Whole-exome sequencing identifies SGCD and ACVRL1 mutations associated with total anomalous pulmonary venous return (TAPVR) in Chinese population

Identification of Six Pathogenic Genes for Tibetan Familial Ventricular Septal Defect by Whole Exome Sequencing

INTRODUCTION

Ventricular septal defect (VSD) is the most common congenital heart malformation in children. This study aimed to investigate potential pathogenic genes associated with Tibetan familial VSD.

METHODS

Whole genomic DNA was extracted from eight Tibetan children with VSD and their healthy parents (a total of 16 individuals). Whole-exome sequencing was performed using the Illumina HiSeq platform. After filtration, detection, and annotation, single nucleotide variations and insertion-deletion markers were examined. Comparative evaluations using the Sorting Intolerant from Tolerant, PolyPhen V2, Mutation Taster, and Combined Annotation Dependent Depletion databases were conducted to predict harmful mutant genes associated with the etiology of Tibetan familial VSD.

RESULTS

A total of six missense mutations in genetic disease-causing genes associated with the development of Tibetan familial VSD were identified: activin A receptor type II-like 1 (c.652 C > T: p.R218 W), ATPase cation transporting 13A2 (c.1363 C > T: p.R455 W), endoplasmic reticulum aminopeptidase 1 (c.481 G > A: p.G161 R), MRI1 (c.629 G > A: p.R210Q), tumor necrosis factor receptor-associated protein 1 (c.224 G > A: p.R75H), and FBN2 (c.2260 G > A: p.G754S). The Human Gene Mutation Database confirmed activin A receptor type II-like 1, MRI1, and tumor necrosis factor receptor-associated protein 1 as pathogenic mutations, while FBN2 was classified as a probable pathogenic mutation.

CONCLUSIONS

This novel study directly screens genetic variations associated with Tibetan familial VSD using whole-exome sequencing, providing new insights into the pathogenesis of VSD.

Research Progress in Pathogenesis of Total Anomalous Pulmonary Venous Connection

Congenital heart defect (CHD) is one of the most common birth defects and the leading course of infant mortality. Total anomalous pulmonary venous connection (TAPVC) is a rare type of cyanotic which accounting for approximately 1-3% of congenital heart disease cases. Based on where the anomalous veins drain, TAPVC can be divided into four subtypes: supracardiac, cardiac, infracardiac, and mixed. In TAPVC, all pulmonary veins fail to link to the left atrium correctly but make abnormal connections to the right atrium or systemic venous system. The mortality of TAPVC patients without proper intervention is nearly 80% in the first year of life and 50% of them died within 3 months after birth. However, the pathogenesis and mechanism of TAPVC remains elusive. In this chapter, we systematically review the epidemiology, anatomy, and pathophysiology of TAPVC and give an overview of the research progress of TAPVC pathogenesis.

A Mechanogenetic Model of Exercise-Induced Pulmonary Haemorrhage in the Thoroughbred Horse

Exercise-induced pulmonary haemorrhage (EIPH) occurs in horses performing high-intensity athletic activity. The application of physics principles to derive a ‘physical model’, which is coherent with existing physiology and cell biology data, shows that critical parameters for capillary rupture are cell–cell adhesion and cell stiffness (cytoskeleton organisation). Specifically, length of fracture in the capillary is a ratio between the energy involved in cell–cell adhesion and the stiffness of cells suggesting that if the adhesion diminishes and/or that the stiffness of cells increases EIPH is more likely to occur. To identify genes associated with relevant cellular or physiological phenotypes, the physical model was used in a post-genome-wide association study (GWAS) to define gene sets associated with the model parameters. The primary study was a GWAS of EIPH where the phenotype was based on weekly tracheal wash samples collected over a two-year period from 72 horses in a flat race training yard. The EIPH phenotype was determined from cytological analysis of the tracheal wash samples, by scoring for the presence of red blood cells and haemosiderophages. Genotyping was performed using the Illumina Equine SNP50 BeadChip and analysed using linear regression in PLINK. Genes within significant genome regions were selected for sets based on their GeneOntology biological process, and analysed using fastBAT. The gene set analysis showed that genes associated with cell stiffness (cytoskeleton organisation) and blood flow have the most significant impact on EIPH risk.

