Molecular Pathways and Animal Models of Atrioventricular Septal Defect.

The development of a fully functional four-chambered heart is critically dependent on the correct formation of the structures that separate the atrial and ventricular chambers. Perturbation of this process typically results in defects that allow mixing of oxygenated and deoxygenated blood. Atrioventricular septal defects (AVSD) form a class of congenital heart malformations that are characterized by the presence of a primary atrial septal defect (pASD), a common atrioventricular valve (cAVV), and frequently also a ventricular septal defect (VSD). While AVSD were historically considered to result from failure of the endocardial atrioventricular cushions to properly develop and fuse, more recent studies have determined that inhibition of the development of other components of the atrioventricular mesenchymal complex can lead to AVSDs as well. The role of the dorsal mesenchymal protrusion (DMP) in AVSD pathogenesis has been well-documented in studies using animal models for AVSDs, and in addition, preliminary data suggest that the mesenchymal cap situated on the leading edge of the primary atrial septum may be involved in certain situations as well. In this chapter, we review what is currently known about the molecular mechanisms and animal models that are associated with the pathogenesis of AVSD.

Germline and Mosaic Variants in PRKACA and PRKACB Cause a Multiple Congenital Malformation Syndrome.

PRKACA and PRKACB code for two catalytic subunits (Cα and Cß) of cAMP-dependent protein kinase (PKA), a pleiotropic holoenzyme that regulates numerous fundamental biological processes such as metabolism, development, memory, and immune response. We report seven unrelated individuals presenting with a multiple congenital malformation syndrome in whom we identified heterozygous germline or mosaic missense variants in PRKACA or PRKACB. Three affected individuals were found with the same PRKACA variant, and the other four had different PRKACB mutations. In most cases, the mutations arose de novo, and two individuals had offspring with the same condition. Nearly all affected individuals and their affected offspring shared an atrioventricular septal defect or a common atrium along with postaxial polydactyly. Additional features included skeletal abnormalities and ectodermal defects of variable severity in five individuals, cognitive deficit in two individuals, and various unusual tumors in one individual. We investigated the structural and functional consequences of the variants identified in PRKACA and PRKACB through the use of several computational and experimental approaches, and we found that they lead to PKA holoenzymes which are more sensitive to activation by cAMP than are the wild-type proteins. Furthermore, expression of PRKACA or PRKACB variants detected in the affected individuals inhibited hedgehog signaling in NIH 3T3 fibroblasts, thereby providing an underlying mechanism for the developmental defects observed in these cases. Our findings highlight the importance of both Cα and Cß subunits of PKA during human development.

OFCD syndrome and extraembryonic defects are revealed by conditional mutation of the Polycomb-group repressive complex 1.1 (PRC1.1) gene BCOR.

BCOR is a critical regulator of human development. Heterozygous mutations of BCOR in females cause the X-linked developmental disorder Oculofaciocardiodental syndrome (OFCD), and hemizygous mutations of BCOR in males cause gestational lethality. BCOR associates with Polycomb group proteins to form one subfamily of the diverse Polycomb repressive complex 1 (PRC1) complexes, designated PRC1.1. Currently there is limited understanding of differing developmental roles of the various PRC1 complexes. We therefore generated a conditional exon 9-10 knockout Bcor allele and a transgenic conditional Bcor expression allele and used these to define multiple roles of Bcor, and by implication PRC1.1, in mouse development. Females heterozygous for Bcor exhibiting mosaic expression due to the X-linkage of the gene showed reduced postnatal viability and had OFCD-like defects. By contrast, Bcor hemizygosity in the entire male embryo resulted in embryonic lethality by E9.5. We further dissected the roles of Bcor, focusing on some of the tissues affected in OFCD through use of cell type specific Cre alleles. Mutation of Bcor in neural crest cells caused cleft palate, shortening of the mandible and tympanic bone, ectopic salivary glands and abnormal tongue musculature. We found that defects in the mandibular region, rather than in the palate itself, led to palatal clefting. Mutation of Bcor in hindlimb progenitor cells of the lateral mesoderm resulted in 2/3 syndactyly. Mutation of Bcor in Isl1-expressing lineages that contribute to the heart caused defects including persistent truncus arteriosus, ventricular septal defect and fetal lethality. Mutation of Bcor in extraembryonic lineages resulted in placental defects and midgestation lethality. Ubiquitous over expression of transgenic Bcor isoform A during development resulted in embryonic defects and midgestation lethality. The defects we have found in Bcor mutants provide insights into the etiology of the OFCD syndrome and how BCOR-containing PRC1 complexes function in development.

