Catenin is required for endothelial-mesenchymal transformation during heart cushion development in the mouse (original) (raw)
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Developmental Biology, 2002
The formation of endocardial cushions in the atrioventricular (AV) canal of the rudimentary heart requires epithelial-tomesenchymal cell transformation (EMT). This is a complex developmental process regulated by multiple extracellular signals and transduction pathways. A collagen gel assay, long used to examine endocardial cushion development in avian models, is now being employed to investigate genetically engineered mouse models with abnormal heart morphogenesis. In this study, we determine interspecies variations for avian and mouse cultured endocardial cushion explants. Considering these observed morphologic differences, we also define the temporal requirements for TGF2 and TGF3 during mouse endocardial cushion morphogenesis. TGF2 and TGF3 blocking antibodies inhibit endothelial cell activation and transformation, respectively, in avian explants. In contrast, neutralizing TGF2 inhibits cell transformation in the mouse, while TGF3 antibodies have no effect on activation or transformation events. This functional requirement for TGF2 is concomitant with expression of TGF2, but not TGF3, within mouse endocardial cushions at a time coincident with transformation. Thus, both TGF2 and TGF3 appear necessary for the full morphogenetic program of EMT in the chick, but only TGF2 is expressed and obligatory for mammalian endocardial cushion cell transformation.
Cytology and Genetics, 2014
Wnt/β catenin signaling has a great and diverse influence on the formation, development, and vital activity of a great number of vertebrate tissues, including heart tissue. The role of Wnt/β catenin signal ing and β catenin itself in the processes of cardiogenesis and adult myocardium functioning is not fully elu cidated to date. The current review regards the attempt to generalize contemporary literature data on partic ipation of this signaling pathway in embryogenesis and postnatal heart development, as well as in adult myo cardium functioning in normal conditions and during stress adaptation, and aging, resulting in hypertrophy and heart remodeling. Based on the experimental articles and reviews, we can assume that Wnt/β catenin sig naling pathway is involved not only in controlling the cardiogenesis but also in processes of adaptation and remodeling of the adult organ. This control can be characterized as complicated and multistep and β catenin appears to be a prospective candidate as a target for development of new approaches to adult myocardium pathologies therapy.
Developmental Biology, 1999
EMTs are the initial cellular components of the cardiac cushions and progenitors of valvular and septal fibroblasts. It has been shown that transforming growth factor  (TGF) mediates EMT in the AV canal, and TGF1 and 2 isoforms are expressed in the mouse heart while TGF 2 and 3 are expressed in the avian heart. Depletion of TGF3 in avian or TGF2 in mouse leads to developmental defects of heart tissue. These observations raise questions as to whether multiple TGF isoforms participate in valve formation. In this study, we examined the localization and function of TGF2 and TGF3 in the chick heart during EMT. TGF2 was present in both endothelium and myocardium before and after EMT. TGF2 antibody inhibited endothelial cell-cell separation. In contrast, TGF3 was present only in the myocardium before EMT and was in the endothelium at the initiation of EMT. TGF3 antibodies inhibited mesenchymal cell formation and migration into the underlying matrix. Both TGF2 and 3 increased fibrillin 2 expression. However, only TGF2 treatment increased cell surface -1,4-galactosyltransferase expression. These data suggest that TGF2 and TGF3 are sequentially and separately involved in the process of EMT. TGF2 mediates initial endothelial cell-cell separation while TGF3 is required for the cell morphological change that enables the migration of cells into the underlying ECM.
