Cardiovascular anomalies associated with chromosome 22q11.2 deletion syndrome

Prenatal cardiac findings and 22q11.2 deletion syndrome: Fetal detection and evaluation

Clinical features of 22q11.2 microdeletion syndrome (22q11.2DS) are highly variable between affected individuals and frequently include a subset of conotruncal and aortic arch anomalies. Many are diagnosed with 22q11.2DS when they present as a fetus, newborn or infant with characteristic cardiac findings and subsequently undergo genetic testing. The presence of an aortic arch anomaly with characteristic intracardiac anomalies increases the likelihood that the patient has 22q11.2 DS, but those with an aortic arch anomaly and normal intracardiac anatomy are also at risk. It is particularly important to identify the fetus at risk for 22q11.2DS in order to prepare the expectant parents and plan postnatal care for optimal outcomes. Fetal anatomy scans now readily identify aortic arch anomalies (aberrant right subclavian artery, right sided aortic arch or double aortic arch) in the three-vessel tracheal view. Given the association of 22q11.2DS with aortic arch anomalies with and without intracardiac defects, this review highlights the importance of recognizing the fetus at risk for 22q11.2 deletion syndrome with an aortic arch anomaly and details current methods for genetic testing. To assist in the prenatal diagnosis of 22q11.2DS, this review summarizes the seminal features of 22q11.2DS, its prenatal presentation and current methods for genetic testing.

Buffering Mechanism in Aortic Arch Artery Formation and Congenital Heart Disease

BACKGROUND

The resiliency of embryonic development to genetic and environmental perturbations has been long appreciated; however, little is known about the mechanisms underlying the robustness of developmental processes. Aberrations resulting in neonatal lethality are exemplified by congenital heart disease arising from defective morphogenesis of pharyngeal arch arteries (PAAs) and their derivatives.

METHODS

Mouse genetics, lineage tracing, confocal microscopy, and quantitative image analyses were used to investigate mechanisms of PAA formation and repair.

RESULTS

The second heart field (SHF) gives rise to the PAA endothelium. Here, we show that the number of SHF-derived endothelial cells (ECs) is regulated by VEGFR2 (vascular endothelial growth factor receptor 2) and Tbx1. Remarkably, when the SHF-derived EC number is decreased, PAA development can be rescued by the compensatory endothelium. Blocking such compensatory response leads to embryonic demise. To determine the source of compensating ECs and mechanisms regulating their recruitment, we investigated 3-dimensional EC connectivity, EC fate, and gene expression. Our studies demonstrate that the expression of VEGFR2 by the SHF is required for the differentiation of SHF-derived cells into PAA ECs. The deletion of 1 VEGFR2 allele (VEGFR2SHF-HET) reduces SHF contribution to the PAA endothelium, while the deletion of both alleles (VEGFR2SHF-KO) abolishes it. The decrease in SHF-derived ECs in VEGFR2SHF-HET and VEGFR2SHF-KO embryos is complemented by the recruitment of ECs from the nearby veins. Compensatory ECs contribute to PAA derivatives, giving rise to the endothelium of the aortic arch and the ductus in VEGFR2SHF-KO mutants. Blocking the compensatory response in VEGFR2SHF-KO mutants results in embryonic lethality shortly after mid-gestation. The compensatory ECs are absent in Tbx1+/- embryos, a model for 22q11 deletion syndrome, leading to unpredictable arch artery morphogenesis and congenital heart disease. Tbx1 regulates the recruitment of the compensatory endothelium in an SHF-non-cell-autonomous manner.

CONCLUSIONS

Our studies uncover a novel buffering mechanism underlying the resiliency of PAA development and remodeling.

On the involvement of the second heart field in congenital heart defects

Congenital heart defects (CHD) affect 1 in 100 live births and result from defects in cardiac development. Growth of the early heart tube occurs by the progressive addition of second heart field (SHF) progenitor cells to the cardiac poles. The SHF gives rise to ventricular septal, right ventricular and outflow tract myocardium at the arterial pole, and atrial, including atrial septal myocardium, at the venous pole. SHF deployment creates the template for subsequent cardiac septation and has been implicated in cardiac looping and in orchestrating outflow tract development with neural crest cells. Genetic or environmental perturbation of SHF deployment thus underlies a spectrum of common forms of CHD affecting conotruncal and septal morphogenesis. Here we review the major properties of SHF cells as well as recent insights into the developmental programs that drive normal cardiac progenitor cell addition and the origins of CHD.

Long-term Outcomes After Interrupted Aortic Arch Repair

BACKGROUND

Interrupted aortic arch (IAA) is associated with left ventricular outflow tract obstruction (LVOTO) and DiGeorge syndrome. High-risk infantile surgery is required to address IAA, with limited data available on long-term outcomes. We used the Pediatric Cardiac Care Consortium, a multicenter US-based registry for pediatric cardiac interventions, to assess long-term outcomes after IAA repair by patient characteristics and surgical approach.

METHODS

This is a retrospective cohort study of patients undergoing IAA repair between 1982 and 2003. Kaplan-Meier plots and Cox proportional hazards regression were used to examine associations with postdischarge deaths tracked by matching with the US National Death Index.

RESULTS

Of 390 patients meeting inclusion criteria, 309 (79.2%) survived to discharge. During a median follow-up of 23.6 years, 30-year survival reached 80.7% for patients surviving hospital discharge after initial IAA repair. Adjusted analysis revealed higher risk of death for type B vs type A (adjusted hazard ratio [aHR], 3.32; 95% CI, 1.48-7.44), staged repair (aHR, 2.50; 95% CI, 1.14-5.50), and LVOTO interventions during initial hospitalization (aHR, 4.12; 95% CI, 1.83-9.27) but not for LVOTO without need for interventions or presence of DiGeorge syndrome. There was a trend toward improved in-hospital and long-term survival over time during the study period.

CONCLUSIONS

Staged repair, type B IAA, and need for LVOTO intervention during initial hospitalization for repair are associated with high risk of death out to 30 years. Survival outcomes are improving, but further efforts need to minimize staged approach and risks associated with LVOTO relief procedures.

Identification of novel buffering mechanisms in aortic arch artery development and congenital heart disease

Rationale

The resiliency of embryonic development to genetic and environmental perturbations has been long appreciated; however, little is known about the mechanisms underlying the robustness of developmental processes. Aberrations resulting in neonatal lethality are exemplified by congenital heart disease (CHD) arising from defective morphogenesis of pharyngeal arch arteries (PAA) and their derivatives.

Objective

To uncover mechanisms underlying the robustness of PAA morphogenesis.

Methods and Results

The second heart field (SHF) gives rise to the PAA endothelium. Here, we show that the number of SHF-derived ECs is regulated by VEGFR2 and Tbx1 . Remarkably, when SHF-derived EC number is decreased, PAA development can be rescued by the compensatory endothelium. Blocking such compensatory response leads to embryonic demise. To determine the source of compensating ECs and mechanisms regulating their recruitment, we investigated three-dimensional EC connectivity, EC fate, and gene expression. Our studies demonstrate that the expression of VEGFR2 by the SHF is required for the differentiation of SHF-derived cells into PAA ECs. The deletion of one VEGFR2 allele (VEGFR2 SHF-HET ) reduces SHF contribution to the PAA endothelium, while the deletion of both alleles (VEGFR2 SHF-KO ) abolishes it. The decrease in SHF-derived ECs in VEGFR2 SHF-HET and VEGFR2 SHF-KO embryos is complemented by the recruitment of ECs from the nearby veins. Compensatory ECs contribute to PAA derivatives, giving rise to the endothelium of the aortic arch and the ductus in VEGFR2 SHF-KO mutants. Blocking the compensatory response in VEGFR2 SHF-KO mutants results in embryonic lethality shortly after mid-gestation. The compensatory ECs are absent in Tbx1 +/- embryos, a model for 22q11 deletion syndrome, leading to unpredictable arch artery morphogenesis and CHD. Tbx1 regulates the recruitment of the compensatory endothelium in an SHF-non-cell-autonomous manner.

