Decreased expression of GATA4 in the diaphragm of nitrofen-induced congenital diaphragmatic hernia

Pbx1, Meis1, and Runx1 Expression Is Decreased in the Diaphragmatic and Pulmonary Mesenchyme of Rats with Nitrofen-Induced Congenital Diaphragmatic Hernia

INTRODUCTION

 Congenital diaphragmatic hernia (CDH) and associated pulmonary hypoplasia (PH) are thought to originate from mesenchymal defects in pleuroperitoneal folds (PPFs) and primordial lungs. Pre-B-cell leukemia homeobox 1 (Pbx1), its binding partner myeloid ecotropic integration site 1 (Meis1), and runt-related transcription factor 1 (Runx1) are expressed in diaphragmatic and lung mesenchyme, functioning as transcription cofactors that modulate mesenchymal cell proliferation. Furthermore, Pbx1 ^-/- mice develop diaphragmatic defects and PH similar to human CDH. We hypothesized that diaphragmatic and pulmonary Pbx1, Meis1, and Runx1 expression is decreased in the nitrofen-induced CDH model.

MATERIALS AND METHODS

 Time-mated rats were exposed to nitrofen or vehicle on gestational day 9 (D9). Fetal diaphragms (n = 72) and lungs (n = 48) were microdissected on D13, D15, and D18, and were divided into control and nitrofen-exposed specimens. Diaphragmatic and pulmonary gene expression levels of Pbx1, Meis1, and Runx1 were analyzed by quantitative real-time polymerase chain reaction. Immunofluorescence-double-staining for Pbx1, Meis1, and Runx1 was combined with mesenchymal/myogenic markers Gata4 and myogenin to evaluate protein expression.

RESULTS

 Relative mRNA expression of Pbx1, Meis1, and Runx1 was significantly decreased in PPFs (D13), developing diaphragms/lungs (D15), and muscularized diaphragms/differentiated lungs (D18) of nitrofen-exposed fetuses compared with controls. Confocal-laser-scanning-microscopy revealed markedly diminished Pbx1, Meis1, and Runx1 immunofluorescence in diaphragmatic and pulmonary mesenchyme, associated with less proliferating mesenchymal cells in nitrofen-exposed fetuses on D13, D15, and D18 compared with controls.

CONCLUSION

 Decreased Pbx1, Meis1, and Runx1 expression during diaphragmatic development and lung branching morphogenesis may reduce mesenchymal cell proliferation, causing malformed PPFs and disrupted airway branching, thus leading to diaphragmatic defects and PH in the nitrofen-induced CDH model.

Basic and translational science advances in congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a birth defect that is characterized by lung hypoplasia, pulmonary hypertension and a diaphragmatic defect that allows herniation of abdominal organs into the thoracic cavity. Although widely unknown to the public, it occurs as frequently as cystic fibrosis (1:2500). There is no monogenetic cause, but different animal models revealed various biological processes and epigenetic factors involved in the pathogenesis. However, the pathobiology of CDH is not sufficiently understood and its mortality still ranges between 30 and 50%. Future collaborative initiatives are required to improve our basic knowledge and advance novel strategies to (prenatally) treat the abnormal lung development. This review focusses on the genetic, epigenetic and protein background and the latest advances in basic and translational aspects of CDH research.

Gata-6 expression is decreased in diaphragmatic and pulmonary mesenchyme of fetal rats with nitrofen-induced congenital diaphragmatic hernia

PURPOSE

Congenital diaphragmatic hernia (CDH) and associated pulmonary hypoplasia are thought to be caused by a malformation of the underlying diaphragmatic and airway mesenchyme. GATA binding protein 6 (Gata-6) is a zinc finger-containing transcription factor that plays a crucial role during diaphragm and lung development. In the primordial diaphragm, Gata-6 expression is restricted to mesenchymal compartments of the pleuroperitoneal folds (PPFs). In addition, Gata-6 is essential for airway branching morphogenesis through upregulation of mesenchymal signaling. Recently, mutations in Gata-6 have been linked to human CDH. We hypothesized that diaphragmatic and pulmonary Gata-6 expression is decreased in the nitrofen-induced CDH model.

