epidermal-growth-factor and Heart-Defects--Congenital

Congenital heart defects are the most common birth defects in humans, and those that affect the proper alignment of the outflow tracts and septation of the ventricles are a highly significant cause of morbidity and mortality in infants. A late differentiating population of cardiac progenitors, referred to as the anterior second heart field (AHF), gives rise to the outflow tract and the majority of the right ventricle and provides an embryological context for understanding cardiac outflow tract alignment and membranous ventricular septal defects. However, the transcriptional pathways controlling AHF development and their roles in congenital heart defects remain incompletely elucidated. Here, we inactivated the gene encoding the transcription factor MEF2C in the AHF in mice. Loss of Mef2c function in the AHF results in a spectrum of outflow tract alignment defects ranging from overriding aorta to double-outlet right ventricle and dextro-transposition of the great arteries. We identify Tdgf1, which encodes a Nodal co-receptor (also known as Cripto), as a direct transcriptional target of MEF2C in the outflow tract via an AHF-restricted Tdgf1 enhancer. Importantly, both the MEF2C and TDGF1 genes are associated with congenital heart defects in humans. Thus, these studies establish a direct transcriptional pathway between the core cardiac transcription factor MEF2C and the human congenital heart disease gene TDGF1. Moreover, we found a range of outflow tract alignment defects resulting from a single genetic lesion, supporting the idea that AHF-derived outflow tract alignment defects may constitute an embryological spectrum rather than distinct anomalies.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Epidermal Growth Factor; Female; Gene Deletion; Gene Expression Regulation, Developmental; Heart; Heart Defects, Congenital; Heart Septal Defects, Ventricular; Heart Ventricles; Humans; In Situ Hybridization; Male; MEF2 Transcription Factors; Membrane Glycoproteins; Mice; Morphogenesis; Neoplasm Proteins; Organogenesis; Sequence Analysis, RNA; Tissue Distribution; Transcription, Genetic; Transposition of Great Vessels

Mutations in the SH3PXD2B gene coding for the Tks4 protein are responsible for the autosomal recessive Frank-ter Haar syndrome. Tks4, a substrate of Src tyrosine kinase, is implicated in the regulation of podosome formation. Here, we report a novel role for Tks4 in the EGF signaling pathway. In EGF-treated cells, Tks4 is tyrosine-phosphorylated and associated with the activated EGF receptor. This association is not direct but requires the presence of Src tyrosine kinase. In addition, treatment of cells with LY294002, an inhibitor of PI 3-kinase, or mutations of the PX domain reduces tyrosine phosphorylation and membrane translocation of Tks4. Furthermore, a PX domain mutant (R43W) Tks4 carrying a reported point mutation in a Frank-ter Haar syndrome patient showed aberrant intracellular expression and reduced phosphoinositide binding. Finally, silencing of Tks4 was shown to markedly inhibit HeLa cell migration in a Boyden chamber assay in response to EGF or serum. Our results therefore reveal a new function for Tks4 in the regulation of growth factor-dependent cell migration.

Topics: Adaptor Proteins, Signal Transducing; Animals; Cell Movement; Chlorocebus aethiops; Chromones; COS Cells; Craniofacial Abnormalities; Developmental Disabilities; Enzyme Inhibitors; Epidermal Growth Factor; ErbB Receptors; Gene Silencing; Heart Defects, Congenital; HeLa Cells; Humans; Morpholines; Mutation; Osteochondrodysplasias; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Structure, Tertiary; Signal Transduction; src-Family Kinases

Jun is essential for fetal development, as fetuses lacking Jun die at mid-gestation with multiple cellular defects in liver and heart. Embryos expressing JunD in place of Jun (Jun(d/d)) can develop to term with normal fetal livers, but display cardiac defects as observed in fetuses lacking Jun. Jun(d/d) mouse embryonic fibroblasts (MEFs) exhibit early senescence, which can be rescued by EGF and HB-EGF stimulation, probably through activation of Akt signaling. Thus, JunD cannot functionally replace Jun in regulating fibroblast proliferation. In Jun(-/-) fetal livers, increased hydrogen peroxide levels are detected and expression of Nrf1 and Nrf2 (nuclear erythroid 2-related transcription factors) is downregulated. Importantly, increased oxidative stress as well as expression of Nrf1 and Nrf2 is rescued by JunD in Jun(d/d) fetal livers. These data show that Jun is of critical importance for cellular protection against oxidative stress in fetal livers and fibroblasts, and Jun-dependent cellular senescence can be restored by activation of the epidermal growth factor receptor pathway.

