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Zhang X, Young C, Liao XH, Refetoff S, Torres M, Tomer Y, Stefan-Lifshitz M, Zhang H, Larkin D, Fang D, Qi L, Arvan P. Perturbation of endoplasmic reticulum proteostasis triggers tissue injury in the thyroid gland. JCI Insight 2023; 8:e169937. [PMID: 37345654 PMCID: PMC10371246 DOI: 10.1172/jci.insight.169937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 05/09/2023] [Indexed: 06/23/2023] Open
Abstract
Defects in endoplasmic reticulum (ER) proteostasis have been linked to diseases in multiple organ systems. Here we examined the impact of perturbation of ER proteostasis in mice bearing thyrocyte-specific knockout of either HRD1 (to disable ER-associated protein degradation [ERAD]) or ATG7 (to disable autophagy) in the absence or presence of heterozygous expression of misfolded mutant thyroglobulin (the most highly expressed thyroid gene product, synthesized in the ER). Misfolding-inducing thyroglobulin mutations are common in humans but are said to yield only autosomal-recessive disease - perhaps because misfolded thyroglobulin protein might undergo disposal by ERAD or ER macroautophagy. We find that as single defects, neither ERAD, nor autophagy, nor heterozygous thyroglobulin misfolding altered circulating thyroxine levels, and neither defective ERAD nor defective autophagy caused any gross morphological change in an otherwise WT thyroid gland. However, heterozygous expression of misfolded thyroglobulin itself triggered significant ER stress and individual thyrocyte death while maintaining integrity of the surrounding thyroid epithelium. In this context, deficiency of ERAD (but not autophagy) resulted in patchy whole-follicle death with follicular collapse and degeneration, accompanied by infiltration of bone marrow-derived macrophages. Perturbation of thyrocyte ER proteostasis is thus a risk factor for both cell death and follicular demise.
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Affiliation(s)
- Xiaohan Zhang
- Division of Metabolism, Endocrinology & Diabetes and
| | - Crystal Young
- Division of Metabolism, Endocrinology & Diabetes and
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Samuel Refetoff
- Department of Medicine
- Department of Pediatrics, and Committee on Genetics, Genomics, and Systems Biology, The University of Chicago, Chicago, Illinois, USA
| | - Mauricio Torres
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Yaron Tomer
- Department of Medicine, Fleischer Institute for Diabetes and Metabolism, Albert Einstein College of Medicine, New York, New York, USA
| | - Mihaela Stefan-Lifshitz
- Department of Medicine, Fleischer Institute for Diabetes and Metabolism, Albert Einstein College of Medicine, New York, New York, USA
| | - Hao Zhang
- Division of Metabolism, Endocrinology & Diabetes and
| | - Dennis Larkin
- Division of Metabolism, Endocrinology & Diabetes and
| | - Deyu Fang
- Department of Pathology, Feinberg School of Medicine, Northwestern Medicine, Chicago, Illinois, USA
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes and
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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Laboulaye MA, Duan X, Qiao M, Whitney IE, Sanes JR. Mapping Transgene Insertion Sites Reveals Complex Interactions Between Mouse Transgenes and Neighboring Endogenous Genes. Front Mol Neurosci 2018; 11:385. [PMID: 30405348 PMCID: PMC6206269 DOI: 10.3389/fnmol.2018.00385] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 09/25/2018] [Indexed: 11/13/2022] Open
Abstract
Transgenic mouse lines are routinely employed to label and manipulate distinct cell types. The transgene generally comprises cell-type specific regulatory elements linked to a cDNA encoding a reporter or other protein. However, off-target expression seemingly unrelated to the regulatory elements in the transgene is often observed, it is sometimes suspected to reflect influences related to the site of transgene integration in the genome. To test this hypothesis, we used a proximity ligation-based method, Targeted Locus Amplification (TLA), to map the insertion sites of three well-characterized transgenes that appeared to exhibit insertion site-dependent expression in retina. The nearest endogenous genes to transgenes HB9-GFP, Mito-P, and TYW3 are Cdh6, Fat4 and Khdrbs2, respectively. For two lines, we demonstrate that expression reflects that of the closest endogenous gene (Fat4 and Cdh6), even though the distance between transgene and endogenous gene is 550 and 680 kb, respectively. In all three lines, the transgenes decrease expression of the neighboring endogenous genes. In each case, the affected endogenous gene was expressed in at least some of the cell types that the transgenic line has been used to mark and study. These results provide insights into the effects of transgenes and endogenous genes on each other's expression, demonstrate that mapping insertion site is valuable for interpreting results obtained with transgenic lines, and indicate that TLA is a reliable method for integration site discovery.
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Affiliation(s)
| | | | | | | | - Joshua R. Sanes
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, United States
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Yu J, Koenig RJ. Thyroid-Specific PPARγ Deletion Is Benign in the Mouse. Endocrinology 2018; 159:1463-1468. [PMID: 29420754 PMCID: PMC5839734 DOI: 10.1210/en.2017-03163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/30/2018] [Indexed: 12/16/2022]
Abstract
Peroxisome proliferator-activated receptor γ (PPARγ) is widely expressed at low levels and regulates many physiological processes. In mice and humans, there is evidence that PPARγ can function as a tumor suppressor. A PAX8-PPARγ fusion protein (PPFP) is oncogenic in a subset of thyroid cancers, suggesting that inhibition of endogenous PPARγ function by the fusion protein could contribute to thyroid oncogenesis. However, the function of PPARγ within thyrocytes has never been directly tested. Therefore, we have created a thyroid-specific genetic knockout of murine Pparg and have studied thyroid biology in these mice. Thyroid size and histology, the expression of thyroid-specific genes, and serum T4 levels all are unaffected by loss of thyroidal PPARγ expression. PPFP thyroid cancers have increased activation of AKT, and mice with thyroid-specific expression of PPFP combined with thyroid-specific loss of PTEN (a negative regulator of AKT) develop thyroid cancer. Therefore we created mice with combined thyroid-specific deletions of Pparg and Pten to test if there is oncogenic synergy between these deletions. Pten deletion alone results in benign thyroid hyperplasia, and this is unchanged when combined with deletion of Pparg. We conclude that, at least in the contexts studied, thyrocyte PPARγ does not play a significant role in the development or function of the thyroid and does not function as a tumor suppressor.
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Affiliation(s)
- Jingcheng Yu
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan 48109
| | - Ronald J. Koenig
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan 48109
- Correspondence: Ronald J. Koenig, MD, PhD, 5560 MSRB-2, SPC 5678, 1150 West Medical Center Drive, Ann Arbor, Michigan 48109. E-mail:
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