Congenital heart disease in Cornelia de Lange syndrome: phenotype and genotype analysis

Gastrulation-stage gene expression in Nipbl+/- mouse embryos foreshadows the development of syndromic birth defects

In animal models, Nipbl deficiency phenocopies gene expression changes and birth defects seen in Cornelia de Lange syndrome, the most common cause of which is Nipbl haploinsufficiency. Previous studies in Nipbl+/- mice suggested that heart development is abnormal as soon as cardiogenic tissue is formed. To investigate this, we performed single-cell RNA sequencing on wild-type and Nipbl+/- mouse embryos at gastrulation and early cardiac crescent stages. Nipbl+/- embryos had fewer mesoderm cells than wild-type and altered proportions of mesodermal cell subpopulations. These findings were associated with underexpression of genes implicated in driving specific mesodermal lineages. In addition, Nanog was found to be overexpressed in all germ layers, and many gene expression changes observed in Nipbl+/- embryos could be attributed to Nanog overexpression. These findings establish a link between Nipbl deficiency, Nanog overexpression, and gene expression dysregulation/lineage misallocation, which ultimately manifest as birth defects in Nipbl+/- animals and Cornelia de Lange syndrome.

Gastrulation-stage gene expression in Nipbl +/- mouse embryos foreshadows the development of syndromic birth defects

In animal models, Nipbl-deficiency phenocopies gene expression changes and birth defects seen in Cornelia de Lange Syndrome (CdLS), the most common cause of which is Nipbl-haploinsufficiency. Previous studies in Nipbl+/- mice suggested that heart development is abnormal as soon as cardiogenic tissue is formed. To investigate this, we performed single-cell RNA-sequencing on wildtype (WT) and Nipbl+/- mouse embryos at gastrulation and early cardiac crescent stages. Nipbl+/- embryos had fewer mesoderm cells than WT and altered proportions of mesodermal cell subpopulations. These findings were associated with underexpression of genes implicated in driving specific mesodermal lineages. In addition, Nanog was found to be overexpressed in all germ layers, and many gene expression changes observed in Nipbl+/- embryos could be attributed to Nanog overexpression. These findings establish a link between Nipbl-deficiency, Nanog overexpression, and gene expression dysregulation/lineage misallocation, which ultimately manifest as birth defects in Nipbl+/- animals and CdLS.

Teaser

Gene expression changes during gastrulation of Nipbl-deficient mice shed light on early origins of structural birth defects.

Epigenetics

Epigenetics is the study of heritable changes to the genome and gene expression patterns that are not caused by direct changes to the DNA sequence. Examples of these changes include posttranslational modifications to DNA-bound histone proteins, DNA methylation, and remodeling of nuclear architecture. Collectively, epigenetic changes provide a layer of regulation that affects transcriptional activity of genes while leaving DNA sequences unaltered. Sequence variants or mutations affecting enzymes responsible for modifying or sensing epigenetic marks have been identified in patients with congenital heart disease (CHD), and small-molecule inhibitors of epigenetic complexes have shown promise as therapies for adult heart diseases. Additionally, transgenic mice harboring mutations or deletions of genes encoding epigenetic enzymes recapitulate aspects of human cardiac disease. Taken together, these findings suggest that the evolving field of epigenetics will inform our understanding of congenital and adult cardiac disease and offer new therapeutic opportunities.

Nipbl Haploinsufficiency Leads to Delayed Outflow Tract Septation and Aortic Valve Thickening

Cornelia de Lange Syndrome (CdLS) patients, who frequently carry a mutation in NIPBL, present an increased incidence of outflow tract (OFT)-related congenital heart defects (CHDs). Nipbl+/- mice recapitulate a number of phenotypic traits of CdLS patients, including a small body size and cardiac defects, but no study has specifically focused on the valves. Here, we show that adult Nipbl+/- mice present aortic valve thickening, a condition that has been associated with stenosis. During development, we observed that OFT septation and neural crest cell condensation was delayed in Nipbl+/- embryos. However, we did not observe defects in the deployment of the main lineages contributing to the semilunar valves. Indeed, endocardial endothelial-to-mesenchymal transition (EndMT), analysed via outflow tract explants, and neural crest migration, analysed via genetic lineage tracing, did not significantly differ in Nipbl+/- mice and their wild-type littermates. Our study provides the first direct evidence for valve formation defects in Nipbl+/- mice and points to specific developmental defects as an origin for valve disease in patients.

Auditory Profile of Children With Some Rare Neurodevelopmental Disorders

Neurodevelopmental disorder is an umbrella term comprising many muscular, skeletal, metabolic, endocrinal, systemic, and immune-related diseases, which are caused due to the improper/inaccurate development of the central nervous system. Most of these disorders are highly prevalent, but some express rarely in human beings. Such disorders with least prevalence rates are known as rare neurodevelopmental disorders. The sensory system is affected in all individuals with these rare neurodevelopmental disorders, although to a varying extent. Sensory processing in terms of hearing loss is reported by many researchers in many rare neurodevelopmental disorders, but the pathophysiology of audiological findings are seldom investigated. In this chapter, the authors highlight the possible relationship between underlying cause and the resultant audiological symptoms in some of the rare neurodevelopmental disorders. Further, the research studies on the audiological profiling in such disorders are discussed.

