RESUMO
The development of endothelial cell precursors is essential for vasculogenesis. We screened for differentially expressed transcripts in endothelial cell precursors in developing mouse embryoid bodies. We cloned a complete cDNA encoding a protein that contains an amino-terminal signal peptide, five cysteine-rich domains, a von Willebrand D domain, and a trypsin inhibitor domain. We termed this protein BMPER (bone morphogenetic protein [BMP]-binding endothelial cell precursor-derived regulator). BMPER is specifically expressed in flk-1-positive cells and parallels the time course of flk-1 induction in these cells. In situ hybridization in mouse embryos demonstrates dorsal midline staining and staining of the aorto-gonadal-mesonephric region, which is known to host vascular precursor cells. BMPER is a secreted protein that directly interacts with BMP2, BMP4, and BMP6 and antagonizes BMP4-dependent Smad5 activation. In Xenopus embryos, ventral injection of BMPER mRNA results in axis duplication and downregulation of the expression of Xvent-1 (downstream target of Smad signaling). In an embryoid body differentiation assay, BMP4-dependent differentiation of endothelial cells in embryoid bodies is also antagonized by BMPER. Taken together, our data indicate that BMPER is a novel BMP-binding protein that is expressed by endothelial cell precursors, has BMP-antagonizing activity, and may play a role in endothelial cell differentiation by modulating local BMP activity.
Assuntos
Proteínas Morfogenéticas Ósseas/antagonistas & inibidores , Proteínas de Transporte/genética , Proteínas de Transporte/farmacologia , Fator de Crescimento Transformador beta , Sequência de Aminoácidos , Animais , Sequência de Bases , Northern Blotting , Western Blotting , Proteína Morfogenética Óssea 2 , Proteína Morfogenética Óssea 4 , Proteína Morfogenética Óssea 6 , Células COS , Diferenciação Celular , Linhagem Celular , Clonagem Molecular , DNA Complementar/metabolismo , Proteínas de Ligação a DNA/metabolismo , Endotélio Vascular/metabolismo , Citometria de Fluxo , Biblioteca Gênica , Genes Reporter , Humanos , Hibridização In Situ , Camundongos , Modelos Genéticos , Dados de Sequência Molecular , Fosfoproteínas/metabolismo , Reação em Cadeia da Polimerase , Testes de Precipitina , Estrutura Terciária de Proteína , RNA/metabolismo , RNA Mensageiro/metabolismo , Proteínas Recombinantes/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteína Smad5 , Fatores de Tempo , Distribuição Tecidual , Transativadores/metabolismo , Transfecção , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Proteínas de Xenopus , Xenopus laevisRESUMO
Members of the T-box family of proteins play a fundamental role in patterning the developing vertebrate heart; however, the precise cellular requirements for any one family member and the mechanism by which individual T-box genes function remains largely unknown. In this study, we have investigated the cellular and molecular relationship between two T-box genes, Tbx5 and Tbx20. We demonstrate that blocking Tbx5 or Tbx20 produces phenotypes that display a high degree of similarity, as judged by overall gross morphology, molecular marker analysis and cardiac physiology, implying that the two genes are required for and have non-redundant functions in early heart development. In addition, we demonstrate that although co-expressed, Tbx5 and Tbx20 are not dependent on the expression of one another, but rather have a synergistic role during early heart development. Consistent with this proposal, we show that TBX5 and TBX20 can physically interact and map the interaction domains, and we show a cellular interaction for the two proteins in cardiac development, thus providing the first evidence for direct interaction between members of the T-box gene family.
Assuntos
Coração/embriologia , Morfogênese , Miocárdio/metabolismo , Proteínas com Domínio T/metabolismo , Xenopus laevis/embriologia , Xenopus laevis/metabolismo , Animais , Contagem de Células , Linhagem Celular , Núcleo Celular/metabolismo , Embrião não Mamífero/embriologia , Embrião não Mamífero/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Camundongos , Miocárdio/citologia , Ligação Proteica , Proteínas com Domínio T/genética , Transcrição Gênica/genética , Xenopus laevis/genéticaRESUMO
The T-box gene family, encoding related DNA-binding transcriptional regulators, plays an essential role in controlling many aspects of embryogenesis in a wide variety of organisms. The T-box genes exhibit diverse patterns of spatial and temporal expression in the developing embryo, and both genetic and molecular embryological studies have demonstrated their importance in regulating cell fate decisions that establish the early body plan, and in later processes underlying organogenesis. Despite these studies, little is known of either the regulation of the T-box genes or the identities of their transcriptional targets. The aim of this review is to examine the diverse yet conserved roles of several T-box genes in regulating early patterning in chordates and to discuss possible mechanisms through which this functional diversity might arise. Developmental Dynamics 229:201-218, 2004.
Assuntos
Desenvolvimento Embrionário e Fetal/genética , Proteínas Fetais , Proteínas com Domínio T/genética , Proteínas de Xenopus , Sequência de Aminoácidos , Animais , Evolução Biológica , Diferenciação Celular , Sequência Conservada , Desenvolvimento Embrionário e Fetal/fisiologia , Endoderma/citologia , Regulação da Expressão Gênica no Desenvolvimento , Mesoderma/citologia , Camundongos , Dados de Sequência Molecular , Morfogênese , Homologia de Sequência de Aminoácidos , Proteínas com Domínio T/fisiologia , XenopusRESUMO
We have isolated the Xenopus orthologue of the T-box gene, Tbx20, and characterized its developmental expression profile. We show that Tbx20 is one of the earliest markers of heart tissue in Xenopus, and is expressed throughout all cardiac tissue during later stages of development. In addition, we also observe expression in the cement gland, the jugular vein, the lung bud, the cloacal aperture, rhombomeres 2, 4, 6 and 8, and in a subset of motor neurons.