Abstract 9665: PKA / CREB Pathway Initiates Endothelial And Hematopoietic Cell Differentiation Via Etv2 Induction

Ets-family protein Etv2 (also called ER71 or Etsrp) is a key factor for vascular and blood development from mesodermal cells. However, regulatory mechanisms and a triggering signal for Etv2 expression have been largely unknown. We previously established an ES cell differentiation system that reproduces early vascular development using vascular endothelial growth factor (VEGF) receptor-2 (VEGFR2)-positive cells as common vascular progenitors. Recently, we revealed that cAMP/protein kinase A (PKA) signaling enhanced differentiation of vascular progenitors into endothelial cells (ECs) and hematopoietic cells (HPCs) using this system. Here we show that PKA activation induces Etv2 expression, which can trigger EC/HPC differentiation. We found that Etv2 was markedly upregulated by PKA activation preceding EC and HPC differentiation. Inhibition of Etv2 using siRNA completely abolished PKA-elicited EC and HPC differentiation from ES cells. We identified two cAMP response element (CRE) sequences in Etv2 promoter region, and confirmed that CRE-binding protein (CREB) directly binds to the CRE sites. Furthermore, PKA activated Etv2 promoter activity in luciferase assay, which was disappeared in CRE-mutant Etv2 promoters. Expression of dominant negative form of CREB completely inhibited PKA-elicited Etv2 expression and induction of EC/HPCs from ES cells. PKA/CREB pathway is, thus, a critical regulator for the initiation of EC/HPC differentiation through Etv2 transcription. This early stage molecular linkage between a triggering signal and transcriptional cascades for differentiation would provide novel insights in vascular and blood development and novel molecular targets for vascular and blood regeneration medicine.