Genetics and developmental biology of oesophageal atresia and tracheo-oesophageal fistula: lessons from mice relevant for paediatric surgeons

CHRND variant in a paternally inherited esophageal atresia and tracheoesophgageal fistula: Report of a case

BACKGROUND

The familial occurrence of esophageal atresia and tracheoesophageal fistula (EA-TEF) is very rare and the genetic basis behind the isolated familial cases have not been identified. A male infant born with EA-TEF and his affected father were evaluated with whole genome sequence to define a genetic causative variation in paternally inherited EA-TEF.

CASE REPORT

A male infant was born to 29-years-old, gravida 1, para 1 women by normal vaginal delivery. The patient was diagnosed as Type-C EA-TEF. In his family history, his father was also operated for EA-TEF during neonatal period. He had no associated anomaly despite patent foramen ovale. Genomic DNAs were extracted from peripheral blood of the patient and the father. When causative genes responsible for EA-TEF were filtered out, four different variants in NOTCH2, SAMD9, SUPT20H and CHRND were found. Except the variant found in CHRND (NM_000751.2, c.381C>G, p.(Tyr127Ter)), other three variants were not found to be segregated with the father who has EA-TEF also. This nonsense variant was not found in GnomAD database.

CONCLUSION

CHRND variant found in both EA-TEF patient and his affected father suggest that CHRND variant might possibly be considered as one of the causative genetic variants in familial isolated EA-TEF patients.

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.

Thoracoscopic versus conventional open repair of tracheoesophageal fistula in neonates: A short-term comparative study

PURPOSE

Esophageal atresia with or without a tracheo-esophageal fistula is a challenging anomaly in neonates. Thoracoscopic repair is gaining popularity now in pediatric surgery community. The present study aims at comparing the short term outcomes of thoracoscopy versus classic thoracotomy for repair of such conditions.

METHODS

Thirty neonates with tracheoesophageal fistula were randomly divided into two equal groups (n=15) after excluding patients with birth weight <2000g, multiple associated anomalies and cardiorespiratory instability. One group had conventional open repair while the other had thoracoscopic repair. Demographic data, intraoperative result and post-operative findings were recorded and compared between both groups.

RESULTS

Both groups showed similar results regarding demographic and patients' characteristics. Thoracoscopic repair had relatively longer, yet non-significant operative time but with highly significant difference in preserving azygos vein. There was low conversion rate with thoracoscopy (6.66%). Open repair resulted in a longer hospital stay (11.73±5.68 vs 9.2±2.95). Complication rate was comparable in both groups; however, thoracoscopy was associated with better cosmetic results as reported by parents and surgeons (p=0.00).

CONCLUSION

Compared to thoracotomy, thoracoscopic repair offers a less invasive, effective and safe technique with similar short term outcomes, but with superior cosmetic results and better ability to spare azygos vein.

TYPE OF STUDY

Therapeutic/Treatment study LEVEL OF EVIDENCE: Level II.

Environmental factors in the etiology of isolated and nonisolated esophageal atresia in a Chinese population: A case-control study

BACKGROUND

Esophageal atresia (EA) is a common birth defect that occurs with tracheoesophageal fistula (TEF), although etiological studies on EA/TEF have produced inconsistent results.

METHODS

The aim of this study was to examine the association between environmental factors during pregnancy and the risk of EA/TEF in a Chinese population. Cases of isolated EA and nonisolated EA and unaffected controls were identified between July 2005 and November 2015, and face-to-face questionnaires concerning exposure to environmental factors were administered to the birth mothers of 130 cases and 400 controls. The adjusted odds ratio (OR) and 95% confidence interval (CI) were calculated to assess the association between environmental factors and the risk of EA/TEF.

RESULTS

The results of this case-control study suggest that lower maternal education (p < 0.0001), maternal binge drinking (OR = 2.63; 95% CI, 1.05-6.6) and pickled food consumption (OR = 2.04; 95% CI, 1.31-3.71) during pregnancy increase the risk of EA in offspring, while maternal folic acid supplementation (OR = 0.45; 95% CI, 0.29-0.71) is significantly associated with a decreased risk of EA.

CONCLUSION

These results suggest a role for environmental exposures in the etiology of EA/TEF; however, further studies are needed to replicate the observed associations. Birth Defects Research (Part A) 106:840-846, 2016. © 2016 Wiley Periodicals, Inc.

