Key Points
VCAM1 is heterogeneously expressed in endothelial cells after TNF-α induction.
Heterogeneous VCAM1 promoter DNA methylation is mitotically heritable.
Heterogeneity in cytokine responsiveness occurs in many endothelial genes.
Abstract
Homogeneous populations of mature differentiated primary cell types can display variable responsiveness to extracellular stimuli, although little is known about the underlying mechanisms that govern such heterogeneity at the level of gene expression. In this article, we show that morphologically homogenous human endothelial cells exhibit heterogeneous expression of VCAM1 after TNF-α stimulation. Variability in VCAM1 expression was not due to stochasticity of intracellular signal transduction but rather to preexisting established heterogeneous states of promoter DNA methylation that were generationally conserved through mitosis. Variability in DNA methylation of the VCAM1 promoter resulted in graded RelA/p65 and RNA polymerase II binding that gave rise to a distribution of VCAM1 transcription in the population after TNF-α stimulation. Microarray analysis and single-cell RNA sequencing revealed that a number of cytokine-inducible genes shared this heterogeneous response pattern. These results show that heritable epigenetic heterogeneity is fundamental in inflammatory signaling and highlight VCAM1 as a metastable epiallele.
Footnotes
This work was supported by Canadian Institutes of Health Grant MOP 142307 to P.A.M.
The microarray data presented in this article have been submitted to the Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/) under accession number GSE141374.
The online version of this article contains supplemental material.
- Received September 26, 2019.
- Accepted December 23, 2019.
- Copyright © 2020 by The American Association of Immunologists, Inc.
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