Topics: Animal Structures; Animals; Antioxidants; Cell Proliferation; Cellular Senescence; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; Embryo, Mammalian; Epidermal Growth Factor; ErbB Receptors; Fibroblasts; Gene Expression; Heart Defects, Congenital; Hepatocytes; Hydrogen Peroxide; Liver; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; NF-E2-Related Factor 2; Nuclear Respiratory Factor 1; Oxidative Stress; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-jun; Signal Transduction; Tumor Suppressor Protein p53

Abnormalities of embryonic patterning are hypothesized to underlie many common congenital malformations in humans including congenital heart defects (CHDs), left-right disturbances (L-R) or laterality, and holoprosencephaly (HPE). Studies in model organisms suggest that Nodal-like factors provide instructions for key aspects of body axis and germ layer patterning; however, the complex genetics of pathogenic gene variant(s) in humans are poorly understood. Here we report our studies of FOXH1, CFC1, and SMAD2 and summarize our mutational analysis of three additional components in the human NODAL-signaling pathway: NODAL, GDF1, and TDGF1. We identify functionally abnormal gene products throughout the pathway that are clearly associated with CHD, laterality, and HPE. Abnormal gene products are most commonly detected in patients within a narrow spectrum of isolated conotruncal heart defects (minimum 5%-10% of subjects), and far less commonly in isolated laterality or HPE patients (approximately 1% for each). The difference in the mutation incidence between these groups is highly significant. We show that apparent gene dosage discrepancies between humans and model organisms can be reconciled by considering a broader combination of sequence variants. Our studies confirm that (1) the genetic vulnerabilities inferred from model organisms with defects in Nodal signaling are indeed analogous to humans; (2) the molecular analysis of an entire signaling pathway is more complete and robust than that of individual genes and presages future studies by whole-genome analysis; and (3) a functional genomics approach is essential to fully appreciate the complex genetic interactions necessary to produce these effects in humans.

Topics: Amino Acid Sequence; Animals; Body Patterning; Case-Control Studies; Codon; Cohort Studies; DNA Mutational Analysis; Embryo, Nonmammalian; Epidermal Growth Factor; Forkhead Transcription Factors; GPI-Linked Proteins; Growth Differentiation Factor 1; Heart Defects, Congenital; Holoprosencephaly; Humans; Intercellular Signaling Peptides and Proteins; Membrane Glycoproteins; Models, Biological; Molecular Sequence Data; Mutation; Neoplasm Proteins; Nodal Protein; Pilot Projects; Sequence Homology, Amino Acid; Signal Transduction; Smad2 Protein; Transforming Growth Factor beta; Zebrafish

The heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is a member of the EGF family of growth factors that binds to and activates the EGF receptor (EGFR) and the related receptor tyrosine kinase, ErbB4. HB-EGF-null mice (HB(del/del)) were generated to examine the role of HB-EGF in vivo. More than half of the HB(del/del) mice died in the first postnatal week. The survivors developed severe heart failure with grossly enlarged ventricular chambers. Echocardiographic examination showed that the ventricular chambers were dilated and that cardiac function was diminished. Moreover, HB(del/del) mice developed grossly enlarged cardiac valves. The cardiac valve and the ventricular chamber phenotypes resembled those displayed by mice lacking EGFR, a receptor for HB-EGF, and by mice conditionally lacking ErbB2, respectively. HB-EGF-ErbB interactions in the heart were examined in vivo by administering HB-EGF to WT mice. HB-EGF induced tyrosine phosphorylation of ErbB2 and ErbB4, and to a lesser degree, of EGFR in cardiac myocytes. In addition, constitutive tyrosine phosphorylation of both ErbB2 and ErbB4 was significantly reduced in HB(del/del) hearts. It was concluded that HB-EGF activation of receptor tyrosine kinases is essential for normal heart function.

Topics: Animals; Epidermal Growth Factor; ErbB Receptors; Female; Gene Targeting; Heart; Heart Defects, Congenital; Heart Valves; Heparin-binding EGF-like Growth Factor; Intercellular Signaling Peptides and Proteins; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Receptor, ErbB-2; Receptor, ErbB-4; Signal Transduction

Heparin-binding epidermal growth factor (HB-EGF) and betacellulin (BTC) are activating ligands for EGF receptor (EGFR/ErbB1) and ErbB4. To identify their physiological functions, we disrupted mouse HB-EGF and BTC alleles by homologous recombination. Most HB-EGF(-/-) mice died before weaning, and survivors had enlarged, dysfunctional hearts and reduced lifespans. Although BTC(-/-) mice were viable and fertile and displayed no overt defects, the lifespan of double null HB-EGF(-/-)/BTC(-/-) mice was further reduced, apparently due to accelerated heart failure. HB-EGF(-/-) newborns had enlarged and malformed semilunar and atrioventricular heart valves, and hypoplastic, poorly differentiated lungs. Defective cardiac valvulogenesis was the result of abnormal mesenchymal cell proliferation during remodeling, and was associated with dramatic increases in activated Smad1/5/8. Consistent with the phenotype, HB-EGF transcripts were localized to endocardial cells lining the margins of wild-type valves. Similarly defective valvulogenesis was observed in newborn mice lacking EGFR and tumor necrosis factor-alpha converting enzyme (TACE). These results suggest that cardiac valvulogenesis is dependent on EGFR activation by TACE-derived soluble HB-EGF, and that EGFR signaling is required to regulate bone morphogenetic protein signaling in this context.

