Tetralogy Of Fallot

A number sign (#) is used with this entry because tetralogy of Fallot (TOF) can be caused by heterozygous mutation in the JAG1 gene (601920) on chromosome 20p12, the NKX2-5 gene (600584) on chromosome 5q35, the GATA4 gene (600576) on chromosome 8p23.

Tetralogy of Fallot is also a well-recognized feature of many syndromes, including the 22q11 microdeletion syndrome (188400) and trisomy 21 (190685), and has been found to be caused by mutations in several genes, including ZFPM2 (603693), TBX1 (602054), and GATA6 (601656).

Pitt (1962) described a family in which 11 persons had either TOF or one of its components. The diagnosis was confirmed at operation or autopsy in 5 of the 11.

The large study of Boon et al. (1972) led to the conclusions that heritability is about 54% and that in sibs the recurrence risk is about 1% for Fallot tetralogy and about 2% for any cardiac defect.

The family that Der Kaloustian et al. (1985) reported may be a special type of Fallot tetralogy, inherited, the authors suggested, as an autosomal recessive. Two daughters of first cousins had tetralogy with pulmonary valve atresia. The bronchial circulation and pulmonary valve anatomy were identical in the 2 sibs. The parental consanguinity was of less significance because the family was Christian Maronite Lebanese, a small group with a relatively high rate of consanguinity. Familial tetralogy was reported also by Lynch et al. (1966) in sibs and by Friedberg (1974) in 3 generations but none of the affected, it seems, had pulmonary valve atresia.

Jones and Waldman (1985) reported a family in which 6 persons in 3 successive generations had some combination of preauricular pits (4/6), tetralogy of Fallot (3/6), fifth finger clinodactyly (6/6), and seemingly characteristic facies (5/6). Features of the facies included broad forehead and 'prominent' eyes.

Pankau et al. (1990) described tetralogy of Fallot in 3 of 5 sibs. Pacileo et al. (1992) also described tetralogy of Fallot in 3 sibs and a cousin.

Hirt-Armon et al. (1996) reported a woman with tetralogy of Fallot in association with absence of the pulmonic valve. She gave birth to a female infant with TOF, extreme hypoplasia and dysplasia of the pulmonary valve, and type III tracheal agenesis (in this type the bronchi originate directly from the esophagus). The authors suggested that this association may represent a distinct syndrome with autosomal dominant inheritance. Familial cases of TOF with congenital absence of the pulmonic valve were reported by Friedberg (1974) and Der Kaloustian et al. (1985).

Digilio et al. (1997) calculated empiric risk figures for recurrence of isolated tetralogy of Fallot in families after exclusion of del(22q11). The investigation covered relatives of 102 patients. Their results showed that the frequency of congenital heart defect was 3% in sibs, 0.5% in parents, 0.3% in grandparents, 0.2% in uncles or aunts, and 0.6% in first cousins. The recurrence risk rate for sibs was the same as that previously estimated, indicating that after exclusion of patients with del(22q11), genetic counseling to patients with isolated TOF should not be modified. Digilio et al. (1997) concluded that gene(s) different from those located on 22q11 must be involved in causing familial aggregation of nonsyndromic tetralogy of Fallot in these cases.

Johnson et al. (1997) conducted a cytogenetic evaluation of 159 cases of tetralogy of Fallot. A del(22q11) was identified in 14% who underwent fluorescence in situ hybridization (FISH) testing with the N25 cosmid probe.

Rauch et al. (2010) found that 22q11.2 deletion was the most common genetic anomaly among 230 patients with TOF, found in 7.4% of patients. The associated cardiac phenotype was distinct for obstruction of the proximal pulmonary artery, hypoplastic central pulmonary arteries, and subclavian artery anomalies. The second most common anomaly was trisomy 21, found in 5.2% of patients, which was often associated with atrioventricular septal defect. Other chromosomal aberrations or submicroscopic copy number changes were found in 3% of patients.

In a cohort of 178 Italian patients with TOF, De Luca et al. (2011) analyzed 5 genes known to be associated with conotruncal defects, including the NKX2-5 (600584), GATA4 (600576), ZFPM2 (603693), GDF1 (602880), and ISL1 (600366) genes, and identified heterozygous missense mutations in the NKX2-5 and ZFPM2 genes in 3 patients. De Luca et al. (2011) concluded that GATA4, GDF1, and ISL1 are not major determinants in the pathogenesis of TOF.