Conclusions

Our studies uncover a novel buffering mechanism underlying the resiliency of PAA development and remodeling.

Nonstandard Abbreviations and Acronyms in Alphabetical Order

CHD - congenital heart disease; ECs - endothelial cells; IAA-B - interrupted aortic arch type B; PAA - pharyngeal arch arteries; RERSA - retro-esophageal right subclavian artery; SHF - second heart field; VEGFR2 - Vascular endothelial growth factor receptor 2.

Human Genetics of Ventricular Septal Defect

Ventricular septal defects (VSDs) are recognized as one of the commonest congenital heart diseases (CHD), accounting for up to 40% of all cardiac malformations, and occur as isolated CHDs as well as together with other cardiac and extracardiac congenital malformations in individual patients and families. The genetic etiology of VSD is complex and extraordinarily heterogeneous. Chromosomal abnormalities such as aneuploidy and structural variations as well as rare point mutations in various genes have been reported to be associated with this cardiac defect. This includes both well-defined syndromes with known genetic cause (e.g., DiGeorge syndrome and Holt-Oram syndrome) and so far undefined syndromic forms characterized by unspecific symptoms. Mutations in genes encoding cardiac transcription factors (e.g., NKX2-5 and GATA4) and signaling molecules (e.g., CFC1) have been most frequently found in VSD cases. Moreover, new high-resolution methods such as comparative genomic hybridization enabled the discovery of a high number of different copy number variations, leading to gain or loss of chromosomal regions often containing multiple genes, in patients with VSD. In this chapter, we will describe the broad genetic heterogeneity observed in VSD patients considering recent advances in this field.

The Genetics of Canine Pulmonary Valve Stenosis

There have been recent advancements in understanding the genetic contribution to pulmonary valve stenosis (PS) in brachycephalic breeds such as the French Bulldog and Bulldog. The associated genes are transcriptions factors involved in cardiac development, which is comparable to the genes that cause PS in humans. However, validation studies and functional follow up is necessary before this information can be used for screening purposes.

22q11.2 Deletion Syndrome Diagnosed 47 Years After Surgery for Tetralogy of Fallot

A 51-year-old man presented with severe hydrocele testis, dyspnea on exertion, and systemic edema. He had a history of surgery for tetralogy of Fallot (TOF). On the second day of admission, he presented with severe nose bleeding followed by CO2 narcosis. Blood gas analysis revealed an extremely low level of Ca2+. An echocardiogram revealed an excessively enlarged right ventricle and severe pulmonary valve regurgitation (PR). Hypocalcemia, history of TOF, and characteristic facial features suggested 22q11.2 deletion syndrome, which was confirmed by fluorescence in-situ hybridization (FISH) chromosome test. Open heart redo-surgery was performed for severe PR. The surgery revealed a severely hypoplastic pulmonary valve, which is characteristic of 22q11.2 deletion syndrome. 22q11.2 syndrome thus could be overlooked until age over 50 and therefore become critical.

Association Between Airway Stenosis Degree and Respiratory Distress in Infants With a Vascular Ring

Background Although the number of cases of prenatally diagnosed vascular rings is increasing, some cases may remain asymptomatic, and no indicator of the appearance of dyspnea has been established. Thus, we aimed to determine the relationship between the degree of airway compression by the vascular ring on contrast-enhanced computed tomography (CT) and respiratory distress. Methods This is a retrospective study of nine patients diagnosed with vascular rings at a single hospital from July 2010 to December 2019. Data regarding the patient's clinical characteristics, such as prenatal diagnosis, vascular ring type, complicated cardiac disease, and presence or absence of surgery, were recorded. Airway assessment on contrast-enhanced CT was measured in the axial cross-section. Statistical analysis was performed using Statistical Product and Service Solutions (SPSS) (version 25.0; IBM SPSS Statistics for Windows, Armonk, NY). Results Five of the eight patients had respiratory distress. Patients with respiratory distress were less likely to have been diagnosed prenatally (p = 0.04) and had smaller stenosis degree of anteroposterior diameter (p = 0.03). Conclusion Contrast-enhanced CT is useful in patients with vascular rings. Our study suggests that the stenosis degree of the anterior-posterior diameter of the airway is related to dyspnea.

Rare CNVs and phenome-wide profiling highlight brain structural divergence and phenotypical convergence

Copy number variations (CNVs) are rare genomic deletions and duplications that can affect brain and behaviour. Previous reports of CNV pleiotropy imply that they converge on shared mechanisms at some level of pathway cascades, from genes to large-scale neural circuits to the phenome. However, existing studies have primarily examined single CNV loci in small clinical cohorts. It remains unknown, for example, how distinct CNVs escalate vulnerability for the same developmental and psychiatric disorders. Here we quantitatively dissect the associations between brain organization and behavioural differentiation across 8 key CNVs. In 534 CNV carriers, we explored CNV-specific brain morphology patterns. CNVs were characteristic of disparate morphological changes involving multiple large-scale networks. We extensively annotated these CNV-associated patterns with ~1,000 lifestyle indicators through the UK Biobank resource. The resulting phenotypic profiles largely overlap and have body-wide implications, including the cardiovascular, endocrine, skeletal and nervous systems. Our population-level investigation established brain structural divergences and phenotypical convergences of CNVs, with direct relevance to major brain disorders.

Clinical Characteristics of Coronary-to-Pulmonary Artery Fistula in Patients with Pulmonary Atresia and Ventricular Septal Defect

The existence of a coronary-to-pulmonary artery fistula (CPF) in pulmonary atresia with ventricular septal defect (PAVSD) potentially affects treatment; however, its clinical features have not been comprehensively described due to the disease's rarity. We reviewed 69 cases from 42 studies to reveal the clinical overview of patients with CPF and PAVSD. Among the included patients, the male-to-female ratio was exactly 1:1, and only two patients (3%) exhibited the 22q11.2 microdeletion syndrome. Regarding anatomical features, CPFs originated from the left coronary artery in 65% of patients, and 62% had other major aortopulmonary collateral arteries. Thirty-nine percent of patients had a definitive CPF diagnosis at 0 years of age, whereas 10% were diagnosed in adulthood. Seventy percent underwent catheter angiography to obtain a definitive CPF diagnosis. Ninety-five percent of patients underwent cardiac surgery, and among them, 43% underwent palliative surgery, whereas 52% underwent one-stage repair. Four patients including three adult patients developed cardiac dysfunction due to myocardial ischemia, and three of them exhibited improved cardiac function after the intervention for CPF. Of all the patients, 88% survived and 12% died. The surgical strategy and prognosis were similar to those in PAVSD patients without CPF. This review provides detailed clinical phenotypes that are potentially useful in enhancing the management of patients with this rare disease.