METHODS

Time-mated rats were exposed to either nitrofen or vehicle on gestational day 9 (D9). Fetal diaphragms (n = 72) and lungs (n = 48) were microdissected on selected timepoints D13, D15 and D18, and divided into control and nitrofen-exposed specimens (n = 12 per sample, timepoint and experimental group, respectively). Diaphragmatic and pulmonary gene expression of Gata-6 was analyzed by qRT-PCR. Immunofluorescence-double staining for Gata-6 was combined with the diaphragmatic mesenchymal marker Gata-4 and the pulmonary mesenchymal marker Fgf-10 to evaluate protein expression and localization in fetal diaphragms and lungs.

RESULTS

Relative mRNA expression levels of Gata-6 were significantly decreased in PPFs on D13 (0.57 ± 0.21 vs. 2.27 ± 1.30; p < 0.05), developing diaphragms (0.94 ± 0.59 vs. 2.28 ± 1.89; p < 0.05) and lungs (0.56 ± 0.16 vs. 0.71 ± 0.39; p < 0.05) on D15 and fully muscularized diaphragms (1.20 ± 1.10 vs. 2.52 ± 1.86; p < 0.05) and differentiated lungs (0.56 ± 0.05 vs. 0.77 ± 0.14; p < 0.05) on D18 of nitrofen-exposed fetuses compared to controls. Confocal laser scanning microscopy demonstrated markedly diminished immunofluorescence of Gata-6 mainly in diaphragmatic and pulmonary mesenchyme, which was associated with a reduction of proliferating mesenchymal cells in nitrofen-exposed fetuses on D13, D15, and D18 compared to controls.

CONCLUSION

Decreased Gata-6 expression during diaphragmatic development and lung branching morphogenesis may disrupt mesenchymal cell proliferation, causing malformed PPFs and reduced airway branching, thus leading to diaphragmatic defects and pulmonary hypoplasia in the nitrofen-induced CDH model.

Decreased Desmin expression in the developing diaphragm of the nitrofen-induced congenital diaphragmatic hernia rat model

PURPOSE

Congenital diaphragmatic hernia (CDH) is presumed to originate from defects in the primordial diaphragmatic mesenchyme, mainly comprising of muscle connective tissue (MCT). Thus, normal diaphragmatic morphogenesis depends on the structural integrity of the underlying MCT. Developmental mutations that inhibit normal formation of diaphragmatic MCT have been shown to result in CDH. Desmin (DES) is a major filament protein in the MCT, which is essential for the tensile strength of the developing diaphragm muscle. DES ^-/- knockout mice exhibit significant reductions in stiffness and elasticity of the developing diaphragmatic muscle tissue. Furthermore, sequence changes in the DES gene have recently been identified in human cases of CDH, suggesting that alterations in DES expression may lead to diaphragmatic defects. This study was designed to investigate the hypothesis that diaphragmatic DES expression is decreased in fetal rats with nitrofen-induced CDH.

METHODS

Time-mated Sprague-Dawley rats were exposed to either nitrofen or vehicle on gestational day 9 (D9). Fetuses were harvested on selected time-points D13, D15 and D18, and dissected diaphragms (n = 72) were divided into control and nitrofen-exposed specimens (n = 12 per time-point and experimental group, respectively). Laser-capture microdissection was used to obtain diaphragmatic tissue elements. Diaphragmatic gene expression of DES was analyzed by quantitative real-time polymerase chain reaction. Immunofluorescence double staining for DES was combined with the mesenchymal marker GATA4 to evaluate protein expression and localization in developing fetal diaphragms.

RESULTS

Relative mRNA expression levels of DES were significantly decreased in pleuroperitoneal folds on D13 (1.49 ± 1.79 vs. 3.47 ± 2.32; p < 0.05), developing diaphragms on D15 (1.49 ± 1.41 vs. 3.94 ± 3.06; p < 0.05) and fully muscularized diaphragms on D18 (2.45 ± 1.47 vs. 5.12 ± 3.37; p < 0.05) of nitrofen-exposed fetuses compared to controls. Confocal laser scanning microscopy demonstrated markedly diminished immunofluorescence of DES mainly in diaphragmatic MCT, which was associated with a reduction of proliferating mesenchymal cells in nitrofen-exposed fetuses on D13, D15 and D18 compared to controls.

