RESUMO
Coronary Artery Fistulae (CAFs) are cardiac congenital anomalies consisting of an abnormal communication of a coronary artery with either a cardiac chamber or another cardiac vessel. In humans, these congenital anomalies can lead to complications such as myocardial hypertrophy, endocarditis, heart dilatation, and failure. Unfortunately, despite their clinical relevance, the aetiology of CAFs remains unknown. In this work, we have used two different species (mouse and avian embryos) to experimentally model CAFs morphogenesis. Both conditional Itga4 (alpha 4 integrin) epicardial deletion in mice and cryocauterisation of chick embryonic hearts disrupted epicardial development and ventricular wall growth, two essential events in coronary embryogenesis. Our results suggest that myocardial discontinuities in the embryonic ventricular wall promote the early contact of the endocardium with epicardial-derived coronary progenitors at the cardiac surface, leading to ventricular endocardial extrusion, precocious differentiation of coronary smooth muscle cells, and the formation of pouch-like aberrant coronary-like structures in direct connection with the ventricular lumen. The structure of these CAF-like anomalies was compared with histopathological data from a human CAF. Our results provide relevant information for the early diagnosis of these congenital anomalies and the molecular mechanisms that regulate their embryogenesis.
Assuntos
Cardiopatias Congênitas , Coração , Camundongos , Humanos , Animais , Miocárdio , Vasos Coronários/patologia , Ventrículos do CoraçãoRESUMO
Dilated cardiomyopathy (DCM) is the most frequent cause of heart failure and the leading indication for heart transplantation. Here we show that epigenetic regulator and central transcriptional instructor in adult stem cells, Bmi1, protects against DCM by repressing cardiac senescence. Cardiac-specific Bmi1 deletion induces the development of DCM, which progresses to lung congestion and heart failure. In contrast, Bmi1 overexpression in the heart protects from hypertrophic stimuli. Transcriptome analysis of mouse and human DCM samples indicates that p16(INK4a) derepression, accompanied by a senescence-associated secretory phenotype (SASP), is linked to severely impaired ventricular dimensions and contractility. Genetic reduction of p16(INK4a) levels reverses the pathology of Bmi1-deficient hearts. In parabiosis assays, the paracrine senescence response underlying the DCM phenotype does not transmit to healthy mice. As senescence is implicated in tissue repair and the loss of regenerative potential in aging tissues, these findings suggest a source for cardiac rejuvenation.
Assuntos
Envelhecimento/metabolismo , Cardiomiopatia Dilatada/metabolismo , Epigênese Genética , Insuficiência Cardíaca/metabolismo , Miocárdio/metabolismo , Complexo Repressor Polycomb 1/genética , Envelhecimento/patologia , Animais , Cardiomiopatia Dilatada/induzido quimicamente , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/patologia , Senescência Celular , Inibidor p16 de Quinase Dependente de Ciclina/genética , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Embrião de Mamíferos , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Insuficiência Cardíaca/induzido quimicamente , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/patologia , Ventrículos do Coração/metabolismo , Ventrículos do Coração/patologia , Humanos , Isoproterenol , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Contração Miocárdica/genética , Miocárdio/patologia , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , Comunicação Parácrina , Complexo Repressor Polycomb 1/metabolismo , TranscriptomaRESUMO
Loss-of-function studies have demonstrated the essential role of Notch in definitive embryonic mouse hematopoiesis. We report here the consequences of Notch gain-of-function in mouse embryo hematopoiesis, achieved by constitutive expression of Notch1 intracellular domain (N1ICD) in angiopoietin receptor tyrosine kinase receptor-2 (Tie2)-derived enhanced green fluorescence protein (EGFP(+)) hematovascular progenitors. At E9.5, N1ICD expression led to the absence of the dorsal aorta hematopoietic clusters and of definitive hematopoiesis. The EGFP(+) transient multipotent progenitors, purified from E9.5 to 10.5 Tie2-Cre;N1ICD yolk sac (YS) cells, had strongly reduced hematopoietic potential, whereas they had increased numbers of hemogenic endothelial cells. Late erythroid cell differentiation stages and mature myeloid cells (Gr1(+), MPO(+)) were also strongly decreased. In contrast, EGFP(+) erythro-myeloid progenitors, immature and intermediate differentiation stages of YS erythroid and myeloid cell lineages, were expanded. Tie2-Cre;N1ICD YS had reduced numbers of CD41(++) megakaryocytes, and these produced reduced below-normal numbers of immature colonies in vitro and their terminal differentiation was blocked. Cells from Tie2-Cre;N1ICD YS had a higher proliferation rate and lower apoptosis than wild-type (WT) YS cells. Quantitative gene expression analysis of FACS-purified EGFP(+) YS progenitors revealed upregulation of Notch1-related genes and alterations in genes involved in hematopoietic differentiation. These results represent the first in vivo evidence of a role for Notch signaling in YS transient definitive hematopoiesis. Our results show that constitutive Notch1 activation in Tie2(+) cells hampers YS hematopoiesis of E9.5 embryos and demonstrate that Notch signaling regulates this process by balancing the proliferation and differentiation dynamics of lineage-restricted intermediate progenitors.
