Chromosome aberrations and gene mutations in patients with esophageal atresia

Disrupted endosomal trafficking of the Vangl-Celsr polarity complex underlies congenital anomalies in Xenopus trachea-esophageal morphogenesis

Disruptions in foregut morphogenesis can result in life-threatening conditions where the trachea and esophagus fail to separate, such as esophageal atresia (EA) and tracheoesophageal fistulas (TEFs). The developmental basis of these congenital anomalies is poorly understood, but recent genome sequencing reveals that de novo variants in intracellular trafficking genes are enriched in EA/TEF patients. Here, we confirm that mutation of orthologous genes in Xenopus disrupts trachea-esophageal separation similar to EA/TEF patients. The Rab11a recycling endosome pathway is required to localize Vangl-Celsr polarity complexes at the luminal cell surface where opposite sides of the foregut tube fuse. Partial loss of endosomal trafficking or Vangl-Celsr complexes disrupts epithelial polarity and cell division orientation. Mutant cells accumulate at the fusion point, fail to relocalize cadherin, and do not separate into distinct trachea and esophagus. These data provide insights into the mechanisms of congenital anomalies and general paradigms of tissue fusion during organogenesis.

Recent Advances in the Genetic Pathogenesis, Diagnosis, and Management of Esophageal Atresia and Tracheoesophageal Fistula: A Review

Infants born with esophageal atresia and tracheoesophageal fistula, a complex congenital malformation occurring in 1/2500-4000 live births, may suffer threats to their cardiac, respiratory, and digestive health in addition to anomalies that may exist in the genitourinary and musculoskeletal systems. Optimal care for these patients throughout their lives is best achieved through a coordinated, multidisciplinary approach that our health care system is not always well-equipped to provide. This review, though not exhaustive, highlights the components of care that pertain to initial surgical reconstruction and subsequent diagnosis and management of the complications that are most frequently encountered. Authors from among the many specialties involved in the care of these patients summarize the current best practice with attention to the most recent advances. Assessment and improvement of quality of life and transition to adult specialists as children grow to adulthood is also reviewed.

Heritability and De Novo Mutations in Oesophageal Atresia and Tracheoesophageal Fistula Aetiology

Tracheoesophageal Fistula (TOF) is a congenital anomaly for which the cause is unknown in the majority of patients. OA/TOF is a variable feature in many (often mono-) genetic syndromes. Research using animal models targeting genes involved in candidate pathways often result in tracheoesophageal phenotypes. However, there is limited overlap in the genes implicated by animal models and those found in OA/TOF-related syndromic anomalies. Knowledge on affected pathways in animal models is accumulating, but our understanding on these pathways in patients lags behind. If an affected pathway is associated with both animals and patients, the mechanisms linking the genetic mutation, affected cell types or cellular defect, and the phenotype are often not well understood. The locus heterogeneity and the uncertainty of the exact heritability of OA/TOF results in a relative low diagnostic yield. OA/TOF is a sporadic finding with a low familial recurrence rate. As parents are usually unaffected, de novo dominant mutations seems to be a plausible explanation. The survival rates of patients born with OA/TOF have increased substantially and these patients start families; thus, the detection and a proper interpretation of these dominant inherited pathogenic variants are of great importance for these patients and for our understanding of OA/TOF aetiology.

Developmental basis of trachea-esophageal birth defects

Trachea-esophageal defects (TEDs), including esophageal atresia (EA), tracheoesophageal fistula (TEF), and laryngeal-tracheoesophageal clefts (LTEC), are a spectrum of life-threatening congenital anomalies in which the trachea and esophagus do not form properly. Up until recently, the developmental basis of these conditions and how the trachea and esophagus arise from a common fetal foregut was poorly understood. However, with significant advances in human genetics, organoids, and animal models, and integrating single cell genomics with high resolution imaging, we are revealing the molecular and cellular mechanisms that orchestrate tracheoesophageal morphogenesis and how disruption in these processes leads to birth defects. Here we review the current understanding of the genetic and developmental basis of TEDs. We suggest future opportunities for integrating developmental mechanisms elucidated from animals and organoids with human genetics and clinical data to gain insight into the genotype-phenotype basis of these heterogeneous birth defects. Finally, we envision how this will enhance diagnosis, improve treatment, and perhaps one day, lead to new tissue replacement therapy.

