Abstract 19560: Etv2 Regulates Endothelial Development via Activation of Sox7
Etv2 has recently been shown to be an important factor for the specification of the endocardial/endothelial and hematopoietic lineages. Transgenic embryos lacking Etv2 die between E9.0 and E9.5 due to absence of the endocardial/endothelial lineage and significant disruption of hematopoietic lineages. Sox 7, Sox 17 and Sox 18 comprise the Sox-F family which has been shown to be important in the regulation of hematopoietic cells and cardiovascular development. Therefore, we examined the hypothesis that the Sox family members were downstream targets of Etv2. Sox 7, Sox 17 and Sox 18 were found to be significantly downregulated in the Etv2 null mice compared to wildtype (WT) littermates at two developmental stages. WT embryoid body (EB) developmental expression profiles supported that Sox 7 and Sox 17, but not Sox 18, were direct downstream targets of Etv2. Studies performed using ES cells generated from the Etv2 null and WT littermate blastocysts confirmed the lack of the endothelial and hemogenic endothelium lineages in the absence of Etv2. The expression of all Sox F family members was also markedly altered in the Etv2 null EB system with a virtual absence of both Sox 7 and Sox18 expression in all developmental timepoints in the Etv2 null EBs when compared to WT controls. We utilized an array of molecular biological techniques to demonstrate that Etv2 is a direct upstream regulator of the Sox 7 gene. We also generated an inducible Sox7 overexpressing embryonic stem (ES) cell line and overexpression of Sox7 resulted in an induction of the endothelial molecular program with an increase in the percentage of Flk-1/Cdh5 double positive endothelial progenitor cells and increased expression of Pecam1 and Cdh5 in Sox7 overexpressing Day6 EBs. Collectively, these studies support the conclusion that Etv2 is essential for the endocardial/endothelial lineage including the hemogenic endothelium and Sox7 is an important factor in this developmental pathway. To further verify the role of Sox 7, we are undertaking rescue experiments of the Etv2 null ES cells by expressing Sox 7 under the control of an inducible lentivirus system. We anticipate that the induction of Sox 7 in Etv2 null EBs will reestablish expression of the endothelial and hemogenic endothelial molecular programs.
- © 2012 by American Heart Association, Inc.