Assuntos
Diferenciação Celular , Proliferação de Células , Hematopoese , Células-Tronco Hematopoéticas/fisiologia , Receptor Notch1/fisiologia , Saco Vitelino/citologia , Animais , Apoptose , Células Cultivadas , Desenvolvimento Embrionário , Células Eritroides/metabolismo , Feminino , Expressão Gênica , Células Progenitoras de Megacariócitos e Eritrócitos/fisiologia , Megacariócitos/fisiologia , Camundongos , Camundongos Transgênicos , Receptor TIE-2/genética , Receptor TIE-2/metabolismoRESUMO
The death inducer obliterator (Dido) locus encodes three protein isoforms, of which Dido3 is the largest and most broadly expressed. Dido3 is a nuclear protein that forms part of the spindle assembly checkpoint (SAC) and is necessary for correct chromosome segregation in somatic and germ cells. Here we report that specific ablation of Dido3 function in mice causes lethal developmental defects at the onset of gastrulation. Although these defects are associated with centrosome amplification, spindle malformation and a DNA damage response, we provide evidence that embryonic lethality of the Dido3 mutation cannot be explained by its impact on chromosome segregation alone. We show that loss of Dido3 expression compromises differentiation of embryonic stem cells in vitro and of epiblast cells in vivo, resulting in early embryonic death at around day 8.5 of gestation. Close analysis of Dido3 mutant embryoid bodies indicates that ablation of Dido3, rather than producing a generalized differentiation blockade, delays the onset of lineage commitment at the primitive endoderm specification stage. The dual role of Dido3 in chromosome segregation and stem cell differentiation supports the implication of SAC components in stem cell fate decisions.
Assuntos
Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Desenvolvimento Embrionário/genética , Pontos de Checagem da Fase M do Ciclo Celular/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Animais , Diferenciação Celular/genética , Linhagem da Célula/genética , Centrossomo/metabolismo , Dano ao DNA/genética , Corpos Embrioides/metabolismo , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Endoderma/citologia , Endoderma/embriologia , Gastrulação/genética , Regulação da Expressão Gênica no Desenvolvimento , Camadas Germinativas/citologia , Camadas Germinativas/crescimento & desenvolvimento , Camundongos , MutaçãoRESUMO
Programmed cell death plays an important role in erythropoiesis under physiological and pathological conditions. In this study, we show that the Notch/RBPjkappa signaling pathway induces erythroid apoptosis in different hematopoietic tissues, including yolk sac and bone marrow as well as in murine erythroleukemia cells. In RBPjkappa(-/-) yolk sacs, erythroid cells have a decreased rate of cell death that results in increased number of Ter119(+) cells. A similar effect is observed when Notch activity is abrogated by incubation with the gamma-secretase inhibitors, DAPT or L685,458. We demonstrate that incubation with Jagged1-expressing cells has a proapoptotic effect in erythroid cells from adult bone marrow that is prevented by blocking Notch activity. Finally, we show that the sole expression of the activated Notch1 protein is sufficient to induce apoptosis in hexametilene-bisacetamide-differentiating murine erythroleukemia cells. Together these results demonstrate that Notch regulates erythroid homeostasis by inducing apoptosis.
