Increase of hematopoietic progenitor and suppression of endothelial gene expression by Runx1 expression during in vitro ES differentiation

Objective. Runx1 is essential for both the establishment of hematopoiesis during development and maintenance of adult hematopoiesis. To reveal the roles of Runx1, we examined how and when Runx1 functions during development of hematopoiesis, and revealed the genes controlled by Runx1. Materials and Methods. A combined in vitro approach involving in vitro hematopoietic differentiation of embryonic stein cells and conditional gene expression of Runx1 was utilized for this study. Then we analyzed the effects of Runx1 on the differentiation and proliferation of hematopoietic cells and carried out DNA microarray analysis. Results. Pulse expression of Runx1 prior to the emergence of hematopoietic cells caused immature hematopoietic cell increase but did not have any effects on the induction of hemogenic cells. During this process, the mRNA level of several endothelial cell-specific genes was downregulated. Conclusion. Runx1 expression play important roles on the proliferation of emerging immature hematopoietic progenitors or the transition process from endothelial to hematopoietic cells presumably by suppressing the genes related to endothelial phenotype. (C) 2009 ISEH - Society for Hematology and Stem Cells. Published by Elsevier Inc.