Semaphorin 3d signaling defects are associated with anomalous pulmonary venous connections

Total Anomalous Pulmonary Venous Connections, Human Genetics

Partial anomalous pulmonary venous connections (PAVC) have been found after abnormal gene expressions involving several syndromes. Total anomalous pulmonary venous connection (TAPVC) is found in conjunction with heterotaxia syndrome as well as several other syndromes. It has been reported with an autosomal dominance with variable expression and incomplete penetrance. The occurrence is also related to environmental factors which may superimpose on a familial susceptibility for TAPVC. Many pathways are involved in the normal development of the pulmonary venous connections and as a consequence disturbance of many genetic and epigenetic pathways lead to partial or total pulmonary venous misconnections. In this chapter, an overview of current knowledge regarding human genetics of anomalous venous connections is provided.

TAPVR: Molecular Pathways and Animal Models

The venous pole of the heart where the pulmonary veins will develop encompasses the sinus venosus and the atrium. In the fourth week of development, the sinus venosus consists of a left and a right part receiving blood from the common cardinal vein, the omphalomesenteric and umbilical veins. Asymmetrical expansion of the common atrium corresponds with a rightward shift of the connection of the sinus to the atrium. The right-sided part of the sinus venosus including its tributing cardinal veins enlarges to form the right superior and inferior vena cava that will incorporate into the right atrium. The left-sided part in human development largely obliterates and remodels to form the coronary sinus in adults. In approximately the same time window (4th-fifth weeks), a splanchnic vascular plexus surrounds the developing lung buds (putative lungs) with a twofold connection. Of note, during early developmental stages, the primary route of drainage from the pulmonary plexus is toward the systemic veins and not to the heart. After lumenization of the so-called mid-pharyngeal endothelial strand (MPES), the first anlage of the pulmonary vein, the common pulmonary vein can be observed in the dorsal mesocardium, and the primary route of drainage will gradually change toward a cardiac drainage. The splanchnic pulmonary venous connections with the systemic cardinal veins will gradually disappear during normal development. In case of absence or atresia of the MPES, the pulmonary-to-systemic connections will persist, clinically resulting in total anomalous pulmonary venous return (TAPVR). This chapter describes the developmental processes and molecular pathways underlying anomalous pulmonary venous connections.

Molecular Pathways and Animal Models of Atrial Septal Defect

The relative simplicity of the clinical presentation and management of an atrial septal defect belies the complexity of the developmental pathogenesis. Here, we describe the anatomic development of the atrial septum and the venous return to the atrial chambers. Experimental models suggest how mutations and naturally occurring genetic variation could affect developmental steps to cause a defect within the oval fossa, the so-called secundum defect, or other interatrial communications, such as the sinus venosus defect or ostium primum defect.

Understanding the Roles of the Hedgehog Signaling Pathway during T-Cell Lymphopoiesis and in T-Cell Acute Lymphoblastic Leukemia (T-ALL)

The Hedgehog (HH) signaling network is one of the main regulators of invertebrate and vertebrate embryonic development. Along with other networks, such as NOTCH and WNT, HH signaling specifies both the early patterning and the polarity events as well as the subsequent organ formation via the temporal and spatial regulation of cell proliferation and differentiation. However, aberrant activation of HH signaling has been identified in a broad range of malignant disorders, where it positively influences proliferation, survival, and therapeutic resistance of neoplastic cells. Inhibitors targeting the HH pathway have been tested in preclinical cancer models. The HH pathway is also overactive in other blood malignancies, including T-cell acute lymphoblastic leukemia (T-ALL). This review is intended to summarize our knowledge of the biological roles and pathophysiology of the HH pathway during normal T-cell lymphopoiesis and in T-ALL. In addition, we will discuss potential therapeutic strategies that might expand the clinical usefulness of drugs targeting the HH pathway in T-ALL.

Lymphangiogenesis Guidance Mechanisms and Therapeutic Implications in Pathological States of the Cornea

Corneal lymphangiogenesis is one component of the neovascularization observed in several inflammatory pathologies of the cornea including dry eye disease and corneal graft rejection. Following injury, corneal (lymph)angiogenic privilege is impaired, allowing ingrowth of blood and lymphatic vessels into the previously avascular cornea. While the mechanisms underlying pathological corneal hemangiogenesis have been well described, knowledge of the lymphangiogenesis guidance mechanisms in the cornea is relatively scarce. Various signaling pathways are involved in lymphangiogenesis guidance in general, each influencing one or multiple stages of lymphatic vessel development. Most endogenous factors that guide corneal lymphatic vessel growth or regression act via the vascular endothelial growth factor C signaling pathway, a central regulator of lymphangiogenesis. Several exogenous factors have recently been repurposed and shown to regulate corneal lymphangiogenesis, uncovering unique signaling pathways not previously known to influence lymphatic vessel guidance. A strong understanding of the relevant lymphangiogenesis guidance mechanisms can facilitate the development of targeted anti-lymphangiogenic therapeutics for corneal pathologies. In this review, we examine the current knowledge of lymphatic guidance cues, their regulation of inflammatory states in the cornea, and recently discovered anti-lymphangiogenic therapeutic modalities.

Sema3d Restrained Hepatocellular Carcinoma Progression Through Inactivating Pi3k/Akt Signaling via Interaction With FLNA

Hepatocellular carcinoma (HCC) is one of the most lethal malignant tumors worldwide due to the high incidence rate of metastasis and recurrence. Semaphorin 3d (Sema3d) has been shown to play a critical role in vascular development during early embryogenesis and several forms of cancer progression via regulating cell migration. However, the function of Sema3d in hepatocellular carcinoma (HCC) remains elusive. This study aimed to explore the function and mechanisms of Sema3d in HCC. In our study, Sema3d expression was significantly downregulated in HCC tissues and cell lines. Downregulated Sema3d was closely correlated with aggressive clinicopathological features and poor clinical outcomes in HCC patients. Moreover, overexpression of Sema3d in HCCLM3 cells was significantly inhibited and knockdown of Sema3d in PLC/PRF/5 cells promoted proliferation, migration, invasion, and epithelial–mesenchymal transition (EMT) of HCC cells in vitro and tumor growth, EMT, and metastasis in vivo. Furthermore, the RNA sequencing and gene set enrichment analysis (GSEA) indicated that these phenotypic and functional changes in Sema3d-interfered HCC cells were mediated by the Pi3k/Akt signaling pathway, and co-IP–combined mass spectrometry indicated Sema3d might interact with FLNA. Finally, we proved that Sema3d exerted its tumor-restraining effect by interacting with FLNA to inactivate the Pi3k/Akt signaling pathway and remodel the cytoskeleton. Our data showed that Sema3d restrained hepatocellular carcinoma proliferation, invasion, and metastasis through inactivating Pi3k/Akt via interaction with FLNA, which may serve as a novel prognostic predictor and a potential therapeutic target for HCC patients.

