San Luis Valley recombinant chromosome 8 and tetralogy of Fallot: a review of chromosome 8 anomalies and congenital heart disease

A rare interstitial duplication of 8q22.1-8q24.3 associated with syndromic bilateral cleft lip/palate

We present a rare case of 8q interstitial duplication derived from maternal balanced translocations in a patient with bilateral cleft lip and palate in syndromic form associated with other congenital malformations. G-banding cytogenetic analysis revealed a chromosomal abnormality in the form of the karyotype 46,XX der(22)t(8;22)(q22.1;p11.1)mat. Chromosome microarray analysis evidenced a 49 Mb duplicated segment of chromosome 8q with no pathogenic imbalances on chromosome 22. Two siblings also carry the balanced translocation. We have compared this case with other “pure” trisomies of 8q patients reported in the literature and with genome wide association studies recently published. This work highlights the involvement of chromosome 8q in orofacial clefts.

Pre- and postnatal findings in a patient with a novel rec(8)dup(8q)inv(8)(p23.2q22.3) associated with San Luis Valley syndrome

San Luis Valley syndrome, which is due to a recombinant chromosome 8 (SLV Rec8) found in Hispanic individuals from Southwestern United States, is a well-established syndrome associated with intellectual disabilities and, frequently, severe cardiac anomalies. We report for the first time on a Moroccan girl with a recombinant chromosome 8 prenatally diagnosed as SLV Rec8 by conventional cytogenetic studies. At birth, an oligo array-CGH (105 K) defined the breakpoints and the size of the imbalanced segments, with a deletion of ≈ 2.27 Mb (8p23.2-pter) and a duplication of ≈ 41.93 Mb (8q22.3-qter); thus this recombinant chromosome 8 differed from that previously reported in SLV Rec8 syndrome. The phenotypic characteristics associated with this SLV Rec8 genotype overlap those commonly found in patients with 8q duplication reported in the literature. We review SLV Rec8 and other chromosome 8 aberrations and suggest that the overexpression of cardiogenic genes located at 8q may be the cause of the cardiac defects in this patient.

New mutations in ZFPM2/FOG2 gene in tetralogy of Fallot and double outlet right ventricle

Conotruncal defects (CTDs) represent 15-20% of all congenital heart defects. Mutations in a number of genes have been associated with CTD in humans and animal models. We investigated the occurrence and the prevalence of GATA4, NKX2.5, ZFPM2/FOG2, GDF1, and ISLET1 gene mutations in a large cohort of individuals with CTD, including tetralogy of Fallot with or without pulmonary atresia (TOF, 178 patients), double outlet right ventricle (DORV, 13 patients), and truncus arteriosus (11 patients). Denaturing high-performance liquid chromatography (DHPLC) analysis followed by bidirectional sequencing disclosed no putative pathogenic mutation in GATA4, ISLET1, and GDF1 genes. Two novel (Ile227Val, Met544Ile) and one previously reported (Glu30Gly) possibly pathogenic missense variants were identified in the ZFPM2/FOG2 gene in 3 sporadic patients of 202 (1.5%) with CTD, including 1 of 178 (0.6%) with TOF and 2 of 13 (15.4%) with DORV. Mutation analysis also detected one known missense change (Arg25Cys) in NKX2.5 gene in two (1.1%) sporadic patients with TOF. These sequence alterations were found to be absent in 500 population-matched controls. In conclusion, the present results (i) indicate and confirm that mutations in the GATA4, GDF1, and ISLET1 genes are not major determinants in the pathogenesis of TOF, (ii) provide supportive evidence of an association between ZFPM2/FOG2 gene and TOF/DORV, and (iii) provide additional examples of the possible contribution of the Arg25Cys change in the NKX2.5 to a small number of TOF cases.

Genetic factors in non-syndromic congenital heart malformations

The genetic defect in most patients with non-syndromic congenital heart malformations (CHM) is unknown, although more than 40 different genes have already been implicated. Only a minority of CHM seems to be due to monogenetic mutations, and the majority occurs sporadically. The multifactorial inheritance hypothesis of common diseases suggesting that the cumulative effect of multiple genetic and environmental risk factors leads to disease, might also apply for CHM. We review here the monogenic disease genes with high-penetrance mutations, susceptibility genes with reduced-penetrance mutations, and somatic mutations implicated in non-syndromic CHM.