Assuntos
Apoptose/fisiologia , Diferenciação Celular , Células Eritroides/citologia , Receptor Notch1/fisiologia , Receptores Notch/fisiologia , Animais , Proteínas de Ligação ao Cálcio , Linhagem Celular Tumoral , Homeostase , Peptídeos e Proteínas de Sinalização Intercelular , Proteína Jagged-1 , Proteínas de Membrana , Camundongos , Camundongos Knockout , Receptores Notch/metabolismo , Proteínas Serrate-JaggedRESUMO
During development, Hox gene transcription is activated in presomitic mesoderm with a time sequence that follows the order of the genes along the chromosome. Here, we show that Hoxd1 and other Hox genes display dynamic stripes of expression within presomitic mesoderm. The underlying transcriptional bursts may reflect the mechanism that coordinates Hox gene activation with somitogenesis. This mechanism appears to depend upon Notch signaling, as mice deficient for RBPJk, the effector of the Notch pathway, showed severely reduced Hoxd gene expression in presomitic mesoderm. These results suggest a molecular link between Hox gene activation and the segmentation clock. Such a linkage would efficiently keep in phase the production of novel segments with their morphological specification.
Assuntos
Relógios Biológicos/genética , Padronização Corporal/genética , Proteínas de Ligação a DNA , Embrião de Mamíferos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Genes Homeobox/genética , Glicosiltransferases , Transcrição Gênica/genética , Alelos , Animais , Embrião de Mamíferos/embriologia , Deleção de Genes , Genes Reporter , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Hibridização In Situ , Masculino , Camundongos , Camundongos Knockout , Família Multigênica/genética , Fenótipo , Proteínas/genética , Proteínas/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ativação TranscricionalRESUMO
Functional inactivation of the tumor susceptibility gene tsg101 in NIH 3T3 fibroblasts results in cellular transformation and the ability to form metastatic tumors in nude mice. The N-terminal region of tsg101 protein is structurally similar to the catalytic domain of ubiquitin-conjugating enzymes, suggesting a potential role of tsg101 in ubiquitin-mediated protein degradation. The C-terminal domain of TSG101 can function as a repressor of transcription. To investigate the physiological function of tsg101, we generated a null mutation of the mouse gene by gene targeting. Homozygous tsg101-/- embryos fail to develop past day 6.5 of embryogenesis (E6.5), are reduced in size, and do not form mesoderm. Mutant embryos show a decrease in cellular proliferation in vivo and in vitro but no increase in apoptosis. Although levels of p53 transcripts were not affected in tsg101-/- embryos, p53 protein accumulated dramatically, implying altered posttranscriptional control of p53. In addition, transcription of the p53 effector, cyclin-dependent kinase inhibitor p21(WAF-1/CIP-1), was increased 5- to 10-fold, whereas activation of MDM2 transcription secondary to p53 elevation was not observed. Introduction of a p53 null mutation into tsg101-/- embryos rescued the gastrulation defect and prolonged survival until E8.5. These results demonstrate that tsg101 is essential for the proliferative burst before the onset of gastrulation and establish a functional connection between tsg101 and the p53 pathway in vivo.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Perda do Embrião/metabolismo , Proteínas Nucleares , Fatores de Transcrição/fisiologia , Proteína Supressora de Tumor p53/metabolismo , Animais , Divisão Celular , Inibidor de Quinase Dependente de Ciclina p21 , Ciclinas/metabolismo , Proteínas de Ligação a DNA/genética , Desenvolvimento Embrionário e Fetal , Endoderma/metabolismo , Complexos Endossomais de Distribuição Requeridos para Transporte , Expressão Gênica , Marcação de Genes , Mesoderma/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-mdm2 , Fatores de Transcrição/genética , Proteína Supressora de Tumor p53/genéticaRESUMO
BACKGROUND: The process of somitogenesis can be divided into three major events: the prepatterning of the mesoderm; the formation of boundaries between the prospective somites; and the cellular differentiation of the somites. Expression and functional studies have demonstrated the involvement of the murine Notch pathway in somitogenesis, although its precise role in this process is not yet well understood. We examined the effect of mutations in the Notch pathway elements Delta like 1 (Dll1), Notch1 and RBPJkappa on genes expressed in the presomitic mesoderm (PSM) and have defined the spatial relationships of Notch pathway gene expression in this region. RESULTS: We have shown that expression of Notch pathway genes in the PSM overlaps in the region where the boundary between the posterior and anterior halves of two consecutive somites will form. The Dll1, Notch1 and RBPJkappa mutations disrupt the expression of Lunatic fringe (L-fng), Jagged1, Mesp1, Mesp2 and Hes5 in the PSM. Furthermore, expression of EphA4, mCer 1 and uncx4.1, markers for the anterior-posterior subdivisions of the somites, is down-regulated to different extents in Notch pathway mutants, indicating a global alteration of pattern in the PSM. CONCLUSIONS: We propose a model for the mechanism of somite border formation in which the activity of Notch in the PSM is restricted by L-fng to a boundary-forming territory in the posterior half of the prospective somite. In this region, Notch function activates a set of genes that are involved in boundary formation and anterior-posterior somite identity.