Early development of the pulmonary vascular system: An anatomical and histochemical reinvestigation of the pulmonary venous return development in mice

Pulmonary venous return development establishes the fetal circulation and is critical for the formation of pulmonary circulation independent of systemic circulation at birth. Anomalous returns lead to inappropriate drainage of blood flow, sometimes resulting in neonatal cyanosis and cardiac failure. While many classical studies have discussed the anatomical features of the pulmonary venous system development, the cellular dynamics of the endothelia based on the molecular marker expression remain unknown. In the present study, we examined the expression of several endothelial markers during early pulmonary vascular system development of murine embryos. We show that Endomucin and CD31 are expressed early in endothelial cells of the splanchnic plexus, which is the precursor of the pulmonary vascular system. Three-dimensional analyses of the expression patterns revealed the spatiotemporal modification of the venous returns to systemic venous systems or sinoatrial canal during the formation of the pulmonary plexus. We herein report the results of spatiotemporal analyses of the early pulmonary venous system development with histochemistry as well as a delineation of the anatomical features of the tentative drainage pathways.

Single cell atlas for 11 non-model mammals, reptiles and birds

The availability of viral entry factors is a prerequisite for the cross-species transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Large-scale single-cell screening of animal cells could reveal the expression patterns of viral entry genes in different hosts. However, such exploration for SARS-CoV-2 remains limited. Here, we perform single-nucleus RNA sequencing for 11 non-model species, including pets (cat, dog, hamster, and lizard), livestock (goat and rabbit), poultry (duck and pigeon), and wildlife (pangolin, tiger, and deer), and investigated the co-expression of ACE2 and TMPRSS2. Furthermore, cross-species analysis of the lung cell atlas of the studied mammals, reptiles, and birds reveals core developmental programs, critical connectomes, and conserved regulatory circuits among these evolutionarily distant species. Overall, our work provides a compendium of gene expression profiles for non-model animals, which could be employed to identify potential SARS-CoV-2 target cells and putative zoonotic reservoirs.

Association of PLXND1 with a novel subtype of anomalous pulmonary venous return

Anomalous pulmonary venous return (APVR) is a potentially lethal congenital heart disease. Elucidating the genetic etiology is crucial for understanding its pathogenesis and improving clinical practice, while its genetic basis remains largely unknown due to complex genetic etiology. We thus performed whole-exome sequencing for 144 APVR patients and 1636 healthy controls and report a comprehensive atlas of APVR-related rare genetic variants. Novel singleton, loss-of-function and deleterious missense variants (DVars) were enriched in patients, particularly for genes highly-expressed in the developing human heart at the critical time point for pulmonary veins draining into the left atrium. Notably, PLXND1, encoding a receptor for semaphorins, represents a strong candidate gene of APVR (adjusted P = 1.1e-03, OR: 10.9-69.3), accounting for 4.17% of APVR. We further validated this finding in an independent cohort consisting of 82 case-control pairs. In these two cohorts, eight DVars were identified in different patients, which convergently disrupt the GTPase-activating protein-related domain of PLXND1. All variant carriers displayed strikingly similar clinical features, in that all anomalous drainage of pulmonary vein(s) occurred on the right side and incorrectly connected to the right atrium, may representing a novel subtype of APVR for molecular diagnosis. Studies in Plxnd1 knockout mice further revealed the effects of PLXND1 deficiency on severe heart and lung defects and cellular abnormalities related to APVR such as abnormal migration and vascular formation of vascular endothelial cells. These findings indicate the important role of PLXND1 in APVR pathogenesis, providing novel insights into the genetic etiology and molecular subtyping for APVR.

The emerging roles of semaphorin4D/CD100 in immunological diseases

In vertebrates, the semaphorin family of proteins is composed of 21 members that are divided into five subfamilies, i.e. classes 3 to 7. Semaphorins play crucial roles in regulating multiple biological processes, such as neural remodeling, tissue regeneration, cancer progression, and, especially, in immunological regulation. Semaphorin 4D (SEMA4D), also known as CD100, is an important member of the semaphorin family and was first characterized as a lymphocyte-specific marker. SEMA4D has diverse effects on immunologic processes, including immune cell proliferation, differentiation, activation, and migration, through binding to its specific membrane receptors CD72, PLXNB1, and PLXNB2. Furthermore, SEMA4D and its underlying signaling have been increasingly linked with several immunological diseases. This review focuses on the significant immunoregulatory role of SEMA4D and the associated underlying mechanisms, as well as the potential application of SEMA4D as a diagnostic marker and therapeutic target for the treatment of immunological diseases.

Primary pulmonary vein stenosis during infancy: state of the art review

Primary pulmonary vein stenosis (PPVS) is an emerging problem among infants. In contrast to acquired disease, PPVS is the development of stenosis in the absence of preceding intervention. While optimal care approaches remain poorly characterized, over the past decade, understanding of potential pathophysiological mechanisms and development of novel therapeutic strategies are increasing. A multidisciplinary team of health care providers was assembled to review the available evidence and provide a common framework for the diagnosis, management, and treatment of PPVS during infancy. To address knowledge gaps, institutional and multi-institutional approaches must be employed to generate knowledge specific to ex-premature infants with PPVS. Within individual institutions, creation of a team comprised of dedicated health care providers from diverse backgrounds is critical to accelerate clinical learning and provide care for infants with PPVS. Multi-institutional collaborations, such as the PVS Network, provide the infrastructure and statistical power to advance knowledge for this rare disease.

Pulmonary Vein Stenosis: Incremental Knowledge Gains to Improve Outcomes

Pulmonary vein stenosis remains a considerable clinical challenge, with high mortality still present in children with progressive disease. In this review, we discuss the clinical spectrum of pulmonary vein stenosis and what is known about the etiology and potential modifying and contributing factors in progressive pulmonary vein stenosis.