Impact of DEL22q11, trisomy 21, and other genetic syndromes on surgical outcome of conotruncal heart defects

OBJECTIVE

Genetic syndromes occur in more than 20% of patients with conotruncal heart defects. We investigated the impact of genetic syndromes on the surgical outcome of conotruncal anomalies in infancy.

METHODS

This retrospective study reviews the outcome of 787 patients (median age 6.3 months) who underwent primary (598) or staged (189) repair of a conotruncal defect between 1992 and 2007.

RESULTS

Proven genetic syndrome was diagnosed in 211 patients (26.8%), including del22q11 (91 patients), trisomy 21 (29 patients), VACTERL (18 patients), and other syndromes (73 patients). Primary repair was accomplished in 80.9% of nonsyndromic patients and 74.4% of syndromic patients (P = .18) Fifteen-year cumulative survival was 84.3% +/- 2.3% in nonsyndromic patients and 73.2% +/- 4.2% in syndromic patients (P < .001). Primary and staged repair allowed similar 15-year survival (81.4% +/- 4.5% vs 79.1% +/- 5.1%, P = .8). Freedom from noncardiac cause of death was significantly lower in syndromic patients (P = .0056). Fifteen-year Kaplan-Meier survival was 87.6% +/- 3.9% for del22q11, 95.8% +/- 4.1% for trisomy 21, 56.8% +/- 6.3% for VACTERL, and 62.3% +/- 12.7% for patients with other syndromes (P = .022). Total intensive care unit stay was 10.8 +/- 4.9 days in syndromic patients and 5.1 +/- 1.7 days in nonsyndromic patients (P < .001). Freedom from reintervention 15 years after repair was 79.6% +/- 4.9% in nonsyndromic patients and 62.4% +/- 7.4% in syndromic patients (P = .007).

CONCLUSION

Del22q11 and trisomy 21 do not represent risk factors for mortality after repair of conotruncal anomalies, whereas other syndromes adversely affect the surgical outcome for predominant noncardiac attrition. Higher morbidity and lower mid-term freedom from reintervention can be predicted in syndromic patients.

Tetralogy of Fallot, hypertrophic cardiomyopathy, and Down's syndrome: a rare and challenging combination

A case of the combination of tetralogy of Fallot, hypertrophic cardiomyopathy, and Down's syndrome is reported here and is the first report on the combination of the 3 entities. Tetralogy of Fallot is often associated with chromosomal aberration, while hypertrophic cardiomyopathy associates with certain gene loci. Our experience with treating this patient, although ultimately unsuccessful, may provide useful information in any future cases.

Genetic heterogeneity and phenotypic anomalies in children with atrioventricular canal defect and tetralogy of Fallot

Tetralogy of Fallot associated with the atrioventricular canal defect has been usually reported in association with Down syndrome. The aim of the present study was to describe the cardiac aspects and the genetic anomalies in children with this association of heart defects. We identified 64 patients with atrioventricular canal defect tetralogy of Fallot. All children underwent complete cardiovascular, clinical phenotypic and genetic evaluation. A genetic syndrome or extracardiac anomalies were found in 56 patients (87.5%). Down syndrome (43 patients, 67.2%) was the most frequent genetic diagnosis. Other syndromes were 8p deletion, trisomy 13, duplication 5p, cranio-cerebello-cardiac syndrome, Cantrell syndrome, CHARGE association, VACTERL association, and DiGeorge syndrome related to maternal diabetes. No patients in our series had 22q11 deletion. Tetralogy of Fallot with extreme dextroposition of the aorta was found in seven patients (only one with Down syndrome). Additional cardiac malformations were present in 23 patients (only 11 with Down syndrome). The association between atrioventricular canal defect and tetralogy of Fallot represents a cardiac phenotype with strong genetic characteristics. For this reason, a careful genetic examination is required. Our study confirms the high prevalence of Down syndrome, but also reveals a significant genetic heterogeneity. Additional cardiac defects are prevalent in patients without Down syndrome.

