Wnt signaling positively regulates endothelial cell fate specification in the Fli1a-positive progenitor population via Lef1

Abstract

During vertebrate embryogenesis, vascular endothelial cells (ECs) and primitive erythrocytes become specified within close proximity in the posterior lateral plate mesoderm (LPM) from a common progenitor. However, the signaling cascades regulating the specification into either lineage remain largely elusive. Here, we analyze the contribution of β-catenin dependent Wnt signaling to EC and erythrocyte specification during zebrafish embryogenesis. We generated novel β-catenin dependent Wnt signaling reporters which, by using destabilized fluorophores (Venus-Pest, dGFP), specifically allow us to detect Wnt signaling responses in narrow time windows as well as in spatially restricted domains, defined by Cre recombinase expression (Tg(axin2:Venus-Pest); Tg(14TCF:loxP-STOP-loxP-dGFP)). We therefore can detect β-catenin dependent Wnt signaling activity in a subset of the Fli1a-positive progenitor population. Additionally, we show that mesodermal Wnt3a-mediated signaling via the transcription factor Lef1 positively regulates EC specification (defined by kdrl expression) at the expense of primitive erythrocyte specification (defined by gata1 expression) in zebrafish embryos. Using mesoderm derived from human embryonic stem cells, we identified the same principle of Wnt signaling dependent EC specification in conjunction with auto-upregulation of LEF1. Our data indicate a novel role of β-catenin dependent Wnt signaling in regulating EC specification during vasculogenesis.

Gfi1aa and Gfi1b set the pace for primitive erythroblast differentiation from hemangioblasts in the zebrafish embryo

“…Notch favors prRBC differentiation in nascent mesoderm, 20 whereas Wnt promotes endothelial development specifically in the PLM. 19 Our finding that Gfi1aa suppresses EC gene expression in prRBCs of the PLM implies that these prRBCs have only recently developed from hemangioblasts.…”

“…In zebrafish, prRBCs and ECs form from hemangioblasts [16][17][18][19][20] and develop in the posterior lateral mesoderm (PLM). [21][22][23][24][25] PLM cells migrate to the midline to form the intermediate cell mass of the trunk and its posterior extension, the posterior blood island of the tail.…”

Dermomyotome-derived endothelial cells migrate to the dorsal aorta to support hematopoietic stem cell emergence

“…However, this view does not take into account putative differences in EC function as a result of different developmental origins. Rather, exposure to embryonic signaling cascades mediated via Wnt (Hubner et al, 2017), Hedgehog (Hh) (Gering and Patient, 2005;Vokes and McMahon, 2004;Wilkinson et al, 2012;Williams et al, 2010), Vascular Endothelial Growth Factor (VEGF) (Casie Chetty et al, 2017;Hong et al, 2006;Lawson et al, 2003;Wythe et al, 2013), and Notch molecules are thought to differentially instruct equipotent angioblasts to each distinct endothelial cell fate (Fang et al, 2017;Lawson et al, 2001;Siekmann and Lawson, 2007;Zhong et al, 2001).…”

Dynamic Expression Profiles of β-Catenin during Murine Cardiac Valve Development

“…The basic protein organization of β-catenin consists of an amino terminal domain, a central region consisting of twelve Armadillo repeats and a carboxyl-terminal region [ 14 , 15 ]. Through the Armadillo repeats, β-catenin serves as both a structural scaffold and signaling protein for a multitude of interaction partners in adherens junctions, the cytoplasm as well as the nucleus [ 16 , 17 , 18 , 19 , 20 ].…”