CONCLUSION

Decreased expression of DES in the fetal diaphragm may disturb the basic integrity of myofibrils and the cytoskeletal network during myogenesis, causing malformed MCT and leading to diaphragmatic defects in the nitrofen-induced CDH model.

Expression of Prx1 and Tcf4 is decreased in the diaphragmatic muscle connective tissue of nitrofen-induced congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Pleuroperitoneal folds (PPFs) are the source of the primordial diaphragm's muscle connective tissue (MCT), and developmental mutations have been shown to result in congenital diaphragmatic hernia (CDH). The protein paired-related homeobox 1 (Prx1) labels migrating PPF cells and stimulates expression of transcription factor 4 (Tcf4), a novel MCT marker that controls morphogenesis of the fetal diaphragm. We hypothesized that diaphragmatic Prx1 and Tcf4 expression is decreased in the nitrofen-induced CDH model.

METHODS

Time-mated rats were exposed to either nitrofen or vehicle on gestational day 9 (D9). Fetal diaphragms were microdissected on D13, D15, and D18, and divided into control and nitrofen-exposed specimens. Gene expression levels of Prx1 and Tcf4 were analyzed by qRT-PCR. Immunofluorescence double staining for Prx1 and Tcf4 was performed to evaluate protein expression and localization.

RESULTS

Relative mRNA expression of Prx1 and Tcf4 was significantly downregulated in PPFs (D13), developing diaphragms (D15) and fully muscularized diaphragms (D18) of nitrofen-exposed fetuses compared to controls. Confocal laser scanning microscopy revealed markedly diminished Prx1 and Tcf4 expression in diaphragmatic MCT of nitrofen-exposed fetuses on D13, D15, and D18 compared to controls.

CONCLUSIONS

Decreased expression of Prx1 and Tcf4 in the fetal diaphragm may cause defects in the PPF-derived MCT, leading to development of CDH in the nitrofen model.

LEVEL OF EVIDENCE

Level 2c (Centre for Evidence-Based Medicine, Oxford).

Decreased expression of hepatocyte growth factor in the nitrofen model of congenital diaphragmatic hernia

PURPOSE

Pleuroperitoneal folds (PPFs) are essential for normal diaphragmatic development, representing the only source of the diaphragm's muscle connective tissue. Hepatocyte growth factor (Hgf), which is secreted in PPFs, plays a crucial role in the formation of the muscular diaphragmatic components by regulating the migration of myogenic progenitor cells into the primordial diaphragm. Hgf is also a known downstream target of Gata4 and it has been demonstrated that the expression of Hgf was significantly downregulated in PPF cells of Gata4 knockouts with congenital diaphragmatic hernia (CDH). Furthermore, mutations in PPF-derived cells have been shown to result in CDH. We hypothesized that Hgf expression is decreased in developing diaphragms of fetal rats with nitrofen-induced CDH.

METHODS

Timed-pregnant rats were exposed to either nitrofen or vehicle on gestational day 9 (D9). Fetuses were harvested on selected time-points D13, D15 and D18. Dissected diaphragms (n = 72) were divided into control and nitrofen-exposed specimens (n = 12 per time-point and experimental group, respectively). Diaphragmatic gene expression of Hgf was analyzed by qRT-PCR. Immunofluorescence double staining for Hgf and the mesenchymal marker Gata4 or muscular progenitor marker Myogenin was performed to evaluate protein expression and localization in fetal diaphragms.

RESULTS

Relative mRNA expression of Hgf was significantly downregulated in PPFs of nitrofen-exposed fetuses on D13 (3.08 ± 1.46 vs. 5.24 ± 1.93; p < 0.05), developing diaphragms of nitrofen-exposed fetuses on D15 (2.01 ± 0.79 vs. 4.10 ± 1.50; p < 0.05) and fully muscularized diaphragms of nitrofen-exposed fetuses on D18 (1.60 ± 0.78 vs. 3.21 ± 1.89; p < 0.05) compared to controls. Confocal laser scanning microscopy revealed markedly diminished diaphragmatic immunofluorescence of Hgf in nitrofen-exposed fetuses on D13, D15 and D18 compared to controls, which was associated with disruptions in muscle connective tissue formation and reduced myogenic progenitor cell invasion.