Subclinical myocardial dysfunction is revealed by speckle tracking echocardiography in patients with Cornelia de Lange syndrome

This study assesses a possible cardiac dysfunction in individuals with Cornelia de Lange syndrome (CdLS) without diagnosed congenital heart disease (CHD) and its association with other factors. Twenty patients and 20 controls were included in the study divided into three age-dependent groups (A: < 10 yrs, B: 10-20 yrs, C: > 20 yrs), and were evaluated using conventional echocardiography, tissue doppler imaging (TDI), two-dimensional speckle tracking and genetic and biochemical analyses. The left ventricular global longitudinal strain (GLS) was altered (< 15.9%) in 55% of patients, being pathological in the older group (A: 19.7 ± 6.6; B: -17.2 ± 4.7; C: -13.6 ± 2.9). The speckle tracking technique revealed a downward trend in the values of strain, strain rate and velocity, especially in the oldest group. Likewise, the ejection fraction (LVEF) and shortening fraction (LVFS) values, although preserved, also showed a decreased with age (p < 0.05). The analytical markers of cardiovascular risk and cardiac function showed no alterations. The molecular analyses revealed 16 individuals carrying pathogenic variants in NIPBL, two with variants in SMC1A, one with a variant in RAD21 and one with a HDAC8 variant. This is the first systematic approach that demonstrates that individuals with CdLS may present early cardiomyopathy, which can be detected by speckle tracking technique even before the appearance of clinical symptoms and the alteration of other echocardiographic or analytical parameters. For all these reasons, cardiological followup is suggested even in the absence of CHD, especially from adolescence onwards.

BRD4 orchestrates genome folding to promote neural crest differentiation

Higher-order chromatin structure regulates gene expression, and mutations in proteins mediating genome folding underlie developmental disorders known as cohesinopathies. However, the relationship between three-dimensional genome organization and embryonic development remains unclear. Here we define a role for bromodomain-containing protein 4 (BRD4) in genome folding, and leverage it to understand the importance of genome folding in neural crest progenitor differentiation. Brd4 deletion in neural crest results in cohesinopathy-like phenotypes. BRD4 interacts with NIPBL, a cohesin agonist, and BRD4 depletion or loss of the BRD4-NIPBL interaction reduces NIPBL occupancy, suggesting that BRD4 stabilizes NIPBL on chromatin. Chromatin interaction mapping and imaging experiments demonstrate that BRD4 depletion results in compromised genome folding and loop extrusion. Finally, mutation of individual BRD4 amino acids that mediate an interaction with NIPBL impedes neural crest differentiation into smooth muscle. Remarkably, loss of WAPL, a cohesin antagonist, rescues attenuated smooth muscle differentiation resulting from BRD4 loss. Collectively, our data reveal that BRD4 choreographs genome folding and illustrates the relevance of balancing cohesin activity for progenitor differentiation.

Echocardiographic diagnosis of congenital double orifice mitral valve malformation: A case report

Double orifice mitral valve (DOMV) is a rare congenital valve malformation. Due to the insufficient understanding and awareness of its echocardiographic characteristics, there is a risk of misdiagnosis. Here, we report a case of echocardiographic diagnosis of congenital DOMV malformation in a 56-year-old male patient who visited our hospital for systematic physical examination, during which DOMV was not diagnosed. The following year, the patient visited our hospital again, and echocardiography showed two approximately circular orifices on the short axis view of the mitral valve. During diastole, two red Doppler blood flow signals were observed entering the left ventricle simultaneously. A small amount of blue Doppler signal revealed reflux into the left atrium during systole, leading to the diagnose of congenital heart disease with DOMV malformation, without other cardiac structural abnormality. Because the patient did not have obvious discomfort, he did not receive any special treatment and is regularly followed-up.

Epigenetics and Heart Development

Epigenetic control of gene expression during cardiac development and disease has been a topic of intense research in recent years. Advances in experimental methods to study DNA accessibility, transcription factor occupancy, and chromatin conformation capture technologies have helped identify regions of chromatin structure that play a role in regulating access of transcription factors to the promoter elements of genes, thereby modulating expression. These chromatin structures facilitate enhancer contacts across large genomic distances and function to insulate genes from cis-regulatory elements that lie outside the boundaries for the gene of interest. Changes in transcription factor occupancy due to changes in chromatin accessibility have been implicated in congenital heart disease. However, the factors controlling this process and their role in changing gene expression during development or disease remain unclear. In this review, we focus on recent advances in the understanding of epigenetic factors controlling cardiac morphogenesis and their role in diseases.