Genetic Syndromes and Outcome After Surgical Correction of Tetralogy of Fallot

BACKGROUND

Genetic syndromes occur in 20% of patients with tetralogy of Fallot (TOF). The impact of genetic syndromes on surgical repair of TOF in infancy is still under investigation.

METHODS

This retrospective study reviews the outcome of 306 consecutive patients (median age, 5.1 months) who underwent primary (266) or staged (40) repair of TOF between 1994 and 2004. Total follow-up was 1,188 patient-years (mean, 57 months).

RESULTS

Genetic syndromes were documented in 85 patients (27.8%), including 22q11 deletion (27), trisomy 21 (13), vertebral, anal, cardiac, tracheoesophageal, renal, and limb abnormalities (VACTERL, 12), and others (33). Hypoplastic pulmonary arteries (PA) were more common in syndromic (19/85 = 22.3%) than nonsyndromic TOF (20/221 = 9.04%) (p < 0.001). Primary repair was performed in 82.4% syndromic and 88.7% nonsyndromic TOF (p = not significant [NS]). Ten-year actuarial survival was 94.1 +/- 2.3% in nonsyndromic and 84.3 +/-4.2% in syndromic TOF (p < 0.001). Ten-year survival was 96.3 +/- 3.6% for del22q11, 100% for trisomy 21, 63.6 +/- 14.5% for VACTERL, and 78.5 +/- 7.3% for patients with other syndromes (p = 0.022). Survival in syndromic TOF with normal PA anatomy was 89.6 +/- 4.2% for primary repair and 85.7 +/- 12.8% for staged repair (p = NS); freedom from reoperation after complete repair was 74.4 +/- 6.4% for primary correction and 56.3 +/- 11.9% for staged repair (p = 0.04). Cox proportional hazard identified the presence of genetic syndrome (p = 0.011) and central PA hypoplasia (p = 0.002) as independent predictors of mortality.

CONCLUSIONS

Pulmonary arborization defects and genetic syndromes other than del22q11 or trisomy 21, are associated with worse outcome after correction of TOF. Primary TOF repair in syndromic patients with normal PA anatomy is a valid surgical strategy, with no additional risk for mortality and higher freedom from reintervention.

Trisomy 8 mosaicism in a patient with heterotaxia

Constitutional trisomy 8 mosaicism (CT8M) is a relatively rare trisomy in humans with a characteristic phenotype. We report an infant with the characteristic CT8M phenotype in addition to heterotaxia. A number of chromosomal abnormalities have been reported in association with laterality defects but this is the first time heterotaxia is reported in CT8M. In addition to expanding CT8M phenotype, our report may provide insight into the mechanism of heterotaxia.

Mutations of ZFPM2/FOG2 gene in sporadic cases of tetralogy of Fallot

Two out of 47 patients with sporadic tetralogy of Fallot (TOF), the most common cyanotic conotruncal heart defect (CTD), showed heterozygous missense mutations of the ZFPM2/FOG2 gene. Knockout mice carrying mutations in the ZFPM2/FOG2 gene have similarly been found to exhibit TOF. While both mutant ZFPM2/FOG2 proteins, E30G (c.88A>G) and S657G (c.1968A>G), retain the ability to bind the partner protein GATA4 and repress GATA4 mediated gene activation, the S657G, but not the E30G, mutation is subtly impaired in this function. ZFPM2/FOG2 gene mutations may contribute to some sporadic cases of TOF.

Deletion of a 5-cM region at chromosome 8p23 is associated with a spectrum of congenital heart defects

BACKGROUND

Cytogenetic evidence suggests that the haploinsufficiency of > or =1 gene located in 8p23 behaves as a dominant mutation, impairing heart differentiation and leading to a wide spectrum of congenital heart defects (CHDs), including conotruncal lesions, atrial septal defects, atrioventricular canal defects, and pulmonary valve stenosis. An 8p heart-defect-critical region was delineated, and the zinc finger transcription factor GATA4 was considered a likely candidate for these defects. We narrowed this region and excluded a major role of GATA4 in these CHDs.