The first post-natal clinical description of true mosaic complete tetrasomy 21: A case report.

Tetrasomy 21 is a rare occurrence. Only 14 cases have been reported in the literature, 8 of which are partial tetrasomy cases and 6 which are complete tetrasomy cases. Of the incidences, no proband with true complete tetrasomy 21 has survived the neonatal period. We report complete mosaic tetrasomy 21 in a female infant with the typical Down syndrome phenotype, including Hirschsprung's disease and atrioventricular (AV) canal defect. This is in contrast to cases of partial tetrasomy 21, which often have an atypical trisomy 21 presentation and multiple nonspecific traits, including short stature, microcephaly, and developmental delays. This case demonstrates the difference in clinical presentation between the partial and complete subtype of tetrasomy 21 and provides the first postnatal clinical picture of an infant with true mosaic complete tetrasomy 21.

Accuracy of Fetal Echocardiography in Defining Pulmonary Artery Anatomy and Source of Pulmonary Blood flow in Pulmonary Atresia with Ventricular Septal Defect (PA/VSD).

Precise delineation of central and branch pulmonary artery anatomy, patent ductus arteriosus, and major aorto-pulmonary collateral artery anatomy in the fetal diagnosis of pulmonary atresia with ventricular septal defect is challenging but important to prenatal counseling and postnatal management. We aimed to evaluate the accuracy of fetal echocardiography to determine these anatomical nuances in pulmonary atresia with ventricular septal defect. This was a retrospective, single-institution, 10-year chart review of consecutive prenatal diagnosis of pulmonary atresia with ventricular septal defect for assessment of pulmonary artery, patent ductus arteriosus, and major aorto-pulmonary collateral artery anatomy and comparison with postnatal imaging including echocardiography, cardiac catheterization, and computerized tomography angiography. Twenty-six fetuses were diagnosed with pulmonary atresia with ventricular septal defect during the review period and complete postnatal follow-up was available in 18, all confirming the basic prenatal diagnosis. Fetal echocardiography accurately predicted central and branch pulmonary artery anatomy in 16 (89%) [confluent in 14, discontinuous in 2], patent ductus arteriosus status in 15 (83%) [present in 10, absent in 5], and major aorto-pulmonary collateral arteries in 17 (94%) [present in 9, absent in 8]. Accuracy increased to 100% for pulmonary artery anatomy (16/16) and major aorto-pulmonary collateral artery (17/17) when excluding patients whose anatomy was reported as uncertain on fetal echocardiography. Fetal echocardiography can provide accurate anatomical details in the vast majority of fetuses with pulmonary atresia with ventricular septal defect. This allows for more anatomy-specific counseling, prognostication, and improved selection of postnatally available management options.

Prenatal exome sequencing in fetuses with congenital heart defects.

The genetic diagnosis of congenital heart defects (CHDs) is challenging because of genetic and phenotypic heterogeneity. The aim of our study was to evaluate the clinical value of whole exome sequencing (WES) in the prenatal diagnosis of CHDs in a large cohort. Trio-based WES was performed in 260 fetuses with CHDs negative for karyotype and chromosome microarray analysis results. WES produced a diagnostic yield of 10% (26/260) in the entire cohort. Relative high diagnostic rate was observed in cases with cardiac rhabdomyoma (60%), complex CHDs (16.7%), septal defect (14.0%), and conotruncal defect (9.9%). There was no significant difference between the diagnostic yields in simple and complex CHDs groups (9.9% vs 16.7%), and in non-isolated and isolated CHDs groups (15.7% vs 7.9%). The diagnostic yields in cases with CHDs with soft markers, CHDs with fetal growth restriction, and CHDs with other structural anomalies (syndromic CHDs) were 0 (0/13), 50% (1/2) and 18.2% (10/55), respectively. Variants of unknown significance were detected in 16 (6.2%) fetuses, and secondary findings in 7 (2.7%) cases. Variants in 14 candidate genes were identified. Our study demonstrates an incremental diagnostic yield by trio-based WES in the prenatal diagnosis of CHDs after routine tests, not as high as expected.

