Notch-induced endoplasmic reticulum-associated degradation governs mouse thymocyte β- selection
- Baylor College of Medicine, United States
- Case Western Reserve University, United States
- Wayne State University, United States
- La Trobe University, Australia
- University of Michigan-Ann Arbor, United States
Abstract
Signals from the pre-T cell receptor and Notch coordinately instruct b-selection of CD4-CD8- double negative (DN) thymocytes to generate ab T cells in the thymus. However, how these signals ensure a high-fidelity proteome and safeguard the clonal diversification of the pre-selection TCR repertoire given the considerable translational activity imposed by b-selection is largely unknown. Here, we identify the endoplasmic reticulum (ER)-associated degradation (ERAD) machinery as a critical proteostasis checkpoint during b-selection. Expression of the SEL1L-HRD1 complex, the most conserved branch of ERAD, is directly regulated by the transcriptional activity of the Notch intracellular domain. Deletion of Sel1l impaired DN3 to DN4 thymocyte transition and severely impaired mouse ab T cell development. Mechanistically, Sel1l deficiency induced unresolved ER stress that triggered thymocyte apoptosis through the PERK pathway. Accordingly, genetically inactivating PERK rescued T cell development from Sel1l-deficient thymocytes. In contrast, IRE1a/XBP1 pathway was induced as a compensatory adaptation to alleviate Sel1l-deficiency induced ER stress. Dual loss of Sel1l and Xbp1 markedly exacerbated the thymic defect. Our study reveals a critical developmental signal controlled proteostasis mechanism that enforces T cell development to ensure a healthy adaptive immunity.
Data availability
Sequencing data have been deposited in GEO under accession code GSE173993.All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for all Figures.
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Notch-Induced Endoplasmic Reticulum-Associated Degradation Governs Thymocyte Beta-SelectionNCBI Gene Expression Omnibus, GSE173993.
Article and author information
Author details
Katharine Umphred-Wilson
Funding
National Heart, Lung, and Blood Institute (R01HL146642)
- Xi Chen
Cancer Prevention and Research Institute of Texas (RP160283)
- Fanglue Peng
National Institute of Allergy and Infectious Diseases (R01 AI1143992)
- Stanley Adoro
National Cancer Institute (R37CA228304)
- Xi Chen
National Cancer Institute (K22CA218467)
- Stanley Adoro
National Cancer Institute (P50CA186784)
- Xi Chen
National Institute of General Medical Sciences (R35GM130292)
- Ling Qi
DOD Peer Reviewed Cancer Research Program (W81XWH1910524)
- Xi Chen
DOD Peer Reviewed Cancer Research Program (W81XWH1910306)
- Stanley Adoro
Congressionally Directed Medical Research Programs (W81XWH1910035)
- Xiangdong Lv
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All protocols described in this study were approved by the Baylor College of Medicine Institutional Animal Care and Use Committee (protocol: AN-6813) or Case Western Reserve University Institutional Animal Care and Use Committee (protocol: 2017-0055).
Copyright
© 2021, Liu 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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Notch-induced endoplasmic reticulum-associated degradation governs mouse thymocyte β- selection
eLife 10:e69975.
https://doi.org/10.7554/eLife.69975
Further reading
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- Developmental Biology
- Stem Cells and Regenerative Medicine
Chromocenters are established after the 2-cell (2C) stage during mouse embryonic development, but the factors that mediate chromocenter formation remain largely unknown. To identify regulators of 2C heterochromatin establishment in mice, we generated an inducible system to convert embryonic stem cells (ESCs) to 2C-like cells. This conversion is marked by a global reorganization and dispersion of H3K9me3-heterochromatin foci, which are then reversibly formed upon re-entry into pluripotency. By profiling the chromatin-bound proteome (chromatome) through genome capture of ESCs transitioning to 2C-like cells, we uncover chromatin regulators involved in de novo heterochromatin formation. We identified TOPBP1 and investigated its binding partner SMARCAD1. SMARCAD1 and TOPBP1 associate with H3K9me3-heterochromatin in ESCs. Interestingly, the nuclear localization of SMARCAD1 is lost in 2C-like cells. SMARCAD1 or TOPBP1 depletion in mouse embryos leads to developmental arrest, reduction of H3K9me3, and remodeling of heterochromatin foci. Collectively, our findings contribute to comprehending the maintenance of chromocenters during early development.
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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.