Etiology of esophageal atresia and tracheoesophageal fistula: "mind the gap"

Esophageal atresia and tracheoesophageal fistula (EA/TEF) are major congenital malformations affecting 1:3500 live births. Current research efforts are focused on understanding the etiology of these defects. We describe well-known animal models, human syndromes, and associations involving EA/TEF, indicating its etiologically heterogeneous nature. Recent advances in genotyping technology and in knowledge of human genetic variation will improve clinical counseling on etiologic factors. This review provides a clinical summary of environmental and genetic factors involved in EA/TEF.

Congenital anomalies of the esophagus

Congenital malformations of the esophagus are frequently encountered by pediatric surgeons, especially esophageal atresia with or without tracheo-esophageal fistula. However, the molecular mechanisms underlying the development of these various anomalies are not clear. Here we present a brief overview of the embryologic development of the tracheoesophageal tube, along with some of the genetic controls which, when defective can lead to abnormal separation of this tube.

Genetics

For many years karyotyping has been a successful tool to identify chromosome aberrations in congenital malformations. It has proven to be a highly reliable technique for identifying numerical chromosome changes and structural chromosomal rearrangements, such as deletions, duplications, translocations, or inversions. However, karyotyping has limited resolution of 5-10 Mb and depends on the availability of metaphases. In the last decade, we have experienced the implementation of molecular cytogenetic techniques, resulting in the identification of chromosomal aberrations smaller than 5 Mbp. Because DNA is used as starting material also analysis of paraffin or frozen biopsies is possible. Several genes and loci have been identified, and careful genotype phenotype correlation has lead to the recognition of new syndromes. A further characterization of these new genes and loci involved in the etiology of congenital anomalies will lead to a better understanding of the underlying developmental pathways.

Genetic and environmental factors in the etiology of esophageal atresia and/or tracheoesophageal fistula: an overview of the current concepts

Esophageal atresia and/or tracheoesophageal fistula (EA/TEF) are severe congenital anomalies. Although recent years have brought significant improvement in clinical treatment, our understanding of the etiology of these defects is lagging. Many genes and genetic pathways have been implicated in the development of EA/TEF, but only a few genes have been shown to be involved in humans, in animals, or in both. Extrapolating data from animal models to humans is not always straightforward. Environmental factors may also carry a risk, but the mechanisms are yet to be elucidated. This review gives an overview of the current state of knowledge about both genetic and environmental risk factors in the etiology of EA/TEF.

Developmental aspects of the upper airway: report from an NHLBI Workshop, March 5-6, 2009

The upper airway serves three important functions: respiration, swallowing, and speech. During development it undergoes significant structural and functional changes that affect its size, shape, and mechanical properties. Abnormalities of the upper airway require prompt attention, because these often alter ventilatory patterns and gas exchange, particularly during sleep when upper airway motor tone and ventilatory drive are diminished. Recognizing the relationship of early life events to lung health and disease, the National Heart, Lung, and Blood Institute (NHLBI), with cofunding from the Office of Rare Diseases (ORD), convened a workshop of extramural experts, from many disciplines. The objective of the workshop was: (1) to review the state of science in pediatric upper airway disorders; (2) to make recommendations to the Institute to fill knowledge gaps; (3) to prioritize new research directions; and (4) to capitalize on scientific opportunities. This report provides recommendations that could facilitate translation of basic research findings into practice to better diagnose, treat, and prevent airway compromise in children.

Maternal periconceptional exposure to cigarette smoking and alcohol and esophageal atresia +/- tracheo-esophageal fistula

BACKGROUND

Esophageal atresia (EA) is a moderately frequent birth defect that often occurs with tracheo-esophageal fistula (TEF). Etiologic studies for EA+/-TEF have produced inconsistent results.

METHODS

This study used data from the National Birth Defects Prevention Study (NBDPS) to examine the association between maternal periconceptional exposure to cigarette smoking and alcohol and EA+/-TEF. Cases of EA+/-TEF and unaffected controls with an estimated date of delivery from October 1997 through December 2003 were identified, and telephone interview reports for smoking and alcohol exposure were obtained from birth mothers of 334 cases and 4,967 controls. Odds ratios (OR)s and 95% confidence intervals (CI)s, adjusted for several covariates, were calculated to assess associations.