Mutation in the NKX2-5 Gene

Benson et al. (1999) evaluated the possibility of mutations in the cardiac-specific homeobox gene (CSX, or NKX2-5; 600584) in 20 patients with tetralogy of Fallot who were negative for del(22q11). In only 1 patient was a CSX mutation found, arg25 to cys (600584.0004). The patient had undergone surgery at 12 months of age for a typical tetralogy of Fallot and 2 small muscular VSDs. She had small pulmonary arteries with areas of peripheral narrowing and had undergone balloon dilation on 2 occasions. There was no family history of heart disease. She did not have AV block or atrial septal defect, which are features of patients with other CSX mutations.

Goldmuntz et al. (2001) genotyped a group of 114 patients with tetralogy of Fallot from whom patients with 22q11 microdeletion (188400) had been excluded. They identified 4 heterozygous mutations in the NKX2-5 gene (600584.0004; 600584.0006-600584.0008) in 6 individuals. Three of these had classical tetralogy of Fallot with differing aortic arch anatomy, while the others had pulmonary valve atresia with or without major aortopulmonary collateral vessels. None had evidence of cardiac conduction system disease. Only one individual had a family history of tetralogy of Fallot. A number of asymptomatic mutation carriers were identified in other families, however, indicating reduced penetrance. Goldmuntz et al. (2001) stated that NKX2-5 mutations were the first gene defects identified for nonsyndromic tetralogy of Fallot, and estimated that NKX2-5 mutations are present in approximately 4% of all patients with TOF.

Among 230 patients with TOF, Rauch et al. (2010) found that 2 patients (0.9%) had a low-penetrance mutation in the NKX2-5 gene (R25C; 600584.0004). Two additional patients had missense variants in the NKX2-5 gene (C270Y and V315L, respectively) that were not detected in 280 controls, but in vitro functional expression studies suggested no change in transcriptional activity as a result of these variants.

In 2 (1.1%) of 178 Italian patients with TOF, De Luca et al. (2011) identified the R25C mutation in the NKX2-5 gene. These 2 sporadic patients both had a left-sided arch, subaortic ventricular septal defect, and patent pulmonary valve.

Mutation in the JAG1 Gene

Eldadah et al. (2001) identified a missense mutation (G274D; 601920.0010) in the JAG1 gene in a large kindred segregating autosomal dominant TOF with reduced penetrance. Nine of 11 mutation carriers manifested cardiac disease, including classic TOF, ventricular septal defect with aortic dextroposition, and isolated peripheral pulmonic stenosis. All forms of TOF were represented, including variants with pulmonic stenosis, pulmonic atresia, and absent pulmonary valve. No individual within this family met diagnostic criteria for any previously described clinical syndrome, including Alagille syndrome-1 (ALGS1; 118450), caused by haploinsufficiency for the JAG1 gene. All mutation carriers had characteristic but variable facial features, including long, narrow, and upslanting palpebral fissures, prominent nasal bridge, square dental arch and broad, prominent chin, which were distinct from those of unaffected family members and typical AGS patients. The glycine residue at position 274 is highly conserved in other EGF-like domains of JAG1 and in those of other proteins. The data supported either a relative loss-of-function or a gain-of-function pathogenetic mechanism in this family and suggested that JAG1 mutations may contribute significantly to common variants of right heart obstructive disease.

Among 230 patients with TOF, Rauch et al. (2010) found that 3 (1.3%) had Alagille syndrome associated with JAG1 mutations.

Mutation in the GATA4 Gene

Tomita-Mitchell et al. (2007) analyzed the GATA4 gene (600576) in 628 patients with cardiac septal or conotruncal defects and identified 4 heterozygous missense mutations in 5 patients, including 1 with TOF (600576.0005) and a vague family history of congenital heart defects. The authors concluded that GATA4 mutations are uncommon in patients with septal defects.

Zhang et al. (2008) analyzed the GATA4 gene (600576) in 486 Chinese patients with congenital heart defects and identified 9 heterozygous mutations in 12 patients, including 2 (3.1%) of 64 patients with TOF (600576.0011; 600576.0012).

Peng et al. (2010) analyzed the GATA4 gene in 135 sporadic pediatric Chinese patients with congenital heart defects and identified a heterozygous missense mutation in 1 of 12 patients with TOF (600576.0007).

Mutation in the ZFPM2 Gene

In 2 of 47 patients with sporadic TOF, Pizzuti et al. (2003) identified heterozygosity for a mutation in the ZFPM2 gene: ser657 to gly (S657G; 603693.0001) or glu30 to gly (E30G; 603693.0002). They suggested that ZFMP2 gene mutations may contribute to some sporadic cases of TOF.

In 1 (0.6%) of 178 Italian patients with TOF, De Luca et al. (2011) identified a missense mutation in the ZFPM2 gene (M544I; 603693.0007). This sporadic patient had a left-sided arch, subaortic ventricular septal defect, and patent pulmonary valve. Parental DNA was unavailable for analysis.

