Mutational analysis of JAG1 gene in non-syndromic tetralogy of Fallot children

Accelerated Growth, Differentiation, and Ploidy with Reduced Proliferation of Right Ventricular Cardiomyocytes in Children with Congenital Heart Defect Tetralogy of Fallot

The myocardium of children with tetralogy of Fallot (TF) undergoes hemodynamic overload and hypoxemia immediately after birth. Comparative analysis of changes in the ploidy and morphology of the right ventricular cardiomyocytes in children with TF in the first years of life demonstrated their significant increase compared with the control group. In children with TF, there was a predominantly diffuse distribution of Connexin43-containing gap junctions over the cardiomyocytes sarcolemma, which redistributed into the intercalated discs as cardiomyocytes differentiation increased. The number of Ki67-positive cardiomyocytes varied greatly and amounted to 7.0–1025.5/10⁶ cardiomyocytes and also were decreased with increased myocytes differentiation. Ultrastructural signs of immaturity and proliferative activity of cardiomyocytes in children with TF were demonstrated. The proportion of interstitial tissue did not differ significantly from the control group. The myocardium of children with TF under six months of age was most sensitive to hypoxemia, it was manifested by a delay in the intercalated discs and myofibril assembly and the appearance of ultrastructural signs of dystrophic changes in the cardiomyocytes. Thus, the acceleration of ontogenetic growth and differentiation of the cardiomyocytes, but not the reactivation of their proliferation, was an adaptation of the immature myocardium of children with TF to hemodynamic overload and hypoxemia.

Novel JAG1 Deletion Variant in Patient with Atypical Alagille Syndrome

Alagille syndrome (AGS) is an autosomal-dominant disorder characterized by various degrees of abnormalities in the liver, heart, eyes, vertebrae, kidneys, face, vasculature, skeleton, and pancreas. This case report describes a newborn child exhibiting a congenital neural tube defect and peculiar craniofacial appearance characterized by a prominent forehead, deep-set eyes, bulbous nasal tip, and subtle upper lip. Just a few hours after birth, congenital heart disease was suspected for cyanosis and confirmed by heart evaluation. In particular, echocardiography indicated pulmonary atresia with ventricular septal defect with severe hypoplasia of the pulmonary branches (1.5 mm), large patent ductus arteriosus and several major aortopulmonary collateral arteries. Due to the association of peculiar craniofacial appearance and congenital heart disease, a form of Alagille syndrome was suspected. In addition, on the fifth day after birth, the patient developed jaundice, had acholic stools, and high levels of conjugated bilirubin and gamma-glutamyltransferase (GGT) were detected in the blood. Genetic testing revealed the novel variant c.802del in a single copy of the JAG1 gene. No variants in the NOTCH2 gene were detected. To the best of our knowledge, this is the first clinical description of a congenital neural tube defect in a molecularly confirmed Alagille patient. This work demonstrates a novel pathogenic heterozygous JAG1 mutation is associated with an atypical form of Alagille syndrome, suggesting an increased risk for neural tube defects compared to other Alagille patients.

The Functional Polymorphism R129W in the BVES Gene Is Associated with Sporadic Tetralogy of Fallot in the Han Chinese Population

Background: Tetralogy of Fallot (TOF) accounts for ∼10% of congenital heart disease cases. The blood vessel epicardial substance (BVES) gene has been reported to play a role in the function of adult hearts. However, whether allelic variants in BVES contribute to the risk of TOF and its possible mechanism remains unknown. Methods: The open reading frame of the BVES gene was sequenced using samples from 146 TOF patients and 100 unrelated healthy controls. qRT-PCR and western blot assays were used to confirm the expression of mutated BVES variants in the TOF samples. The online software Polyphen2 and SIFT were used to predict the deleterious effects of the observed allelic variants. The effects of these allelic variants on the transcriptional activities of genes were examined using dual-fluorescence reporter assays. Results: We genotyped four single nucleotide polymorphisms (SNPs) in the BVES gene from each of the 146 TOF patients. Among them, the minor allelic frequencies of c.385C>T (p.R129W) were 0.035% in TOF, but ∼0.025% in 100 controls and the Chinese Millionome Database. This allelic variant was predicted to be a potentially harmful alteration by the Polyphen2 and SIFT softwares. qRT-PCR and western blot analyses indicated that the expression of BVES in the six right ventricular outflow tract samples with the c.385C>T allelic variant was significantly downregulated. A dual-fluorescence reporter system showed that the c.385C>T allelic variant significantly decreased the transcriptional activity of the BVES gene and also decreased transcription from the GATA4 and NKX2.5 promoters. Conclusions: c.385C>T (p.R129W) is a functional SNP of the BVES gene that reduces the transcriptional activity of BVES in vitro and in vivo in TOF tissues. This subsequently affects the transcriptional activities of GATA4 and NKX2.5 related to TOF. These findings suggest that c.385C>T may be associated with the risk of TOF in the Han Chinese population.