RESULTS

ORs were near unity for all EA+/-TEF cases combined and any periconceptional exposure to cigarette smoking (OR = 1.1; CI = 0.8,1.6) or alcohol (OR = 1.2; CI = 0.8,1.8). For cigarette smoking, some elevated ORs were found but varied by type of smoking exposure. No consistent patterns were identified for number of cigarettes smoked per day. For alcohol, ORs were weak to moderately elevated with increasing number of drinks consumed and for binge drinkers compared to non-binge drinkers. ORs were further elevated among mothers who reported active+passive exposure to cigarette smoking and alcohol (OR = 2.5; CI = 1.1,5.6). For both exposures, ORs were higher for cases with additional major defects compared to isolated cases.

CONCLUSIONS

These results, based on one of the largest published samples of EA+/-TEF cases, suggest a role for these exposures in the etiology of EA+/-TEF, although further study is needed to replicate the observed associations.

The current state of congenital tracheal stenosis

Congenital tracheal stenosis (CTS) is an uncommon condition that has challenged pediatric surgeons for decades. Patients with CTS can present with a wide spectrum of symptoms and varying degrees of severity. In addition, a variety of techniques have been devised to repair this malformation. A review of these procedures and our suggestions for clinical standards and practice guidelines will be presented in this paper. A retrospective review of the literature on CTS from 1964 to 31 March, 2006. There is not one standard technique for the repair of CTS, as individualized approach to each patient and airway lesion is necessary to optimize patient management; nevertheless there is a consensus about segmental resection and anastomosis being best for short segment stenosis while slide tracheoplasty is most effective for the long-segment ones. Conservative management is also an option for select group of patients with careful and close follow up. Survival following surgery over the years has improved, but mortality remained high, particularly in a specific subset of patients presenting at the age less than 1 month with associated cardiac malformations. In conclusion, CTS remains a significant challenge for pediatric surgeons. Additional research is required to improve our understanding of the pathogenesis of CTS, and to develop evidence-based treatment protocols for the entire spectrum of presentation including conservative management.

Adriamycin produces a reproducible teratogenic model of vertebral, anal, cardiovascular, tracheal, esophageal, renal, and limb anomalies in the mouse

BACKGROUND/PURPOSE

The Adriamycin rat model is an established model for vertebral, anal, cardiac, tracheal, esophageal, renal, and limb (VACTERL) anomalies and gastrointestinal atresias. Mice are the foremost mammal studied by developmental biologists, providing greater availability of molecular probes, antibodies, and transferable knowledge with transgenic studies. Only tracheoesophageal malformations have been previously described in the Adriamycin mouse model. The aim of this study was to carry out a dose-response analysis of the teratogenicity of Adriamycin in the mouse to determine the effect of the dose and timing of exposure in producing tracheoesophageal malformations and show if it causes other VACTERL anomalies.

METHODS

CBA/Ca mice were accurately time mated (n = 30). Four different doses (0 [saline], 4, 5, and 6 mg/kg) of Adriamycin (EBEWE Pharma Ges.m.b.H. Nfg.KG, A-4866 Unterach, Austria) at 3 different timings of injections were compared. Dams received 2 intraperitoneal injections, 24 hours apart, commencing on day 7, 7.5, or 8. Fetuses were harvested on day 18. Anomalies were examined using a dissecting microscope and serial transverse sections.

RESULTS

Administering Adriamycin at 6 mg/kg on days 7 and 8 had the most teratogenic effect, with 80% of fetuses having 3 or more VACTERL anomalies: anorectal malformation, 100%; tracheoesophageal malformation, 50%; right-sided aortic arch, 58.3%; bladder agenesis/bilateral hydronephrosis, 100%.

CONCLUSION

This study establishes a mouse model that should provide insights into the cellular and molecular mechanisms underlying VACTERL anomalies.

Esophageal atresia and tracheoesophageal fistula in children of women exposed to diethylstilbestrol in utero

OBJECTIVE

This study was undertaken to study the possible risk to mothers exposed in utero to diethylstilbestrol for offspring with esophageal atresia/tracheoesophageal fistula.

STUDY DESIGN

Information on the mothers' in utero exposure to diethylstilbestrol was obtained from 3 sources: questionnaires completed by members of the parents' association of children with esophageal atresia/tracheoesophageal fistula; records of patients with esophageal atresia/tracheoesophageal fistula from a hospital database; and files from the Northern Netherlands EUROCAT birth defects registry.