Clinical and molecular analysis in a cohort of Chinese children with Cornelia de Lange syndrome

Cornelia de Lange Syndrome (CdLS) is a rare genetic disorder, which causes a range of physical, cognitive, and medical challenges. To retrospectively analyze the clinical characteristics and genetic variations of Chinese patients, and to provide experience for further diagnosis and treatment of CdLS in Chinese children, we identified 15 unrelated Chinese children who presented with unusual facial features, short stature, developmental delay, limb abnormalities, and a wide range of health conditions. In this study, targeted-next generation sequencing was used to screen for causal variants and the clinically relevant variants were subsequently verified using Sanger sequencing. DNA sequencing identified 15 genetic variations, including 11 NIPBL gene variants, two SMC1A gene variants, one RAD21 gene variant, and one HDAC8 variant. The phenotype of these patients was summarized and differences between this cohort and another four groups were compared. The clinical manifestations of the patients in this cohort were mostly consistent with other ethnicities, but several clinical features in our cohort had different frequencies compared with other groups. We identified 15 deleterious variants of which 11 were novel. Variants in the NIPBL gene were the most common cause in our cohort. Our study not only expands upon the spectrum of genetic variations in CdLS, but also broadens our understanding of the clinical features of CdLS.

Analysis of clinical and genetic characteristics in 10 Chinese individuals with Cornelia de Lange syndrome and literature review

Background

Cornelia de Lange syndrome (CdLS) is a rare congenital developmental disorder with variable multisystem involvement and genetic heterogeneity. We aimed to analyze the clinical and genetic characteristics of Chinese individuals with CdLS.

Methods

We collected data regarding the neonatal period, maternal status, clinical manifestation, including facial dimorphisms and development, and follow‐up treatment for individuals diagnosed with CdLS. In individuals with suspected CdLS, high‐throughput sequencing, Sanger sequencing, and real‐time qualitative PCR were used to verify the diagnosis.

Results

Variants, including six that were novel, were concentrated in the NIPBL (70%), HDAC8 (20%), and SMC3 (10%) genes. We found two nonsense, three splicing, and two deletion variants in NIPBL; a missense variant and an absence variant in HDAC8; and a missense variant in SMC3. Eleven cardinal features of CdLS were present in more than 80% of Chinese individuals. Compared with non‐Chinese individuals of diverse ancestry, there were significant differences in the clinical characteristics of eight of these features.

Conclusion

Six novel pathological variants were identified; thus, the study expanded the gene variant spectrum. Furthermore, most cardinal features of CdLS found in Chinese individuals were also found in individuals from other countries. However, there were significant differences in eight clinical features.

Cecal Volvulus in a child with congenital dilated cardiomyopathy: A case report

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Cecal volvulus is a very rare cause of intestinal obstruction in children.

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Novel association between Congenital dilated cardiomyopathy and cecal volvulus.

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Cecal volvulus should be suspected in a child presenting with bilious vomiting.

Introduction

Cecal volvulus is an extremely rare cause of intestinal obstruction in the pediatric age group and its incidence is unknown.

Presentation of case

We present a unique case of cecal volvulus in a 3 year old female with congenital dilated cardiomyopathy.

Discussion

Cecal mobility due to malfixation and malrotation is the main cause. Cecal Volvulus usually presents with constipation, abdominal pain and distention. Common complications entail strangulation, ischemia and gangrene. Cecal volvulus has been reported in association with various abnormalities. However, Incidence of cecal volvulus in a child with congenital dilated cardiomyopathy has not been reported. Surgery is the mainstay of management.

Conclusion

Cecal volvulus should be kept in mind in a child presenting with signs suggestive of intestinal obstruction.

The expanding phenotypes of cohesinopathies: one ring to rule them all!

