Abstract 2109: Ets Related Protein 71 Transactivates Brachyury and Regulates Cardiovascular Development
The molecular cascades that direct fate decisions during embryogenesis remain an area of intense interest. Previous studies support the notion that hematopoietic and endothelial cell populations share a common multipotent progenitor, often referred to as the hemangioblast. Ets related protein 71 (ER71) was discovered as a downstream target of Nkx2.5 in the developing endocardium. Further experiments have demonstrated that ER71 null mice are embryonic lethal and that ER71 is essential for development of embryonic blood and vasculature. In the null embryos, Tie2, a marker of the endothelial lineage, is absent. Using an array of biochemical techniques, we demonstrate that Tie2 is a direct downstream target of ER71. Likewise, Brachyury (T), a mesodermal marker which has also been implicated in marking the hemangioblast, has been identified as a direct downstream target using ChIP and transcriptional assays. Microarrays of whole ER71 null embryos suggest that a number of transcripts that identify the endothelial and hematopoietic pools of cells are absent in the ER71 null. To examine whether ER71 is a novel marker or master regulator of the hemangioblast population, a 3.9 kb ER71-EYFP transgenic animal has been engineered with the goal of isolating the cells at discrete stages of development. Using FACS analysis, we isolated the ER71-EYFP positive cells at E9.0, isolated the RNA and defined the molecular program using transcriptome analysis. To complement these molecular studies, we utilized FACS analysis to define that the ER71-EYFP positive cells express known endothelial and hematopoietic surface markers. Together, these studies define a new ER71-brachyury cascade that directs cardiovascular development and further supports the conclusion that ER71 functions to regulate derivatives of the hemangioblast.
This research has received full or partial funding support from the American Heart Association, National Center.