RESUMO
In vertebrate embryos, the earliest definitive marker for the neural plate, which will give rise to the entire central nervous system, is the transcription factor Sox2. Although some of the extracellular signals that regulate neural plate fate have been identified, we know very little about the mechanisms controlling Sox2 expression and thus neural plate identity. Here, we use electroporation for gain- and loss-of-function in the chick embryo, in combination with bimolecular fluorescence complementation, two-hybrid screens, chromatin immunoprecipitation, and reporter assays to study protein interactions that regulate expression of N2, the earliest enhancer of Sox2 to be activated and which directs expression to the largest part of the neural plate. We show that interactions between three coiled-coil domain proteins (ERNI, Geminin, and BERT), the heterochromatin proteins HP1alpha and HP1gamma acting as repressors, and the chromatin-remodeling enzyme Brm acting as activator control the N2 enhancer. We propose that this mechanism regulates the timing of Sox2 expression as part of the process of establishing neural plate identity.
Assuntos
Proteínas de Ligação a DNA/biossíntese , Proteínas HMGB/biossíntese , Placa Neural/metabolismo , Fatores de Transcrição/biossíntese , Sequência de Aminoácidos , Animais , Proteínas Aviárias/metabolismo , Proteínas de Ciclo Celular/metabolismo , Embrião de Galinha , Homólogo 5 da Proteína Cromobox , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Ligação a DNA/genética , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica no Desenvolvimento , Proteínas HMGB/genética , Dados de Sequência Molecular , Proteínas do Tecido Nervoso/metabolismo , Placa Neural/embriologia , Ligação Proteica , Fatores de Transcrição SOXB1 , Fatores de Transcrição/genéticaRESUMO
When, where and how is the head-tail axis of the embryo set up during development? These are such fundamental and intensely studied questions that one might expect them to have been answered long ago. Not so; we still understand very little about the cellular or molecular mechanisms that lead to the orderly arrangement of body elements along the head-tail axis in vertebrates. In this paper, we outline some of the major outstanding problems and controversies and try to identify some reasons why it has been so difficult to resolve this important issue.
Assuntos
Padronização Corporal/fisiologia , Embrião de Mamíferos/anatomia & histologia , Embrião de Mamíferos/fisiologia , Embrião não Mamífero , Animais , Padronização Corporal/genética , Embrião de Mamíferos/citologia , Modelos Anatômicos , Modelos BiológicosRESUMO
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.