Assuntos
Glicosiltransferases , Proteínas de Membrana/metabolismo , Proteínas Nucleares , Proteínas/metabolismo , Transdução de Sinais , Animais , Padronização Corporal , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Desenvolvimento Embrionário e Fetal , Feminino , Proteína de Ligação a Sequências Sinal de Recombinação J de Imunoglobina , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Proteínas de Membrana/genética , Mesoderma , Camundongos , Mutagênese , Receptores Notch , SomitosRESUMO
Platelet/endothelial cell adhesion molecule-1 (PECAM-1; CD31), a member of the Ig superfamily, is expressed strongly at endothelial cell-cell junctions, on platelets, and on most leukocytes. CD31 has been postulated to play a role in vasculogenesis and angiogenesis, and has been implicated as a key mediator of the transendothelial migration of leukocytes. To further define the physiologic role of CD31, we used targeted gene disruption of the CD31 gene in embryonic stem cells to generate CD31-deficient mice. CD31-deficient mice (CD31KO) are viable and born at the expected Mendelian frequency, remain healthy, and exhibit no obvious vascular developmental defects. In response to inflammatory challenge, polymorphonuclear leukocytes of CD31KO mice are arrested between the vascular endothelium and the basement membrane of inflammatory site mesenteric microvessels, confirming a role for CD31 in the migration of neutrophils through the subendothelial extracellular matrix. Normal numbers of leukocytes are recovered from inflammatory sites in CD31KO mice, however, suggesting that the defect in leukocyte migration across basal lamina observed in the absence of CD31 may be compensated for by the use of other adhesion molecules, or possibly an increased rate of migration. Homing of T lymphocytes in vivo is normal, and CD31KO mice are able to mount a cutaneous hypersensitivity response normally. In addition, CD31-mediated homophilic adhesion does not appear to play a role in platelet aggregation in vitro. This study provides genetic evidence that CD31 is involved in transbasement membrane migration, but does not play an obligatory role in either vascular development or leukocyte migration.
Assuntos
Molécula-1 de Adesão Celular Endotelial a Plaquetas/fisiologia , Animais , Contagem de Células Sanguíneas , Plaquetas/fisiologia , Movimento Celular , Feminino , Leucócitos/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Linfócitos T/fisiologiaRESUMO
The stress signaling kinase SEK1/MKK4 is a direct activator of stress-activated protein kinases (SAPKs; also called Jun-N-terminal kinases, JNKs) in response to a variety of cellular stresses, such as changes in osmolarity, metabolic poisons, DNA damage, heat shock or inflammatory cytokines. We have disrupted the sek1 gene in mice using homologous recombination. Sek1(-/- )embryos display severe anemia and die between embryonic day 10.5 (E10.5) and E12.5. Haematopoiesis from yolk sac precursors and vasculogenesis are normal in sek1(-/- )embryos. However, hepatogenesis and liver formation were severely impaired in the mutant embryos and E11.5 and E12.5 sek1(-/- )embryos had greatly reduced numbers of parenchymal hepatocytes. Whereas formation of the primordial liver from the visceral endoderm appeared normal, sek1(-/-) liver cells underwent massive apoptosis. These results provide the first genetic link between stress-responsive kinases and organogenesis in mammals and indicate that SEK1 provides a crucial and specific survival signal for hepatocytes.