Impact of sample collection participation on the validity of estimated measures of association in the National Birth Defects Prevention Study when assessing gene-environment interactions.

To better understand the impact that nonresponse for specimen collection has on the validity of estimates of association, we examined associations between self-reported maternal periconceptional smoking, folic acid use, or pregestational diabetes mellitus and six birth defects among families who did and did not submit buccal cell samples for DNA following a telephone interview as part of the National Birth Defects Prevention Study (NBDPS). Analyses included control families with live born infants who had no birth defects (N = 9,465), families of infants with anorectal atresia or stenosis (N = 873), limb reduction defects (N = 1,037), gastroschisis (N = 1,090), neural tube defects (N = 1,764), orofacial clefts (N = 3,836), or septal heart defects (N = 4,157). Estimated dates of delivery were between 1997 and 2009. For each exposure and birth defect, odds ratios and 95% confidence intervals were calculated using logistic regression stratified by race-ethnicity and sample collection status. Tests for interaction were applied to identify potential differences between estimated measures of association based on sample collection status. Significant differences in estimated measures of association were observed in only four of 48 analyses with sufficient sample sizes. Despite lower than desired participation rates in buccal cell sample collection, this validation provides some reassurance that the estimates obtained for sample collectors and noncollectors are comparable. These findings support the validity of observed associations in gene-environment interaction studies for the selected exposures and birth defects among NBDPS participants who submitted DNA samples.

Cilia gene mutations cause atrioventricular septal defects by multiple mechanisms.

Atrioventricular septal defects (AVSDs) are a common severe form of congenital heart disease (CHD). In this study we identified deleterious non-synonymous mutations in two cilia genes, Dnah11 and Mks1, in independent N-ethyl-N-nitrosourea-induced mouse mutant lines with heritable recessive AVSDs by whole-exome sequencing. Cilia are required for left/right body axis determination and second heart field (SHF) Hedgehog (Hh) signaling, and we find that cilia mutations affect these requirements differentially. Dnah11avc4 did not disrupt SHF Hh signaling and caused AVSDs only concurrently with heterotaxy, a left/right axis abnormality. In contrast, Mks1avc6 disrupted SHF Hh signaling and caused AVSDs without heterotaxy. We performed unbiased whole-genome SHF transcriptional profiling and found that cilia motility genes were not expressed in the SHF whereas cilia structural and signaling genes were highly expressed. SHF cilia gene expression predicted the phenotypic concordance between AVSDs and heterotaxy in mice and humans with cilia gene mutations. A two-step model of cilia action accurately predicted the AVSD/heterotaxyu phenotypic expression pattern caused by cilia gene mutations. We speculate that cilia gene mutations contribute to both syndromic and non-syndromic AVSDs in humans and provide a model that predicts the phenotypic consequences of specific cilia gene mutations.

Anatomy of the retro-oesophageal major aortopulmonary collateral arteries in patients with pulmonary atresia with ventricular septal defect: results from preoperative CTA.

OBJECTIVES: To assess the frequency and anatomy of retro-oesophageal aortopulmonary collateral arteries (REMs) in patients with pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries (PA-VSD-MAPCAs). METHODS: A total of 130 consecutive PA-VSD-MAPCA patients with preoperative CT angiography (CTA) data who underwent cardiac surgery were included. A detailed analysis of MAPCA anatomy was performed using CTA. RESULTS: A REM was identified in 82/130 included patients (63 %). A total of 277 MAPCAs were observed in these 82 patients and were divided into groups based on REM status: REM (n=94) and non-REM (n=183). Compared with non-REMs, REMs originated at a lower level and tended to originate from the lateral side of the aorta (all p<0.01). REMs had a higher probability of suffering stenosis (χ2=9.79, p<0.01), particularly midsegment stenosis (χ2=6.27, p=0.01). REMs were more posterior to the bronchus at the pulmonary hilum than non-REMs (91 % vs. 51 %) (χ2=50.81, p<0.01). CONCLUSIONS: REMs are associated with a lower level, more lateral origin, stenosis and more posterior location with respect to the bronchus at the pulmonary hilum. The unique CTA data obtained in this study showing the anatomy of REMs will be highly useful for surgeons in identifying REMs. KEY POINTS: • Unifocalization is a very important surgical approach for PA-VSD-MAPCA patients. • The anatomical variability of REMs becomes clinically relevant in unifocalization. • CTA provides a non-invasive way to observe the anatomy of REMs. • REMs are associated with lower level, more lateral origin, more midsegment stenosis. • REMs tend to be posterior to the bronchus at the pulmonary hilum.

