ETS factors are required but not sufficient for specific patterns of enhancer activity in different endothelial subtypes

Alice Neal,Svanhild Nornes,Pakavarin Louphrasitthiphol,Natalia Sacilotto,Mark D Preston,Lucija Fleisinger,Sophie Payne,Sarah De Val

doi:10.1016/j.ydbio.2021.01.002

Alice Neal, Svanhild Nornes + Show 6 more

Open Access

https://doi.org/10.1016/j.ydbio.2021.01.002

Copy DOI

Abstract

Correct vascular differentiation requires distinct patterns of gene expression in different subtypes of endothelial cells. Members of the ETS transcription factor family are essential for the transcriptional activation of arterial and angiogenesis-specific gene regulatory elements, leading to the hypothesis that they play lineage-defining roles in arterial and angiogenic differentiation directly downstream of VEGFA signalling. However, an alternative explanation is that ETS binding at enhancers and promoters is a general requirement for activation of many endothelial genes regardless of expression pattern, with subtype-specificity provided by additional factors. Here we use analysis of Ephb4 and Coup-TFII (Nr2f2) vein-specific enhancers to demonstrate that ETS factors are equally essential for vein, arterial and angiogenic-specific enhancer activity patterns. Further, we show that ETS factor binding at these vein-specific enhancers is enriched by VEGFA signalling, similar to that seen at arterial and angiogenic enhancers. However, while arterial and angiogenic enhancers can be activated by VEGFA in vivo, the Ephb4 and Coup-TFII venous enhancers are not, suggesting that the specificity of VEGFA-induced arterial and angiogenic enhancer activity occurs via non-ETS transcription factors. These results support a model in which ETS factors are not the primary regulators of specific patterns of gene expression in different endothelial subtypes.

Highlights

The endothelial cell (EC) layer is the first part of the vascular system to form, initially via differentiation from progenitors, and later through the formation of new vessels from existing ones
Similar to arterial and angiogenic enhancers, ETS factor binding at these venous enhancers is necessary for enhancer activation and vein-specific patterns of reporter gene expression, and that this binding is enriched by vascular endothelial growth factor A (VEGFA) signalling
Unlike arterial and angiogenic enhancers, these venous enhancers cannot be directly activated by overexpression of VEGFA in vivo. These results indicate that within the endothelium, VEGFA-stimulated ETS factor binding is a shared feature at enhancers associated with multiple different patterns of gene expression, and suggests that additional transcription factors may be primarily responsible for directing arterial, angiogenic and venousspecific gene expression patterns downstream of different growth factor signalling inputs

Summary

Introduction

The endothelial cell (EC) layer is the first part of the vascular system to form, initially via differentiation from progenitors (vasculogenesis), and later through the formation of new vessels from existing ones (angiogenesis). The vascular system is subdivided into arteries, veins, lymphatics and capillaries, each comprised of genetically distinct ECs expressing specific fate-determining genes (Lin et al, 2007; dela Paz and D’Amore, 2009). The essential balance of endothelial sprouting, proliferation and quiescence during angiogenesis involves multiple genetically distinct EC subtypes (Potente et al, 2011; Rocha and Adams, 2009). While gene expression in the endothelium is known to involve dynamic transcriptional regulation, the signalling cascades and transcriptional effectors that establish and maintain these different endothelial cell fates have not been fully defined. Transcriptional regulation at gene enhancers is known to directly involve members of the ETS (E-26 transformation-specific) transcription factor family (De Val and Black, 2009).

Methods

Results

Conclusion