Assuntos
Apoptose , Fígado/embriologia , MAP Quinase Quinase 4 , Quinases de Proteína Quinase Ativadas por Mitógeno , Proteínas Quinases/fisiologia , Proteínas Serina-Treonina Quinases/fisiologia , Proteínas Tirosina Quinases/fisiologia , Animais , Dano ao DNA , Marcação de Genes , Hematopoese/genética , Fígado/citologia , Camundongos , Camundongos Knockout , Mutagênese , Neovascularização Fisiológica/genética , Proteínas Quinases/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas Tirosina Quinases/genéticaRESUMO
BACKGROUND: Germ-line and sporadic mutations in the tumor suppressor gene PTEN (also known as MMAC or TEP1), which encodes a dual-specificity phosphatase, cause a variety of cancers such as Cowden disease, glioblastoma, endometrial carcinoma and prostatic cancer. PTEN is widely expressed, and Cowden disease consistently affects various organ systems, suggesting that the PTEN protein must have an important, although as yet poorly understood, function in cellular physiology. RESULTS: Homozygous mutant mice lacking exons 3-5 of the PTEN gene (mPTEN3-5) had severely expanded and abnormally patterned cephalic and caudal regions at day 8.5 of gestation. Embryonic death occurred by day 9.5 and was associated with defective chorio-allantoic development. Heterozygous mPTEN3-5 mice had an increased incidence of tumors, especially T-cell lymphomas; gamma-irradiation reduced the time lapse of tumor formation. DNA analysis of these tumors revealed the deletion of the mPTEN gene due to loss of heterozygosity of the wild-type allele. Tumors associated with loss of heterozygosity in mPTEN showed elevated phosphorylation of protein kinase B (PKB, also known as Akt kinase), thus providing a functional connection between mPTEN and a murine proto-oncogene (c-Akt) involved in the development of lymphomas. CONCLUSIONS: The mPTEN gene is fundamental for embryonic development in mice, as mPTEN3-5 mutant embryos died by day 9.5 of gestation, with patterning defects in cephalic and caudal regions and defective placentation. Heterozygous mice developed lymphomas associated with loss of heterozygosity of the wild-type mPTEN allele, and tumor appearance was accelerated by gamma-irradiation. These lymphomas had high levels of activated Akt/PKB, the protein product of a murine proto-oncogene with anti-apoptotic function, associated with thymic lymphomas. This suggests that tumors associated with mPTEN loss of heterozygosity may arise as a consequence of an acquired survival advantage. We provide direct evidence of the role of mPTEN as a tumor suppressor gene in mice, and establish the mPTEN mutant mouse as an experimental model for investigating the role of PTEN in cancer progression.
Assuntos
Genes Supressores de Tumor , Predisposição Genética para Doença/genética , Linfoma de Células T/genética , Neoplasias/genética , Monoéster Fosfórico Hidrolases/genética , Proto-Oncogenes , Deleção de Sequência , Proteínas Supressoras de Tumor , Animais , Desenvolvimento Embrionário e Fetal/genética , Éxons , Feminino , Morte Fetal/genética , Raios gama , Genótipo , Camundongos , Camundongos Mutantes , PTEN Fosfo-Hidrolase , Fenótipo , Reação em Cadeia da Polimerase , Gravidez , Recombinação GenéticaRESUMO
PTEN is a tumor suppressor with sequence homology to protein tyrosine phosphatases and the cytoskeletal protein tensin. mPTEN-mutant mouse embryos display regions of increased proliferation. In contrast, mPTEN-deficient immortalized mouse embryonic fibroblasts exhibit decreased sensitivity to cell death in response to a number of apoptotic stimuli, accompanied by constitutively elevated activity and phosphorylation of protein kinase B/Akt, a crucial regulator of cell survival. Expression of exogenous PTEN in mutant cells restores both their sensitivity to agonist-induced apoptosis and normal pattern of PKB/Akt phosphorylation. Furthermore, PTEN negatively regulates intracellular levels of phosphatidylinositol (3,4,5) trisphosphate in cells and dephosphorylates it in vitro. Our results show that PTEN may exert its role as a tumor suppressor by negatively regulating the PI3'K/PKB/Akt signaling pathway.
Assuntos
Apoptose , Genes Supressores de Tumor , Monoéster Fosfórico Hidrolases , Proteínas Serina-Treonina Quinases , Proteínas Tirosina Fosfatases/fisiologia , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Supressoras de Tumor , Animais , Divisão Celular , Sobrevivência Celular , Células Cultivadas , Feminino , Fibroblastos/citologia , Camundongos , Mutagênese , PTEN Fosfo-Hidrolase , Fosfatos de Fosfatidilinositol/metabolismo , Proteínas Tirosina Fosfatases/genética , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-akt , Especificidade por SubstratoRESUMO
Mutation of Caspase 9 (Casp9) results in embryonic lethality and defective brain development associated with decreased apoptosis. Casp9-/- embryonic stem cells and embryonic fibroblasts are resistant to several apoptotic stimuli, including UV and gamma irradiation. Casp9-/- thymocytes are also resistant to dexamethasone- and gamma irradiation-induced apoptosis, but are surprisingly sensitive to apoptosis induced by UV irradiation or anti-CD95. Resistance to apoptosis is accompanied by retention of the mitochondrial membrane potential in mutant cells. In addition, cytochrome c is translocated to the cytosol of Casp9-/- ES cells upon UV stimulation, suggesting that Casp9 acts downstream of cytochrome c. Caspase processing is inhibited in Casp9-/- ES cells but not in thymocytes or splenocytes. Comparison of the requirement for Casp9 and Casp3 in different apoptotic settings indicates the existence of at least four different apoptotic pathways in mammalian cells.