Developmental Dynamics, 2001
During the early stages of heart development, progenitors for the heart valves and septa come from endothelial cells via a developmental process known as "epithelial-mesenchymal cell transformation." This process is restricted to the atrioventricular (AV) canal and outflow tract portions of the embryonic heart. TGF signal transduction pathways play critical roles during epithelial-mesenchymal cell transformation in heart development. Previously, we showed that both TGF Type II (TRII) and Type III (TRIII) receptors are required to mediate epithelial mesenchymal cell transformation in chick heart. Further, distinct TGF2 and TGF3 activities correspond to separate components of the embryonic cell transformation process. Studies by others of TGF-mediated inhibition of cell proliferation produced a model where TRIII functions by facilitating TGF2 binding to TRII. In the present study, we provide evidence that TRIII mediates distinct cellular responses from those of TRII. Blocking antibody for TRIII, but not antibody against TRII, specifically inhibits the endothelial cell-cell separation step. Examination of developmental markers, perturbed by blocking TRIII antibody, revealed a pattern of expression distinctively different from that of TRII antibody treatment. These data show that a distinct TRIII-mediated process is required for endothelial cell-cell separation during epithelial mesenchymal cell transformation. As TGF2 mediates endothelial cellcell separation, the data point to a specific association of TGF2 and TRIII in the cell separation step of epithelial mesenchymal cell transformation. We conclude that distinct TRII and TRIII signal transduction pathways mediate epithelial-mesenchymal cell transformation in the heart.
Molecular markers of cardiac endocardial cushion development
Developmental Dynamics, 2003
Endocardial cushions are precursors of mature heart valves. They form within the looped heart tube as discrete swellings and develop into thin, pliable leaflets that prevent regurgitation of blood. The embryonic origins of cardiac valves include endothelial, myocardial, and neural crest cells. Recently, an increasing number of animal models derived from mutational screens, gene inactivation, and transgenic studies have identified specific molecules required for normal development of the cardiac valves, and critical molecular pathways are beginning to emerge. To further this process, we have sought to assemble a diverse set of molecular markers encompassing all stages of cardiac valve development. Here, we provide a detailed comparative gene expression analysis of thirteen endocardial cushion markers. We identify endocardial cushion expression of the transcription factor Fog1, and we demonstrate active Wnt/-catenin signaling in developing endocardial cushions suggesting pathways that have not been previously appreciated to participate in cardiac valve formation.
Cells Tissues Organs, 2007
Epithelial-mesenchymal cell transformation (EMT) is a critical process during development of the heart valves. Transition of endothelial cells into mesenchymal cells in the atrioventricular (AV) canal and the outflow tract regions of the heart form the cardiac cushions that eventually form the heart valves. Collagen gel invasion assay has aided in the identification of molecules that regulate EMT. Among those, transforming growth factor-β (TGF-β) ligands and receptors demonstrate a critical role during EMT. In the chick, TGF-β ligands and some receptors have specific functions during EMT. TGF-β2 mediates endothelial cell-cell activation and separation, and TGF-β3 mediates cell invasion into the extracellular matrix. Receptors involved in the EMT process include TGF-β receptor type II (TBRII), TBRIII, endoglin and the TBRI receptors, ALK2 and ALK5. In contrast, in the mouse model, TGF-β2 is the only ligand involved in EMT. The TGF-β2 null mouse has either increased EMT or a mesenchym...
Journal of Cell Science, 2015
During vertebrate development, mesodermal fate choices are regulated by interactions between morphogens such as activin/nodal, BMPs and Wnt/β-catenin that define anterior-posterior patterning and specify downstream derivatives including cardiomyocyte, endothelial and hematopoietic cells. We used human embryonic stem cells to explore how these pathways control mesodermal fate choices in vitro. Varying doses of activin A and BMP4 to mimic cytokine gradient polarization in the anterior-posterior axis of the embryo led to differential activity of Wnt/β-catenin signaling and specified distinct anterior-like (high activin/ low BMP) and posterior-like (low activin/high BMP) mesodermal populations. Cardiogenic mesoderm was generated under conditions specifying anterior-like mesoderm, whereas blood-forming endothelium was generated from posterior-like mesoderm, and vessel-forming CD31 + endothelial cells were generated from all mesoderm origins. Surprisingly, inhibition of β-catenin signaling led to the highly efficient respecification of anterior-like endothelium into beating cardiomyocytes. Cardiac respecification was not observed in posterior-derived endothelial cells. Thus, activin/BMP gradients specify distinct mesodermal subpopulations that generate cell derivatives with unique angiogenic, hemogenic and cardiogenic properties that should be useful for understanding embryogenesis and developing therapeutics.
