RESUMO
Serum response factor (SRF) is a transcription factor essential for cell proliferation, differentiation, and migration and is required for primitive streak and mesoderm formation in the embryo. The canonical roles of SRF are mediated by a diverse set of context-dependent cofactors. Here, we show that SRF physically interacts with CTCF and cohesin subunits at topologically associating domain (TAD) boundaries and loop anchors. SRF promotes long-range chromatin loop formation and contributes to TAD insulation. In embryonic stem cells (ESCs), SRF associates with SOX2 and NANOG and contributes to the formation of three-dimensional (3D) pluripotency hubs. Our findings reveal additional roles of SRF in higher-order chromatin organization.
Assuntos
Cromatina , Proteína Homeobox Nanog , Fatores de Transcrição SOXB1 , Fator de Resposta Sérica , Fator de Resposta Sérica/metabolismo , Cromatina/metabolismo , Animais , Camundongos , Proteína Homeobox Nanog/metabolismo , Proteína Homeobox Nanog/genética , Fatores de Transcrição SOXB1/metabolismo , Fatores de Transcrição SOXB1/genética , Fator de Ligação a CCCTC/metabolismo , Humanos , Células-Tronco Pluripotentes/metabolismo , Células-Tronco Pluripotentes/citologia , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Coesinas , Diferenciação Celular , Ligação Proteica , Células-Tronco Embrionárias/metabolismo , Células-Tronco Embrionárias/citologiaRESUMO
SOX2 is a transcription factor involved in the regulatory network maintaining the pluripotency of embryonic stem cells in culture as well as in early embryos. In addition, SOX2 plays a pivotal role in neural stem cell formation and neurogenesis. How SOX2 can serve both processes has remained elusive. Here, we identified a set of SOX2-dependent neural-associated enhancers required for neural lineage priming. They form a distinct subgroup (1,898) among 8,531 OCT4/SOX2/NANOG-bound enhancers characterized by enhanced SOX2 binding and chromatin accessibility. Activation of these enhancers is triggered by neural induction of wild-type cells or by default in Smad4-ablated cells resistant to mesoderm induction and is antagonized by mesodermal transcription factors via Sox2 repression. Our data provide mechanistic insight into the transition from the pluripotency state to the early neural fate and into the regulation of early neural versus mesodermal specification in embryonic stem cells and embryos.
Assuntos
Elementos Facilitadores Genéticos , Mesoderma , Células-Tronco Neurais , Fatores de Transcrição SOXB1 , Fatores de Transcrição SOXB1/metabolismo , Fatores de Transcrição SOXB1/genética , Animais , Camundongos , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Mesoderma/citologia , Mesoderma/metabolismo , Neurogênese , Regulação da Expressão Gênica no Desenvolvimento , Fator 3 de Transcrição de Octâmero/metabolismo , Fator 3 de Transcrição de Octâmero/genética , Diferenciação Celular/genética , Proteína Homeobox Nanog/metabolismo , Proteína Homeobox Nanog/genética , Linhagem da Célula/genética , Proteína Smad4/metabolismo , Proteína Smad4/genética , Células-Tronco Embrionárias/metabolismo , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias Murinas/metabolismo , Células-Tronco Embrionárias Murinas/citologia , Cromatina/metabolismo , Ligação ProteicaRESUMO
Cardiac lineage specification in the mouse is controlled by TGFß and WNT signaling. From fly to fish, BMP has been identified as an indispensable heart inducer. A detailed analysis of the role of Bmp4 and its effectors Smad1/5, however, was still missing. We show that Bmp4 induces cardiac mesoderm formation in murine embryonic stem cells in vitro. Bmp4 first activates Wnt3 and upregulates Nodal. pSmad1/5 and the WNT effector Tcf3 form a complex, and together with pSmad2/3 activate mesoderm enhancers and Eomes. They then cooperate with Eomes to consolidate the expression of many mesoderm factors, including T. Eomes and T form a positive- feedback loop and open additional enhancers regulating early mesoderm genes, including the transcription factor Mesp1, establishing the cardiac mesoderm lineage. In parallel, the neural fate is suppressed. Our data confirm the pivotal role of Bmp4 in cardiac mesoderm formation in the mouse. We describe in detail the consecutive and cooperative actions of three signaling pathways, BMP, WNT and Nodal, and their effector transcription factors, during cardiac mesoderm specification.