Dysregulated endocardial TGFß signaling and mesenchymal transformation result in heart outflow tract septation failure.

Heart outflow tract septation in mouse embryos carrying mutations in retinoic acid receptor genes fails with complete penetrance. In this mutant background, ectopic TGFß signaling in the distal outflow tract is responsible for septation failure, but it was uncertain what tissue was responsive to ectopic TGFß and why this response interfered with septation. By combining RAR gene mutation with tissue-specific Cre drivers and a conditional type II TGFß receptor (Tgfbr2) allele, we determined that ectopic activation of TGFß signaling in the endocardium is responsible for septation defects. Ectopic TGFß signaling results in ectopic mesenchymal transformation of the endocardium and thereby in improperly constituted distal OFT cushions. Our analysis highlights the interactions between myocardium, endocardium, and neural crest cells in outflow tract morphogenesis, and demonstrates the requirement for proper TGFß signaling in outflow tract cushion organization and septation.

A genetic variant in a homocysteine metabolic gene that increases the risk of congenital cardiac septal defects in Han Chinese populations.

Elevated homocysteine levels are known to be a risk factor for congenital cardiac septal defects (CCSDs), but the mechanism underlying this effect is unknown. The genetic variants that were significantly associated with circulating homocysteine concentrations have been systematically identified through the genome-wide association studies of one-carbon core metabolites. To examine the role of the genome-wide significant homocysteine related variants in the occurrence of CCSDs, we investigated the association between these variants and CCSDs in Han Chinese populations. Five variants of the genome-wide significant homocysteine-related genes were selected for analysis in two stages of case-controlled studies with a total of 904 CCSD patients and 997 controls. SYT9 expression was detected in human cardiovascular tissue using qRT-PCR. The intronic variant rs11041321 of the SYT9 gene was associated with an increased risk of developing CCSDs in both the separate and combined case-controlled studies. Combined samples from the two stage cohorts had a significant elevation in CCSD risk for the T allele (OR = 1.43, P = 2.6 × 10-6 ), CT genotype and TT genotype (CT: OR = 1.30, TT: OR = 2.21; P = 1 × 10-4 ) compared with the wild-type C allele and CC genotype, respectively. The risky T allele carriers exhibited decreased SYT9 mRNA expression, compared with wild-type C allele carriers. The intronic SYT9 variant rs11041321, which exhibits a significant genome-wide association with circulating homocysteine, was associated with the occurrence of CCSDs. This finding helps to characterize the unexpected role of SYT9 in homocysteine metabolism and the development of CCSDs, which further highlighted the interplay of diet, genetics, and human birth defects. © 2017 IUBMB Life, 69(9):700-705, 2017.

Extracorporeal Membrane Oxygenation Outcomes After the Comprehensive Stage II Procedure in Patients With Single Ventricles.

Outcomes for extracorporeal membrane oxygenation (ECMO) have been described for patients with single ventricle physiology (SVP) undergoing cavopulmonary connection (Glenn procedure). An alternative surgical pathway for patients with SVP consists of an initial hybrid procedure followed by a comprehensive Stage II procedure. No data exist describing the outcomes of patients requiring ECMO after the comprehensive Stage II procedure. The goal of this study is to describe the outcomes for patients who required ECMO after the comprehensive Stage II procedure. Data from the Extracorporeal Life Support Organization (ELSO) registry from 2001 to 2015 for children undergoing the comprehensive Stage II procedure older than 3 months of age were retrospectively analyzed. Demographics and ECMO characteristics were recorded. A total of six children required ECMO support after the comprehensive Stage II procedure (2 males, 4 females). Four patients had the diagnosis of hypoplastic left heart syndrome and two patients had the diagnosis of an unbalanced atrioventricular septal defect. Bypass time was 242.8 ± 110.9 min and cross-clamp time was 91.2 ± 46.2 min for the surgical procedure. Weight was 5.8 ± 1.3 kg and age was 150.2 + 37.9 days at time of ECMO. ECMO duration was 276.0 ± 218.1 h. Complications during the ECMO run included hemorrhage in four patients (67%), renal dysfunction in two patients (33%), and neurologic injury in two patients (33%). Four patients (67%) were discharged alive after ECMO decannulation. Despite being a much more extensive surgical procedure, the morbidity and mortality after ECMO in patients undergoing the comprehensive Stage II procedure are similar to those in patients undergoing the Glenn procedure. If needed, ECMO support is reasonable for patients after the comprehensive Stage II procedure.

