Frances A. Bu’Lock

Contribution of global rare copy-number variants to the risk of sporadic congenital heart disease.

Previous studies have shown that copy-number variants (CNVs) contribute to the risk of complex developmental phenotypes. However, the contribution of global CNV burden to the risk of sporadic congenital heart disease (CHD) remains incompletely defined. We generated genome-wide CNV data by using Illumina 660W-Quad SNP arrays in 2,256 individuals with CHD, 283 trio CHD-affected families, and 1,538 controls. We found association of rare genic deletions with CHD risk (odds ratio [OR] = 1.8, p = 0.0008). Rare deletions in study participants with CHD 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 (p = 1 × 10(-5)). Recurrent 15q11.2 deletions were associated with CHD risk (OR = 8.2, p = 0.02). Rare de novo CNVs were observed in ~5% of CHD trios; 10 out 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 and GJA5). Rare genic deletions contribute ~4% of the population-attributable risk of sporadic CHD. Second to previously described CNVs at 1q21.1, deletions at 15q11.2 and those implicating Wnt signaling are the most significant contributors to the risk of sporadic CHD. Rare de novo CNVs identified in CHD trios exhibit paternal origin bias.

Rare variants in NR2F2 cause congenital heart defects in humans

Congenital heart defects (CHDs) are the most common birth defect worldwide and are a leading cause of neonatal mortality. Nonsyndromic atrioventricular septal defects (AVSDs) are an important subtype of CHDs for which the genetic architecture is poorly understood. We performed exome sequencing in 13 parent-offspring trios and 112 unrelated individuals with nonsyndromic AVSDs and identified five rare missense variants (two of which arose de novo) in the highly conserved gene NR2F2, a very significant enrichment (p = 7.7 × 10(-7)) compared to 5,194 control subjects. We identified three additional CHD-affected families with other variants in NR2F2 including a de novo balanced chromosomal translocation, a de novo substitution disrupting a splice donor site, and a 3 bp duplication that cosegregated in a multiplex family. NR2F2 encodes a pleiotropic developmental transcription factor, and decreased dosage of NR2F2 in mice has been shown to result in abnormal development of atrioventricular septa. Via luciferase assays, we showed that all six coding sequence variants observed in individuals significantly alter the activity of NR2F2 on target promoters.

Towards a safety net for management of 22q11.2 deletion syndrome: guidelines for our times.

The commonest autosomal deletion, 22q11.2 deletion syndrome (22q11DS) is a multisystem disorder varying greatly in severity and age of identification between affected individuals. Holistic care is best served by a multidisciplinary team, with an anticipatory approach. Priorities tend to change with age, from feeding difficulties, infections and surgery of congenital abnormalities particularly of the heart and velopharynx in infancy and early childhood to longer-term communication, learning, behavioural and mental health difficulties best served by evaluation at intervals to consider and initiate management. Regular monitoring of growth, endocrine status, haematological and immune function to enable early intervention helps in maintaining health. Conclusion: Guidelines to best practice management of 22q11DS based on a literature review and consensus have been developed by a national group of professionals with consideration of the limitations of available medical and educational resources.

Low-frequency intermediate penetrance variants in the ROCK1 gene predispose to Tetralogy of Fallot

BackgroundEpidemiological studies indicate a substantial excess familial recurrence of non-syndromic Tetralogy of Fallot (TOF), implicating genetic factors that remain largely unknown. The Rho induced kinase 1 gene (ROCK1) is a key component of the planar cell polarity signalling pathway, which plays an important role in normal cardiac development. The aim of this study was to investigate the role of genetic variation in ROCK1 on the risk of TOF.ResultsROCK1 was sequenced in a discovery cohort of 93 non-syndromic TOF probands to identify rare variants. TagSNPs were selected to capture commoner variation in ROCK1. Novel variants and TagSNPs were genotyped in a discovery cohort of 458 TOF cases and 1331 healthy controls, and positive findings were replicated in a further 209 TOF cases and 1290 healthy controls. Association between genotypes and TOF was assessed using LAMP.A rare SNP (c.807C > T; rs56085230) discovered by sequencing was associated with TOF risk (p = 0.006) in the discovery cohort. The variant was also significantly associated with the risk of TOF in the replication cohort (p = 0.018). In the combined cohorts the odds ratio for TOF was 2.61 (95% CI 1.58-4.30); p < 0.0001. The minor allele frequency of rs56085230 in the cases was 0.02, and in the controls it was 0.007. The variant accounted for 1% of the population attributable risk (PAR) of TOF. We also found significant association with TOF for an uncommon TagSNP in ROCK1, rs288979 (OR 1.64 [95% CI 1.15-2.30]; p = 1.5x10-5). The minor allele frequency of rs288979 in the controls was 0.043, and the variant accounted for 11% of the PAR of TOF. These association signals were independent of each other, providing additional internal validation of our result.ConclusionsLow frequency intermediate penetrance (LFIP) variants in the ROCK1 gene predispose to the risk of TOF.

