Ets1-Related Protein Is a Key Regulator of Vasculogenesis in Zebrafish

Abstract

During embryonic development, multiple signaling pathways control specification, migration, and differentiation of the vascular endothelial cell precursors, angioblasts. No single gene responsible for the commitment of mesenchymal cells to the angioblast cell fate has been identified as yet. Here we report characterization and functional studies of Etsrp, a novel zebrafish ETS domain protein. etsrp embryonic expression is only restricted to vascular endothelial cells and their earliest precursors. Morpholino knockdown of Etsrp protein function resulted in the complete absence of circulation in zebrafish embryos. Angioblasts in etsrp–morpholino-injected embryos (morphants) failed to undergo migration and differentiation and did not coalesce into functional blood vessels. Expression of all vascular endothelial molecular markers tested was severely reduced in etsrp morphants, whereas hematopoietic markers were not affected. Overexpression of etsrp RNA caused multiple cell types to express vascular endothelial markers. etsrp RNA restored expression of vascular markers in cloche mutants, defective in hematopoietic and endothelial cell formation, arguing that etsrp functions downstream of cloche in angioblast formation. etsrp gene function was also required for endothelial marker induction by the vascular endothelial growth factor (vegf) and stem cell leukemia (scl/tal1). These results demonstrate that Etsrp is necessary and sufficient for the initiation of vasculogenesis.

LSD1/KDM1A promotes hematopoietic commitment of hemangioblasts through downregulation of Etv2

“…S7), suggesting that the up-regulation of endothelial markers did not lead to excess endothelialization. Considering these results, together with the previous finding that the zebrafish Etv2 was a positive regulator of endothelial and anterior hematopoietic development (35,39,40), we speculated that the hematopoietic cells in the ICM region of lsd1 it627 mutants were maintained in an undifferentiated state with endothelial characteristics.…”

“…A dramatic down-regulation of Etv2 during hematopoietic differentiation is also observed in zebrafish (35) and Xenopus (57). The importance of the Etv2 shutdown in hematopoiesis has been experimentally demonstrated in mice (58).…”

“…S5B). Because etv2 has been shown to regulate the expression of endothelial genes positively (35)(36)(37), the expression of fli1a and other endothelial markers (flk1 and tie1) was analyzed at later developmental stages ( Fig. 3 B and C and Fig.…”

Molecular and developmental biology of the hemangioblast

“…This represents the first single gene mutation that eliminates both endothelial and hematopoietic lineages, probably in the level of hemangioblasts. Epistasis analyses have shown that cloche acts upstream of zbp-89, scl, lmo2, gata1, gata2, runx1, c-myb, fli1, flk1, tie2, hhex, and etsrp in hematopoietic and endothelial cell development in zebrafish (Stainier et al, 1995;Fouquet et al, 1997;Liao et al, 1997Liao et al, , 1998Liao et al, , 2000Brown et al, 2000;Burns et al, 2002;Patterson et al, 2005Patterson et al, , 2007Li et al, 2006;Pham et al, 2006;Sumanas and Lin, 2006). In addition, microarray analyses by comparing cloche mutant and wild-type embryos have revealed that cloche specifically regulates a panel of hematopoietic and endothelial genes (Qian et al, 2005;Sumanas et al, 2005;Weber et al, 2005).…”

“…Zebrafish cloche mutant affects both endothelial and hematopoietic lineages (Stainier et al, 1995). Gain-of-function analysis in zebrafish embryos suggests that scl, lmo2, hhex, and etsrp can specify the hemangioblast from the posterior lateral plate mesoderm (LPM) at the expense of other mesodermal cell fates (Gering et al, 1998;Liao et al, 2000;Gering et al, 2003;Dooley et al, 2005;Pham et al, 2006;Sumanas and Lin, 2006;Patterson et al, 2007). However, it remains to be revealed how these known and other unknown players interact in hemangioblast development and differentiation.…”