Olig2-Induced Semaphorin Expression Drives Corticospinal Axon Retraction After Spinal Cord Injury

Axon regeneration is limited in the central nervous system, which hinders the reconstruction of functional circuits following spinal cord injury (SCI). Although various extrinsic molecules to repel axons following SCI have been identified, the role of semaphorins, a major class of axon guidance molecules, has not been thoroughly explored. Here we show that expression of semaphorins, including Sema5a and Sema6d, is elevated after SCI, and genetic deletion of either molecule or their receptors (neuropilin1 and plexinA1, respectively) suppresses axon retraction or dieback in injured corticospinal neurons. We further show that Olig2+ cells are essential for SCI-induced semaphorin expression, and that Olig2 binds to putative enhancer regions of the semaphorin genes. Finally, conditional deletion of Olig2 in the spinal cord reduces the expression of semaphorins, alleviating the axon retraction. These results demonstrate that semaphorins function as axon repellents following SCI, and reveal a novel transcriptional mechanism for controlling semaphorin levels around injured neurons to create zones hostile to axon regrowth.

Development of the human heart

In 2014, an extensive review discussing the major steps of cardiac development focusing on growth, formation of primary and chamber myocardium and the development of the cardiac electrical system, was published. Molecular genetic lineage analyses have since furthered our insight in the developmental origin of the various component parts of the heart, which currently can be unambiguously identified by their unique molecular phenotype. Moreover, genetic, molecular and cell biological analyses have driven insights into the mechanisms underlying the development of the different cardiac components. Here, we build on our previous review and provide an insight into the molecular mechanistic revelations that have forwarded the field of cardiac development. Despite the enormous advances in our knowledge over the last decade, the development of congenital cardiac malformations remains poorly understood. The challenge for the next decade will be to evaluate the different developmental processes using newly developed molecular genetic techniques to further unveil the gene regulatory networks operational during normal and abnormal cardiac development.

Simultaneous isolation of endothelial and alveolar epithelial type I and type II cells during mouse lung development in the absence of a transgenic reporter

Mouse lung developmental maturation and final alveolarization phase begin at birth. During this dynamic process, alveolar cells modify their morphology and anchorage to the extracellular matrix. In particular, alveolar epithelial cell (AEC) type I undergo cytoplasmic flattening and folding to ensure alveoli lining. We developed FACS conditions for simultaneous isolation of alveolar epithelial and endothelial cells in the absence of specific reporters during the early and middle alveolar phase. We evidenced for the first time a pool of extractable epithelial cell populations expressing high levels of podoplanin at postnatal day (pnd)2, and we confirmed by RT-qPCR that these cells are already differentiated but still immature AEC type I. Maturation causes a decrease in isolation yields, reflecting the morphological changes that these cell populations are undergoing. Moreover, we find that major histocompatibility complex II (MHCII), reported as a good marker of AEC type II, is poorly expressed at pnd2 but highly present at pnd8. Combined experiments using LysoTracker and MHCII demonstrate the de novo acquisition of MCHII in AEC type II during lung alveolarization. The lung endothelial populations exhibit FACS signatures from vascular and lymphatic compartments. They can be concomitantly followed throughout alveolar development and were obtained with a noticeable increased yield at the last studied time point (pnd16). Our results provide new insights into early lung alveolar cell isolation feasibility and represent a valuable tool for pure AEC type I preparation as well as further in vitro two- and three-dimensional studies.

Role of genomics in asthma exacerbations

PURPOSE OF REVIEW

Asthma exacerbations have been suggested to result from complex interactions between genetic and nongenetic components. In this review, we provide an overview of the genetic association studies of asthma exacerbations, their main results and limitations, as well as future directions of this field.

RECENT FINDINGS

Most studies on asthma exacerbations have been performed using a candidate-gene approach. Although few genome-wide association studies of asthma exacerbations have been conducted up to date, they have revealed promising associations but with small effect sizes. Additionally, the analysis of interactions between genetic and environmental factors has contributed to better understand of genotype-specific responses in asthma exacerbations.

SUMMARY

Genetic association studies have allowed identifying the 17q21 locus and the ADRB2 gene as the loci most consistently associated with asthma exacerbations. Future studies should explore the full spectrum of genetic variation and will require larger sample sizes, a better representation of racial/ethnic diversity and a more precise definition of asthma exacerbations. Additionally, the analysis of important environmental gene-environment analysis and the integration of multiple omics will allow understanding the genetic factors and biological processes underlying the risk for asthma exacerbations.

Research Progress in Pathogenesis of Total Anomalous Pulmonary Venous Connection

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

Semaphorin 3E/PlexinD1 signaling is required for cardiac ventricular compaction

Left ventricular noncompaction (LVNC) is one of the most common forms of genetic cardiomyopathy characterized by excessive trabeculation and impaired myocardial compaction during fetal development. Patients with LVNC are at higher risk of developing left/right ventricular failure or both. Although the key regulators for cardiac chamber development are well studied, the role of semaphorin (Sema)/plexin signaling in this process remains poorly understood. In this article, we demonstrate that genetic deletion of Plxnd1, a class-3 Sema receptor in endothelial cells, leads to severe cardiac chamber defects. They were characterized by excessive trabeculation and noncompaction similar to patients with LVNC. Loss of Plxnd1 results in decreased expression of extracellular matrix proteolytic genes, leading to excessive deposition of cardiac jelly. We demonstrate that Plxnd1 deficiency is associated with an increase in Notch1 expression and its downstream target genes. In addition, inhibition of the Notch signaling pathway partially rescues the excessive trabeculation and noncompaction phenotype present in Plxnd1 mutants. Furthermore, we demonstrate that Semaphorin 3E (Sema3E), one of PlexinD1's known ligands, is expressed in the developing heart and is required for myocardial compaction. Collectively, our study uncovers what we believe to be a previously undescribed role of the Sema3E/PlexinD1 signaling pathway in myocardial trabeculation and the compaction process.