Clinical Risk Factors for Aortic Root Dilation in Patients with 22q11.2 Deletion Syndrome: A Longitudinal Single-Center Study

BACKGROUND

Aortic root dilation (ARD) has been described in 22q11.2DS, even without congenital heart disease (CHD). However, the clinical implications and longitudinal course are unclear. In this study, we evaluated aortic root (AR) dimensions in 22q112.DS adolescents/adults without major intracardiac CHDs, analyzed the progression over time and investigated correlations with extracardiac comorbidities.

METHODS

AR dimensions were evaluated in 74 patients, measuring the sinus of Valsalva (VS) and proximal ascending aorta (AA), using Z-score to define mild, moderate and severe degrees. Changes in AR dimensions during longitudinal echocardiographic follow-up were investigated. Phenotypic characteristics have been collected.

RESULTS

Twenty-four patients (32.4%) showed ARD in terms of VS Z-score (2.43; IQR 2.08-3.01), eight (33.3%) of a moderate/severe degree. Thirteen (54.2%) had concomitant AAD (Z-score 2.34; IQR 1.60-2.85). The risk of ARD was significantly directly related to skeletal/connective tissue disorders (OR 12.82, 95% CI 1.43-115.31; p = 0.023) and inversely related to BMI (OR 0.86, 95% CI 0.77-0.97; p = 0.011). A significant increase in AR diameter's absolute value (p = 0.001) over time has been detected.

CONCLUSION

Isolated ARD is common in 22q11.2DS. Although some clinical risk factors have been identified, pathogenetic mechanisms and risk of complications are undefined. Regular cardiac evaluations should be part of the 22q11.2DS follow-up, and also in non-CHDs patients, to improve long-term outcome.

Aberrant right subclavian artery: embryology, prenatal diagnosis and clinical significance

Introduction

The right subclavian artery normally arises as the first vessel from the brachiocephalic trunk. An aberrant right subclavian artery (ARSA) arises directly from the aortic arch and crosses behind the trachea towards the right arm. This variant occurs in approximately 1-2% of the population; however, the frequency increases in individuals with chromosomal abnormalities such as trisomy 21 and 22q11.2 microdeletion. Prenatal identification of ARSA therefore has a role in screening for such conditions.

Methods

Databases were searched for studies reporting the prenatal ultrasound evaluation of ARSA and its frequency in normal fetuses and in those with chromosomal abnormalities.

Results

A total of 23 studies were evaluated. Feasibility for the ultrasound evaluation of ARSA was 85-95%. The sonographic detection of ARSA is best in the three-vessel trachea view; however, sagittal and coronal imaging of the aortic arch may be useful. ARSA in isolation was not found to be associated with chromosomal abnormalities. The prevalence of ARSA in chromosomally abnormal fetuses was up to 24-fold higher than in normal fetuses, but the majority of chromosomally abnormal fetuses with ARSA had additional abnormal ultrasound findings, particularly cardiac abnormalities.

Conclusions

The prenatal detection of ARSA is a clinically useful prenatal marker for chromosomal abnormalities. In isolation, it is unlikely to be associated with pathogenic genetic variants. The ultrasound diagnosis of ARSA should prompt meticulous assessment of associated abnormalities. Invasive diagnostic testing should be offered to patients with non-isolated ARSA or in the presence of non-reassuring screening results or other risk factors.

Cardiac function in adolescents and young adults with 22q11.2 deletion syndrome without congenital heart disease

BACKGROUND

Diagnosis and treatment of 22q11.2 deletion syndrome (22q11.2DS) have led to improved life expectancy and achievement of adulthood. Limited data on long-term outcomes reported an increased risk of premature death for cardiovascular causes, even without congenital heart disease (CHD). The aim of this study was to assess the cardiac function in adolescents and young adults with 22q11.2DS without CHDs.

METHODS

A total of 32 patients (20M, 12F; mean age 26.00 ± 8.08 years) and a healthy control group underwent transthoracic echocardiography, including Tissue Doppler Imaging (TDI) and 2-dimensional Speckle Tracking Echocardiography (2D-STE).

RESULTS

Compared to controls, 22q11.2DS patients showed a significant increase of the left ventricle (LV) diastolic and systolic diameters (p = 0.029 and p = 0.035 respectively), interventricular septum thickness (p = 0.005), LV mass index (p < 0.001) and aortic root size (p < 0.001). 2D-STE analysis revealed a significant reduction of LV global longitudinal strain (p < 0.001) in 22q11.2DS than controls. Moreover, several LV diastolic parameters were significantly different between groups.

CONCLUSIONS

Our results suggest that an echocardiographic follow-up in 22q11.2DS patients without CHDs can help to identify subclinical impairment of the LV and evaluate a potential progression of aortic root dilation over time, improving outcomes, reducing long-term complications and allowing for a better prognosis.

Aortic Arch Laterality in Chromosome 22q11.2 Deletion Syndrome: Male-Female Difference

We reviewed patients with chromosome 22q11.2 deletion syndrome. We analyzed cardiovascular findings in patients with confirmed chromosome 22q11.2 deletion syndrome live-born in Nevada between March 2007 and September 2020. We identified 60 patients. Of the 60 patients, 32 (53%) were female. Of the 60, 48 (80%) had a conotruncal abnormality (including isolated vascular rings): 23 of 32 (72%) for females versus 25 of 28 (89%) for males, P = .41. However, 11 (34%) of 32 females had a right aortic arch; whereas, 21 (75%) of 28 males had a right aortic arch, P = .007. In conclusion, in our patient cohort, we found conotruncal malformations were common. However, we noted males were statistically more likely to have a right aortic arch than females. To the best of our knowledge, this male-female aortic arch laterality difference in patients with chromosome 22q11.2 deletion syndrome has not been previously noted.

22q11.2 Deletion Syndrome: Impact of Genetics in the Treatment of Conotruncal Heart Defects

Congenital heart diseases represent one of the hallmarks of 22q11.2 deletion syndrome. In particular, conotruncal heart defects are the most frequent cardiac malformations and are often associated with other specific additional cardiovascular anomalies. These findings, together with extracardiac manifestations, may affect perioperative management and influence clinical and surgical outcome. Over the past decades, advances in genetic and clinical diagnosis and surgical treatment have led to increased survival of these patients and to progressive improvements in postoperative outcome. Several studies have investigated long-term follow-up and results of cardiac surgery in this syndrome. The aim of our review is to examine the current literature data regarding cardiac outcome and surgical prognosis of patients with 22q11.2 deletion syndrome. We thoroughly evaluate the most frequent conotruncal heart defects associated with this syndrome, such as tetralogy of Fallot, pulmonary atresia with major aortopulmonary collateral arteries, aortic arch interruption, and truncus arteriosus, highlighting the impact of genetic aspects, comorbidities, and anatomical features on cardiac surgical treatment.

Crossed pulmonary arteries and DiGeorge syndrome: case reports and literature review

DiGeorge syndrome has heterogeneous clinical presentation, and for this reason, its diagnosis can be challenging and may be missed. Since CHDs are very common in this patients, they can be considered pillars of clinical diagnosis of the syndrome. Therefore, accurate echocardiography is needed to detect even minor cardiac anomalies, as some specific malformation like crossed pulmonary arteries can be associated with 22q11 syndrome. We report two cases of newborns where the diagnosis of DiGeorge syndrome was suspected after finding crossed pulmonary arteries on echocardiography. In order to reach a timely diagnosis of DiGeorge syndrome, we suggest a careful echocardiographic examination of the pulmonary arteries position in all patients and genetic analysis for 22q11.2 microdeletion in patients in whom malposition has been detected.

