cyclin-d1 and Heart-Defects--Congenital

Maternal diabetes in mice induces heart defects similar to those observed in human diabetic pregnancies. Diabetes enhances apoptosis and suppresses cell proliferation in the developing heart, yet the underlying mechanism remains elusive. Apoptosis signal-regulating kinase 1 (ASK1) activates the proapoptotic c-Jun NH2-terminal kinase 1/2 (JNK1/2) leading to apoptosis, suggesting a possible role of ASK1 in diabetes-induced heart defects. We aimed to investigate whether ASK1 is activated in the heart and whether deleting the Ask1 gene blocks diabetes-induced adverse events and heart defect formation. The ASK1-JNK1/2 pathway was activated by diabetes. Deleting Ask1 gene significantly reduced the rate of heart defects, including ventricular septal defects (VSDs) and persistent truncus arteriosus (PTA). Additionally, Ask1 deletion diminished diabetes-induced JNK1/2 phosphorylation and its downstream transcription factors and endoplasmic reticulum (ER) stress markers. Consistent with this, caspase activation and apoptosis were blunted. Ask1 deletion blocked the increase in cell cycle inhibitors (p21 and p27) and the decrease in cyclin D1 and D3 and reversed diabetes-repressed cell proliferation. Ask1 deletion also restored the expression of BMP4, NKX2.5, and GATA5, Smad1/5/8 phosphorylation, whose mutations or deletion result in reduced cell proliferation, VSD, and PTA formation. We conclude that ASK1 may mediate the teratogenicity of diabetes through activating the JNK1/2-ER stress pathway and inhibiting cell cycle progression, thereby impeding the cardiogenesis pathways essential for ventricular septation and outflow tract development.

Topics: Animals; Apoptosis; Bone Morphogenetic Protein 4; Cell Proliferation; Cyclin D1; Cyclin D3; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; Endoplasmic Reticulum Stress; Female; GATA5 Transcription Factor; Heart; Heart Defects, Congenital; Heart Septal Defects, Ventricular; Homeobox Protein Nkx-2.5; Homeodomain Proteins; MAP Kinase Kinase Kinase 5; Mice; Mice, Knockout; Mitogen-Activated Protein Kinase 8; Mitogen-Activated Protein Kinase 9; Phosphorylation; Pregnancy; Pregnancy in Diabetics; Signal Transduction; Smad1 Protein; Smad5 Protein; Smad8 Protein; Teratogenesis; Transcription Factors; Truncus Arteriosus, Persistent

In pregnant women, the diabetic condition results in a three- to fivefold increased risk for fetal cardiac malformations as a result of elevated glucose concentrations and the resultant osmotic stress in the developing embryo and fetus. Heart development before septation in the chick embryo was studied under two hyperglycemic conditions. Pulsed hyperglycemia induced by daily administration of glucose during 3 days of development caused daily spikes in plasma glucose concentration. In a second model, sustained hyperglycemia was induced with a single injection of glucose into the yolk on day 0. The sustained model raised the average plasma glucose concentration from 70 mg/dL to 180 mg/dL and led to decreased gene expression of glucose transporter GLUT1. Both models of hyperglycemia reduced embryo size, increased mortality, and delayed development. Within the heart outflow tract, reduced proliferation of myocardial and endocardial cells resulted from the sustained hyperglycemia and hyperosmolarity. The cell cycle inhibitor p21 was significantly increased, whereas cyclin D1, a cell cycle promoter, decreased in sustained hyperglycemia compared with controls. The evidence suggests that hyperglycemia-induced developmental delays are associated with slowed cell cycle progression, leading to reduced cellular proliferation. The suppression of critical developmental steps may underlie the cardiac defects observed during late gestation under hyperglycemic conditions.

Topics: Animals; Blood Glucose; Cell Cycle; Cell Proliferation; Chick Embryo; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; Embryonic Development; Female; Glucose Transporter Type 1; Heart Defects, Congenital; Humans; Hyperglycemia; Pregnancy; Pregnancy in Diabetics