METHODS AND RESULTS

We studied 12 patients (7 had CHD and 5 did not) with distal 8p deletions from 9 families by defining their chromosome rearrangements at the molecular level by fluorescent in situ hybridization and short-tandem repeat analysis. Subjects with 8p deletions distal to D8S1706, at approximately 10 cM from the 8p telomere, did not have CHD, whereas subjects with a deletion that included the more proximal region suffered from the spectrum of heart defects reported in patients with 8p distal deletions. The 5-cM critical region is flanked distally by D8S1706 and WI-8327, both at approximately 10 cM, and proximally by D8S1825, at 15 cM. Neither GATA4 nor angiopoietin-2 (ANGPT2; a gene in 8p23 involved in blood vessel formation) were found to be deleted in some of the critical patients. We also found that CHDs are not related to the parental origin of deletion.

CONCLUSIONS

Haploinsufficiency for a gene between WI-8327 and D8S1825 is critical for heart development. A causal relationship does not seem to exist between GATA4 and ANGPT2 haploinsufficiency and CHDs.

A syndrome of tricuspid atresia in mice with a targeted mutation of the gene encoding Fog-2

Tricuspid atresia (TA) is a common form of congenital heart disease, accounting for 1-3% of congenital cardiac disorders. TA is characterized by the congenital agenesis of the tricuspid valve connecting the right atrium to the right ventricle and both an atrial septal defect (ASD) and a ventricular septal defect (VSD). Some patients also have pulmonic stenosis, persistence of a left-sided superior vena cava or transposition of the great arteries. Most cases of TA are sporadic, but familial occurrences with disease in multiple siblings have been reported. Gata4 is a zinc-finger transcription factor with a role in early cardiac development. Gata4-deficient mice fail to form a ventral heart tube and die of circulatory failure at embryonic day (E) 8.5 (refs 6,7). Zfpm2 (also known as Fog-2) is a multi-zinc-finger protein that is co-expressed with Gata4 in the developing heart beginning at E8.5 (refs 8-10). Zfpm2 interacts specifically with the N-terminal zinc finger of Gata4 and represses Gata4-dependent transcription. Here we use targeted mutagenesis to explore the role of Zfpm2 in normal cardiac development. Zfpm2-deficient mice died of congestive heart failure at E13 with a syndrome of tricuspid atresia that includes an absent tricuspid valve, a large ASD, a VSD, an elongated left ventricular outflow tract, rightward displacement of the aortic valve and pulmonic stenosis. These mice also display hypoplasia of the compact zone of the left ventricle. Our findings indicate the importance of Zfpm2 in the normal looping and septation of the heart and suggest a genetic basis for the syndrome of tricuspid atresia.

FOG-2, a cofactor for GATA transcription factors, is essential for heart morphogenesis and development of coronary vessels from epicardium

We disrupted the FOG-2 gene in mice to define its requirement in vivo. FOG-2(-/-) embryos die at midgestation with a cardiac defect characterized by a thin ventricular myocardium, common atrioventricular canal, and the tetralogy of Fallot malformation. Remarkably, coronary vasculature is absent in FOG-2(-/-) hearts. Despite formation of an intact epicardial layer and expression of epicardium-specific genes, markers of cardiac vessel development (ICAM-2 and FLK-1) are not detected, indicative of failure to activate their expression and/or to initiate the epithelial to mesenchymal transformation of epicardial cells. Transgenic reexpression of FOG-2 in cardiomyocytes rescues the FOG-2(-/-) vascular phenotype, demonstrating that FOG-2 function in myocardium is required and sufficient for coronary vessel development. Our findings provide the molecular inroad into the induction of coronary vasculature by myocardium in the developing heart.

Delineation of the critical deletion region for congenital heart defects, on chromosome 8p23.1

Deletions in the distal region of chromosome 8p (del8p) are associated with congenital heart malformations. Other major manifestations include microcephaly, intrauterine growth retardation, mental retardation, and a characteristic hyperactive, impulsive behavior. We studied genotype-phenotype correlations in nine unrelated patients with a de novo del8p, by using the combination of classic cytogenetics, FISH, and the analysis of polymorphic DNA markers. With the exception of one large terminal deletion, all deletions were interstitial. In five patients, a commonly deleted region of approximately 6 Mb was present, with breakpoints clustering in the same regions. One patient without a heart defect or microcephaly but with mild mental retardation and characteristic behavior had a smaller deletion within this commonly deleted region. Two patients without a heart defect had a more proximal interstitial deletion that did not overlap with the commonly deleted region. Taken together, these data allowed us to define the critical deletion regions for the major features of a del8p.