Common Arterial Trunk Associated with Functionally Univentricular Heart: Anatomical Study and Review of the Literature

Common arterial trunk (CAT) is a rare congenital heart disease that is commonly included into the spectrum of conotruncal heart defects. CAT is rarely associated with functionally univentricular hearts, and only few cases have been described so far. Here, we describe the anatomical characteristics of CAT associated with a univentricular heart diagnosed in children and fetuses referred to our institution, and we completed the anatomical description of this rare condition through an extensive review of the literature. The complete cohort ultimately gathered 32 cases described in the literature completed by seven cases from our unit (seven fetuses and one child). Four types of univentricular hearts associated with CAT were observed: tricuspid atresia or hypoplastic right ventricle in 16 cases, mitral atresia or hypoplastic left ventricle in 12 cases, double-inlet left ventricle in 2 cases, and unbalanced atrioventricular septal defect in 9 cases. Our study questions the diagnosis of CAT as the exclusive consequence of an anomaly of the wedging process, following the convergence between the embryonic atrioventricular canal and the common outflow tract. We confirm that some forms of CAT can be considered to be due to an arrest of cardiac development at the stages preceding the convergence.

MicroRNA-451a attenuates angiotensin II-induced cardiac fibrosis and inflammation by directly targeting T-box1

Hypertension or angiotensin II (Ang II) induces cardiac inflammation and fibrosis, thus contributing to cardiac remodeling. MicroRNAs (miRNAs) are considered crucial regulators of cardiac homeostasis and remodeling in response to various types of stress. It has been reported that miR-451a is involved in regulating ischemic heart injury. However, its role in Ang II-induced cardiac fibrosis remains unknown. Cardiac remodeling was induced in mice by infusion of low-dose Ang II (490 ng/kg/min) with a minipump for 2 weeks. Echocardiography and histological examinations were performed to evaluate cardiac function and pathological changes. We observed that miR-451a expression was the most significantly downregulated in the hearts of Ang II-infused mice and in both primary cardiac myocytes and fibroblasts. Overexpression of miR-451a in mice significantly attenuated Ang II-induced cardiac fibrosis and inflammation. Conversely, knockdown of miR-451a in mice aggravated this effect. Bioinformatics analysis and a luciferase reporter assay revealed that TBX1 was a direct target of miR-451a. Mechanistically, miR-451a directly targeted TBX1 expression, which inhibited TGF-β1 production in both cardiac myocytes and fibroblasts, inactivating of TGF-β1/SMAD2/3 signaling, inhibiting myofibroblast differentiation and proinflammatory cytokine expression, and leading to attenuation of cardiac fibrosis and inflammation. In conclusion, these results indicate that miR-451a acts as a novel regulator of Ang II-induced cardiac fibrosis and inflammation by directly targeting TBX1, and may be a promising therapeutic target for treating hypertensive cardiac diseases.

Vascular rings

Vascular rings are congenital aortic arch anomalies that lead to compression of the trachea or esophagus. The goal of this review is to summarize our current recommendations for the management of patients with a diagnosis of a vascular ring. We review the history, classification methods, and epidemiology of the various types of vascular rings. We then propose a management strategy for the relatively new paradigm of fetal diagnosis, including the management of asymptomatic vascular rings. Finally, we finish with a review of the operative techniques and outcomes for the four main categories of vascular rings.

Clinical Manifestations of 22q11.2 Deletion Syndrome

DiGeorge syndrome (DGS), also known as "22q11.2 deletion syndrome" (22q11DS) (MIM # 192430 # 188400), is a genetic disorder caused by hemizygous microdeletion of the long arm of chromosome 22. In the last decades, the introduction of fluorescence in situ hybridization assays, and in selected cases the use of multiplex ligation-dependent probe amplification, has allowed the detection of chromosomal microdeletions that could not be previously identified using standard karyotype analysis. The aim of this review is to address cardiovascular and systemic involvement in children with DGS, provide genotype-phenotype correlations, and discuss their medical management and therapeutic options.

Congenital Heart Disease: An Immunological Perspective

Congenital heart disease (CHD) poses a significant global health and economic burden-despite advances in treating CHD reducing the mortality risk, globally CHD accounts for approximately 300,000 deaths yearly. Children with CHD experience both acute and chronic cardiac complications, and though treatment options have improved, some remain extremely invasive. A challenge in addressing these morbidity and mortality risks is that little is known regarding the cause of many CHDs and current evidence suggests a multifactorial etiology. Some studies implicate an immune contribution to CHD development; however, the role of the immune system is not well-understood. Defining the role of the immune and inflammatory responses in CHD therefore holds promise in elucidating mechanisms underlying these disorders and improving upon current diagnostic and treatment options. In this review, we address the current knowledge coinciding CHDs with immune and inflammatory associations, emphasizing conditions where this understanding would provide clinical benefit, and challenges in studying these mechanisms.

The Cardiac Neural Crest Cells in Heart Development and Congenital Heart Defects

The neural crest (NC) is a multipotent and temporarily migratory cell population stemming from the dorsal neural tube during vertebrate embryogenesis. Cardiac neural crest cells (NCCs), a specified subpopulation of the NC, are vital for normal cardiovascular development, as they significantly contribute to the pharyngeal arch arteries, the developing cardiac outflow tract (OFT), cardiac valves, and interventricular septum. Various signaling pathways are shown to orchestrate the proper migration, compaction, and differentiation of cardiac NCCs during cardiovascular development. Any loss or dysregulation of signaling pathways in cardiac NCCs can lead to abnormal cardiovascular development during embryogenesis, resulting in abnormalities categorized as congenital heart defects (CHDs). This review focuses on the contributions of cardiac NCCs to cardiovascular formation, discusses cardiac defects caused by a disruption of various regulatory factors, and summarizes the role of multiple signaling pathways during embryonic development. A better understanding of the cardiac NC and its vast regulatory network will provide a deeper insight into the mechanisms of the associated abnormalities, leading to potential therapeutic advancements.

Cardiac Defects and Genetic Syndromes: Old Uncertainties and New Insights

Recent advances in understanding the genetic causes and anatomic subtypes of cardiac defects have revealed new links between genetic etiology, pathogenetic mechanisms and cardiac phenotypes. Although the same genetic background can result in different cardiac phenotypes, and similar phenotypes can be caused by different genetic causes, researchers’ effort to identify specific genotype–phenotype correlations remains crucial. In this review, we report on recent advances in the cardiac pathogenesis of three genetic diseases: Down syndrome, del22q11.2 deletion syndrome and Ellis–Van Creveld syndrome. In these conditions, the frequent and specific association with congenital heart defects and the recent characterization of the underlying molecular events contributing to pathogenesis provide significant examples of genotype–phenotype correlations. Defining these correlations is expected to improve diagnosis and patient stratification, and it has relevant implications for patient management and potential therapeutic options.

Polyhydramnios is associated with postnatal dysphagia determining short-term prognosis of the newborn with 22q11.2 deletion syndrome - A case series analysis

OBJECTIVE

We experienced a case of 22q11.2 deletion syndrome (22qDS), with severe polyhydramnios, and dysphagia, which prompted us to review prognosis in neonates with 22qDS, with a focus on dysphagia.