Trabecular myocardium accounts for the majority of the ventricles during early cardiogenesis, but compact myocardium is the primary component at later developmental stages. Elucidation of the genes regulating compact myocardium development is essential to increase our understanding of left ventricular noncompaction (LVNC), a cardiomyopathy characterized by increased ratios of trabecular to compact myocardium. 14-3-3ε is an adapter protein expressed in the lateral plate mesoderm, but its in vivo cardiac functions remain to be defined. Here we show that 14-3-3ε is expressed in the developing mouse heart as well as in cardiomyocytes. 14-3-3ε deletion did not appear to induce compensation by other 14-3-3 isoforms but led to ventricular noncompaction, with features similar to LVNC, resulting from a selective reduction in compact myocardium thickness. Abnormal compaction derived from a 50% decrease in cardiac proliferation as a result of a reduced number of cardiomyocytes in G(2)/M and the accumulation of cardiomyocytes in the G(0)/G(1) phase of the cell cycle. These defects originated from downregulation of cyclin E1 and upregulation of p27(Kip1), possibly through both transcriptional and posttranslational mechanisms. Our work shows that 14-3-3ε regulates cardiogenesis and growth of the compact ventricular myocardium by modulating the cardiomyocyte cell cycle via both cyclin E1 and p27(Kip1). These data are consistent with the long-held view that human LVNC may result from compaction arrest, and they implicate 14-3-3ε as a new candidate gene in congenital human cardiomyopathies.

Topics: 14-3-3 Proteins; Animals; Base Sequence; Cell Cycle; Cyclin D1; Cyclin E; Cyclin-Dependent Kinase Inhibitor p27; Disease Models, Animal; DNA Primers; Female; Fetal Heart; Gene Expression Regulation, Developmental; Heart Defects, Congenital; Heart Ventricles; Humans; Male; Mice; Mice, 129 Strain; Mice, Knockout; Myocytes, Cardiac; Oncogene Proteins

Glycogen storage disease type IV (GSD-IV) is an autosomal recessive disease caused by a deficiency in glycogen-branching enzyme (GBE1) activity that results in the accumulation of amylopectin-like polysaccharide, which presumably leads to osmotic swelling and cell death. This disease is extremely heterogeneous in terms of tissue involvement, age of onset and clinical manifestation. The most severe fetal form presents as hydrops fetalis; however, its pathogenetic mechanisms are largely unknown. In this study, mice carrying a stop codon mutation (E609X) in the Gbe1 gene were generated using a gene-driven mutagenesis approach. Homozygous mutants (Gbe(-/-) mice) recapitulated the clinical features of hydrops fetalis and the embryonic lethality of the severe fetal form of GSD-IV. However, contrary to conventional expectations, little amylopectin accumulation and no cell degeneration were found in Gbe(-/-) embryonic tissues. Glycogen accumulation was reduced in developing hearts of Gbe(-/-)embryos, and abnormal cardiac development, including hypertrabeculation and noncompaction of the ventricular wall, was observed. Further, Gbe1 ablation led to poor ventricular function in late gestation and ultimately caused heart failure, fetal hydrops and embryonic lethality. We also found that the cell-cycle regulators cyclin D1 and c-Myc were highly expressed in cardiomyocytes and likely contributed to cardiomyocyte proliferation and trabeculation/compaction of the ventricular wall. Our results reveal that early molecular events associated with Gbe1 deficiency contribute to abnormal cardiac development and fetal hydrops in the fetal form of GSD-IV.

Topics: 1,4-alpha-Glucan Branching Enzyme; Amylopectin; Animals; Cell Cycle Proteins; Cell Proliferation; Codon, Terminator; Cyclin D1; Embryo Loss; Fluorescent Antibody Technique; Genes, myc; Glycogen; Glycogen Storage Disease Type IV; Heart; Heart Defects, Congenital; Heart Failure; Heart Rate; Hydrops Fetalis; Mice; Myocytes, Cardiac; Polymerase Chain Reaction; Sequence Analysis, DNA; Ventricular Function

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

The Jun and JunB components of the AP-1 transcription factor are known to have antagonistic functions. Here we show, by a knock-in strategy and a transgenic complementation approach, that Junb can substitute for absence of Jun during mouse development. Junb can rescue both liver and cardiac defects in Jun-null mice in a manner dependent on gene dosage. JunB restores the expression of genes regulated by Jun/Fos, but not those regulated by Jun/ATF, thereby rescuing Jun-dependent defects in vivo as well as in primary fibroblasts and fetal hepatoblasts in vitro. Thus, the transcriptionally less active JunB has the potential to substitute for Jun, indicating that the spatial and temporal regulation of expression of the transcription factor AP-1 may be more important than the coding sequence of its components.

Topics: Animals; Cell Division; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; Embryonic and Fetal Development; Gene Expression Regulation, Developmental; Genes, fos; Genes, jun; Heart Defects, Congenital; Liver; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Phenotype; Proto-Oncogene Proteins c-jun; Transcription Factor AP-1; Tumor Suppressor Protein p53