Genome-Wide Analysis of the Zebrafish ETS Family Identifies Three Genes Required for Hemangioblast Differentiation or Angiogenesis

Abstract

Abstract-ETS domain transcription factors have been linked to hematopoiesis, vasculogenesis, and angiogenesis.However, their biological functions and the mechanisms of action, remain incompletely understood. Here, we have performed a systematic analysis of zebrafish ETS domain genes and identified 31 in the genome. Detailed gene expression profiling revealed that 12 of them are expressed in blood and endothelial precursors during embryonic development. Combined with a phylogenetic tree assay, this suggests that some of the coexpressed genes may have redundant or additive functions in these cells. Loss-of-function analysis of 3 of them, erg, fli1, and etsrp, demonstrated that erg and fli1 act cooperatively and are required for angiogenesis possibly via direct regulation of an endothelial cell junction molecule, VE-cadherin, whereas etsrp is essential for primitive myeloid/endothelial progenitors (hemangioblasts) in zebrafish. Taken together, these results provide a global view of the ETS genes in the zebrafish genome during embryogenesis and provide new insights on the functions and biology of erg, fli1, and etsrp, which could be applicable to higher vertebrates, including mice and humans. (Circ Res. 2008;103:1147-1154.)Key Words: zebrafish Ⅲ gene duplication Ⅲ ETS transcription factors Ⅲ hemangioblast Ⅲ angiogenesis Z ebrafish has been recognized as an excellent genetic and developmental biology model to study hematopoiesis and vessel development. Large numbers of genetic mutants and transgenic lines in both blood and endothelial lineages have become available. More importantly, developmental mechanisms, including the functions of many known important regulators involved in both blood and vessel development, are conserved between higher vertebrates and zebrafish. 1 It has been proposed that hematopoietic and endothelial cells share a common progenitor, termed the hemangioblast. 2 This idea was initially conceived from the observation that these 2 cell types develop in close proximity within the embryo. 3 Coexpression of many important regulators of hematopoiesis and vasculogenesis in early embryos further supports the existence of a common progenitor for hematopoietic and endothelial cells. Furthermore, loss of function of several of these regulators, including the zebrafish cloche (clo) mutant, affects both cell types. 4 -7 Recent work by us and others subsequently showed that several important hematopoietic and endothelial regulators in mammals, such as Scl/Tal1 and Lmo2, also play similar roles in zebrafish. 8 -10 ETS domain genes encode a super family of transcription factors organized into 11 subfamilies based on domain structures, which are conserved from worm and fly to mammals. 11 These transcription factors are involved in cell fate specification, proliferation, migration, and differentiation during embryonic development and adulthood and have been linked with diverse biological processes, from hematopoiesis, vasculogenesis, and angiogenesis to neurogenesis. Many important blood and endothelial regul...

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

“…3A). Previous reports demonstrated that etv2 plays no role in erythroid and posterior myeloid differentiation (39,40), although it is strongly required for posterior endothelial development (36,39). These findings, combined with our findings, indicate that the importance of the LSD1/ Etv2 paradigm in hemangioblast differentiation may be restricted in the posterior hemangioblasts.…”

“…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.…”

Etiology of intracerebral hemorrhage (ICH): novel insights from Zebrafish embryos

“…Both erg and fli1 transcripts are detected in endothelial precursors/hemangioblasts as well as mature blood vessels during zebrafish development. Injection of morpholino-oligonucleotides against either erg or fli1 induces ICH phenotypes in developing zebrafish (Liu and Patient, 2008). Consistently, the mRNA levels of VE-cadherin were significantly diminished in the morphants prior to the onset of ICH, suggesting that the hemorrhages arise, in part, due to downregulation of VE-cadherin levels (Liu and Patient, 2008) (Fig.…”

“…The conserved transcription regulators, erythroblast transformationspecific-related gene (erg) and Friend leukemia integration 1 (fli1), both of which are required for hematopoetic and angiogenic processes, are important in neurovascular stabilization, because they regulate VE-cadherin dynamics (via regulating VE-cadherin mRNA enrichment levels) (Liu and Patient, 2008). Both erg and fli1 transcripts are detected in endothelial precursors/hemangioblasts as well as mature blood vessels during zebrafish development.…”

Regulatory Pathways Affecting Vascular Stabilization via VE-Cadherin Dynamics: Insights from Zebrafish (Danio Rerio)

“…27 Ets-related gene, Erg and Friend leukemia integration 1, Fli1 Molecular characterization of E26 transformation-specific family genes in zebrafish have led to the identification of two transcription factors involved in hematopoesis and angiogenesis, namely, erg and fli1 (Ets-related gene and Friend leukemia integration 1), both of which have been associated with vascular stabilization. 30 Both erg and fli1 exhibit expression profiles restricted to angioblasts and developing blood vessels in zebrafish embryos. 30 Injection of nonoverlapping morpholinos designed against erg or fli1 induce identical hemorrhage phenotypes in the central nervous system.…”