RESULTS

Three of 124 (2.4%) mothers from the parents' association and 6 of 192 (3.1%) mothers from the hospital cases reported in utero exposure to diethylstilbestrol. For 8848 children registered by EUROCAT, 33 (0.37%) mothers reported in utero exposure to diethylstilbestrol. Of 117 infants with esophageal atresia/tracheoesophageal fistula, 4 (3.4%) had a mother with in utero exposure to diethylstilbestrol; this association was statistically significant (P = .001).

CONCLUSION

We report a possible transgenerational effect of diethylstilbestrol exposure in the cause of some cases of esophageal atresia/tracheoesophageal fistula.

Stephen L. Gans Distinguished Overseas Lecture. The neural crest in pediatric surgery

AIM

This review highlights the relevance of the neural crest (NC) as a developmental control mechanism involved in several pediatric surgical conditions and the investigative interest of following some of its known signaling pathways.

METHODS

The participation of the NC in facial clefts, ear defects, branchial fistulae and cysts, heart outflow tract and aortic arch anomalies, pigmentary disorders, abnormal enteric innervation, neural tumors, hemangiomas, and vascular anomalies is briefly reviewed. Then, the literature on clinical and experimental esophageal atresia-tracheoesophageal fistula (EA-TEF) and congenital diaphragmatic hernia (CDH) is reviewed for the presence of associated NC defects. Finally, some of the molecular signaling pathways involved in both conditions (sonic hedgehog, Hox genes, and retinoids) are summarized.

RESULTS

The association of facial, cardiovascular, thymic, parathyroid, and C-cell defects together with anomalies of extrinsic and intrinsic esophageal innervation in babies and/or animals with both EA-TEF and CDH strongly supports the hypothesis that NC is involved in the pathogenesis of these malformative clusters. On the other hand, both EA-TEF and CDH are observed in mice mutant for genes involved in the previously mentioned signaling pathways.

CONCLUSIONS

The investigation of NC-related molecular pathogenic pathways involved in malformative associations like EA-TEF and CDH that are induced by chromosomal anomalies, chemical teratogens, and engineered mutations is a promising way of clarifying why and how some pediatric surgical conditions occur. Pediatric surgeons should be actively involved in these investigations.

Congenital anomalies of the esophagus

Normal anatomy, embryology, and congenital anomalies of the esophagus are discussed in this article. The classification, epidemiology, embryology, diagnosis, and management, including outcome following repair of esophageal atresia with or without an associated tracheoesophageal fistula, are described. The diagnosis and management of less common anomalies, such as congenital esophageal stenosis and congenital esophageal duplication, are outlined.

Abnormal separation of the respiratory primordium in the adriamycin mouse model of tracheoesophageal malformations

BACKGROUND/PURPOSE

Organogenesis relies on temperospatially coordinated signaling systems. The adriamycin rat model provided insights into the dysmorphogenesis of tracheoesophageal malformations. An adriamycin mouse model (AMM) would facilitate the investigation of their molecular pathogenesis. To transfer the knowledge gained from the rat, we describe a histological account of the critical period of organogenesis of these malformations in the AMM.

METHOD

CBA/Ca mice were accurately time-mated (n = 18). Dams received intraperitoneal injections of adriamycin (6 mg/kg) (n = 12) or saline control (n = 6) on days 7 and 8. Fetuses were harvested on days 9, 9.5, 10, 11, 12, and 13, resin embedded, and 1-mum sections of the developing foregut were examined.

RESULTS

Day 11 control fetuses showed normal separation of the respiratory primordium, with apoptotic bodies at the point of separation. A more caudal point of separation of the distal foregut without apoptotic bodies was found in 4 of 10 AMM fetuses. Day 13 AMM fetuses had dorsal or ventral outpouchings of the foregut, indicating which malformation they would develop. Abnormal branching of the notochord was seen from day 9.5 in AMM fetuses. This was not always associated with abnormal tracheoesophageal development.

CONCLUSION

This study confirms that the abnormal observations made in the rat model apply to the mouse.

Chromosomal anomalies in the aetiology of oesophageal atresia and tracheo-oesophageal fistula

Oesophageal atresia (OA) and tracheo-oesophageal fistula (TOF) are severe congenital anomalies of which the aetiology is largely unknown. Several chromosomal anomalies have been described in patients presenting with these anatomical malformations, but until now none of these has led to the identification of a single aetiological factor. This paper reviews the chromosomal abnormalities reported in cases of OA/TOF and serves as a starting point to identify chromosomal regions harbouring genes involved in the aetiology of OA/TOF.