Developmental Biology, 1997
Valvuloseptal morphogenesis of the primitive heart tube into a four-chambered organ requires the formation of endocardial cushion tissue. The latter is the outcome of an inductive interaction in which endocardial (endothelial) cells are induced to transform into mesenchyme by paracrine signals secreted by the adjacent myocardium. In this study, we propose that transforming endothelial/mesenchymal cells themselves secrete a factor-TGFbeta-3-that functions in an autocrine mode to promote/sustain mesenchyme formation and possibly in a paracrine manner to amplify the original (myocardial) inductive event. Cushion mesenchyme-conditioned medium, previously demonstrated to be an endogenous source of autocrine, migration-promoting factors, was found in the present study to contain TGFbeta-3, as detected by immunoblot analysis. Immunoneutralization of TGFbeta-3 in preparations of cushion mesenchyme-conditioned medium resulted in a failure of treated target endocardial cells to migrate as mesenchyme, whereas inclusion of a control antibody did not inhibit the migration-promoting activity of the conditioned medium. Similar to treatment with the conditioned medium, direct addition of TGFbeta-3 to target endocardial cells also elicited invasive migration but only in cultures which had been activated in vivo by inductive interaction with the myocardium prior to treatment. Selective inhibition of TGFbeta-3-mediated autocrine signaling in continuous cocultures of endocardium plus myocardium resulted in endocardial cells which did not migrate, even though they had expressed early markers associated with endocardial cell activation (e.g., alpha-smooth muscle actin, ES/130, and TGFbeta-3). Collectively, these results suggest that (i) two signaling pathways, myocardial and endocardial, are required to start and complete epithelial-mesenchymal transformation in cushion-forming regions of the heart and (ii) the endocardial pathway signals through iteration of TGFbeta-3 and is not functionally redundant to the myocardial pathway.
Developmental Dynamics, 1997
During early cardiac morphogenesis, outflow tract (OT) and atrio-ventricular (AV) endothelial cells differentiate into mesenchymal cells, which have characteristics of smooth muscle-like myofibroblasts, and which form endocardial cushion tissue, the primordia of valves, and septa in the adult heart. During this embryonic event, transforming growth factor beta3 (TGF beta3) is an essential element in the progression of endothelial-transformation into mesenchyme. TGF beta(s) are known to be a potent inducer for mesodermal differentiation and a promoter for differentiation of endothelial cells into smooth muscle-like cells. Using a monoclonal antibody against smooth muscle-specific alpha-actin (SMA), we examined the immunohistochemical staining of this form of actin in avian endocardial cushion tissue formation. To determine whether TGF beta3 initiates the expression of SMA, the pre-migratory AV endothelial monolayer was cultured with or without chicken recombinant TGF beta3 and the expression of SMA was examined immunochemically. Migrating mesenchymal cells expressed SMA beneath the cell surface membrane. These cells showed a reduction of endothelial specific marker antigen, QH1. Stationary endothelial cells did not express SMA. The deposition of SMA in the mesenchymal tissue persisted until the end of the fetal period. Pre-migratory endothelial cells cultured in complete medium (CM199) that contained TGF beta3 expressed SMA, whereas cells cultured in CM199 alone did not. At the onset of the endothelial-mesenchymal transformation, migrating mesenchymal cells express SMA and the expression of this form of actin is upregulated by TGF beta3. The induction of the expression of SMA by TGF beta3 is one of the initial events in the cytoskeletal reorganization in endothelial cells which separate from one another during the initial phenotypic change associated with the endothelial-mesenchymal transformation.