Topics: ADAM Proteins; ADAM17 Protein; Animals; Betacellulin; Bone Morphogenetic Proteins; Epidermal Growth Factor; ErbB Receptors; Gene Expression Regulation, Developmental; Heart Defects, Congenital; Heart Valves; Heparin-binding EGF-like Growth Factor; Intercellular Signaling Peptides and Proteins; Lung; Metalloendopeptidases; Mice; Mice, Inbred C57BL; Mice, Knockout; Receptor, ErbB-4

Heparin-binding EGF-like growth factor (HB-EGF) is first synthesized as a membrane-anchored form (proHB-EGF), and its soluble form (sHB-EGF) is released by ectodomain shedding from proHB-EGF. To examine the significance of proHB-EGF processing in vivo, we generated mutant mice by targeted gene replacement, expressing either an uncleavable form (HBuc) or a transmembrane domain-truncated form (HBdeltatm) of the molecule. HB(uc/uc) mice developed severe heart failure and enlarged heart valves, phenotypes similar to those in proHB-EGF null mice. On the other hand, mice carrying HBdeltatm exhibited severe hyperplasia in both skin and heart. These results indicate that ectodomain shedding of proHB-EGF is essential for HB-EGF function in vivo, and that this process requires strict control.

Topics: Animals; Cell Surface Extensions; Epidermal Growth Factor; Gene Targeting; Heart Defects, Congenital; Heart Valves; Heparin-binding EGF-like Growth Factor; Hyperplasia; Intercellular Signaling Peptides and Proteins; Mice; Mice, Mutant Strains; Mutation; Protein Processing, Post-Translational; Protein Structure, Tertiary; Skin Abnormalities; Solubility

A series of inductive signals are necessary to subdivide the mesoderm in order to allow the formation of the progenitor cells of the heart. Mesoderm-endogenous transcription factors, such as those encoded by twist and tinman, seem to cooperate with these signals to confer correct context and competence for a cardiac cell fate. Additional factors are likely to be required for the appropriate specification of individual cell types within the forming heart. Similar to tinman, the zinc finger- and homeobox-containing gene, zfh-1, is expressed in the early mesoderm and later in the forming heart, suggesting a possible role in heart development. Here, we show that zfh-1 is specifically required for formation of the even-skipped (eve)-expressing subset of pericardial cells (EPCs), without affecting the formation of their siblings, the founders of a dorsal body wall muscle (DA1). In addition to zfh-1, mesodermal eve itself appears to be needed for correct EPC differentiation, possibly as a direct target of zfh-1. Epistasis experiments show that zfh-1 specifies EPC development independently of numb, the lineage gene that controls DA1 founder versus EPC cell fate. We discuss the combinatorial control mechanisms that specify the EPC cell fate in a spatially precise pattern within the embryo.

Topics: Animals; Animals, Genetically Modified; Bacterial Proteins; Binding Sites; Cell Differentiation; DNA-Binding Proteins; Drosophila; Drosophila Proteins; Embryo, Nonmammalian; Enhancer Elements, Genetic; Epidermal Growth Factor; Gene Expression Regulation, Developmental; Heart; Heart Defects, Congenital; Homeodomain Proteins; Juvenile Hormones; Mesoderm; Mutation; Myocardium; Repressor Proteins; Stem Cells; Trans-Activators; Transcription Factors

Progressive pulmonary hypertension is characterized by smooth muscle cell proliferation and migration leading to occlusive arterial lesions. Previously, using cultured smooth muscle cells, we demonstrated that epidermal growth factor (EGF)-dependent proliferation and migration are dependent on tenascin-C (Tn) and cellular fibronectin (Fn), respectively. In this study we applied immunohistochemistry to lung biopsy tissue from patients with congenital heart defects and pulmonary hypertension to determine how the distribution and intensity of Tn, EGF, proliferating cell nuclear antigen (PCNA), and Fn expression related to arterial abnormalities. With mildly increased wall thickness, minimal Tn, PCNA, and EGF was evident. With progressive hypertrophy, moderately intense foci of Tn were apparent in the adventitia, periendothelium, and occasionally the media but not consistently co-distributing with EGF and PCNA. With obstructive lesions, intense neointimal Tn expression co-localized with EGF and PCNA. Fn accumulation in the periendothelium increased with medial hypertrophy and became more widespread in a diffuse pattern with neointimal formation. The neointima was predominantly composed of alpha-smooth-muscle-actin-positive cells, occasional inflammatory cells with no evidence of apoptosis. These studies are consistent with Tn modulating EGF-dependent neointimal smooth muscle cell proliferation and Fn providing a gradient for smooth muscle cell migration from media to neointima.

Topics: Adolescent; Apoptosis; Cell Division; Child; Child, Preschool; Endothelium, Vascular; Epidermal Growth Factor; Female; Fibronectins; Heart Defects, Congenital; Humans; Hypertension, Pulmonary; Infant; Male; Proliferating Cell Nuclear Antigen; Tenascin; Tunica Intima; Tunica Media