The Contribution of Gene Mutations to the Pathogenesisof Tetralogy of Fallot

Congenital heart disease (CHD) is considered as an important and developing area in the medical community. Since these patients can reach maturity and have children, the role of genetic determinants in increasing risk of CHD is extremely evident among children of these patients. Because genetic studies related to CHD are increasing, and each day the role of new genetic markers is more and more clarified, this review re-examined the effects of gene mutations in the pathogenesis of tetralogy of Fallot (TOF) as an important pathological model among other CHDs. Due to the complexity of heart development, it is not astonishing that numerous signaling pathways and transcription factors, and many genes are involved in pathogenesis of TOF. This review focuses on the jag1, nkx2.5, gata4, zfpm2/fog2 and cited2 genes previously reported to be involved in TOF.

Functional polymorphisms of the neuropilin 1 gene are associated with the risk of tetralogy of Fallot in a Chinese Han population

Tetralogy of Fallot (TOF) is one of the most severe forms of cyanotic congenital heart disease (CHD) and is also the most common. Previous genome-wide association study (GWAS) and replication studies have suggested that a polymorphism in the neuropilin 1 (NRP1) gene is significantly associated with the risk of TOF. To further confirm the association between the NRP1 polymorphism and the risk of TOF and to identify additional positive functional single-nucleotide polymorphisms (SNPs) for TOF risk, we systematically screened for functional polymorphisms throughout the regulatory and coding regions of the NRP1 gene. A total of 11 functional SNPs in 747 Chinese Han individuals, including 314 TOF patients and 433 healthy controls, were genotyped using the MassARRAY system and GeneScan. The results revealed that the allelic and genotypic frequencies of the NRP1 polymorphism rs2228638 were strongly associated with the risk of TOF (p = 0.002 and 0.001, respectively). To increase the robustness of rs2228638 as a TOF risk SNP, we conducted a meta-analysis that combined published studies and our current case-control study. The meta-analysis showed that the T allele of the NRP1 polymorphism rs2228638 was significantly associated with an increased risk of TOF in the combined population, which included European and Chinese Han individuals [combined p < 0.00001, odds ratio (OR) = 1.53, 95% confidence interval (95% CI) = 1.35-1.73]. In addition, the association analysis suggested for the first time that there is a strong association between the allele distribution of rs10080 and susceptibility to TOF (p = 0.001). Our data provide further evidence of the association between NRP1 polymorphisms and TOF risk, and suggest that rs2228638 may be an excellent marker for TOF risk in European and Chinese Han populations.

Integration of Drosophila and Human Genetics to Understand Notch Signaling Related Diseases

Notch signaling research dates back to more than one hundred years, beginning with the identification of the Notch mutant in the fruit fly Drosophila melanogaster. Since then, research on Notch and related genes in flies has laid the foundation of what we now know as the Notch signaling pathway. In the 1990s, basic biological and biochemical studies of Notch signaling components in mammalian systems, as well as identification of rare mutations in Notch signaling pathway genes in human patients with rare Mendelian diseases or cancer, increased the significance of this pathway in human biology and medicine. In the 21st century, Drosophila and other genetic model organisms continue to play a leading role in understanding basic Notch biology. Furthermore, these model organisms can be used in a translational manner to study underlying mechanisms of Notch-related human diseases and to investigate the function of novel disease associated genes and variants. In this chapter, we first briefly review the major contributions of Drosophila to Notch signaling research, discussing the similarities and differences between the fly and human pathways. Next, we introduce several biological contexts in Drosophila in which Notch signaling has been extensively characterized. Finally, we discuss a number of genetic diseases caused by mutations in genes in the Notch signaling pathway in humans and we expand on how Drosophila can be used to study rare genetic variants associated with these and novel disorders. By combining modern genomics and state-of-the art technologies, Drosophila research is continuing to reveal exciting biology that sheds light onto mechanisms of disease.

Existence of mutations in the homeodomain-encoding region of NKX2.5 gene in Iranian patients with tetralogy of Fallot

Background:

Tetralogy of Fallot (TOF), the most common cyanotic heart defect and one of the most common congenital heart diseases, occurs mostly sporadically and nonsyndromically. The underlying molecular genetic mechanism is not known. Therefore, the existence of mutations in the homeodomain-encoding region of NKX2.5 gene in Iranian patients with tetralogy of Fallot is evaluated.

Materials and Methods:

In the present study, we analyzed the peripheral blood samples of27 patients in order to find any mutation in the 180 bp homeodomain-encoding region of NKX2.5 gene, which is known to be involved in heart development and diseases. DNA was extracted and all the samples were amplified by polymerase chain reaction (PCR) and sequenced.