Deficiency in the secreted protein Semaphorin3d causes abnormal parathyroid development in mice

Primary hyperparathyroidism (PHPT) is a common endocrinopathy characterized by hypercalcemia and elevated levels of parathyroid hormone. The primary cause of PHPT is a benign overgrowth of parathyroid tissue causing excessive secretion of parathyroid hormone. However, the molecular etiology of PHPT is incompletely defined. Here, we demonstrate that semaphorin3d (Sema3d), a secreted glycoprotein, is expressed in the developing parathyroid gland in mice. We also observed that genetic deletion of Sema3d leads to parathyroid hyperplasia, causing PHPT. In vivo and in vitro experiments using histology, immunohistochemistry, biochemical, RT-qPCR, and immunoblotting assays revealed that Sema3d inhibits parathyroid cell proliferation by decreasing the epidermal growth factor receptor (EGFR)/Erb-B2 receptor tyrosine kinase (ERBB) signaling pathway. We further demonstrate that EGFR signaling is elevated in Sema3d ^-/- parathyroid glands and that pharmacological inhibition of EGFR signaling can partially rescue the parathyroid hyperplasia phenotype. We propose that because Sema3d is a secreted protein, it may be possible to use recombinant Sema3d or derived peptides to inhibit parathyroid cell proliferation causing hyperplasia and hyperparathyroidism. Collectively, these findings identify Sema3d as a negative regulator of parathyroid growth.

A Novel Mouse Model for Cilia-Associated Cardiovascular Anomalies with a High Penetrance of Total Anomalous Pulmonary Venous Return

Primary cilia are small organelles projecting from the cell surface of many cell types. They play a crucial role in the regulation of various signaling pathway. In this study, we investigated the importance of cilia for heart development by conditionally deleting intraflagellar transport protein Ift88 using the col3.6-cre mouse. Analysis of col3.6;Ift88 offspring showed a wide spectrum of cardiovascular defects including double outlet right ventricle and atrioventricular septal defects. In addition, we found that in the majority of specimens the pulmonary veins did not properly connect to the developing left atrium. The abnormal connections found resemble those seen in patients with total anomalous pulmonary venous return. Analysis of mutant hearts at early stages of development revealed abnormal development of the dorsal mesocardium, a second heart field-derived structure at the venous pole intrinsically related to the development of the pulmonary veins. Data presented support a crucial role for primary cilia in outflow tract development and atrioventricular septation and their significance for the formation of the second heart field-derived tissues at the venous pole including the dorsal mesocardium. Furthermore, the results of this study indicate that proper formation of the dorsal mesocardium is critically important for the development of the pulmonary veins. Anat Rec, 302:136-145, 2019. © 2018 Wiley Periodicals, Inc.

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

Background

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

Methods

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

Findings

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

Interpretation

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

Fund

National Natural Science Foundation of China.

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

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

SOX9 is dispensable for the initiation of epigenetic remodeling and the activation of marker genes at the onset of chondrogenesis

SOX9 controls cell lineage fate and differentiation in major biological processes. It is known as a potent transcriptional activator of differentiation-specific genes, but its earliest targets and its contribution to priming chromatin for gene activation remain unknown. Here, we address this knowledge gap using chondrogenesis as a model system. By profiling the whole transcriptome and the whole epigenome of wild-type and Sox9-deficient mouse embryo limb buds, we uncover multiple structural and regulatory genes, including Fam101a, Myh14, Sema3c and Sema3d, as specific markers of precartilaginous condensation, and we provide evidence of their direct transactivation by SOX9. Intriguingly, we find that SOX9 helps remove epigenetic signatures of transcriptional repression and establish active-promoter and active-enhancer marks at precartilage- and cartilage-specific loci, but is not absolutely required to initiate these changes and activate transcription. Altogether, these findings widen our current knowledge of SOX9 targets in early chondrogenesis and call for new studies to identify the pioneer and transactivating factors that act upstream of or along with SOX9 to prompt chromatin remodeling and specific gene activation at the onset of chondrogenesis and other processes.

Surgical Approaches to Total Anomalous Pulmonary Venous Connection

Total anomalous pulmonary venous connection (TAPVC) constitutes a spectrum of congenital lesions whereby the pulmonary veins remain connected to systemic venous vessels or aberrantly connect to the right atrium. Definitive management requires surgical intervention and, in patients with obstruction to pulmonary venous flow, urgent operation is required. Use of temporizing catheter-based interventions allow for optimization in hemodynamically unstable neonates. Overall, survival has significantly improved over the past decades through better perioperative management and evolution of surgical approaches to minimize post-repair pulmonary vein stenosis, which persists as a major determinant of long-term outcomes.

Duplication and Deletion of 22q11 Associated with Anomalous Pulmonary Venous Connection

Anomalous pulmonary venous connection (APVC) is an uncommon congenital anomaly in which pulmonary venous blood flows directly into the right side of the heart or into the systemic veins. To identify whether there is any association between 22q11 CNVs and APVC, we analyzed the clinical data of 86 APVC patients and then studied the CNVs of 22q11 in 86 sporadic APVC patients by multiplex ligation-dependent probe amplification. The results showed that two patients carried the CNVs of 22q11, one patient had the deletion of 22q11 and the other had the duplication of 22q11. The incidence was significantly higher than that in the normal population (P < 0.01) that suggests a possible etiologic association between the duplication or deletion of 22q11 and the APVC in our patients.

Semaphorins and Their Roles in Airway Biology: Potential as Therapeutic Targets

Semaphorins are a large family of proteins originally identified as axon guidance cues that play a crucial role in neural development. They are also ubiquitously expressed beyond the nervous system and contribute to regulation of essential cell functions, such as cell migration, proliferation, and adhesion. Binding of semaphorins to their receptors, including plexins and neuropilins, triggers diverse signaling pathways, which are involved in the pathogenesis of various diseases, from cancer to autoimmune and allergic disorders. Despite emerging evidence suggestive of nonredundant roles of semaphorins in cellular and molecular mechanisms of the airway biology, their precise expression and function have not been fully addressed. Here, we first provide an overview about the semaphorin family, their receptors, signaling pathways, and their cellular functions. Then, we highlight the novel findings on the role of semaphorins in airway biology under developmental, homeostatic, and pathological conditions. In particular, we discuss the dual roles of semaphorins in respiratory disorders where they can up- or downregulate processes underlying the pathophysiology of the airway diseases. Next, our recent findings on the expression and function of semaphorin 3E in allergic asthma are further emphasized, and its potential mechanism of action in allergic airway inflammation and remodeling is discussed. Finally, we raise some unanswered questions aiming to develop future research directions.