Assuntos
Apoptose/genética , Caspases , Cisteína Endopeptidases/fisiologia , Transdução de Sinais/genética , Animais , Apoptose/efeitos dos fármacos , Apoptose/efeitos da radiação , Caspase 9 , Linhagem Celular , Córtex Cerebral/anormalidades , Cisteína Endopeptidases/genética , Grupo dos Citocromos c/metabolismo , Dexametasona/farmacologia , Embrião de Mamíferos , Ativação Enzimática/genética , Fibroblastos/citologia , Fibroblastos/enzimologia , Raios gama , Regulação da Expressão Gênica no Desenvolvimento , Ativação Linfocitária , Potenciais da Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Camundongos Knockout , Mitocôndrias/enzimologia , Especificidade de Órgãos/genética , Prosencéfalo/anormalidades , Baço/citologia , Baço/imunologia , Baço/efeitos da radiação , Células-Tronco , Timo/citologia , Timo/enzimologiaRESUMO
The NEUROGENINS (NGNs) are neural-specific basic helix-loop-helix (bHLH) transcription factors. Mouse embryos lacking ngn1 fail to generate the proximal subset of cranial sensory neurons. ngn1 is required for the activation of a cascade of downstream bHLH factors, including NeuroD, MATH3, and NSCL1. ngn1 is expressed by placodal ectodermal cells and acts prior to neuroblast delamination. Moreover, NGN1 positively regulates the Delta homolog DLL1 and can be negatively regulated by Notch signaling. Thus, ngn1 functions similarly to the proneural genes in Drosophila. However, the initial pattern of ngn1 expression appears to be Notch independent. Taken together with the fact that ectopic ngn1 expression can convert ectodermal cells to neurons in Xenopus (Ma et al., 1996), these data and those of Fode et al. (1998 [this issue of Neuron]) identify ngns as vertebrate neuronal determination genes, analogous to myoD and myf5 in myogenesis.
Assuntos
Proteínas do Tecido Nervoso/genética , Neurônios Aferentes/química , Células-Tronco/química , Fatores de Transcrição , Gânglio Trigeminal/citologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Quimera , Feminino , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Sequências Hélice-Alça-Hélice/fisiologia , Masculino , Proteínas de Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Mutagênese/fisiologia , Proteínas do Tecido Nervoso/metabolismo , Crista Neural/citologia , Neurônios Aferentes/fisiologia , Gravidez , RNA Mensageiro/análise , Receptores de Superfície Celular/fisiologia , Receptores Notch , Transdução de Sinais/fisiologia , Células-Tronco/fisiologia , Gânglio Trigeminal/embriologiaRESUMO
FADD (also known as Mort-1) is a signal transducer downstream of cell death receptor CD95 (also called Fas). CD95, tumor necrosis factor receptor type 1 (TNFR-1), and death receptor 3 (DR3) did not induce apoptosis in FADD-deficient embryonic fibroblasts, whereas DR4, oncogenes E1A and c-myc, and chemotherapeutic agent adriamycin did. Mice with a deletion in the FADD gene did not survive beyond day 11.5 of embryogenesis; these mice showed signs of cardiac failure and abdominal hemorrhage. Chimeric embryos showing a high contribution of FADD null mutant cells to the heart reproduce the phenotype of FADD-deficient mutants. Thus, not only death receptors, but also receptors that couple to developmental programs, may use FADD for signaling.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , Apoptose , Proteínas de Transporte/fisiologia , Desenvolvimento Embrionário e Fetal , Coração/embriologia , Animais , Proteínas de Transporte/genética , Transformação Celular Neoplásica , Células Cultivadas , Doxorrubicina/farmacologia , Endotélio Vascular/embriologia , Proteína de Domínio de Morte Associada a Fas , Feminino , Expressão Gênica , Marcação de Genes , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mutação , Oncogenes , Receptores do Fator de Necrose Tumoral/genética , Receptores do Fator de Necrose Tumoral/fisiologia , Transdução de Sinais , Fator de Necrose Tumoral alfa/farmacologia , Receptor fas/genética , Receptor fas/fisiologiaRESUMO