CASE REPORT

A patient was referred to our hospital at 35 gestational weeks because of polyhydramnios. After amniotic fluid reduction, labor was induced at 38 weeks. The neonate had serious dysphagia, and 22qDS was diagnosed postnatally by fluorescent in situ hybridization analysis. This prompted a retrospective analysis of 9 cases with 22qDS experienced in our facility. Three out of these nine cases showed polyhydramnios, and had severe dysphagia postnatally. In total, 4 cases had dysphagia, while mortality was observed in 2 of these 4 cases. Additionally, 5 cases without dysphagia had normal development and no major complications.

CONCLUSION

Polyhydramnios associated with postnatal dysphagia might be a risk factor related to short-term prognostic outcomes in newborns with 22qDS.

Prenatal sonographic and cytogenetic/molecular findings of 22q11.2 microdeletion syndrome in 48 confirmed cases in a single tertiary center

PURPOSE

We aimed to present the fetal ultrasound, cytogenetic/molecular testing and postmortem or postnatal clinical findings of cases with 22q11.2DS diagnosed prenatally.

MATERIALS AND METHODS

A retrospective medical record review of 48 prenatal cases diagnosed with 22q11.2DS were evaluated in our institution. Detailed ultrasound examination was performed on all fetuses. Postmortem and postnatal examinations were evaluated. The microdeletions were detected by karyotyping or microarray, then confirmed by FISH. Descriptive statistical analysis was performed.

RESULTS

Demographic data of 48 prenatal cases including 46 singletons and 1 dichorionic diamniotic twin pregnancy were evaluated. The most common extracardiac anomaly was skeletal system anomalies (25%), in which PEV was the most frequent one (20.8%). Polyhydramnios rate was detected as 31%, in 6.6% as an isolated finding. Microdeletion has been detected by karyotyping in 13 cases (13/47, 27.7%) (including 2 unbalanced translocations), by FISH in 28 cases (28/48, 58.3%), by microarray/a-CGH testing in 7 cases. Microarray analysis showed that in one case with unbalanced translocation had two consecutive deletions; one was proximal and other one distal to critical region and not encompassing TBX1 gene but CRKL and LZTR1 genes.

CONCLUSION

The current study demonstrates the whole spectrum of atypical phenotypic and genotypic variations of 22q11.2DS in the largest prenatal case series reported to date. Therefore, differential diagnosis should be considered not solely in CHD, but also in the presence of isolated clubfeet and polyhydramnios. Establishing the diagnosis in the prenatal period may allow a postnatal multidisciplinary approach, as well as affect the actual prevalence of the disease.

Hospital Survival After Surgical Repair of Truncus Arteriosus with Interrupted Aortic Arch: Results from a Multi-institutional Database

Truncus arteriosus (TA) is a major congenital cardiac malformation that requires surgical repair in the first few weeks of life. Interrupted aortic arch (IAA) is an associated malformation that significantly impacts the complexity of the TA operation. The aim of this study was to (1) define the comorbid conditions associated with TA and (2) determine the hospital survival and morbidity of patients with TA with and without an IAA. Data was collected from the Vizient Clinical Database/Resource Manager, formerly University HealthSystem Consortium, which encompasses more than 160 academic medical centers in the United States. The database was queried for patients admitted from 2002 to 2016 who were ≤ 4 months of age at initial admission, diagnosed with TA, and underwent complete surgical repair during that hospitalization. Of the 645 patients with TA who underwent surgery, 98 (15%) had TA with an interrupted aortic arch (TA-IAA). Both TA and TA-IAA were associated with a high prevalence of comorbidities, including DiGeorge syndrome, prematurity, and other congenital malformations. There was no difference in mortality between TA and TA-IAA (13.7-18.4%, p value = 0.227). No comorbid conditions were associated with an increased mortality in either group. However, patients with TA-IAA had a longer post-operative length of stay (LOS) compared to those without IAA (30 versus 40.3 days, p value = 0.001) and this effect was additive with each additional comorbid condition. In conclusion, the addition of IAA to TA is associated with an increased post-operative LOS, but does not increase in-hospital mortality.

Genetic and epigenetic mechanisms in the development of congenital heart diseases

Congenital heart disease (CHD) is the most common of congenital cardiovascular malformations associated with birth defects, and it results in significant morbidity and mortality worldwide. The classification of CHD is still elusive owing to the complex pathogenesis of CHD. Advances in molecular medicine have revealed the genetic basis of some heart anomalies. Genes associated with CHD might be modulated by various epigenetic factors. Thus, the genetic and epigenetic factors are gradually accepted as important triggers in the pathogenesis of CHD. However, few literatures have comprehensively elaborated the genetic and epigenetic mechanisms of CHD. This review focuses on the etiology of CHD from genetics and epigenetics to discuss the role of these factors in the development of CHD. The interactions between genetic and epigenetic in the pathogenesis of CHD are also elaborated. Chromosome abnormalities and gene mutations in genetics, and DNA methylations, histone modifications and on-coding RNAs in epigenetics are summarized in detail. We hope the summative knowledge of these etiologies may be useful for improved diagnosis and further elucidation of CHD so that morbidity and mortality of children with CHD can be reduced in the near future.

Neonates with Right Aortic Arch Requiring Arch Reconstruction: A Single-Institution Experience

BACKGROUND

Reconstruction of a right aortic arch (RAA) is rarely required in the newborn period and has rarely been reported.

METHODS

All patients who underwent a RAA repair in the neonatal period from a single institution were retrospectively reviewed. The primary outcome measures included survival, complications, and reintervention.

RESULTS

Between 1984 to 2020, 15 patients were identified. Nine patients (60%) presented with an interrupted aortic arch (IAA), five (33%) with a hypoplastic arch, and one (7%) with anomalous origin of the brachiocephalic vessels. All patients had associated complex congenital heart disease. Median age at surgery was six days (range, 2-29), median weight 3.11 kg (range, 2.5-4.18). Genetic syndromes were prevalent and 77% of IAA patients had DiGeorge syndrome. Surgical techniques included end-to-side (27%), end-to-end (27%) or side-to-side anastomosis (13%) and placement of an interposition graft (7%). 65% required patch augmentation. Median intensive care unit and total hospital length of stay were 20 days (range, 7 - 92) and 28 days (range, 10 - 240), respectively. At median follow-up of 3.97 years (range, 0.19-36), 13 of 15 (87%) patients were alive. Vocal cord paralysis was found in 27%, hemidiaphragm paralysis in 13% and significant airway compression in 27%. Overall, 27% patients required reintervention on the aortic arch; two surgical and two percutaneous balloon dilation.

CONCLUSIONS

RAA reconstruction in the newborn period is rare and associated with complex lesions with an acceptable reintervention rate.

In Vivo and In Vitro Genetic Models of Congenital Heart Disease

Congenital cardiovascular malformations represent the most common type of birth defect and encompass a spectrum of anomalies that range from mild to severe. The etiology of congenital heart disease (CHD) is becoming increasingly defined based on prior epidemiologic studies that supported the importance of genetic contributors and technological advances in human genome analysis. These have led to the discovery of a growing number of disease-contributing genetic abnormalities in individuals affected by CHD. The ever-growing population of adult CHD survivors, which are the result of reductions in mortality from CHD during childhood, and this newfound genetic knowledge have led to important questions regarding recurrence risks, the mechanisms by which these defects occur, the potential for novel approaches for prevention, and the prediction of long-term cardiovascular morbidity in adult CHD survivors. Here, we will review the current status of genetic models that accurately model human CHD as they provide an important tool to answer these questions and test novel therapeutic strategies.