Comparative developmental biology of the cardiac inflow tract

The vertebrate heart receives the blood through the cardiac inflow tract. This area has experienced profound changes along the evolution of vertebrates; changes that have a reflection in the cardiac ontogeny. The development of the inflow tract involves dynamic changes due to the progressive addition of tissue derived from the secondary heart field. The inflow tract is the site where oxygenated blood coming from lungs is received separately from the systemic return, where the cardiac pacemaker is established and where the proepicardium develops. Differential cell migration towards the inflow tract breaks the symmetry of the primary heart tube and determines the direction of the cardiac looping. In air-breathing vertebrates, an inflow tract reorganization is essential to keep separate blood flows from systemic and pulmonary returns. Finally, the sinus venosus endocardium has recently been recognized as playing a role in the constitution of the coronary vasculature. Due to this developmental complexity, congenital anomalies of the inflow tract can cause severe cardiac diseases. We aimed to review the recent literature on the cellular and molecular mechanisms that regulate the morphogenesis of the cardiac inflow tract, together with comparative and evolutionary details, thus providing a basis for a better understanding of these mechanisms.

Cardiomyocytes of the Heart and Pulmonary Veins: Novel Contributors to Asthma?

Recent genome-wide association studies have implicated both cardiac and pulmonary vein-related genes in the pathogenesis of asthma. Since cardiac cells are not present in lung airways or viewed to affect the immune system, interpretation of these findings in the context of more well-established contributors to asthma has remained challenging. However, cardiomyocytes are present in the lung, specifically along pulmonary veins, and recent murine models suggest that cardiac cells lining the pulmonary veins may contribute to allergic airway disease. Notably, the cardiac cell-junction protein αT-catenin (αT-cat, CTNNA3), which is implicated in occupational and steroid-resistant asthma by clinical genetic data, appears to play an important role in regulating inflammation around the cardiac cells of pulmonary veins. Beyond the potential contribution of pulmonary veins, clinical data directly examining cardiac function through echocardiography have found strong associations between asthmatic phenotypes and the mechanical properties of the heart. Together, these data suggest that targeting the function of cardiac cells in the pulmonary veins and/or heart may allow for novel and potentially efficacious therapies for asthma, particularly in challenging cases of steroid-resistant asthma.

Testing the Ret and Sema3d genetic interaction in mouse enteric nervous system development

For most multigenic disorders, clinical manifestation (penetrance) and presentation (expressivity) are likely to be an outcome of genetic interaction between multiple susceptibility genes. Here, using gene knockouts in mice, we evaluated genetic interaction between loss of Ret and loss of Sema3d, two Hirschsprung disease susceptibility genes. We intercrossed Ret and Sema3d double null heterozygotes to generate mice with the nine possible genotypes and assessed survival by counting various genotypes, myenteric plexus presence by acetylcholinesterase staining and embryonic day 12.5 (E12.5) intestine transcriptome by RNA-sequencing. Survival rates of Ret wild-type, null heterozygote and null homozygote mice at E12.5, birth and weaning were not influenced by the genotypes at Sema3d locus and vice versa. Loss of myenteric plexus was observed only in all Ret null homozygotes, irrespective of the genotypes at Sema3d locus, and Sema3d null heterozygote and homozygote mice had normal intestinal innervation. As compared with wild-type mice intestinal gene expression, loss of Ret in null homozygotes led to differential expression of ∼300 genes, whereas loss of Sema3d in null homozygotes had no major consequence and there was no evidence supporting major interaction between the two genes influencing intestine transcriptome. Overall, given the null alleles and phenotypic assays used, we did not find evidence for genetic interaction between Ret and Sema3d affecting survival, presence of myenteric plexus or intestine transcriptome.

A radial axis defined by semaphorin-to-neuropilin signaling controls pancreatic islet morphogenesis

The islets of Langerhans are endocrine organs characteristically dispersed throughout the pancreas. During development, endocrine progenitors delaminate, migrate radially and cluster to form islets. Despite the distinctive distribution of islets, spatially localized signals that control islet morphogenesis have not been discovered. Here, we identify a radial signaling axis that instructs developing islet cells to disperse throughout the pancreas. A screen of pancreatic extracellular signals identified factors that stimulated islet cell development. These included semaphorin 3a, a guidance cue in neural development without known functions in the pancreas. In the fetal pancreas, peripheral mesenchymal cells expressed Sema3a, while central nascent islet cells produced the semaphorin receptor neuropilin 2 (Nrp2). Nrp2 mutant islet cells developed in proper numbers, but had defects in migration and were unresponsive to purified Sema3a. Mutant Nrp2 islets aggregated centrally and failed to disperse radially. Thus, Sema3a-Nrp2 signaling along an unrecognized pancreatic developmental axis constitutes a chemoattractant system essential for generating the hallmark morphogenetic properties of pancreatic islets. Unexpectedly, Sema3a- and Nrp2-mediated control of islet morphogenesis is strikingly homologous to mechanisms that regulate radial neuronal migration and cortical lamination in the developing mammalian brain.

Pdgfrα functions in endothelial-derived cells to regulate neural crest cells and the development of the great arteries

Originating as a single vessel emerging from the embryonic heart, the truncus arteriosus must septate and remodel into the aorta and pulmonary artery to support postnatal life. Defective remodeling or septation leads to abnormalities collectively known as conotruncal defects, which are associated with significant mortality and morbidity. Multiple populations of cells must interact to coordinate outflow tract remodeling, and the cardiac neural crest has emerged as particularly important during this process. Abnormalities in the cardiac neural crest have been implicated in the pathogenesis of multiple conotruncal defects, including persistent truncus arteriosus, double outlet right ventricle and tetralogy of Fallot. However, the role of the neural crest in the pathogenesis of another conotruncal abnormality, transposition of the great arteries, is less well understood. In this report, we demonstrate an unexpected role of Pdgfra in endothelial cells and their derivatives during outflow tract development. Loss of Pdgfra in endothelium and endothelial-derived cells results in double outlet right ventricle and transposition of the great arteries. Our data suggest that loss of Pdgfra in endothelial-derived mesenchyme in the outflow tract endocardial cushions leads to a secondary defect in neural crest migration during development.

Summary: Loss of Pdgfrα in endothelial-derived mesenchyme results in defective neural crest behavior and is associated with conotruncal defects including, surprisingly, transposition of the great arteries.

Endothelial Myocyte Enhancer Factor 2c Inhibits Migration of Smooth Muscle Cells Through Fenestrations in the Internal Elastic Lamina

OBJECTIVE

Laminar flow activates myocyte enhancer factor 2 (MEF2) transcription factors in vitro to induce expression of atheroprotective genes in the endothelium. Here we sought to establish the role of Mef2c in the vascular endothelium in vivo.