Whole-Exome Sequencing Reveals Novel Genetic Variation for Dilated Cardiomyopathy in Pediatric Chinese Patients

Dilated cardiomyopathy (DCM) is characterized by left or bilateral ventricular dilation and systolic dysfunction without rational conditions, which can lead to progressive heart failure and sudden cardiac death. Most of the pathogenic genes have been reported in adult population by locus mapping in familial cases and animal model studies. However, it still remains challenging to decipher the role of genetics in the etiology of pediatric DCM. We applied whole-exome sequencing (WES) for 30 sporadic pediatric DCM subjects and 100 non-DCM local controls. We identified the pathogenic mutations using bioinformatics tools based on genomic strategies synergistically and confirmed mutations by Sanger sequencing. We identified compound heterozygous nonsense mutations in DSP (c.3799C > T, p.R1267X; c.4444G > T, p.E1482X). In sporadic cases, the two heterozygous mutations in XIRP2 were identified. Then we performed an exome-wide association study with 30 case and 100 control subjects. Interestingly, we could not identify TTN truncating variants in all cases. Collectively, we observed a significant risk signal between carriers of TTN deleterious missense variants and DCM risk (odds ratio 4.0, 95% confidence interval 1.1-22.2, p = 3.12 × 10^-2). Our observations expanded the spectrum of mutations and were valuable in the pre- and postnatal screening and genetic diagnosis for DCM.

Rare Copy Number Variants Identify Novel Genes in Sporadic Total Anomalous Pulmonary Vein Connection

Total anomalous pulmonary venous connection (TAPVC) is a rare congenital heart anomaly. Several genes have been associated TAPVC but the mechanisms remain elusive. To search novel CNVs and candidate genes, we screened a cohort of 78 TAPVC cases and 100 healthy controls for rare copy number variants (CNVs) using whole exome sequencing (WES). Then we identified pathogenic CNVs by statistical comparisons between case and control groups. After that, we identified altogether eight pathogenic CNVs of seven candidate genes (PCSK7, RRP7A, SERHL, TARP, TTN, SERHL2, and NBPF3). All these seven genes have not been described previously to be related to TAPVC. After network analysis of these candidate genes and 27 known pathogenic genes derived from the literature and publicly database, PCSK7 and TTN were the most important genes for TAPVC than other genes. Our study provides novel candidate genes potentially related to this rare congenital birth defect (CHD) which should be further fundamentally researched and discloses the possible molecular pathogenesis of TAPVC.

Next-generation sequencing identifies novel genes with rare variants in total anomalous pulmonary venous connection

Background

Total anomalous pulmonary venous connection (TAPVC) is recognized as a rare congenital heart defect (CHD). With a high mortality rate of approximately 80%, the survival rate and outcomes of TAPVC patients are not satisfactory. However, the genetic aetiology and mechanism of TAPVC remain elusive. This study aimed to investigate the underlying genomic risks of TAPVC through next-generation sequencing (NGS).

Methods

Rare variants were identified through whole exome sequencing (WES) of 78 sporadic TAPVC cases and 100 healthy controls using Fisher's exact test and gene-based burden test. We then detected candidate gene expression patterns in cells, pulmonary vein tissues, and embryos. Finally, we validated these genes using target sequencing (TS) in another 100 TAPVC cases.

Findings

We identified 42 rare variants of 7 genes (CLTCL1, CST3, GXYLT1, HMGA2, SNAI1, VAV2, ZDHHC8) in TAPVC cases compared with controls. These genes were highly expressed in human umbilical vein endothelial cells (HUVECs), mouse pulmonary veins and human embryonic hearts. mRNA levels of these genes in human pulmonary vein samples were significantly different between cases and controls. Through network analysis and expression patterns in zebrafish embryos, we revealed that SNAI1, HMGA2 and VAV2 are the most important genes for TAPVC.

Interpretation

Our study identifies novel candidate genes potentially related to TAPVC and elucidates the possible molecular pathogenesis of this rare congenital birth defect. Furthermore, SNAI1, HMGA2 and VAV2 are novel TAPVC candidate genes that have not been reported previously in either humans or animals.

Fund

National Natural Science Foundation of China.

Familial total anomalous pulmonary venous return with 15q11.2 (BP1-BP2) microdeletion

A 15q11.2 microdeletion (BP1-BP2) is associated with congenital heart diseases (CHDs), developmental delay, and epilepsy. This deletion co-occurs with CHD in 20-30% patients, but a familial case of CHD and a 15q11.2 deletion has not been identified. Here we report the first familial (three siblings) case of total anomalous pulmonary venous return associated with 15q11.2 deletion. Array comparative genomic hybridization identified a ~395 kb deletion at 15q11.2 in patient 1. This deletion was confirmed by fluorescence in situ hybridization in patients 1 and 3 and their asymptomatic father. No deleterious mutation was identified by proband-only exome sequencing of patient 1. One healthy sibling and their mother did not carry the deletion. This deletion is often inherited from asymptomatic parents with an estimated low penetrance of 10.4%. Conversely, we observed high penetrance of this deletion, but secondary copy-number variants or pathogenic variants were not detected in this family.