Prevalence of associated extracardiac anomalies in prenatally diagnosed congenital heart diseases

Objective

To investigate the prevalence of extracardiac anomalies (ECA) in prenatally diagnosed congenital heart diseases (CHD), and to provide more information for counseling of women with prenatally diagnosed fetal CHD.

Methods

This was a retrospective cohort study of 791 cases of fetal CHD diagnosed by prenatal ultrasound from January 2005 to April 2018. Associated ECAs included extracardiac structural malformation (ECM), chromosomal anomaly, and 22q11.2 microdeletion. CHD was classified into 10 groups according to a modified anatomic and clinical classification of congenital heart defects.

Results

The overall prevalence of ECA in our CHD cohort was 28.6% (226/791): ECM, 25.3%; chromosomal anomaly, 11.7%; and 22q11.2 microdeletion, 5.5%. For those with ECM, ventricular septal defect (VSD) had the highest prevalence (34.5%), followed by anomalies of atrioventricular junctions and valves (28.8%) and heterotaxy (26.9%). For those with chromosomal anomaly, anomalies of atrioventricular junctions and valves had the highest prevalence (37.5%), followed by anomalies of atria and interatrial communications (25.0%) and VSD (22.9%). 22q11.2 microdeletion was detected only in those with anomalies of extrapericardial arterial trunks (14.3%) or ventricular outflow tracts (6.4%).

Conclusion

ECM, chromosomal anomaly, and 22q11.2 microdeletion have different prevalence according to the type of CHD.

Cell-Extracellular Matrix Interactions Play Multiple Essential Roles in Aortic Arch Development

RATIONALE

Defects in the morphogenesis of the fourth pharyngeal arch arteries (PAAs) give rise to lethal birth defects. Understanding genes and mechanisms regulating PAA formation will provide important insights into the etiology and treatments for congenital heart disease.

OBJECTIVE

Cell-ECM (extracellular matrix) interactions play essential roles in the morphogenesis of PAAs and their derivatives, the aortic arch artery and its major branches; however, their specific functions are not well-understood. Previously, we demonstrated that integrin α5β1 and Fn1 (fibronectin) expressed in the Isl1 lineages regulate PAA formation. The objective of the current studies was to investigate cellular mechanisms by which integrin α5β1 and Fn1 regulate aortic arch artery morphogenesis.

METHODS AND RESULTS

Using temporal lineage tracing, whole-mount confocal imaging, and quantitative analysis of the second heart field (SHF) and endothelial cell (EC) dynamics, we show that the majority of PAA EC progenitors arise by E7.5 in the SHF and contribute to pharyngeal arch endothelium between E7.5 and E9.5. Consequently, SHF-derived ECs in the pharyngeal arches form a plexus of small blood vessels, which remodels into the PAAs by 35 somites. The remodeling of the vascular plexus is orchestrated by signals dependent on the pharyngeal ECM microenvironment, extrinsic to the endothelium. Conditional ablation of integrin α5β1 or Fn1 in the Isl1 lineages showed that signaling by the ECM regulates aortic arch artery morphogenesis at multiple steps: (1) accumulation of SHF-derived ECs in the pharyngeal arches, (2) remodeling of the EC plexus in the fourth arches into the PAAs, and (3) differentiation of neural crest-derived cells adjacent to the PAA endothelium into vascular smooth muscle cells.

CONCLUSIONS

PAA formation is a multistep process entailing dynamic contribution of SHF-derived ECs to pharyngeal arches, the remodeling of endothelial plexus into the PAAs, and the remodeling of the PAAs into the aortic arch artery and its major branches. Cell-ECM interactions regulated by integrin α5β1 and Fn1 play essential roles at each of these developmental stages.

Left subclavian artery originating from left pulmonary artery in DiGeorge syndrome

Left subclavian artery originating from the left pulmonary artery is a rare aortic arch anomaly. Herein, we, for the first time in Turkey, present a case of left subclavian artery originating from the left pulmonary artery via ductus arteriosus in DiGeorge syndrome and causing subclavian steal syndrome.

Isolated subclavian or brachiocephalic arteries with tetralogy of Fallot, left retro-aortic brachiocephalic vein

BACKGROUND

Isolated subclavian or brachiocephalic artery are uncommon aortic arch anomalies. Here we report the anatomy and histology of this disease.

METHODS

Four cases of congenital isolated subclavian or brachiocephalic artery in fetuses are described.

RESULTS

We identified one case of right aortic arch with isolated left subclavian artery associated with the tetralogy of Fallot, two cases of right aortic arch with isolated left brachiocephalic artery (one case with left retro-aortic brachiocephalic vein), and one case of left aortic arch with isolated right subclavian artery associated with coarctation of the aorta and cervical aortic arch. The proximal subclavian or brachiocephalic artery is arterial duct.

CONCLUSION

Aortic arches with an isolated subclavian or brachiocephalic artery are often associated with the tetralogy of Fallot. It also can be associated with rare abnormalities such as left retro-aortic brachiocephalic vein or cervical aortic arch. Isolated LBA can be associated with microdeletion chromosome 22q11.

The Prevalence of Congenital Heart Diseases in Syndromic Children at King Khalid National Guard Hospital from 2005 to 2016

Background Congenital heart diseases (CHDs) are abnormalities that present in the heart since birth and are one of the leading causes of infant mortality in the world. CHDs are more common among children with dysmorphic syndromes. The current study aims to estimate the prevalence of many CHDs in different dysmorphic syndromes. Methods This was a retrospective chart review study conducted on all dysmorphic syndrome patients who attended genetic clinics at King Khalid National Guard Hospital in King Abdulaziz Medical City (KAMC), Jeddah, Saudi Arabia from 2005 to 2016. Dysmorphic pediatric patients less than 14 years old who had genetic testing to confirm their diagnosis were included in the study. Patients who did not have any previous echocardiography were excluded. Results A total of 212 individuals (47% males and 53% females) were included. Eighty-five percent of Down syndrome patients had CHDs, and the most common CHD was an atrial septal defect (ASD) (51%). In patients with Turner syndrome, 45% of them had CHDs, and bicuspid aortic valve (BAV) (40%) was the most common defect. In DiGeorge syndrome, 81% of patients had CHDs, and ventricular septal defect (VSD) (41%) was the most common. In Williams syndrome, 83% of patients had CHDs. All patients with Noonan, Edwards, CHARGE (coloboma, heart defects, atresia choanae (also known as choanal atresia), growth retardation, genital abnormalities, and ear abnormalities), and Rubinstein-Taybi syndromes were found to have CHDs. In Patau syndrome and Joubert syndrome, 50% of patients in each had CHDs. Patients with Prader Willi syndrome had normal findings in the echocardiogram. Conclusion The highest prevalence of CHDs was found in Down syndrome. This study has a significant impact on the future of managing and directing the resources to improve the quality of life for syndromic patients. Further studies are needed to confirm these findings and to increase the local data in the field of CHDs in Saudi Arabia among syndromic patients.

Impact of a 22q11.2 Microdeletion on Adult All-Cause Mortality in Tetralogy of Fallot Patients

BACKGROUND

Because of the importance of identifying factors that affect late outcomes in the increasing population of those with tetralogy of Fallot (TOF), we aimed to determine the effect of a 22q11.2 microdeletion on adult mortality, while accounting for pulmonary atresia, known to be enriched in 22q11.2 deletion syndrome (22q11.2DS).