APPROACH AND RESULTS

To study endothelial Mef2c, we generated endothelial-specific deletion of Mef2c using Tie2-Cre or Cdh5-Cre-ER^T2 and examined aortas and carotid arteries by en face immunofluorescence. We observed enhanced actin stress fiber formation in the Mef2c-deleted thoracic aortic endothelium (laminar flow region), similar to those observed in normal aortic inner curvature (disturbed flow region). Furthermore, Mef2c deletion resulted in the de novo formation of subendothelial intimal cells expressing markers of differentiated smooth muscle in the thoracic aortas and carotids. Lineage tracing showed that these cells were not of endothelial origin. To define early events in intimal development, we induced endothelial deletion of Mef2c and examined aortas at 4 and 12 weeks postinduction. The number of intimal cell clusters increased from 4 to 12 weeks, but the number of cells within a cluster peaked at 2 cells in both cases, suggesting ongoing migration but minimal proliferation. Moreover, we identified cells extending from the media through fenestrations in the internal elastic lamina into the intima, indicating transfenestral smooth muscle migration. Similar transfenestral migration was observed in wild-type carotid arteries ligated to induce neointimal formation.

CONCLUSIONS

These results indicate that endothelial Mef2c regulates the endothelial actin cytoskeleton and inhibits smooth muscle cell migration into the intima.

Sema3d controls collective endothelial cell migration by distinct mechanisms via Nrp1 and PlxnD1

Semaphorins regulate guidance during cell migration. In addition to repelling endothelial cells, Hamm et al. identify a novel mechanism by which Semaphorin3d/Neuropilin1 regulates collective endothelial cell migration through activating a kinase cascade, which regulates Actin network organization and cell–cell contacts.

During cardiovascular development, tight spatiotemporal regulation of molecular cues is essential for controlling endothelial cell (EC) migration. Secreted class III Semaphorins play an important role in guidance of neuronal cell migration and were lately linked to regulating cardiovascular development. Recently, SEMA3D gene disruptions were associated with cardiovascular defects in patients; however, the mechanisms of action were not revealed. Here we show for the first time that Sema3d regulates collective EC migration in zebrafish through two separate mechanisms. Mesenchymal Sema3d guides outgrowth of the common cardinal vein via repulsion and signals through PlexinD1. Additionally, within the same ECs, we identified a novel function of autocrine Sema3d signaling in regulating Actin network organization and EC morphology. We show that this new function requires Sema3d signaling through Neuropilin1, which then regulates Actin network organization through RhoA upstream of Rock, stabilizing the EC sheet. Our findings are highly relevant for understanding EC migration and the mechanisms of collective migration in other contexts.

Variable phenotypic presentation of a novel FOXF1 missense mutation in a single family

BACKGROUND

Heterozygous mutations in the FOXF1 transcription factor gene are implicated in alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), a developmental disorder of the lungs classically presenting with pulmonary hypertension and early demise. Evidence has suggested haploinsufficiency and partial paternal imprinting. We present a family with several affected members with an extremely variable phenotype.

PATIENTS

The index patient presented several hours after birth with severe pulmonary hypertension. She is now 3-years old, thriving on maximal pulmonary hypertension therapy, chronic steroids, and oxygen. One of the patient's siblings died at 16 days with pulmonary hypertension and an annular pancreas, consistent with classical ACDMPV.

METHODS

Whole exome sequencing was performed in the index case. The identified variant was confirmed by Sanger sequencing, and tested in the remaining family members. Parental origin was determined by PCR amplification and cloning, sequencing, and identification of adjacent single nucleotide polymorphisms. Echocardiography was performed in the asymptomatic carriers.

RESULTS

Whole exome analysis revealed a novel, predictably pathogenic heterozygous missense mutation, g.chr16:86544406 C>A NM_001451, c.C231A, p.F77L, in the FOXF1 gene. The mutation arose in the father, de novo, early postzygotically, with 70% somatic mosaicism in the blood, on the grandpaternal chromosome. It was also present in the proband's asymptomatic sister, found to have partial anomalous pulmonary venous return.

CONCLUSION

FOXF1 mutations may have an extremely variable phenotype, possibly as a result of somatic mosaicism and complex gene regulation including unorthodox imprinting of the gene locus. The prolonged survival of the proband suggests the need for aggressive treatment. Pediatr Pulmonol. 2016; 51:921-927. © 2016 Wiley Periodicals, Inc.

Attractant and repellent cues cooperate in guiding a subset of olfactory sensory axons to a well-defined protoglomerular target

Olfactory sensory axons target well-defined intermediate targets in the zebrafish olfactory bulb called protoglomeruli well before they form odorant receptor-specific glomeruli. A subset of olfactory sensory neurons are labeled by expression of the or111-7:IRES:GAL4 transgene whose axons terminate in the central zone (CZ) protoglomerulus. Previous work has shown that some of these axons misproject to the more dorsal and anterior dorsal zone (DZ) protoglomerulus in the absence of Netrin 1/Dcc signaling. In search of additional cues that guide these axons to the CZ, we found that Semaphorin 3D (Sema3D) is expressed in the anterior bulb and acts as a repellent that pushes them towards the CZ. Further analysis indicates that Sema3D signaling is mediated through Nrp1a, while Nrp2b also promotes CZ targeting but in a Sema3D-independent manner. nrp1a, nrp2b and dcc transcripts are detected in or111-7 transgene-expressing neurons early in development and both Nrp1a and Dcc act cell-autonomously in sensory neurons to promote accurate targeting to the CZ. dcc and nrp1a double mutants have significantly more DZ misprojections than either single mutant, suggesting that the two signaling systems act independently and in parallel to direct a specific subset of sensory axons to their initial protoglomerular target.

Class 3 semaphorins in cardiovascular development

Secreted class 3 semaphorins (Sema3), which signal through holoreceptor complexes that are formed by different subunits, such as neuropilins (Nrps), proteoglycans, and plexins, were initially characterized as fundamental regulators of axon guidance during embryogenesis. Subsequently, Sema3A, Sema3C, Sema3D, and Sema3E were discovered to play crucial roles in cardiovascular development, mainly acting through Nrp1 and Plexin D1, which funnels the signal of multiple Sema3 in vascular endothelial cells. Mechanistically, Sema3 proteins control cardiovascular patterning through the enzymatic GTPase-activating-protein activity of the cytodomain of Plexin D1, which negatively regulates the function of Rap1, a small GTPase that is well-known for its ability to drive vascular morphogenesis and to elicit the conformational activation of integrin adhesion receptors.