Preservation and development of life depend on the adequate segregation of sister chromatids during mitosis and meiosis. This process is ensured by the cohesin multi-subunit complex. Mutations in this complex have been associated with an increasing number of diseases, termed cohesinopathies. The best characterized cohesinopathy is Cornelia de Lange syndrome (CdLS), in which intellectual and growth retardations are the main phenotypic manifestations. Despite some overlap, the clinical manifestations of cohesinopathies vary considerably. Novel roles of the cohesin complex have emerged during the past decades, suggesting that important cell cycle regulators exert important biological effects through non-cohesion-related functions and broadening the potential pathomechanisms involved in cohesinopathies. This review focuses on non-cohesion-related functions of the cohesin complex, gene dosage effect, epigenetic regulation and TGF-β in cohesinopathy context, especially in comparison to Chronic Atrial and Intestinal Dysrhythmia (CAID) syndrome, a very distinct cohesinopathy caused by a homozygous Shugoshin-1 (SGO1) mutation (K23E) and characterized by pacemaker failure in both heart (sick sinus syndrome followed by atrial flutter) and gut (chronic intestinal pseudo-obstruction) with no intellectual or growth delay. We discuss the possible impact of SGO1 alterations in human pathologies and the potential impact of the SGO1 K23E mutation in the sinus node and gut development and functions. We suggest that the human phenotypes observed in CdLS, CAID syndrome and other cohesinopathies can inform future studies into the less well-known non-cohesion-related functions of cohesin complex genes. Abbreviations: AD: Alzheimer Disease; AFF4: AF4/FMR2 Family Member 4; ANKRD11: Ankyrin Repeat Domain 11; APC: Anaphase Promoter Complex; ASD: Atrial Septal Defect; ATRX: ATRX Chromatin Remodeler; ATRX: Alpha Thalassemia X-linked intellectual disability syndrome; BIRC5: Baculoviral IAP Repeat Containing 5; BMP: Bone Morphogenetic Protein; BRD4: Bromodomain Containing 4; BUB1: BUB1 Mitotic Checkpoint Serine/Threonine Kinase; CAID: Chronic Atrial and Intestinal Dysrhythmia; CDK1: Cyclin Dependent Kinase 1; CdLS: Cornelia de Lange Syndrome; CHD: Congenital Heart Disease; CHOPS: Cognitive impairment, coarse facies, Heart defects, Obesity, Pulmonary involvement, Short stature, and skeletal dysplasia; CIPO: Chronic Intestinal Pseudo-Obstruction; c-kit: KIT Proto-Oncogene Receptor Tyrosine Kinase; CoATs: Cohesin Acetyltransferases; CTCF: CCCTC-Binding Factor; DDX11: DEAD/H-Box Helicase 11; ERG: Transcriptional Regulator ERG; ESCO2: Establishment of Sister Chromatid Cohesion N-Acetyltransferase 2; GJC1: Gap Junction Protein Gamma 1; H2A: Histone H2A; H3K4: Histone H3 Lysine 4; H3K9: Histone H3 Lysine 9; HCN4: Hyperpolarization Activated Cyclic Nucleotide Gated Potassium and Sodium Channel 4;p HDAC8: Histone deacetylases 8; HP1: Heterochromatin Protein 1; ICC: Interstitial Cells of Cajal; ICC-MP: Myenteric Plexus Interstitial cells of Cajal; ICC-DMP: Deep Muscular Plexus Interstitial cells of Cajal; If: Pacemaker Funny Current; IP3: Inositol trisphosphate; JNK: C-Jun N-Terminal Kinase; LDS: Loeys-Dietz Syndrome; LOAD: Late-Onset Alzheimer Disease; MAPK: Mitogen-Activated Protein Kinase; MAU: MAU Sister Chromatid Cohesion Factor; MFS: Marfan Syndrome; NIPBL: NIPBL, Cohesin Loading Factor; OCT4: Octamer-Binding Protein 4; P38: P38 MAP Kinase; PDA: Patent Ductus Arteriosus; PDS5: PDS5 Cohesin Associated Factor; P-H3: Phospho Histone H3; PLK1: Polo Like Kinase 1; POPDC1: Popeye Domain Containing 1; POPDC2: Popeye Domain Containing 2; PP2A: Protein Phosphatase 2; RAD21: RAD21 Cohesin Complex Component; RBS: Roberts Syndrome; REC8: REC8 Meiotic Recombination Protein; RNAP2: RNA polymerase II; SAN: Sinoatrial node; SCN5A: Sodium Voltage-Gated Channel Alpha Subunit 5; SEC: Super Elongation Complex; SGO1: Shogoshin-1; SMAD: SMAD Family Member; SMC1A: Structural Maintenance of Chromosomes 1A; SMC3: Structural Maintenance of Chromosomes 3; SNV: Single Nucleotide Variant; SOX2: SRY-Box 2; SOX17: SRY-Box 17; SSS: Sick Sinus Syndrome; STAG2: Cohesin Subunit SA-2; TADs: Topology Associated Domains; TBX: T-box transcription factors; TGF-β: Transforming Growth Factor β; TGFBR: Transforming Growth Factor β receptor; TOF: Tetralogy of Fallot; TREK1: TREK-1 K(+) Channel Subunit; VSD: Ventricular Septal Defect; WABS: Warsaw Breakage Syndrome; WAPL: WAPL Cohesin Release Factor.