In lymphocytes, the expression of early immune response genes is regulated by NF-AT transcription factors which translocate to the nucleus after dephosphorylation by the Ca2+-dependent phosphatase, calcineurin. We report here that mice bearing a disruption in the NF-ATc gene fail to develop normal cardiac valves and septa and die of circulatory failure before day 14.5 of development. NF-ATc is first expressed in the heart at day 7.5, and is restricted to the endocardium, a specialized endothelium that gives rise to the valves and septum. Within the endocardium, specific inductive events appear to activate NF-ATc: it is localized to the nucleus only in endocardial cells that are adjacent to the interface with the cardiac jelly and myocardium, which are thought to give the inductive stimulus to the valve primordia. Treatment of wild-type embryos with FK506, a specific calcineurin inhibitor, prevents nuclear localization of NF-ATc. These data indicate that the Ca2+/calcineurin/NF-ATc signalling pathway is essential for normal cardiac valve and septum morphogenesis; hence, NF-ATc and its regulatory pathways are candidates for genetic defects underlying congenital human heart disease.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Septos Cardíacos/embriologia , Valvas Cardíacas/embriologia , Proteínas Nucleares , Fatores de Transcrição/fisiologia , Animais , Calcineurina/metabolismo , Inibidores de Calcineurina , Cálcio/metabolismo , Linhagem Celular , Técnicas de Cultura , Proteínas de Ligação a DNA/genética , Endotélio/metabolismo , Morte Fetal , Marcação de Genes , Defeitos dos Septos Cardíacos/embriologia , Valvas Cardíacas/anormalidades , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Morfogênese/fisiologia , Mutagênese , Fatores de Transcrição NFATC , Transdução de Sinais , Tacrolimo/farmacologia , Fatores de Transcrição/genéticaRESUMO
Mutations in the SMAD4/DPC4 tumor suppressor gene, a key signal transducer in most TGFbeta-related pathways, are involved in 50% of pancreatic cancers. Homozygous Smad4 mutant mice die before day 7.5 of embryogenesis. Mutant embryos have reduced size, fail to gastrulate or express a mesodermal marker, and show abnormal visceral endoderm development. Growth retardation of the Smad4-deficient embryos results from reduced cell proliferation rather than increased apoptosis. Aggregation of mutant Smad4 ES cells with wild-type tetraploid morulae rescues the gastrulation defect. These results indicate that Smad4 is initially required for the differentiation of the visceral endoderm and that the gastrulation defect in the epiblast is secondary and non-cell autonomous. Rescued embryos show severe anterior truncations, indicating a second important role for Smad4 in anterior patterning during embryogenesis.
Assuntos
Desenvolvimento Embrionário e Fetal/fisiologia , Proteínas Fetais , Gástrula/fisiologia , Genes Supressores de Tumor , Proteínas com Domínio T , Transativadores/fisiologia , Alelos , Animais , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Testes de Carcinogenicidade , Linhagem Celular , Proteínas de Ligação a DNA/metabolismo , Desenvolvimento Embrionário e Fetal/genética , Endoderma/fisiologia , Feminino , Deleção de Genes , Fator 4 Nuclear de Hepatócito , Heterozigoto , Homozigoto , Masculino , Mesoderma/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Fosfoproteínas/metabolismo , Proteína Smad4 , Células-Tronco/citologia , Transativadores/biossíntese , Transativadores/genética , Fatores de Transcrição/metabolismoRESUMO
In humans, the inheritance of mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 increases the risk of developing breast and ovarian cancer. To study their biological function and to create animal models for these cancer susceptibility genes, several strains of mice mutated in the homologous genes Brca1 and Brca2 have been generated by gene targeting. Analyses of these "knock-out" mouse mutants have provided invaluable knowledge about the function of these genes. Brca1 and Brca2 null mutants are similar in phenotype: mutations in both genes result in embryonic lethality and the developing embryos show signs of a cellular proliferation defect associated with activation of the p53 pathway. The significance of this activation, as well as the role of these cancer susceptibility genes in DNA damage repair, is discussed.