Morphogenesis of the trachea and esophagus: current players and new roles for noggin and Bmps

The development of the anterior foregut of the mammalian embryo involves changes in the behavior of both the epithelial endoderm and the adjacent mesoderm. Morphogenetic processes that occur include the extrusion of midline notochord cells from the epithelial definitive endoderm, the folding of the endoderm into a foregut tube, and the subsequent separation of the foregut tube into trachea and esophagus. Defects in foregut morphogenesis underlie the constellation of human birth defects known as esophageal atresia (EA) and tracheoesophageal fistula (TEF). Here, we review what is known about the cellular events in foregut morphogenesis and the gene mutations associated with EA and TEF in mice and humans. We present new evidence that about 70% of mouse embryos homozygous null for Nog, the gene encoding noggin, a bone morphogenetic protein (Bmp) antagonist, have EA/TEF as well as defects in lung branching. This phenotype appears to correlate with abnormal morphogenesis of the notochord and defects in its separation from the definitive endoderm. The abnormalities in foregut and lung morphogenesis of Nog null mutant can be rescued by reducing the gene dose of Bmp4 by 50%. This suggests that normal foregut morphogenesis requires that the level of Bmp4 activity is carefully controlled by means of antagonists such as noggin. Several mechanisms are suggested for how Bmps normally function, including by regulating the intercellular adhesion and behavior of notochord and foregut endoderm cells. Future research must determine how Noggin/Bmp antagonism fits into the network of other factors known to regulate tracheal and esophagus development, both in mouse or humans.

Retinoic acid regulates morphogenesis and patterning of posterior foregut derivatives

Retinoic acid (RA) is an embryonic signaling molecule regulating a wide array of target genes, thereby being a master regulator of patterning and differentiation in a variety of organs. Here we show that mouse embryos deficient for the RA-synthesizing enzyme retinaldehyde dehydrogenase 2 (RALDH2), if rescued from early lethality by maternal RA supplementation between E7.5 and E8.5, lack active RA signaling in the foregut region. The resulting mutants completely fail to develop lungs. Development of more posterior foregut derivatives (stomach and duodenum), as well as liver growth, is also severely affected. A primary lung bud is specified in the RA-deficient embryos, which fails to outgrow due to defective FGF10 signaling and lack of activation of FGF-target genes, such as Pea3 and Bmp4 in the epithelium. Specific Hox and Tbx genes may mediate these RA regulatory effects. Development of foregut derivatives can be partly restored in mutants by extending the RA supplementation until at least E10.5, but lung growth and branching remain defective and a hypoplastic lung develops on the right side only. Such conditions poorly restore FGF10 signaling in the lung buds. Explant culture of RALDH2-deficient foreguts show a capacity to undergo lung budding and early branching in the presence of RA or FGF10. Our data implicate RA as a regulator of gene expression in the early embryonic lung and stomach region upstream of Hox, Tbx and FGF10 signaling.

Oesophageal atresia, tracheo-oesophageal fistula, and the VACTERL association: review of genetics and epidemiology

Oesophageal atresia and/or tracheo-oesophageal fistula are relatively common malformations occurring in approximately 1 in 3500 births. In around half of the cases (syndromic oesophageal atresia), there are associated anomalies, with cardiac malformations being the most common. In the remainder (non-syndromic cases), oesophageal atresia/tracheo-oesophageal fistula occur in isolation. Data from twin and family studies suggest that genetic factors do not play a major role, and yet there are well-defined instances of this malformation where genetic factors clearly are important. This is highlighted by the recent identification of no fewer than three separate genes with a role in the aetiology of oesophageal atresia: those for Feingold syndrome (N-MYC), anophthalmia-oesophageal-genital (AEG) syndrome (SOX2), and CHARGE syndrome (CHD7). Additional support for genetic factors in this malformation comes from chromosomal studies and mouse models. This paper reviews current knowledge of the genetics and epidemiology of the different oesophageal atresia/tracheo-oesophageal fistula syndromes and associations.

Genetic players in esophageal atresia and tracheoesophageal fistula

Esophageal atresia is a common and serious developmental anomaly, of which the causes remain largely unknown. Studies in vertebrate models indicate the importance of the sonic hedgehog pathway in esophageal atresia, but its relevance to the human condition remains to be defined. Now, three genes have been identified that cause syndromic forms of esophageal atresia when mutated. NMYC and SOX2 are transcription factors, whereas CHD7 is encoded by a chromodomain helicase DNA-binding gene, important for chromatin structure and gene expression. These new genes broaden our view of human foregut development.