Cornelia de Lange syndrome in diverse populations

Cornelia de Lange syndrome (CdLS) is a dominant multisystemic malformation syndrome due to mutations in five genes-NIPBL, SMC1A, HDAC8, SMC3, and RAD21. The characteristic facial dysmorphisms include microcephaly, arched eyebrows, synophrys, short nose with depressed bridge and anteverted nares, long philtrum, thin lips, micrognathia, and hypertrichosis. Most affected individuals have intellectual disability, growth deficiency, and upper limb anomalies. This study looked at individuals from diverse populations with both clinical and molecularly confirmed diagnoses of CdLS by facial analysis technology. Clinical data and images from 246 individuals with CdLS were obtained from 15 countries. This cohort included 49% female patients and ages ranged from infancy to 37 years. Individuals were grouped into ancestry categories of African descent, Asian, Latin American, Middle Eastern, and Caucasian. Across these populations, 14 features showed a statistically significant difference. The most common facial features found in all ancestry groups included synophrys, short nose with anteverted nares, and a long philtrum with thin vermillion of the upper lip. Using facial analysis technology we compared 246 individuals with CdLS to 246 gender/age matched controls and found that sensitivity was equal or greater than 95% for all groups. Specificity was equal or greater than 91%. In conclusion, we present consistent clinical findings from global populations with CdLS while demonstrating how facial analysis technology can be a tool to support accurate diagnoses in the clinical setting. This work, along with prior studies in this arena, will assist in earlier detection, recognition, and treatment of CdLS worldwide.

Molecular characterization of two novel intronic variants of NIPBL gene detected in unrelated Cornelia de Lange syndrome patients

Background

Cornelia de Lange syndrome (CdLS), a rare, multisystemic disorder, has been linked to genetic alterations in NIPBL, SMC1A, SMC3, HDAC8, and RAD21 genes. Approximately 60% of CdLS patients harbor various NIPBL variants. Genetic changes predicted to affect NIPBL gene splicing represent 15% of all NIPBL genetic abnormalities. Yet, only a few studies have investigated the molecular consequences of such variants.

Case presentation

This study reports two novel, intronic NIPBL genetic variants in unrelated CdLS patients with the characteristic phenotype. A c.6954 + 3A > C substitution and a c.5862 + 1delG deletion were identified, one of each, in a 6 year-old boy and 39 month-old girl. Further studies confirmed that both variants introduce premature termination codons, resulting in the formation of truncated proteins p.(Ser2255LeufsTer20) and p.(Leu1955Ter), respectively.

Conclusion

Single nucleotide alterations located within the conserved splice-donor site of intronic regions of the NIPBL gene can give rise to a premature termination of the translation and cause significant changes in the sequence of mRNA transcripts and NIPBL protein structure and function. The latter underline development of Cornelia de Lange syndrome phenotype.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0738-y) contains supplementary material, which is available to authorized users.

Next-generation sequencing identified genetic variations in families with fetal non-syndromic atrioventricular septal defects

Atrioventricular septal defects (AVSDs) account for approximately 5% of all congenital heart disease (CHD). About half of AVSDs are diagnosed in cases with trisomy 21 (Down's syndrome, DS). However, many AVSDs occur sporadically and manifest as non-syndromic. The pathogenesis is complex and has not yet been fully elucidated. In the present study, we applied two advanced applications of next-generation sequencing (NGS) to explore the genetic variations in families with fetal non-syndromic AVSDs. Our study was mainly divided into two steps: (1) low-pass whole-genome sequencing (WGS) was used to detect the genome-wide copy number variations (CNVs) for included subjects; (2) whole-exome sequencing (WES) was used to detect the gene mutations for the subjects without AVSD-associated CNVs. A total of 17 heterozygous de novo CNVs and 19 heterozygous de novo gene mutations were selected, and 15 candidate genes were involved in these variations. Among these heterozygous de novo variations, most have potential pathogenicity for AVSDs, but the others require further investigation to confirm their pathogenicity. Our study not only shows the genetic diversity and the etiological complexity of AVSDs but also shows the rationality and practicability of this sequential genetic detection and analysis strategy.

NIPBL+/- haploinsufficiency reveals a constellation of transcriptome disruptions in the pluripotent and cardiac states

Cornelia de Lange syndrome (CdLS) is a complex disorder with multiple structural and developmental defects caused by mutations in structural and regulatory proteins involved in the cohesin complex. NIPBL, a cohesin regulatory protein, has been identified as a critical protein responsible for the orchestration of transcriptomic regulatory networks necessary for embryonic development. Mutations in NIPBL are responsible for the majority of cases of CdLS. Through RNA-sequencing of human induced pluripotent stem cells and in vitro-derived cardiomyocytes, we identified hundreds of mRNAs, pseudogenes, and non-coding RNAs with altered expression in NIPBL^+/− patient-derived cells. We demonstrate that NIPBL haploinsufficiency leads to upregulation of gene sets identified in functions related to nucleosome, chromatin assembly, RNA modification and downregulation of Wnt signaling, cholesterol biosynthesis and vesicular transport in iPSC and cardiomyocytes. Mutations in NIPBL result in the dysregulation of many genes responsible for normal heart development likely resulting in the variety of structural cardiac defects observed in the CdLS population.

[Research advances in the mechanism of congenital heart disease induced by pregestational diabetes mellitus]

Congenital heart disease (CHD) is the most common birth defect at present and has a complex etiology which involves the combined effect of genetic and environmental factors. Pregestational diabetes mellitus is significantly associated with the development of CHD, but the detailed mechanism remains unknown. This article reviews the research advances in the molecular mechanism of CHD caused by pregestational diabetes mellitus.

