Enhancer architecture sensitizes cell-specific responses to Notch gene dose via a bind and discard mechanism
- Cincinnati Children's Hospital Research Foundation, United States
- Tel Aviv University, Israel
- Cincinnati Children's Hospital Medical Center, United States
- University of Cincinnati, United States
- Emory University, United States
- Cincinnati Children's hospital, United States
Abstract
Notch pathway haploinsufficiency can cause severe developmental syndromes with highly variable penetrance. Currently, we have a limited mechanistic understanding of phenotype variability due to gene dosage. Here, we unexpectedly found that inserting an enhancer containing pioneer transcription factor sites coupled to Notch dimer sites can induce a subset of Notch haploinsufficiency phenotypes in Drosophila with wild type Notch gene dose. Using Drosophila genetics, we show that this enhancer induces Notch phenotypes in a Cdk8-dependent, transcription-independent manner. We further combined mathematical modeling with quantitative trait and expression analysis to build a model that describes how changes in Notch signal production versus degradation differentially impact cellular outcomes that require long versus short signal duration. Altogether, these findings support a 'bind and discard' mechanism in which enhancers with specific binding sites promote rapid Cdk8-dependent Notch turnover, and thereby reduce Notch-dependent transcription at other loci and sensitize tissues to gene dose based upon signal duration.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files.
Article and author information
Author details
Collin J Christensen
Funding
National Science Foundation (1715822)
- David Sprinzak
- Brian Gebelein
National Institutes of Health (CA163653)
- Raphael Kopan
National Institutes of Health (CA178974)
- Rhett A Kovall
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Kuang et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Enhancer architecture sensitizes cell-specific responses to Notch gene dose via a bind and discard mechanism
eLife 9:e53659.
https://doi.org/10.7554/eLife.53659
Further reading
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- Developmental Biology
Notch signaling has been identified as a key regulatory pathway in patterning the endocardium through activation of endothelial-to-mesenchymal transition (EMT) in the atrioventricular canal (AVC) and proximal outflow tract (OFT) region. However, the precise mechanism underlying Notch activation remains elusive. By transiently blocking the heartbeat of E9.5 mouse embryos, we found that Notch activation in the arterial endothelium was dependent on its ligand Dll4, whereas the reduced expression of Dll4 in the endocardium led to a ligand-depleted field, enabling Notch to be specifically activated in AVC and OFT by regional increased shear stress. The strong shear stress altered the membrane lipid microdomain structure of endocardial cells, which activated mTORC2 and PKC and promoted Notch1 cleavage even in the absence of strong ligand stimulation. These findings highlight the role of mechanical forces as a primary cue for endocardial patterning and provide insights into the mechanisms underlying congenital heart diseases of endocardial origin.
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