Tissue-specific modifier alleles determine Mertk loss-of-function traits
Abstract
Knockout (KO) mouse models play critical roles in elucidating biological processes behind disease-associated or disease-resistant traits. As a presumed consequence of gene KO, mice display certain phenotypes. Based on insight into the molecular role of said gene in a biological process, it is inferred that the particular biological process causally underlies the trait. This approach has been crucial towards understanding the basis of pathological and/or advantageous traits associated with Mertk KO mice. Mertk KO mice suffer from severe, early-onset retinal degeneration. MERTK, expressed in retinal pigment epithelia, is a receptor tyrosine kinase with a critical role in phagocytosis of apoptotic cells or cellular debris. Therefore, early-onset, severe retinal degeneration was described to be a direct consequence of failed MERTK-mediated phagocytosis of photoreceptor outer segments by retinal pigment epithelia. Here we report that the loss of Mertk alone is not sufficient for retinal degeneration. The widely used Mertk KO mouse carries multiple coincidental changes in its genome that affect the expression of a number of genes, including the Mertk paralog Tyro3. Retinal degeneration manifests only when the function of Tyro3 is concomitantly lost. Furthermore, Mertk KO mice display improved anti-tumor immunity. MERTK is expressed in macrophages. Therefore, enhanced anti-tumor immunity was inferred to result from the failure of macrophages to dispose of cancer cell corpses, resulting in a pro-inflammatory tumor microenvironment. The resistance against two syngeneic mouse tumor models observed in Mertk KO mice is not, however, phenocopied by the loss of Mertk alone. Neither Tyro3, nor macrophage phagocytosis by alternate genetic redundancy, account for the absence of anti-tumor immunity. Collectively, our results indicate that context-dependent epistasis of independent modifier alleles determines Mertk KO traits.
Data availability
RNA-sequencing data sets and the processed data that support the findings of this study have been deposited to the Gene Expression Omnibus (GEO) under accession ID: GSE205070. All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been provided for all figures included.
-
Tissue-specific modifier alleles determine Mertk loss-of-function traitsNCBI Gene Expression Omnibus,GSE205070.
Article and author information
Author details
Funding
National Institutes of Health (R01CA212376)
- Carla V Rothlin
- Sourav Ghosh
Howard Hughes Medical Institute
- Carla V Rothlin
Yale Cancer Center (YSPORE Career Development Award DRP27)
- Carla V Rothlin
Fordham University (Kim B. and Stephen E. Bepler Professorship in Biology)
- Silvia C Finnemann
Dutch Cancer Society (BUIT 2012-5347)
- Marleen Ansems
National Science Foundation (DGE-1122492)
- Lindsey D Hughes
Yale University (Richard K. Gershon Fellowship)
- Lindsey D Hughes
National Cancer Institute (2T32CA193200-06)
- James Nevin
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Florent Ginhoux, Agency for Science Technology and Research, Singapore
Ethics
Animal experimentation: All experiments involving animals were performed in accordance with regulatory guidelines and standards set by the Institutional Animal Care and Use Committee (IACUC) protocol (#2021-11312) of Yale University.
Version history
- Preprint posted: May 23, 2022 (view preprint)
- Received: May 24, 2022
- Accepted: August 13, 2022
- Accepted Manuscript published: August 15, 2022 (version 1)
- Version of Record published: August 31, 2022 (version 2)
Copyright
© 2022, Akalu 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.
Metrics
-
- 1,785
- views
-
- 338
- downloads
-
- 22
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Further reading
-
- Immunology and Inflammation
We studied lysosomal Ca2+ in inflammasome. Lipopolysaccharide (LPS) + palmitic acid (PA) decreased lysosomal Ca2+ ([Ca2+]Lys) and increased [Ca2+]i through mitochondrial ROS, which was suppressed in Trpm2-KO macrophages. Inflammasome activation and metabolic inflammation in adipose tissue of high-fat diet (HFD)-fed mice were ameliorated by Trpm2 KO. ER→lysosome Ca2+ refilling occurred after lysosomal Ca2+ release whose blockade attenuated LPS + PA-induced inflammasome. Subsequently, store-operated Ca2+entry (SOCE) was activated whose inhibition suppressed inflammasome. SOCE was coupled with K+ efflux whose inhibition reduced ER Ca2+ content ([Ca2+]ER) and impaired [Ca2+]Lys recovery. LPS + PA activated KCa3.1 channel, a Ca2+-activated K+ channel. Inhibitors of KCa3.1 channel or Kcnn4 KO reduced [Ca2+]ER, attenuated increase of [Ca2+]i or inflammasome activation by LPS + PA, and ameliorated HFD-induced inflammasome or metabolic inflammation. Lysosomal Ca2+ release induced delayed JNK and ASC phosphorylation through CAMKII-ASK1. These results suggest a novel role of lysosomal Ca2+ release sustained by ER→lysosome Ca2+ refilling and K+ efflux through KCa3.1 channel in inflammasome activation and metabolic inflammation.
-
- Immunology and Inflammation
The autoimmune disease lupus erythematosus (lupus) is characterized by photosensitivity, where even ambient ultraviolet radiation (UVR) exposure can lead to development of inflammatory skin lesions. We have previously shown that Langerhans cells (LCs) limit keratinocyte apoptosis and photosensitivity via a disintegrin and metalloprotease 17 (ADAM17)-mediated release of epidermal growth factor receptor (EGFR) ligands and that LC ADAM17 sheddase activity is reduced in lupus. Here, we sought to understand how the lupus skin environment contributes to LC ADAM17 dysfunction and, in the process, differentiate between effects on LC ADAM17 sheddase function, LC ADAM17 expression, and LC numbers. We show through transcriptomic analysis a shared IFN-rich environment in non-lesional skin across human lupus and three murine models: MRL/lpr, B6.Sle1yaa, and imiquimod (IMQ) mice. IFN-I inhibits LC ADAM17 sheddase activity in murine and human LCs, and IFNAR blockade in lupus model mice restores LC ADAM17 sheddase activity, all without consistent effects on LC ADAM17 protein expression or LC numbers. Anti-IFNAR-mediated LC ADAM17 sheddase function restoration is associated with reduced photosensitive responses that are dependent on EGFR signaling and LC ADAM17. Reactive oxygen species (ROS) is a known mediator of ADAM17 activity; we show that UVR-induced LC ROS production is reduced in lupus model mice, restored by anti-IFNAR, and is cytoplasmic in origin. Our findings suggest that IFN-I promotes photosensitivity at least in part by inhibiting UVR-induced LC ADAM17 sheddase function and raise the possibility that anifrolumab ameliorates lupus skin disease in part by restoring this function. This work provides insight into IFN-I-mediated disease mechanisms, LC regulation, and a potential mechanism of action for anifrolumab in lupus.