RESUMEN
The molecular mechanism triggering the organization of endothelial cells (ECs) in multicellular tubules is mechanistically still poorly understood. We demonstrate that cell-autonomous endothelial functions of the AP-1 subunit JunB are required for proper endothelial morphogenesis both in vivo in mouse embryos with endothelial-specific ablation of JunB and in in vitro angiogenesis models. By cDNA microarray analysis, we identified core-binding factor beta (CBFbeta), which together with the Runx proteins forms the heterodimeric core-binding transcription complex CBF, as a novel JunB target gene. In line with our findings, expression of the CBF target MMP-13 was impaired in JunB-deficient ECs. Reintroduction of CBFbeta into JunB-deficient ECs rescued the tube formation defect and MMP-13 expression, indicating an important role for CBFbeta in EC morphogenesis.
Asunto(s)
Subunidad beta del Factor de Unión al Sitio Principal/metabolismo , Endotelio Vascular/citología , Morfogénesis , Proteínas Proto-Oncogénicas c-jun/fisiología , Animales , Aorta/citología , Aorta/metabolismo , Western Blotting , Hipoxia de la Célula , Movimiento Celular , Células Cultivadas , Inmunoprecipitación de Cromatina , Colágeno Tipo II/genética , Colágeno Tipo II/fisiología , Subunidades alfa del Factor de Unión al Sitio Principal/metabolismo , Subunidad beta del Factor de Unión al Sitio Principal/genética , Endotelio Vascular/metabolismo , Técnica del Anticuerpo Fluorescente , Integrasas/metabolismo , Pulmón/citología , Pulmón/metabolismo , Metaloproteinasa 13 de la Matriz/genética , Metaloproteinasa 13 de la Matriz/fisiología , Ratones , Ratones Transgénicos , Invasividad Neoplásica , Neovascularización Patológica , Análisis de Secuencia por Matrices de Oligonucleótidos , Reacción en Cadena de la Polimerasa , Regiones Promotoras Genéticas , Proteínas Proto-Oncogénicas c-jun/genética , Transcripción GenéticaRESUMEN
Regulation of vascular endothelial growth factor (VEGF) expression is a complex process involving a plethora of transcriptional regulators. The AP-1 transcription factor is considered as facilitator of hypoxia-induced VEGF expression through interaction with hypoxia-inducible factor (HIF) which plays a major role in mediating the cellular hypoxia response. As yet, both the decisive AP-1 subunit leading to VEGF induction and the molecular mechanism by which this subunit is activated have not been deciphered. Here, we demonstrate that the AP-1 subunit junB is a target gene of hypoxia-induced signaling via NF-kappaB. Loss of JunB in various cell types results in severely impaired hypoxia-induced VEGF expression, although HIF is present and becomes stabilized. Thus, we identify JunB as a critical independent regulator of VEGF transcription and provide a mechanistic explanation for the inherent vascular phenotypes seen in JunB-deficient embryos, ex vivo allantois explants and in vitro differentiated embryoid bodies. In support of these findings, tumor angiogenesis was impaired in junB(-/-) teratocarcinomas because of severely impaired paracrine-acting VEGF and the subsequent inability to efficiently recruit host-derived vessels.