Complex congenital heart malformations in mosaic tetrasomy 8p: case report and review of the literature

We describe a 5-month-old boy with complex congenital heart defects (dTGA, DORV, VSD, ASD, and PDA), minor facial and ear anomalies, deep palmar creases, multiple vertebral anomalies, agenesis of the corpus callosum, and mosaic tetrasomy 8p (47,XY,+i(8)(p10)[88%]/46,XY[12%] in blood with normal chromosomes in cultured skin fibroblasts. This infant represents the eleventh reported case of mosaic tetrasomy 8p since its first description by Kristofferson et al. [1988: Clin Genet 34:201-203]. The pattern of heart malformations and discordance of blood and fibroblast karyotypes make our case unique. Our report and review suggest that an important distinction between mosaic tetrasomy 8p and other chromosome 8 aneuploidies involves the increased incidence and complexity of congenital heart malformations.

Chromosome abnormalities in congenital heart disease

Refinements in cytogenetic techniques have promoted progress in understanding the role that chromosome abnormalities play in the cause of congenital heart disease. To determine if mutations at specific loci cause congenital heart disease, irrespective of the presence of other defects, and to estimate the prevalence of chromosome abnormalities in selected conotruncal cardiac defects, we reviewed retrospectively cytogenetic and clinical databases at St. Louis Children's Hospital. Patients with known 7q11.23 deletion (Williams syndrome), Ullrich-Turner syndrome (UTS), and most autosomal trisomies were excluded from this analysis. Two groups of patients were studied. Over a 6.5-year period, 57 patients with chromosomal abnormalities and congenital heart disease were identified. Of these, 37 had 22q11 deletions; 5 had abnormalities of 8p; and 15 had several other chromosome abnormalities. The prevalence of chromosome abnormalities in selected conotruncal or aortic arch defects was estimated by analysis of a subgroup of patients from a recent 22-month period. Chromosome abnormalities were present in 12% of patients with tetralogy of Fallot, 26% in tetralogy of Fallot/pulmonary atresia, 44% in interrupted aortic arch, 12% in truncus arteriosus, 5% in double outlet right ventricle, and 60% in absent pulmonary valve. We conclude that chromosome analysis should be considered in patients with certain cardiac defects. Specifically, fluorescent in situ hybridization (FISH) analysis of 22q11 is indicated in patients with conotruncal defects or interrupted aortic arch. High resolution analysis should include careful evaluation of the 8p region in patients with either conotruncal or endocardial cushion defects.

Prenatal diagnosis of trisomy 8 mosaicism in CVS after abnormal ultrasound findings at 12 weeks

We describe a case of trisomy 8 mosaicism in which fetal chromosome analysis was prompted by ultrasound abnormalities, i.e., hygroma colli and dilatation of the renal pelves. Chorionic villus sampling (CVS) was performed, with a false-negative result on direct karyotype analysis, although cultured trophoblasts revealed trisomy 8 mosaicism. Fetal autopsy confirmed the abnormalities found on ultrasound examinations and fetal tissue examination showed different levels of trisomy 8 mosaicism. To our knowledge, this is the first prenatal diagnosis of trisomy 8 made on ultrasound findings.

Natural history of the recombinant (8) syndrome

The recombinant 8[Rec(8)] syndrome [rec(8), (8qter-->8q22.1::8p23.1-->8qter] is due to a parental inv(8)(8pter-->8p23.1::8q22.1-->8p23.1::8q22+ ++.1-->8qter). All inv(8) parents we have studied were of Hispanic origin. The Rec(8) phenotype consists of a characteristic set of minor facial anomalies, cardiovascular and other major malformations, and moderate to severe mental retardation. The clinical phenotype is relatively consistent in all published cases; however the natural history of the condition has remained unknown. Retrospective and prospective information on 42 propositi, spanning a period from 5 days to 23 years, allowed us to define the natural history of this syndrome, tabulate the frequency and the evolution of phenotypic abnormalities, and share our experience with different therapeutic approaches.