Isolated double-orifice mitral valve in a young girl

BACKGROUND

Double-orifice mitral valve (DOMV) is an extremely rare cardiac malformation. It has been found to be accompanied by congenital anomalies (CAs), however, it can be detected as an isolated anomaly. The clinical findings of a DOMV are variable and depend predominantly on the associated cardiac abnormalities, particularly atrioventricular septal defects or mitral valve (MV) regurgitation and/or stenosis.

CASE REPORT

In this regard, we describe an isolated DOMV in an 18-year-old young girl who complained of a short-term nonspecific chest pain. She underwent transthoracic and transesophageal echocardiographic examinations. The examinations revealed a DOMV without any valvular or structural malformations. Other examinations were unremarkable. The patient did need neither medical nor surgical interventions.

CONCLUSION

The isolated cases of DOMV do not need therapy and might be only followed up using echocardiographic examinations. However, a careful echocardiographic examination for detection of concomitant structural malformations would be of great importance in the management of such cases.

Cornelia de Lange syndrome: Congenital heart disease in 149 patients

INTRODUCTION

Cornelia de Lange syndrome (CdLS) is produced by mutations in genes that encode regulatory or structural proteins of the cohesin complex. Congenital heart disease (CHD) is not a major criterion of the disease, but it affects many individuals. The objective of this study was to study the incidence and type of CHD in patients with CdLS.

MATERIAL AND METHOD

Cardiological findings were evaluated in 149 patients with CdLS and their possible relationship with clinical and genetic variables.

RESULTS

A percentage of 34.9 had CHD (septal defects 50%, pulmonary stenosis 27%, aortic coarctation 9.6%). The presence of CHD was related with neonatal hospitalisation (P=.04), hearing loss (P=.002), mortality (P=.09) and lower hyperactivity (P=.02), it being more frequent in HDAC8+ patients (60%), followed by NIPBL+ (33%) and SMC1A+ (28.5%). While septal defects predominate in NIPBL+, pulmonary stenosis is more common in HDAC8+.

CONCLUSIONS

Patients with CdLS have a high incidence of CHD, which varies according to the affected gene, the most frequent findings being septal defects and pulmonary stenosis. Perform a cardiologic study in all these patients is suggested.

Phenotypes and genotypes in individuals with SMC1A variants

SMC1A encodes one of the proteins of the cohesin complex. SMC1A variants are known to cause a phenotype resembling Cornelia de Lange syndrome (CdLS). Exome sequencing has allowed recognizing SMC1A variants in individuals with encephalopathy with epilepsy who do not resemble CdLS. We performed an international, interdisciplinary study on 51 individuals with SMC1A variants for physical and behavioral characteristics, and compare results to those in 67 individuals with NIPBL variants. For the Netherlands all known individuals with SMC1A variants were studied, both with and without CdLS phenotype. Individuals with SMC1A variants can resemble CdLS, but manifestations are less marked compared to individuals with NIPBL variants: growth is less disturbed, facial signs are less marked (except for periocular signs and thin upper vermillion), there are no major limb anomalies, and they have a higher level of cognitive and adaptive functioning. Self-injurious behavior is more frequent and more severe in the NIPBL group. In the Dutch group 5 of 13 individuals (all females) had a phenotype that shows a remarkable resemblance to Rett syndrome: epileptic encephalopathy, severe or profound intellectual disability, stereotypic movements, and (in some) regression. Their missense, nonsense, and frameshift mutations are evenly spread over the gene. We conclude that SMC1A variants can result in a phenotype resembling CdLS and a phenotype resembling Rett syndrome. Resemblances between the SMC1A group and the NIPBL group suggest that a disturbed cohesin function contributes to the phenotype, but differences between these groups may also be explained by other underlying mechanisms such as moonlighting of the cohesin genes.

The Complex Genetic Basis of Congenital Heart Defects

Twenty years ago, chromosomal abnormalities were the only identifiable genetic causes of a small fraction of congenital heart defects (CHD). Today, a de novo or inherited genetic abnormality can be identified as pathogenic in one-third of cases. We refer to them here as monogenic causes, insofar as the genetic abnormality has a readily detectable, large effect. What explains the other two-thirds? This review considers a complex genetic basis. That is, a combination of genetic mutations or variants that individually may have little or no detectable effect contribute to the pathogenesis of a heart defect. Genes in the embryo that act directly in cardiac developmental pathways have received the most attention, but genes in the mother that establish the gestational milieu via pathways related to metabolism and aging also have an effect. A growing body of evidence highlights the pathogenic significance of genetic interactions in the embryo and maternal effects that have a genetic basis. The investigation of CHD as guided by a complex genetic model could help estimate risk more precisely and logically lead to a means of prevention.