Giant Right Atrial Aneurysm Antenatal Diagnosis and Surgical Treatment

Giant congenital right atrial aneurysms are rare, with their natural history complicated by death, heart failure, arrhythmias, and thrombosis. Prenatal diagnosis of the defect is feasible and allows an early preparation of a plan for management. We present details of a patient diagnosed prenatally with a giant right atrial aneurysm, which was successfully treated surgically as soon as the patient became symptomatic.

Intramural Left Coronary Artery in Truncus Arteriosus

An intramural coronary artery in the setting of truncus arteriosus (common arterial trunk) is an uncommon association. Following an uneventful surgical repair, a neonate developed a low cardiac output state deteriorating into cardiac arrest shortly after arrival into the intensive care unit, requiring extracorporeal membrane oxygenation support. Echocardiography and angiography showed occlusion of the left coronary artery, prompting emergency surgical reexploration. A “slit-like” orifice with an intramural left coronary artery was successfully unroofed, allowing full recovery. Full definition of the proximal coronary anatomy beyond the orifices should be investigated preoperatively in truncus arteriosus, as a missed intramural segment could lead to significant morbidity or mortality.

Association Between C677T Polymorphism of Methylene Tetrahydrofolate Reductase and Congenital Heart DiseaseClinical Perspective

Background—Association between the C677T polymorphism of the methylene tetrahydrofolate reductase (MTHFR) gene and congenital heart disease (CHD) is contentious. Methods and Results—We compared genotypes between CHD cases and controls and between mothers of CHD cases and controls. We placed our results in context by conducting meta-analyses of previously published studies. Among 5814 cases with primary genotype data and 10 056 controls, there was no evidence of association between MTHFR C677T genotype and CHD risk (odds ratio [OR], 0.96 [95% confidence interval, 0.87–1.07]). A random-effects meta-analysis of all studies (involving 7697 cases and 13 125 controls) suggested the presence of association (OR, 1.25 [95% confidence interval, 1.03–1.51]; P=0.022) but with substantial heterogeneity among contributing studies (I2=64.4%) and evidence of publication bias. Meta-analysis of large studies only (defined by a variance of the log OR <0.05), which together contributed 83% of all cases, yielded no evidence of association (OR, 0.97 [95% confidence interval, 0.91–1.03]) without significant heterogeneity (I2=0). Moreover, meta-analysis of 1781 mothers of CHD cases (829 of whom were genotyped in this study) and 19 861 controls revealed no evidence of association between maternal C677T genotype and risk of CHD in offspring (OR, 1.13 [95% confidence interval, 0.87–1.47]). There was no significant association between MTHFR genotype and CHD risk in large studies from regions with different levels of dietary folate. Conclusions—The MTHFR C677T polymorphism, which directly influences plasma folate levels, is not associated with CHD risk. Publication biases appear to substantially contaminate the literature with regard to this genetic association.

Association Between C677T Polymorphism of Methylene Tetrahydrofolate Reductase and Congenital Heart DiseaseClinical Perspective: Meta-Analysis of 7697 Cases and 13 125 Controls

Background—Association between the C677T polymorphism of the methylene tetrahydrofolate reductase (MTHFR) gene and congenital heart disease (CHD) is contentious. Methods and Results—We compared genotypes between CHD cases and controls and between mothers of CHD cases and controls. We placed our results in context by conducting meta-analyses of previously published studies. Among 5814 cases with primary genotype data and 10 056 controls, there was no evidence of association between MTHFR C677T genotype and CHD risk (odds ratio [OR], 0.96 [95% confidence interval, 0.87–1.07]). A random-effects meta-analysis of all studies (involving 7697 cases and 13 125 controls) suggested the presence of association (OR, 1.25 [95% confidence interval, 1.03–1.51]; P=0.022) but with substantial heterogeneity among contributing studies (I2=64.4%) and evidence of publication bias. Meta-analysis of large studies only (defined by a variance of the log OR <0.05), which together contributed 83% of all cases, yielded no evidence of association (OR, 0.97 [95% confidence interval, 0.91–1.03]) without significant heterogeneity (I2=0). Moreover, meta-analysis of 1781 mothers of CHD cases (829 of whom were genotyped in this study) and 19 861 controls revealed no evidence of association between maternal C677T genotype and risk of CHD in offspring (OR, 1.13 [95% confidence interval, 0.87–1.47]). There was no significant association between MTHFR genotype and CHD risk in large studies from regions with different levels of dietary folate. Conclusions—The MTHFR C677T polymorphism, which directly influences plasma folate levels, is not associated with CHD risk. Publication biases appear to substantially contaminate the literature with regard to this genetic association.