CONCLUSION

Decreased diaphragmatic expression of Hgf may disturb the formation of muscle connective tissue in PPFs and thus prevent essential migration of muscle progenitor cells into the developing diaphragm, leading to diaphragmatic defects in the nitrofen CDH model.

Conditional deletion of WT1 in the septum transversum mesenchyme causes congenital diaphragmatic hernia in mice

Congenital diaphragmatic hernia (CDH) is a severe birth defect. Wt1-null mouse embryos develop CDH but the mechanisms regulated by WT1 are unknown. We have generated a murine model with conditional deletion of WT1 in the lateral plate mesoderm, using the G2 enhancer of the Gata4 gene as a driver. 80% of G2-Gata4^Cre;Wt1^fl/fl embryos developed typical Bochdalek-type CDH. We show that the posthepatic mesenchymal plate coelomic epithelium gives rise to a mesenchyme that populates the pleuroperitoneal folds isolating the pleural cavities before the migration of the somitic myoblasts. This process fails when Wt1 is deleted from this area. Mutant embryos show Raldh2 downregulation in the lateral mesoderm, but not in the intermediate mesoderm. The mutant phenotype was partially rescued by retinoic acid treatment of the pregnant females. Replacement of intermediate by lateral mesoderm recapitulates the evolutionary origin of the diaphragm in mammals. CDH might thus be viewed as an evolutionary atavism.

DOI:http://dx.doi.org/10.7554/eLife.16009.001

Mesenchymal expression of the FRAS1/FREM2 gene unit is decreased in the developing fetal diaphragm of nitrofen-induced congenital diaphragmatic hernia

PURPOSE

Developmental mutations that inhibit normal formation of extracellular matrix (ECM) in fetal diaphragms have been identified in congenital diaphragmatic hernia (CDH). FRAS1 and FRAS1-related extracellular matrix 2 (FREM2), which encode important ECM proteins, are secreted by mesenchymal cells during diaphragmatic development. The FRAS1/FREM2 gene unit has been shown to form a ternary complex with FREM1, which plays a crucial role during formation of human and rodent diaphragms. Furthermore, it has been demonstrated that the diaphragmatic expression of FREM1 is decreased in the nitrofen-induced CDH model. We hypothesized that FRAS1 and FREM2 expression is decreased in the developing diaphragms of fetal rats with nitrofen-induced CDH.

METHODS

Pregnant rats were exposed to either nitrofen or vehicle on gestational day 9 (D9), and fetuses were harvested on D13, D15 and D18. Microdissected diaphragms were divided into nitrofen-exposed/CDH and control samples (n = 12 per time-point and experimental group, respectively). Diaphragmatic gene expression levels of FRAS1 and FREM2 were analyzed by qRT-PCR. Immunofluorescence double staining for FRAS1 and FREM2 was combined with the mesenchymal marker GATA4 in order to evaluate protein expression and localization in pleuroperitoneal folds (PPFs) and fetal diaphragmatic tissue.

RESULTS

Relative mRNA expression of FRAS1 and FREM2 were significantly reduced in PPFs of nitrofen-exposed fetuses on D13 (1.76 ± 0.86 vs. 3.09 ± 1.15; p < 0.05 and 0.47 ± 0.26 vs. 0.82 ± 0.36; p < 0.05), developing diaphragms of nitrofen-exposed fetuses on D15 (1.45 ± 0.80 vs. 2.63 ± 0.84; p < 0.05 and 0.41 ± 0.16 vs. 1.02 ± 0.49; p < 0.05) and fully muscularized diaphragms of CDH fetuses on D18 (1.35 ± 0.75 vs. 2.32 ± 0.92; p < 0.05 and 0.37 ± 0.24 vs. 0.70 ± 0.32; p < 0.05) compared to controls. Confocal laser scanning microscopy revealed markedly diminished FRAS1 and FREM2 immunofluorescence in diaphragmatic mesenchyme, which was associated with reduced proliferation of mesenchymal cells in nitrofen-exposed PPFs and fetal CDH diaphragms on D13, D15 and D18 compared to controls.

CONCLUSION

Decreased mesenchymal expression of FRAS1 and FREM2 in the nitrofen-induced CDH model may cause failure of the FRAS1/FREM2 gene unit to activate FREM1 signaling, disturbing the formation of diaphragmatic ECM and thus contributing to the development of diaphragmatic defects in CDH.