Heterozygous truncation mutations of the SMC1A gene cause a severe early onset epilepsy with cluster seizures in females: Detailed phenotyping of 10 new cases

OBJECTIVE

The phenotype of seizure clustering with febrile illnesses in infancy/early childhood is well recognized. To date the only genetic epilepsy consistently associated with this phenotype is PCDH19, an X-linked disorder restricted to females, and males with mosaicism. The SMC1A gene, which encodes a structural component of the cohesin complex is also located on the X chromosome. Missense variants and small in-frame deletions of SMC1A cause approximately 5% of Cornelia de Lange Syndrome (CdLS). Recently, protein truncating mutations in SMC1A have been reported in five females, all of whom have been affected by a drug-resistant epilepsy, and severe developmental impairment. Our objective was to further delineate the phenotype of SMC1A truncation.

METHOD

Female cases with de novo truncation mutations in SMC1A were identified from the Deciphering Developmental Disorders (DDD) study (n = 8), from postmortem testing of an affected twin (n = 1), and from clinical testing with an epilepsy gene panel (n = 1). Detailed information on the phenotype in each case was obtained.

RESULTS

Ten cases with heterozygous de novo mutations in the SMC1A gene are presented. All 10 mutations identified are predicted to result in premature truncation of the SMC1A protein. All cases are female, and none had a clinical diagnosis of CdLS. They presented with onset of epileptic seizures between <4 weeks and 28 months of age. In the majority of cases, a marked preponderance for seizures to occur in clusters was noted. Seizure clusters were associated with developmental regression. Moderate or severe developmental impairment was apparent in all cases.

SIGNIFICANCE

Truncation mutations in SMC1A cause a severe epilepsy phenotype with cluster seizures in females. These mutations are likely to be nonviable in males.

Conditional Creation and Rescue of Nipbl-Deficiency in Mice Reveals Multiple Determinants of Risk for Congenital Heart Defects

Elucidating the causes of congenital heart defects is made difficult by the complex morphogenesis of the mammalian heart, which takes place early in development, involves contributions from multiple germ layers, and is controlled by many genes. Here, we use a conditional/invertible genetic strategy to identify the cell lineage(s) responsible for the development of heart defects in a Nipbl-deficient mouse model of Cornelia de Lange Syndrome, in which global yet subtle transcriptional dysregulation leads to development of atrial septal defects (ASDs) at high frequency. Using an approach that allows for recombinase-mediated creation or rescue of Nipbl deficiency in different lineages, we uncover complex interactions between the cardiac mesoderm, endoderm, and the rest of the embryo, whereby the risk conferred by genetic abnormality in any one lineage is modified, in a surprisingly non-additive way, by the status of others. We argue that these results are best understood in the context of a model in which the risk of heart defects is associated with the adequacy of early progenitor cell populations relative to the sizes of the structures they must eventually form.

The Hole and the Whole: Lessons from Manipulation of Nipbl Deficiency

Congenital heart defects (CHDs) affect 2%–3% of newborns and remain challenging clinically. There is an ongoing project to elucidate the causes of CHDs, focusing primarily on genetics as dictated by the epidemiology. In a paper published in this issue, Santos and colleagues describe studies of Cornelia de Lange syndrome-associated secundum atrial septal defects (ASDs) caused by NIPBL mutations, undertaken with a targeted trapping allele in mice. They show that Nipbl haploinsufficiency in either of two cell populations was sufficient to engender ASDs but that expression solely in either one of those populations was sufficient to rescue them. This work provides novel insights into incomplete penetrance and oligogenic effects underlying CHDs.

Using mouse and zebrafish models to understand the etiology of developmental defects in Cornelia de Lange Syndrome

Cornelia de Lange Syndrome (CdLS) is a multisystem birth defects disorder that affects every tissue and organ system in the body. Understanding the factors that contribute to the origins, prevalence, and severity of these developmental defects provides the most direct approach for developing screens and potential treatments for individuals with CdLS. Since the majority of cases of CdLS are caused by haploinsufficiency for NIPBL (Nipped-B-like, which encodes a cohesin-associated protein), we have developed mouse and zebrafish models of CdLS by using molecular genetic tools to create Nipbl-deficient mice and zebrafish (Nipbl(+/-) mice, zebrafish nipbl morphants). Studies of these vertebrate animal models have yielded novel insights into the developmental etiology and genes/gene pathways that contribute to CdLS-associated birth defects, particularly defects of the gut, heart, craniofacial structures, nervous system, and limbs. Studies of these mouse and zebrafish CdLS models have helped clarify how deficiency for NIPBL, a protein that associates with cohesin and other transcriptional regulators in the nucleus, affects processes important to the emergence of the structural and physiological birth defects observed in CdLS: NIPBL exerts chromosome position-specific effects on gene expression; it influences long-range interactions between different regulatory elements of genes; and it regulates combinatorial and synergistic actions of genes in developing tissues. Our current understanding is that CdLS should be considered as not only a cohesinopathy, but also a "transcriptomopathy," that is, a disease whose underlying etiology is the global dysregulation of gene expression throughout the organism. © 2016 Wiley Periodicals, Inc.