Results:

Twenty-seven patients were included in the study. Twenty-five of them were infants and children (6 days to 11 years of age), one was a teenager (14-years of age), and another was a 33-year-old man [mean ± standard deviation (SD): 5.80 ± 3.90 years]. Thirteen patents were males (mean ± SD: 6.587077 ± 5.02 years) and 14 were females (mean ± SD: 5.0726 ± 2.81 years). One synonymous variant, i.e., c.543G>A was identified in one patient.

Conclusion:

Mutations in the homeodomain-encoding region of NKX2.5 gene may not have an outstanding role in etiology of tetralogy of Fallot patients in Iran.

Genetic variants at 10p11 confer risk of Tetralogy of Fallot in Chinese of Nanjing

A recent genome-wide association study (GWAS) has identified a new subset of susceptibility loci of Tetralogy of Fallot (TOF), one form of cyanotic congenital heart disease (CHD), on chromosomes 10p11, 10p14, 12q24, 13q31, 15q13 and 16q12 in Europeans. In the current study, we conducted a case-control study in a Chinese population including 1,010 CHD cases [atrial septal defect (ASD), ventricular septal defect (VSD) and TOF] and 1,962 controls to evaluate the associations of these loci with risk of CHD. We found that rs2228638 in NRP1 on 10p11 was significantly increased the risk of TOF (OR = 1.52, 95% CI = 1.13–2.04, P = 0.006), but not in other subgroups including ASD and VSD. In addition, no significant associations were observed between the other loci and the risk of ASD, VSD or TOF. Our results suggested that the genetic variants on 10p11 may serve as candidate markers for TOF susceptibility in Chinese population.

Mutational and functional analysis of the BVES gene coding region in Chinese patients with non-syndromic tetralogy of Fallot

Tetralogy of Fallot (TOF) is a common congenital heart defect (CHD). However, the genetic causes are largely unknown. Blood vessel epicardial substance (BVES) is postulated to play a role in embryonic development, and we previously found that the expression of BVES is upregulation in patients with congenital septal defect and that BVES participates in cardiocyte differentiation. We hypothesized that BVES is a candidate gene of TOF. In the present study, the entire coding sequence and splice junctions of BVES were sequenced in 114 unrelated patients with TOF and 400 unrelated healthy individuals used as controls. The functional effects of the exon mutant BVES were characterized in contrast to its wild-type counterpart using a luciferase reporter assay system. Four novel BVES mutations (c.166T>C, c.909C>T, c.540-80C>T, c.958+30A>G) were identified in patients with TOF but not in the 400 controls. Functional analysis indicated that the c.166T>C mutation of BVES was associated with an increased transcriptional activity. This finding suggests that BVES as a novel TOF gene may provide further insight into the molecular mechanisms involved in TOF.

Cellular decisions in cardiac outflow tract and coronary development: an act by VEGF and NOTCH

Congenital cardiac abnormalities are, due to their relatively high frequency and severe impact on quality of life, an important focus in cardiovascular research. Recently, various human studies have revealed a high coincidence of VEGF and NOTCH polymorphisms with cardiovascular outflow tract anomalies, such as bicuspid aortic valves and Tetralogy of Fallot, next to predisposition for cardiovascular pathologies, including atherosclerosis and aortic valve calcification. This genetic association between VEGF/NOTCH mutations and congenital cardiovascular defects in humans has been supported by substantial proof from animal models, revealing interaction of both pathways in cellular processes that are crucial for cardiac development. This review focuses on the role of VEGF and NOTCH signaling and their interplay in cardiogenesis with special interest to coronary and outflow tract development. An overview of the association between congenital malformations and VEGF/NOTCH polymorphisms in humans will be discussed along with their potential mechanisms and processes as revealed by transgenic mouse models. The molecular and cellular interaction of VEGF and subsequent Notch-signaling in these processes will be highlighted.

Notch signaling in human development and disease

Mutations in Notch signaling pathway members cause developmental phenotypes that affect the liver, skeleton, heart, eye, face, kidney, and vasculature. Notch associated disorders include the autosomal dominant, multi-system, Alagille syndrome caused by mutations in both a ligand (Jagged1 (JAG1)) and receptor (NOTCH2) and autosomal recessive spondylocostal dysostosis, caused by mutations in a ligand (Delta-like-3 (DLL3)), as well as several other members of the Notch signaling pathway. Mutations in NOTCH2 have also recently been connected to Hajdu-Cheney syndrome, a dominant disorder causing focal bone destruction, osteoporosis, craniofacial morphology and renal cysts. Mutations in the NOTCH1 receptor are associated with several types of cardiac disease and mutations in NOTCH3 cause the dominant adult onset disorder CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), a vascular disorder with onset in the 4th or 5th decades. Studies of these human disorders and their inheritance patterns and types of mutations reveal insights into the mechanisms of Notch signaling.