Occurrence of Esophageal Atresia With Tracheoesophageal Fistula in Siblings From Three-Generation Family Affected by Variable Expressivity MYCN Mutation: A Case Report

The MYCN oncogene encodes a transcription factor belonging to the MYC family. It is primarily expressed in normal developing embryos and is thought to be critical in brain and other neural development. Loss-of-function variants resulting in haploinsufficiency of MYCN, which encodes a protein with a basic helix-loop-helix domain causes Feingold syndrome (OMIM 164280, ORPHA 391641). We present an occurrence of esophageal atresia (EA) with tracheoesophageal fistula in siblings from a three-generation family affected by variable expressivity of MYCN mutation p.(Ser90GlnfsTer176) as a diagnostic effect of searching the cause of familial esophageal atresia using NGS-based whole-exome sequencing (WES). All of our affected patients showed microcephaly and toe syndactyly, which were frequently reported in the literature. Just one patient exhibited clinodactyly. None of the patients exhibited brachymesophalangy or hypoplastic thumbs. The latest report noted that patients with EA and Feingold syndrome were also those with the more complex and severe phenotype. However, following a thorough review of the present literature, the same association was not found, which is also confirmed by the case we described. The variable phenotypic expression of the patients we described and the data from the literature guide a careful differential diagnosis of Feingold syndrome even in cases of poorly expressed and non-specific symptoms.

Care recommendations for the respiratory complications of esophageal atresia-tracheoesophageal fistula

Tracheoesophageal fistula (TEF) with esophageal atresia (EA) is a common congenital anomaly that is associated with significant respiratory morbidity throughout life. The objective of this document is to provide a framework for the diagnosis and management of the respiratory complications that are associated with the condition. As there are no randomized controlled studies on the subject, a group of experts used a modification of the Rand Appropriateness Method to describe the various aspects of the condition in terms of their relative importance, and to rate the available diagnostic methods and therapeutic interventions on the basis of their appropriateness and necessity. Specific recommendations were formulated and reported as Level A, B, and C based on whether they were based on "strong", "moderate" or "weak" agreement. The tracheomalacia that exists in the site of the fistula was considered the main abnormality that predisposes to all other respiratory complications due to airway collapse and impaired clearance of secretions. Aspiration due to impaired airway protection reflexes is the main underlying contributing mechanism. Flexible bronchoscopy is the main diagnostic modality, aided by imaging modalities, especially CT scans of the chest. Noninvasive positive airway pressure support, surgical techniques such as tracheopexy and rarely tracheostomy are required for the management of severe tracheomalacia. Regular long-term follow-up by a multidisciplinary team was considered imperative. Specific templates outlining the elements of the clinical respiratory evaluation according to the patients' age were also developed.

Gastrointestinal diseases among relatives of patients with esophageal atresia with or without tracheoesophageal fistula

BACKGROUND

Several studies have identified genetic factors that are associated with the formation of isolated and non-isolated esophageal atresia with or without tracheoesophageal fistula (EA/TEF) in human and mice. Some of these genetic factors like FOXF1/Foxf1 are associated with Barrett syndrome, esophageal carcinoma or tumors of the gastrointestinal tract. Here, we investigated the prevalence of common gastrointestinal diseases among EA/TEF patients and their first- and second-degree relatives (parents and grandparents).

METHODS

We send out a questionnaire to 280 EA/TEF families asking for the presence of Barrett syndrome, Achalasia and carcinoma of the esophagus, the stomach, the small and large intestine among first- and second-degree relatives.

RESULTS

In 32 of 124 families we found at least one affected family member with a possible association of colon carcinoma and the occurrence of EA/TEF within the same family.

CONCLUSIONS

Further studies are needed to evaluate a possible association.

Isolated choanal and gut atresias: pathogenetic role of serine protease inhibitor type 2 (SPINT2) gene mutations unlikely

Background

Choanal (CA) and gastrointestinal atresias (GA) are an important feature of syndromic congenital sodium diarrhea (sCSD), a disorder recently associated with mutations in the gene for serine protease inhibitor type 2 (SPINT2). It is, however, not known whether isolated non-syndromic CA and GA themselves might result from SPINT2 mutations.

Methods

We performed a prospective cohort study to investigate 19 CA and/or GA patients without diarrhea (“non-sCSD”) for potential sCSD characteristic clinical features and SPINT2 mutations.