Mutation in the TBX1 gene

In a Turkish female patient with tetralogy of Fallot, Rauch et al. (2010) identified a heterozygous 30-bp duplication in the TBX1 gene on chromosome 22q11.2 (602054.0006). She had facial asymmetry, scoliosis, absent pulmonary vein, isolated left pulmonary artery, ventricular septal defect, and normal cognitive development. She did not have the facial gestalt of 22q11.2 deletion syndrome. The insertion was shown to result in the expansion of a polyalanine tract, which caused decreased transcriptional activity and cytoplasmic aggregation of the protein in cellular studies.

Mutation in the GATA6 Gene

In a Hispanic patient with tetralogy of Fallot, Maitra et al. (2010) identified heterozygosity for a missense mutation in the GATA6 gene (L198V; 601656.0003). The patient had a single malalignment ventricular septal defect with subvalvar/valvar pulmonary stenosis and a normal aortic arch. The mutation was also detected in the patient's unaffected mother, but was not found in 288 control individuals, including 96 of Hispanic ethnicity.

In a 7-month-old Chinese boy with tetralogy of Fallot, Lin et al. (2010) identified heterozygosity for a missense mutation in GATA6 (S184N; 601656.0005). The mutation was detected in heterozygosity in his unaffected father, but was not found in 500 ethnically matched controls. The patient had an overriding aorta (50% override), pulmonary stenosis, ventricular septal defect, and right atrial and ventricular hypertrophy; he had no other abnormalities. The S184N GATA6 mutation was also identified in 2 Chinese patients with atrial septal defect (ASD9; 614475).

Other Genetic Associations

Lambrechts et al. (2005) found that a haplotype of 2 common SNPs in the promoter and 1 common SNP in the leader sequence of the VEGF (192240) gene, which are known to lower VEGF levels, increased the risk for TOF. Genotyping of 148 families with isolated, nonsyndromic TOF revealed that the low-VEGF haplotype (-2578A, -1154A, -634G), called AAG, was overtransmitted to affected children (p = 0.008). VEGF was said to be the first modifier gene identified for TOF.

Greenway et al. (2009) performed a genomewide survey of 114 subjects with TOF and their unaffected parents and identified 11 de novo copy number variants that were absent or extremely rare (less than 0.1%) in 2,265 controls. Greenway et al. (2009) then examined a second independent TOF cohort of 398 individuals for additional copy number variants (CNVs) at these loci. They identified CNVs at chromosome 1q21.1 in 1% (5/512, P = 0.0002, odds ratio = 22.3) of nonsyndromic sporadic TOF cases. Greenway et al. (2009) also identified recurrent CNVs at 3p25.1, 7p21.3 (gain), and 22q11.2 (loss). CNVs in a single subject with TOF occurred at 6 loci, 2 of which encode disease-associated genes (NOTCH1, 190198 and JAG1). Greenway et al. (2009) concluded that their findings predicted at least 10% (4.5 to 15.5%, 95% confidence interval) of sporadic nonsyndromic TOF cases result from de novo CNVs and suggest that mutations within these loci might be etiologic in other cases of TOF. The chromosome 1q21 region overlaps those described in 612474 and 612475.

Using Illumina SNP arrays, Soemedi et al. (2012) generated genomewide CNV data in 2,256 individuals with congenital heart disease, 283 trio congenital heart disease-affected families, and 1,538 controls. There was a slight overrepresentation of patients with tetralogy of Fallot, but all sporadic congenital heart disease was represented. Soemedi et al. (2012) found association of rare genic deletions with congenital heart disease risk (OR = 1.8, p = 0.0008). Rare deletions in study participants with congenital heart disease had higher gene content (p = 0.001) with higher haploinsufficiency scores (p = 0.03) than they did in controls, and they were enriched with Wnt signaling genes (see 606359) (p = 1 x 10(-5)). Recurrent 15q11.2 deletions were associated with congenital heart disease risk (OR = 8.2, p = 0.02). Rare de novo CNVs were observed in approximately 5% of congenital heart disease trios; 10 of 11 occurred on the paternally transmitted chromosome (p = 0.01). Some of the rare de novo CNVs spanned genes known to be involved in heart development (e.g., HAND2 (602407) and GJA5 (121013)). Rare genic deletions contributed to about 4% of the population-attributable risk of sporadic congenital heart disease. Second to CNV at 1q21.1, deletions at 15q11.2 and those implicating Wnt signaling are the most significant contributors to the risk of sporadic congenital heart disease. Rare de novo CNVs identified in congenital heart disease trios exhibit paternal origin bias.