The cardiomyocyte protein αT-catenin contributes to asthma through regulating pulmonary vein inflammation

BACKGROUND

Recent genome-wide association studies have identified single nucleotide polymorphisms in the gene encoding the protein αT-catenin (CTNNA3) that correlate with both steroid-resistant atopic asthma and asthmatic exacerbations. α-Catenins are important mediators of cell-cell adhesion, and αT-catenin is predominantly expressed in cardiomyocytes. In the lung αT-catenin appears to be exclusively expressed in cardiomyocytes surrounding the pulmonary veins (PVs), but its contribution to atopic asthma remains unknown.

OBJECTIVE

We sought to understand the role of αT-catenin in asthma pathogenesis.

METHODS

We used αT-catenin knockout mice and a house dust mite (HDM) extract model of atopic asthma, with assessment by means of forced oscillation, bronchoalveolar lavage, and histologic analysis.

RESULTS

We found that the genetic loss of αT-catenin in mice largely attenuated HDM-induced airway inflammation and airway hyperresponsiveness to methacholine. Mice lacking αT-catenin that were exposed to HDM extract had reduced PV inflammation, specifically near the large veins surrounded by cardiac cells. The proximity of the airways to PVs correlated with the severity of airway goblet cell metaplasia, suggesting that PVs can influence the inflammatory milieu of adjacent airways. Loss of αT-catenin led to compensatory upregulation of αE-catenin, which itself has a defined anti-inflammatory function.

CONCLUSION

These data mechanistically support previous clinical and genetic associations between αT-catenin and the development of atopic asthma and suggest that PVs might have an underappreciated role in allergic airway inflammation.

Coronary vasculature patterning requires a novel endothelial ErbB2 holoreceptor

Organogenesis and regeneration require coordination of cellular proliferation, regulated in part by secreted growth factors and cognate receptors, with tissue nutrient supply provided by expansion and patterning of blood vessels. Here we reveal unexpected combinatorial integration of a growth factor co-receptor with a heterodimeric partner and ligand known to regulate angiogenesis and vascular patterning. We show that ErbB2, which can mediate epidermal growth factor (EGF) and neuregulin signalling in multiple tissues, is unexpectedly expressed by endothelial cells where it partners with neuropilin 1 (Nrp1) to form a functional receptor for the vascular guidance molecule semaphorin 3d (Sema3d). Loss of Sema3d leads to improper patterning of the coronary veins, a phenotype recapitulated by endothelial loss of ErbB2. These findings have implications for possible cardiovascular side-effects of anti-ErbB2 therapies commonly used for cancer, and provide an example of integration at the molecular level of pathways involved in tissue growth and vascular patterning.

Semaphorin ligands and cognate receptors are important in patterning the vasculature. Here, Aghajanian et al. report an unexpected role for ErbB2 in endothelial cells where it partners with Nrp1 to form a novel semaphoring holoreceptor required for embryonic vascular patterning.

Blood vessel crosstalk during organogenesis-focus on pancreas and endothelial cells

Blood vessels form a highly branched, interconnected, and largely stereotyped network of tubes that sustains every organ and tissue in vertebrates. How vessels come to take on their particular architecture, or how they are 'patterned,' and in turn, how they influence surrounding tissues are fundamental questions of organogenesis. Decades of work have begun to elucidate how endothelial progenitors arise and home to precise locations within tissues, integrating attractive and repulsive cues to build vessels where they are needed. Conversely, more recent findings have revealed an exciting facet of blood vessel interaction with tissues, where vascular cells provide signals to developing organs and progenitors therein. Here, we discuss the exchange of reciprocal signals between endothelial cells and neighboring tissues during embryogenesis, with a special focus on the developing pancreas. Understanding the mechanisms driving both sides of these interactions will be crucial to the development of therapies, from improving organ regeneration to efficient production of cell based therapies. Specifically, elucidating the interface of the vasculature with pancreatic lineages, including endocrine cells, will instruct approaches such as generation of replacement beta cells for Type I diabetes. WIREs Dev Biol 2016, 5:598-617. doi: 10.1002/wdev.240 For further resources related to this article, please visit the WIREs website.

CTNNA3 and SEMA3D: Promising loci for asthma exacerbation identified through multiple genome-wide association studies

BACKGROUND

Asthma exacerbations are a major cause of morbidity and medical cost.

OBJECTIVE

The objective of this study was to identify genetic predictors of exacerbations in asthmatic subjects.

METHODS

We performed a genome-wide association study meta-analysis of acute asthma exacerbation in 2 pediatric clinical trials: the Childhood Asthma Management Program (n = 581) and the Childhood Asthma Research and Education (n = 205) network. Acute asthma exacerbations were defined as treatment with a 5-day course of oral steroids. We obtained a replication cohort from Biobank of Vanderbilt University Medical Center (BioVU; n = 786), the Vanderbilt University electronic medical record-linked DNA biobank. We used CD4(+) lymphocyte genome-wide mRNA expression profiling to identify associations of top single nucleotide polymorphisms with mRNA abundance of nearby genes.

RESULTS

A locus in catenin (cadherin-associated protein), alpha 3 (CTNNA3), reached genome-wide significance (rs7915695, P = 2.19 × 10(-8); mean exacerbations, 6.05 for minor alleles vs 3.71 for homozygous major alleles). Among the 4 top single nucleotide polymorphisms replicated in BioVU, rs993312 in Sema domain, immunoglobulin domain (Ig), short basic domain, secreted, (semaphorin) 3D (SEMA3D) was significant (P = .0083) and displayed stronger association among African Americans (P = .0004 in BioVU [mean exacerbations, 3.91 vs 1.53]; P = .0089 in the Childhood Asthma Management Program [mean exacerbations, 6.0 vs 3.25]). CTNNA3 variants did not replicate in BioVU. A regulatory variant in the CTNNA3 locus was associated with CTNNA3 mRNA expression in CD4(+) cells from asthmatic patients (P = .00079). CTNNA3 appears to be active in the immune response, and SEMA3D has a plausible role in airway remodeling. We also provide a replication of a previous association of purinergic receptor P2X, ligand-gated ion channel, 7 (P2RX7), with asthma exacerbation.