Foxf genes integrate tbx5 and hedgehog pathways in the second heart field for cardiac septation.

The Second Heart Field (SHF) has been implicated in several forms of congenital heart disease (CHD), including atrioventricular septal defects (AVSDs). Identifying the SHF gene regulatory networks required for atrioventricular septation is therefore an essential goal for understanding the molecular basis of AVSDs. We defined a SHF Hedgehog-dependent gene regulatory network using whole genome transcriptional profiling and GLI-chromatin interaction studies. The Forkhead box transcription factors Foxf1a and Foxf2 were identified as SHF Hedgehog targets. Compound haploinsufficiency for Foxf1a and Foxf2 caused atrioventricular septal defects, demonstrating the biological relevance of this regulatory network. We identified a Foxf1a cis-regulatory element that bound the Hedgehog transcriptional regulators GLI1 and GLI3 and the T-box transcription factor TBX5 in vivo. GLI1 and TBX5 synergistically activated transcription from this cis-regulatory element in vitro. This enhancer drove reproducible expression in vivo in the posterior SHF, the only region where Gli1 and Tbx5 expression overlaps. Our findings implicate Foxf genes in atrioventricular septation, describe the molecular underpinnings of the genetic interaction between Hedgehog signaling and Tbx5, and establish a molecular model for the selection of the SHF gene regulatory network for cardiac septation.

Adverse reproductive effects of maternal low-dose melamine exposure during pregnancy in rats.

Melamine is a heterocyclic, aromatic amine and nitrogen-enriched environmental toxicant, found in not only adulterated foodstuffs but also industrial household tableware and paints. Previous studies demonstrated adverse effects of high-dose melamine on human infants and pregnant animals, but effects of low-dose melamine on pregnancy have not been reported. In this study, reproductive effects of low-dose melamine were investigated in pregnant rats. Melamine in the range of 12.5-50 mg/kg was administered to pregnant rats at different gestational stages. Maternal weight gain was not significantly affected, and other maternal morbidity was not observed. Low-dose melamine exposure during pregnancy increased fetal size but reduced somite number in gastrulation (GD8.5-GD10.5) and organogenesis (GD10.5-GD16.5) periods, and increased incidence of stillbirth in whole gestational period (GD0.5 to delivery). Embryotoxicity of melamine was further confirmed by whole embryo culture in vitro that melamine retarded embryonic growth, impaired development of brain and heart, and induced open neural tube and atrioventricular defects with increased apoptosis. In conclusion, adverse reproductive effects of low-dose melamine during pregnancy were identified in the developing rat embryos and the perinatal effects of melamine were gestational and developmental stage dependent. Detailed hazard and risk assessment of melamine in reproduction system are warrant. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 131-138, 2017.

Experience in the corrective treatment of patients with atrioventricular septum.

INTRODUCTION: Atrioventricular septal defects are a wide spectrum of cardiac malformations, from partial until complete with one unique atrioventricular valve, atrioventricular valve communication, and leaky left heart valve. Its fast evolution to pulmonary vascular disease calls for early surgical management. Corrective treatment has a high percentage of re-operations and 8.6% mortality. OBJECTIVES: To describe the results of corrective treatments of atrioventricular septum defects in our institution's patients. MATERIALS AND METHODS: Observational, cross-sectional, analytical, and retrospective study of the atrioventricular septum defect patients during the period from March 2013 until March 2015. RESULTS: 51 atrioventricular septum defect patients were operated, nine with incomplete defect and 42 with complete defect, predominance type A of Rastell (35, 81.3%). Age at diagnosis was from 2.9 to 7.4 months; 82.3% of the patients have Down's syndrome. The cardiopathy with more association was the patient ductus arteriosus in 61.9% of cases. Average stay in intensive care was 3.8-9.9 days. Eight (15.6%) patients died. CONCLUSION: Diagnosis and surgical treatment of atrioventricular septum defects in our institution it is made early. Results from surgical correction are comparable to that reported in the international literature.

