journal Vol. 13, No. 2, July 2017; 67-71