CONCLUSIONS

We identified 2 loci associated with exacerbations through a genome-wide association study. CTNNA3 met genome-wide significance thresholds, and SEMA3D replicated in a clinical biobank database.

Insights regarding the normal and abnormal formation of the atrial and ventricular septal structures

Knowledge of cardiac development can provide the basis for understanding the morphogenesis of congenital cardiac malformations. Only recently, however, has the quality of information regarding cardiac embryology been sufficient to justify this approach. In this review, we show how such knowledge of development of the normal atrial and ventricular septal structures underscores the interpretation of the lesions that provide the basis for interatrial and interventricular shunting of blood. We show that current concepts of atrial septation, which frequently depend on a suggested formation of an extensive secondary septum, are simplistic. There are additional contributions beyond growth of the primary septum, but the new tissue is added to form the ventral buttress of the definitive atrial septum, rather than its cranial margin, as is usually depicted. We show that the ventricular septum possesses muscular and membranous components, with the entirety of the muscular septum produced concomitant with the so-called ballooning of the apical ventricular component. It is expansion of the atrioventricular canal that creates the inlet of the right ventricle, with no separate formation of an "inlet" septum. The proximal parts of the outflow cushions initially form a septal structure between the developing ventricular outlets, but this becomes converted into the free-standing muscular subpulmonary infundibulum as the aortic outlet is transferred to the left ventricle. These features of normal development are then shown to provide the basis for understanding of the channels that provide the means for interatrial and interventricular shunting.

Functional loss of semaphorin 3C and/or semaphorin 3D and their epistatic interaction with ret are critical to Hirschsprung disease liability

Innervation of the gut is segmentally lost in Hirschsprung disease (HSCR), a consequence of cell-autonomous and non-autonomous defects in enteric neuronal cell differentiation, proliferation, migration, or survival. Rare, high-penetrance coding variants and common, low-penetrance non-coding variants in 13 genes are known to underlie HSCR risk, with the most frequent variants in the ret proto-oncogene (RET). We used a genome-wide association (220 trios) and replication (429 trios) study to reveal a second non-coding variant distal to RET and a non-coding allele on chromosome 7 within the class 3 Semaphorin gene cluster. Analysis in Ret wild-type and Ret-null mice demonstrates specific expression of Sema3a, Sema3c, and Sema3d in the enteric nervous system (ENS). In zebrafish embryos, sema3 knockdowns show reduction of migratory ENS precursors with complete ablation under conjoint ret loss of function. Seven candidate receptors of Sema3 proteins are also expressed within the mouse ENS and their expression is also lost in the ENS of Ret-null embryos. Sequencing of SEMA3A, SEMA3C, and SEMA3D in 254 HSCR-affected subjects followed by in silico protein structure modeling and functional analyses identified five disease-associated alleles with loss-of-function defects in semaphorin dimerization and binding to their cognate neuropilin and plexin receptors. Thus, semaphorin 3C/3D signaling is an evolutionarily conserved regulator of ENS development whose dys-regulation is a cause of enteric aganglionosis.

Semaphorin signaling in cardiovascular development

Semaphorins were originally identified as neuronal guidance molecules mediating their attractive or repulsive signals by forming complexes with plexin and neuropilin receptors. Subsequent research has identified functions for semaphorin signaling in many organs and tissues outside of the nervous system. Vital roles for semaphorin signaling in vascular patterning and cardiac morphogenesis have been demonstrated, and impaired semaphorin signaling has been associated with various human cardiovascular disorders, including persistent truncus arteriosus, sinus bradycardia and anomalous pulmonary venous connections. Here, we review the functions of semaphorins and their receptors in cardiovascular development and disease and highlight important recent discoveries in the field.

Congenital diseases and semaphorin signaling: overview to date of the evidence linking them

Semaphorins and their receptors, neuropilins and plexins, were initially characterized as a modulator of axonal guidance during development, but are now recognized as a regulator of a wide range of developmental events including morphogenesis and angiogenesis, and activities of the immune system. Owing to the development of next-generation sequencing technologies together with other useful DNA assays, it has also become clear that semaphorin signaling plays a crucial role in many congenital diseases such as retinal degeneration and congenital heart defects. This review summarizes the recent knowledge about the relationship between a variety of congenital diseases and semaphorin signaling.

Total anomalous pulmonary venous return in siblings

Total anomalous pulmonary venous return (TAPVR) is a rare and critical congenital vascular anomaly that requires an early operation. However, initial symptoms of TAPVR may be non-specific, and cardiovascular findings may be minimal. The heart may not be enlarged and there is often no cardiac murmur. Without cardiac murmur, these symptoms are similar to those of respiratory distress syndrome in newborns. Therefore, a high degree of suspicion and an early diagnosis of TAPVR are important. This condition generally occurs without a family history and has a low recurrence rate, but several familial cases, including siblings, have been reported worldwide. Additionally, several chromosomal or gene abnormalities associated with TAPVR have been reported. In the case presented here, two brothers with a 6-year age gap were diagnosed with TAPVR. Surgery was performed without cardiac or neurological complications. This is the first report on TAPVR in siblings in Korea.

Mesodermal expression of integrin α5β1 regulates neural crest development and cardiovascular morphogenesis

Integrin α5-null embryos die in mid-gestation from severe defects in cardiovascular morphogenesis, which stem from defective development of the neural crest, heart and vasculature. To investigate the role of integrin α5β1 in cardiovascular development, we used the Mesp1(Cre) knock-in strain of mice to ablate integrin α5 in the anterior mesoderm, which gives rise to all of the cardiac and many of the vascular and muscle lineages in the anterior portion of the embryo. Surprisingly, we found that mutant embryos displayed numerous defects related to the abnormal development of the neural crest such as cleft palate, ventricular septal defect, abnormal development of hypoglossal nerves, and defective remodeling of the aortic arch arteries. We found that defects in arch artery remodeling stem from the role of mesodermal integrin α5β1 in neural crest proliferation and differentiation into vascular smooth muscle cells, while proliferation of pharyngeal mesoderm and differentiation of mesodermal derivatives into vascular smooth muscle cells was not defective. Taken together our studies demonstrate a requisite role for mesodermal integrin α5β1 in signaling between the mesoderm and the neural crest, thereby regulating neural crest-dependent morphogenesis of essential embryonic structures.