Disruption of myocardial Gata4 and Tbx5 results in defects in cardiomyocyte proliferation and atrioventricular septation.

Mutations in GATA4 and TBX5 are associated with congenital heart defects in humans. Interaction between GATA4 and TBX5 is important for normal cardiac septation, but the underlying molecular mechanisms are not well understood. Here, we show that Gata4 and Tbx5 are co-expressed in the embryonic atria and ventricle, but after E15.5, ventricular expression of Tbx5 decreases. Co-localization and co-immunoprecipitation studies demonstrate an interaction of Gata4 and Tbx5 in the developing atria and ventricles, but the ventricular interaction declines after E14.5. Gata4(+/-);Tbx5(+/-) mouse embryos display decreased atrial and ventricular myocardial thickness at E11.5, prior to cardiac septation. To determine the cell lineage in which the interaction was functionally significant in vivo, mice heterozygous for Gata4 in the myocardium or endocardium and heterozygous for Tbx5 (Gata4(MyoDel/wt);Tbx5(+/-) and Gata4(EndoDel/wt);Tbx5(+/-), respectively) were generated. Gata4(MyoDel/wt);Tbx5(+/-) mice displayed embryonic lethality, thin myocardium with reduced cell proliferation, and atrioventricular septation defects similar to Gata4;Tbx5 compound heterozygotes while Gata4(EndoDel/wt);Tbx5(+/-) embryos were normal. Cdk4 and Cdk2, cyclin-dependent kinases required for myocardial development and septation were reduced in Gata4(+/-);Tbx5(+/-) hearts. Cdk4 is a known direct target of Gata4 and the regulation of Cdk2 in the developing heart has not been studied. Chromatin immunoprecipitation and transactivation studies demonstrate that Gata4 and Tbx5 directly regulate Cdk4 while only Tbx5 activates Cdk2 expression. These findings highlight the mechanisms by which disruption of the Gata4 and Tbx5 interaction in the myocardium contributes to cardiac septation defects in humans.

Twenty-five-year survival for aboriginal and caucasian children with congenital heart defects in Western Australia, 1980 to 2010.

BACKGROUND: Australian Aboriginal children have increased infant and childhood mortality compared with Caucasian children, but their mortality related to congenital heart defects (CHDs) throughout life is unknown. METHODS: We conducted a retrospective cohort study using data on 8,110 live born, singleton infants with CHDs born January 1980 to December 2010 from the Western Australian Register of Developmental Anomalies. Vital status was determined from death and medical records. Data for infants with chromosomal anomalies (except Down syndrome) were excluded. Kaplan-Meier Product-Limit estimates and 95% confidence intervals (CIs) were computed by Aboriginality. Hazard ratios (HRs) and 95% CIs were calculated from multivariable Cox-Proportional Hazard Regression models. RESULTS: Aboriginal children had lower survival than Caucasians for all CHDs combined but most notably during the neonatal period for functional single ventricle (50.0% vs. 86.1%; p = 0.015) and during the postneonatal period for tetralogy of Fallot (87.0% vs. 97.4%; p = 0.021) and atrioventricular septal defect (60.0% vs. 94.6%; p = 0.010). After adjusting for covariates except remoteness and socioeconomic status (SES), Aboriginal children with all CHDs combined (HR = 1.4; 95% CI, 1.0-1.9), with transposition of the great arteries (HR = 4.3; 95% CI, 1.0-18.9) or functional single ventricle (HR = 8.6; 95% CI, 1.3-57.9) had increased risk of mortality compared with Caucasian children. When remoteness and SES were included, the risks were not statistically significant. CONCLUSION: Long-term survival was lower for Aboriginal children with CHDs, and Aboriginal children with specific CHD phenotypes had increased risk of mortality throughout life. Increased risk may be due to SES and environmental factors. Birth Defects Research (Part A), 2016. © 2016 Wiley Periodicals, Inc. Birth Defects Research (Part A) 106:1016-1031, 2016. © 2016 Wiley Periodicals, Inc.