CHD associated with syndromic diagnoses: peri-operative risk factors and early outcomes

CHD is frequently associated with a genetic syndrome. These syndromes often present specific cardiovascular and non-cardiovascular co-morbidities that confer significant peri-operative risks affecting multiple organ systems. Although surgical outcomes have improved over time, these co-morbidities continue to contribute substantially to poor peri-operative mortality and morbidity outcomes. Peri-operative morbidity may have long-standing ramifications on neurodevelopment and overall health. Recognising the cardiovascular and non-cardiovascular risks associated with specific syndromic diagnoses will facilitate expectant management, early detection of clinical problems, and improved outcomes--for example, the development of syndrome-based protocols for peri-operative evaluation and prophylactic actions may improve outcomes for the more frequently encountered syndromes such as 22q11 deletion syndrome.

A neural crest origin for cohesinopathy heart defects

Mutations in subunits or regulators of cohesin cause a spectrum of disorders in humans known as the 'cohesinopathies'. Cohesinopathies, including the best known example Cornelia de Lange syndrome (CdLS), are characterized by broad spectrum, multifactorial developmental anomalies. Heart defects occur at high frequency and can reach up to 30% in CdLS. The mechanisms by which heart defects occur are enigmatic, but assumed to be developmental in origin. In this study, we depleted cohesin subunit Rad21 by 70-80% in a zebrafish cohesinopathy model. The hearts of Rad21-depleted animals were smaller, often failed to loop, and functioned less efficiently than size-matched controls. Functional deficiency was accompanied by valve defects and reduced ejection fraction. Interestingly, neural crest cells failed to populate the heart and instead exhibited a wandering behavior. Consequently, these cells also failed to condense correctly into pharyngeal arches. Transcriptome analysis revealed that Wnt pathway, chemokine and cadherin genes are dysregulated at the time of cardiac neural crest development. Our results give insight into the etiology of heart defects in the cohesinopathies, and raise the possibility that mild mutations in cohesin genes may be causative of a fraction of congenital heart disease in human populations.

Exome sequencing identifies rare variants in multiple genes in atrioventricular septal defect

Purpose

The genetic etiology of atrioventricular septal defect (AVSD) is unknown in 40% cases. Conventional sequencing and arrays have identified the etiology in only a minority of non-syndromic individuals with AVSD.

Methods

Whole exome sequencing was performed in 81 unrelated probands with AVSD to identify potentially causal variants in a comprehensive set of 112 genes with strong biological relevance to AVSD.

Results

A significant enrichment of rare and rare/damaging variants was identified in the gene set, compared with controls (odds ratio 1.52, 95% confidence interval 1.35–1.71, p = 4.8 x 10^-11). The enrichment was specific to AVSD probands compared with a non-AVSD cohort with tetralogy of Fallot (odds ratio 2.25, 95% confidence interval 1.84-2.76, p = 2.2 x 10^-16). Six genes (NIPBL, CHD7, CEP152, BMPR1a, ZFPM2 and MDM4) were enriched for rare variants in AVSD compared to controls, including three syndrome-associated genes (NIPBL, CHD7, CEP152). The findings were confirmed in a replication cohort of 81 AVSD probands.

Conclusion

Mutations in genes with strong biological relevance to AVSD, including syndrome-associated genes, can contribute to AVSD even in those with isolated heart disease. The identification of a gene set associated with AVSD will facilitate targeted genetic screening in this cohort.

De novo heterozygous mutations in SMC3 cause a range of Cornelia de Lange syndrome-overlapping phenotypes

Cornelia de Lange syndrome (CdLS) is characterized by facial dysmorphism, growth failure, intellectual disability, limb malformations, and multiple organ involvement. Mutations in five genes, encoding subunits of the cohesin complex (SMC1A, SMC3, RAD21) and its regulators (NIPBL, HDAC8), account for at least 70% of patients with CdLS or CdLS-like phenotypes. To date, only the clinical features from a single CdLS patient with SMC3 mutation has been published. Here, we report the efforts of an international research and clinical collaboration to provide clinical comparison of 16 patients with CdLS-like features caused by mutations in SMC3. Modeling of the mutation effects on protein structure suggests a dominant-negative effect on the multimeric cohesin complex. When compared with typical CdLS, many SMC3-associated phenotypes are also characterized by postnatal microcephaly but with a less distinctive craniofacial appearance, a milder prenatal growth retardation that worsens in childhood, few congenital heart defects, and an absence of limb deficiencies. While most mutations are unique, two unrelated affected individuals shared the same mutation but presented with different phenotypes. This work confirms that de novo SMC3 mutations account for ∼ 1%-2% of CdLS-like phenotypes.