METHODS

We studied 612 individuals with TOF recruited as adults at a single centre, 80 (13.1%) with molecularly confirmed 22q11.2 deletions and 532 without 22q11.2DS, followed for a total of 5961.3 person-years. Using a case-control design, Cox proportional hazard regression and Kaplan-Meier curves, we evaluated the effect of a 22q11.2 deletion on mortality and survival.

RESULTS

All-cause mortality was 1.87% per person-year in the 22q11.2DS-TOF group and 0.80% in the other-TOF group. The presence of a 22q11.2 microdeletion was a significant predictor of adult mortality in TOF (hazard ratio, 5.00; P < 0.0001), after accounting for pulmonary atresia (hazard ratio, 2.71; P = 0.0106) and other factors. Overall, individuals with 22q11.2DS died on average 17.7 years earlier (P = 0.0055) than others with TOF, predominantly of cardiovascular causes, with proportionately more sudden cardiac deaths in those with 22q11.2DS-TOF (n = 5 [38.5%] vs n = 5 [11.9%], other-TOF; P = 0.0447). Kaplan-Meier curves showed reduced survival for those with 22q11.2DS (P < 0.0001); probability of survival to age 45 years, without pulmonary atresia, was 72% (22q11.2DS-TOF) and 98% (other-TOF).

CONCLUSIONS

The results suggest that the 22q11.2 deletion significantly contributes to premature mortality in adults with TOF, mediated only in part by greater anatomic complexity. The interpretation of late outcome data in TOF will likely benefit from further genetic subtyping.

Prenatal screening of DiGeorge (22q11.2 deletion) syndrome by abnormalities of the great arteries among Thai pregnant women

Objective

22q11.2DS (deletion syndrome) is one of the common serious anomalies resulting in high perinatal morbidity and mortality rate. Nevertheless, prenatal diagnosis of 22q11.2DS in Southeast Asia has never been described and its prevalence in prenatal series has never been explored. The objective of this study was to describe the experience of prenatal diagnosis of 22q11.2DS in the Thai population and to determine its prevalence among fetuses prenatally diagnosed with abnormalities of the great arteries.

Methods

A prospective study was conducted on pregnant Thai women prenatally diagnosed with abnormalities of the great arteries in the second trimester. The recruited cases were investigated for fetal 22q11.2 deletion by in situ hybridization with a probe specific to the DiGeorge/VCFS TUPLE 1 region located on chromosome 22 for the locus D22S75, and 22qter for a telomere specific sequence clone as the control region.

Results

Five out of the 42 (11.9%) fetuses with abnormalities of the great arteries meeting the inclusion criteria were proven to have 22q11.2DS. The most common abnormalities were the tetralogy of Fallot (or variants) and right-sided aortic arch, followed by a thymic hypoplasia.

Conclusion

As observed in the western countries, we have documented that, among pregnant Thai women, 22q11.2DS is highly prevalent in fetuses with abnormalities of the great arteries (approximately 12%). This information is important when counselling couples to undergo prenatal testing for 22q11.2DS, since this information is vital in the patients' decision of termination or continuation of pregnancy and in a well-prepared management of the affected child.

22q11.2 deletion syndrome and congenital heart disease

The 22q11.2 deletion syndrome has an estimated prevalence of 1 in 4-6,000 livebirths. The phenotype varies widely; the most common features include: facial dysmorphia, hypocalcemia, palate and speech disorders, feeding and gastrointestinal disorders, immunodeficiency, recurrent infections, neurodevelopmental and psychiatric disorders, and congenital heart disease. Approximately 60-80% of patients have a cardiac malformation most commonly including a subset of conotruncal defects (tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B), conoventricular and/or atrial septal defects, and aortic arch anomalies. Cardiac patients with a 22q11.2 deletion do not generally experience higher mortality upon surgical intervention but suffer more peri-operative complications than their non-syndromic counterparts. New guidelines suggest screening for a 22q11.2 deletion in the patient with tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B, conoventricular septal defects as well as those with an isolated aortic arch anomaly. Early identification of a 22q11.2 deletion in the neonate or infant when other syndromic features may not be apparent allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features. Screening the at-risk child or adult allows for important age-specific clinical, neurodevelopmental, psychiatric, and reproductive issues to be addressed.

Genetic abnormalities/syndromes significantly impact perioperative outcomes of conotruncal heart defects

Objectives:

The main objective of the study is to characterize the effects of genetic abnormalities/syndromes (GA/S) on perioperative outcomes of cardiac surgeries involving repair of conotruncal heart defects (CTHD).

Design:

The study involves a single-center retrospective analysis of patients who underwent complete repair of CTHDs (tetralogy of Fallot [TOF], truncus arteriosus, interrupted aortic arch, and ventricular septal defect with coarctation) between January 2000 and December 2015. The primary outcome was the post operative length of stay (PLOS). The secondary outcomes were mortality, cardiac complications, hematologic complications, infections, and number of medications-at-discharge.

Setting:

Cardiac intensive care unit in a tertiary pediatric hospital in South Florida that performs around 300 open-heart surgeries a year.

Subjects:

A total of 177 patients with CTHDs who underwent cardiac surgeries in the stated time period were included in the final study cohort.

Measurements and Main Results:

Majority of patients had TOF (72.5%) and 46 (26%) had GA/S. The most common GA/S was 22q11 deletion (37%). PLOS was significantly increased in patients with GA/S (P < 0.05). Patients with GA/S were 4.5 times more likely to have a postoperative cardiac complication, 4.2 times more likely to have a postoperative infection, and received 1.6 times more medications at discharge than those without GA/S. However, GA/S was not associated with increased perioperative mortality. Black patients were three times more likely to have a longer PLOS than White patients.

Conclusions:

Perioperative outcomes in patients with GA/S suggested an increased residual cardiovascular disease and increased resource usage. Notably, this is the first study demonstrating the effect of race and ethnicity on PLOS in CTHD patients.

Pax9 is required for cardiovascular development and interacts with Tbx1 in the pharyngeal endoderm to control 4th pharyngeal arch artery morphogenesis

Developmental defects affecting the heart and aortic arch arteries are a significant phenotype observed in individuals with 22q11 deletion syndrome and are caused by a microdeletion on chromosome 22q11. TBX1, one of the deleted genes, is expressed throughout the pharyngeal arches and is considered a key gene, when mutated, for the arch artery defects. Pax9 is expressed in the pharyngeal endoderm and is downregulated in Tbx1 mutant mice. We show here that Pax9-deficient mice are born with complex cardiovascular malformations that affect the outflow tract and aortic arch arteries with failure of the 3rd and 4th pharyngeal arch arteries to form correctly. Transcriptome analysis indicated that Pax9 and Tbx1 may function together, and mice double heterozygous for Tbx1/Pax9 presented with a significantly increased incidence of interrupted aortic arch when compared with Tbx1 heterozygous mice. Using a novel Pax9Cre allele, we demonstrated that the site of this Tbx1-Pax9 genetic interaction is the pharyngeal endoderm, therefore revealing that a Tbx1-Pax9-controlled signalling mechanism emanating from the pharyngeal endoderm is required for crucial tissue interactions during normal morphogenesis of the pharyngeal arch artery system.

Summary: A strong genetic interaction between Tbx1 and Pax9 that leads to 4th PAA-derived defects in double heterozygous mice is cell-autonomous within the pharyngeal endoderm.