Bioinformatic Analysis of Genes and MicroRNAs Associated With Atrioventricular Septal Defect in Down Syndrome Patients.

Down syndrome (DS) is a common chromosome 21 abnormality disease, leading to various health problems, especially atrioventricular septal defect (AVSD). Genes and microRNAs (miRNAs) associated with AVSD in DS patients still need in-depth study.Gene expression data (GSE34457) of 22 DS patients without congenital heart disease and 7 DS patients with AVSD were downloaded from Gene Expression Omnibus. After screening differentially expressed genes (DEGs) based on limma package in R (criteria: P < 0.05 and |log2 fold change (FC)| > 0.5), pathway and functional enrichment analyses were performed using the online software DAVID (criterion: P < 0.05). The protein-protein interaction (PPI) networks of DEGs were constructed based on the online server STRING (criterion: combined score > 0.4). Next, miRNAs that targeted DEGs were predicted based on Webgestalt (criteria: P < 0.05 and target DEGs ≥ 2), and miRNA-DEG regulatory networks were visualized through Cytoscape.A total of 179 DEGs were identified. Next, 5 functions and 1 pathway were enriched by up-regulated DEGs, while 4 functions were enriched by down-regulated DEGs. Furthermore, miRNA-DEG regulatory networks were constructed. IL1B was the hub-gene of PPI networks, and AUTS2 and KIAA2022 were predicted to be targeted by miR-518a, miR518e, miR-518f, miR-528a, and miR-96.IL1B, IL12RB2, AUTS2, and KIAA2022 might participate in AVSD in DS patients, and AUTS2 and KIAA2022 might be targeted by miR-518a, miR-518e, miR-518f, miR-528a, and miR-96. The identified genes and miRNAs might provide a theoretical basis for understanding AVSD in DS patients.

CONGENITAL CLEFT PALATE AND CARDIAC SEPTAL DEFECTS IN A NEONATAL SOUTHERN BLACK RHINOCEROS (DICEROS BICORNIS MINOR).

A female Southern black rhinoceros ( Diceros bicornis minor) calf died unexpectedly at less than 12 hr of age, after an uncomplicated birth and uneventful early postpartum period. Gross necropsy revealed a 15-cm full thickness cleft palate, a patent foramen ovale, and four septal defects ranging from 0.3 to 1 cm in diameter. Histologic findings did not reveal any significant abnormalities. Karyotyping did not indicate any significant numerical or structural chromosomal abnormalities.

A potential molecular pathogenesis of cardiac/laterality defects in Oculo-Facio-Cardio-Dental syndrome.

Pitx2 is the last effector of the left-right (LR) cascade known to date and plays a crucial role in the patterning of LR asymmetry. In Xenopus embryos, the expression of Pitx2 gene in the left lateral plate mesoderm (LPM) is directly regulated by Xnr1 signaling, which is mediated by Smads and FoxH1. Previous studies suggest that the suppression of Pitx2 gene in the left LPM is a potential cause of cardiac/laterality defects in Oculo-Facio-Cardio-Dental (OFCD) syndrome, which is known to be caused by mutations in BCL6 co-repressor (BCOR) gene. Recently, our work has revealed that the BCL6/BCOR complex blocks Notch-dependent transcriptional activity to protect the expression of Pitx2 in the left LPM from the inhibitory activity of Notch signaling. These studies indicated that uncontrolled Notch activity in the left LPM caused by dysfunction of BCOR may result in cardiac/laterality defects of OFCD syndrome. However, this Notch-dependent inhibitory mechanism of Pitx2 gene transcription still remains unknown. Here we report that transcriptional repressor ESR1, which acts downstream of Notch signaling, inhibits the expression of Pitx2 gene by binding to a left side-specific enhancer (ASE) region in Pitx2 gene and recruiting histone deacetylase 1 (HDAC1) to this region. Once HDAC1 is tethered, histone acetyltransferase p300 is no longer recruited to the Xnr1-dependent transcriptional complex on the ASE region, leading to the suppression of Pitx2 gene in the left LPM. The study presented here uncovers the regulatory mechanism of Pitx2 gene transcription which may contribute to an understanding of pathogenesis of OFCD syndrome.