Results

We found a heterozygous SPINT2 splice mutation (c.593-1G>A), previously demonstrated in sCSD in homozygous form, in only 1 of the 19 patients of the “non-sCSD” cohort. This patient presented with isolated anal atresia and borderline low laboratory parameters of sodium balance. In the remaining 18 non-sCSD CA/GA patients investigated, SPINT2 sequence analysis and clinical markers of sodium homeostasis were normal. None of the 188 healthy controls tested in a regional Tyrolean population harbored the c.593-1G>A mutation, which is also not listed in the ExAc and gnomAD databases.

Conclusions

The finding of only one heterozygous SPINT2 mutation in 19 patients with isolated CA/GA was not statistically significant. Therefore, SPINT2 mutations are an unlikely cause of non-sCSD atresia.

Trial registration ISRCTN73824458. Retrospectively registered 28 September 2014

Copy number variations in 375 patients with oesophageal atresia and/or tracheoesophageal fistula

Oesophageal atresia (OA) with or without tracheoesophageal fistula (TOF) are rare anatomical congenital malformations whose cause is unknown in over 90% of patients. A genetic background is suggested, and among the reported genetic defects are copy number variations (CNVs). We hypothesized that CNVs contribute to OA/TOF development. Quantifying their prevalence could aid in genetic diagnosis and clinical care strategies. Therefore, we profiled 375 patients in a combined Dutch, American and German cohort via genomic microarray and compared the CNV profiles with their unaffected parents and published control cohorts. We identified 167 rare CNVs containing genes (frequency<0.0005 in our in-house cohort). Eight rare CNVs - in six patients - were de novo, including one CNV previously associated with oesophageal disease. (hg19 chr7:g.(143820444_143839360)_(159119486_159138663)del) 1.55% of isolated OA/TOF patients and 1.62% of patients with additional congenital anomalies had de novo CNVs. Furthermore, three (15q13.3, 16p13.3 and 22q11.2) susceptibility loci were identified based on their overlap with known OA/TOF-associated CNV syndromes and overlap with loci in published CNV association case-control studies in developmental delay. Our study suggests that CNVs contribute to OA/TOF development. In addition to the identified likely deleterious de novo CNVs, we detected 167 rare CNVs. Although not directly disease-causing, these CNVs might be of interest, as they can act as a modifier in a multiple hit model, or as the second hit in a recessive condition.

Esophageal development and epithelial homeostasis

The esophagus is a relatively simple organ that evolved to transport food and liquids through the thoracic cavity. It is the only part of the gastrointestinal tract that lacks any metabolic, digestive, or absorptive function. The mucosa of the adult esophagus is covered by a multilayered squamous epithelium with a remarkable similarity to the epithelium of the skin despite the fact that these tissues originate from two different germ layers. Here we review the developmental pathways involved in the establishment of the esophagus and the way these pathways regulate gut-airway separation. We summarize current knowledge of the mechanisms that maintain homeostasis in esophageal epithelial renewal in the adult and the molecular mechanism of the development of Barrett's metaplasia, the precursor lesion to esophageal adenocarcinoma. Finally, we examine the ongoing debate on the hierarchy of esophageal epithelial precursor cells and on the presence or absence of a specific esophageal stem cell population. Together the recent insights into esophageal development and homeostasis suggest that the pathways that establish the esophagus during development also play a role in the maintenance of the adult epithelium. We are beginning to understand how reflux of gastric content and the resulting chronic inflammation can transform the squamous esophageal epithelium to columnar intestinal type metaplasia in Barrett's esophagus.

Modeling human lung development and disease using pluripotent stem cells

Directed differentiation of human pluripotent stem cells (hPSCs) into mature cells, tissues and organs holds major promise for the development of novel approaches in regenerative medicine, and provides a unique tool for disease modeling and drug discovery. Sometimes underappreciated is the fact that directed differentiation of hPSCs also provides a unique model for human development, with a number of important advantages over model organisms. Here, I discuss the importance of using human stem cell models for understanding human lung development and disease.

Difficult esophageal atresia: trick and treat

Although most patients with esophageal atresia (EA) and tracheo-esophageal fistula (TEF) may benefit from "standard" management, which is deferred emergency surgery, some may present unexpected elements that change this paradigm. Birth weight, associated anomalies, and long gap can influence the therapeutic schedule of the patients with EA/TEF and can make their treatment tricky. As a consequence, detailed information on these aspects gives the power to develop a decision-making process as correct as possible. In this article, we will review the most important factors influencing the treatment of patients with EA/TEF and will share our experience on the diagnostic and therapeutic tips that may provide pivotal help in the management of such patients.