WHIM Syndrome: from Pathogenesis Towards Personalized Medicine and Cure

WHIM syndrome is a rare combined primary immunodeficiency disease named by acronym for the diagnostic tetrad of warts, hypogammaglobulinemia, infections, and myelokathexis. Myelokathexis is a unique form of non-cyclic severe congenital neutropenia caused by accumulation of mature and degenerating neutrophils in the bone marrow; monocytopenia and lymphopenia, especially B lymphopenia, also commonly occur. WHIM syndrome is usually caused by autosomal dominant mutations in the G protein-coupled chemokine receptor CXCR4 that impair desensitization, resulting in enhanced and prolonged G protein- and β-arrestin-dependent responses. Accordingly, CXCR4 antagonists have shown promise as mechanism-based treatments in phase 1 clinical trials. This review is based on analysis of all 105 published cases of WHIM syndrome and covers current concepts, recent advances, unresolved enigmas and controversies, and promising future research directions.

T-box genes and retinoic acid signaling regulate the segregation of arterial and venous pole progenitor cells in the murine second heart field

The arterial and venous poles of the mammalian heart are hotspots of congenital heart defects (CHD) such as those observed in 22q11.2 deletion (or DiGeorge) and Holt-Oram syndromes. These regions of the heart are derived from late differentiating cardiac progenitor cells of the Second Heart Field (SHF) located in pharyngeal mesoderm contiguous with the elongating heart tube. The T-box transcription factor Tbx1, encoded by the major 22q11.2 deletion syndrome gene, regulates SHF addition to both cardiac poles from a common progenitor population. Despite the significance of this cellular addition the mechanisms regulating the deployment of common progenitor cells to alternate cardiac poles remain poorly understood. Here we demonstrate that Tbx5, mutated in Holt-Oram syndrome and essential for venous pole development, is activated in Tbx1 expressing cells in the posterior region of the SHF at early stages of heart tube elongation. A subset of the SHF transcriptional program, including Tbx1 expression, is subsequently downregulated in Tbx5 expressing cells, generating a transcriptional boundary between Tbx1-positive arterial pole and Tbx5-positive venous pole progenitor cell populations. We show that normal downregulation of the definitive arterial pole progenitor cell program in the posterior SHF is dependent on both Tbx1 and Tbx5. Furthermore, retinoic acid (RA) signaling is required for Tbx5 activation in Tbx1-positive cells and blocking RA signaling at the time of Tbx5 activation results in atrioventricular septal defects at fetal stages. Our results reveal sequential steps of cardiac progenitor cell patterning and provide mechanistic insights into the origin of common forms of CHD.

Rare Copy Number Variations Might Not be Involved in the Molecular Pathogenesis of PA-IVS in an Unselected Chinese Cohort

Congenital heart defect (CHD) is one of the most common birth defects in China, while pulmonary atresia with intact ventricular septum (PA-IVS) is the life-threatening form of CHD. Numerous previous studies revealed that rare copy number variants (CNVs) play important roles in CHD, but little is known about the prevalence and role of rare CNVs in PA-IVS. In this study, we conducted a genome-wide scanning of rare CNVs in an unselected cohort consisted of 54 Chinese patients with PA-IVS and 20 patients with pulmonary atresia with ventricular septal defect (PA-VSD). CNVs were identified in 6/20 PA-VSD patients (30%), and three of these CNVs (15%) were considered potentially pathogenic. Two pathogenic CNVs occurred at a known CHD locus (22q11.2) and one likely pathogenic deletion located at 13q12.12. However, no rare CNVs were detected in patients with PA-IVS. Potentially pathogenic CNVs were more enriched in PA-VSD patients than in PA-IVS patients (p = 0.018). No rare CNVs were detected in patients with PA-IVS in our study. PA/IVS might be different from PA/VSD in terms of genetics as well as anatomy.

Identification of Rare Copy Number Variants Associated With Pulmonary Atresia With Ventricular Septal Defect

Copy number variants (CNVs) are major variations contributing to the gene heterogeneity of congenital heart diseases (CHD). pulmonary atresia with ventricular septal defect (PA-VSD) is a rare form of cyanotic CHD characterized by complex manifestations and the genetic determinants underlying PA-VSD are still largely unknown. We investigated rare CNVs in a recruited cohort of 100 unrelated patients with PA-VSD, PA-IVS, or TOF and a population-matched control cohort of 100 healthy children using whole-exome sequencing. Comparing rare CNVs in PA-VSD cases and that in PA-IVS or TOF positive controls, we observed twenty-two rare CNVs only in PA-VSD, five rare CNVs only in PA-VSD and TOF as well as thirteen rare CNVs only in PA-VSD and PA-IVS. Six of these CNVs were considered pathogenic or potentially pathogenic to PA-VSD: 16p11.2 del (PPP4C and TBX6), 5q35.3 del (FLT4), 5p13.1 del (RICTOR), 6p21.33 dup (TNXB), 7p15.2 del (HNRNPA2B1), and 19p13.3 dup (FGF22). The gene networks showed that four putative candidate genes for PA-VSD, PPP4C, FLT4, RICTOR, and FGF22 had strong interaction with well-known cardiac genes relevant to heart or blood vessel development. Meanwhile, the analysis of transcriptome array revealed that PPP4C and RICTOR were also significantly expressed in human embryonic heart. In conclusion, three rare novel CNVs were identified only in PA-VSD: 16p11.2 del (PPP4C), 5q35.3 del (FLT4) and 5p13.1 del (RICTOR), implicating novel candidate genes of interest for PA-VSD. Our study provided new insights into understanding for the pathogenesis of PA-VSD and helped elucidate critical genes for PA-VSD.

Persistent truncus arteriosus with absent semilunar valve in first trimester

Persistent truncus arteriosus (PTA) is a relatively uncommon congenital heart disease, accounting for approximately 0.7-1.4% of all congenital cardiac abnormalities worldwide. PTA is usually accompanied by a single semilunar valve, with leaflets ranging from one to six in number. However, absent semilunar valve (ASV) is rarely seen in PTA. Here, we report a case of prenatally diagnosed PTA accompanied by ASV (PTA-ASV) confirmed by postmortem autopsy.

Common Arterial Trunk: Physiology, Imaging, and Management

Common arterial trunk (CAT), or truncus arteriosus, is a rare form of cyanotic congenital heart disease and is highly associated with DiGeorge syndrome (microdeletion 22q11.2). Prenatal diagnosis is highly feasible, allowing proper delivery planning and postnatal management. The clinical presentation is highly variable depending on the anatomical variation; however, most commonly presenting with mild cyanosis and significant tachypnea, although these patients can often go undetected in the immediate newborn period. Transthoracic echocardiography is adequate for diagnosis and detailed anatomical delineation in the majority. Additional imaging modalities such as cardiac catheterization, computed tomography angiography, or cardiac magnetic resonance imaging can be helpful in those with more complex pulmonary artery (PA) or aortic anatomy, or in the older repaired. The surgical management of CAT is complete repair in the neonatal period with resection of branch PAs from the CAT with placement of a right ventricular (RV)-to-PA conduit and patch closure of the ventricular septal defect. Overall surgical outcomes are excellent in most centers, with the expectation that the child will eventually outgrow the RV-to-PA conduit and require reoperation. Other potential reoperations or postsurgical interventions in addition to the RV-to-PA conduit may involve the truncal valve or branch PAs.