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Glendenning LM, Reynero KM, Cobb BA. Glycosylation as a tracer of off-target Cre-lox activation in development. Glycobiology 2024; 34:cwae023. [PMID: 38438159 PMCID: PMC11031139 DOI: 10.1093/glycob/cwae023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/25/2024] [Accepted: 02/25/2024] [Indexed: 03/06/2024] Open
Abstract
The Cre-lox system is one of the most widely used methods for lineage-specific and inducible genome editing in vivo. However, incomplete penetrance and off-target effects due to transient promoter expression in a stem or pluripotent precursor cell can be problematic and difficult to detect, especially if the target gene is not normally present in the fully differentiated but off-target cells. Yet, the loss of the target gene through the transient expression of Cre may impact the differentiation of those cells by virtue of transient expression in a precursor population. In these situations, off-target effects in an unknown precursor cell can, at best, complicate conclusions drawn from the model, and at worst, invalidate all data generated from that knockout strain. Thus, identifying Cre-driver promoter expression along entire cell lineages is crucial to improve rigor and reproducibility. As an example, transient expression in an early precursor cell has been documented in a variety of Cre strains such as the Tie2-based Cre-driver system that is used as an "endothelial cell-specific" model 1. Yet, Tie2 is now known to be transiently expressed in a stem cell upstream of both hematopoietic and endothelial cell lineages. Here, we use the Tie2 Cre-driver strain to demonstrate that due to its ubiquitous nature, plasma membrane glycans are a useful marker of both penetrance and specificity of a Cre-based knockout.
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Affiliation(s)
- Leandre M Glendenning
- Department of Pathology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-7288, United States
| | - Kalob M Reynero
- Department of Pathology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-7288, United States
| | - Brian A Cobb
- Department of Pathology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-7288, United States
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Glendenning LM, Zhou JY, Kukan EN, Gao C, Cummings RD, Joshi S, Whiteheart SW, Cobb BA. Platelet-localized ST6Gal1 does not impact IgG sialylation. Glycobiology 2023; 33:943-953. [PMID: 37379323 PMCID: PMC10859628 DOI: 10.1093/glycob/cwad052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 06/30/2023] Open
Abstract
The IgG antibody class forms an important basis of the humoral immune response, conferring reciprocal protection from both pathogens and autoimmunity. IgG function is determined by the IgG subclass, as defined by the heavy chain, as well as the glycan composition at N297, the conserved site of N-glycosylation within the Fc domain. For example, lack of core fucose promotes increased antibody-dependent cellular cytotoxicity, whereas α2,6-linked sialylation by the enzyme ST6Gal1 helps to drive immune quiescence. Despite the immunological significance of these carbohydrates, little is known about how IgG glycan composition is regulated. We previously reported that mice with ST6Gal1-deficient B cells have unaltered IgG sialylation. Likewise, ST6Gal1 released into the plasma by hepatocytes does not significantly impact overall IgG sialylation. Since IgG and ST6Gal1 have independently been shown to exist in platelet granules, it was possible that platelet granules could serve as a B cell-extrinsic site for IgG sialylation. To address this hypothesis, we used a platelet factor 4 (Pf4)-Cre mouse to delete ST6Gal1 in megakaryocytes and platelets alone or in combination with an albumin-Cre mouse to also remove it from hepatocytes and the plasma. The resulting mouse strains were viable and had no overt pathological phenotype. We also found that despite targeted ablation of ST6Gal1, no change in IgG sialylation was apparent. Together with our prior findings, we can conclude that in mice, neither B cells, the plasma, nor platelets have a substantial role in homeostatic IgG sialylation.
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Affiliation(s)
- Leandre M Glendenning
- Department of Pathology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-7288, USA
| | - Julie Y Zhou
- Department of Pathology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-7288, USA
| | - Emily N Kukan
- Department of Pathology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-7288, USA
| | - Chao Gao
- Harvard Medical School Center for Glycoscience, National Center for Functional Glycomics, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA
| | - Richard D Cummings
- Harvard Medical School Center for Glycoscience, National Center for Functional Glycomics, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA
| | - Smita Joshi
- Department of Molecular and Cellular Biochemistry, University of Kentucky, 741 S Limestone Street, Lexington, KY 40536-0509, USA
| | - Sidney W Whiteheart
- Department of Molecular and Cellular Biochemistry, University of Kentucky, 741 S Limestone Street, Lexington, KY 40536-0509, USA
| | - Brian A Cobb
- Department of Pathology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-7288, USA
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Glendenning LM, Reynero KM, Kukan EN, Long MD, Cobb BA. IgG sialylation occurs via the FcRn-mediated recycling pathway in endothelial cells. bioRxiv 2023:2023.06.30.547255. [PMID: 37886533 PMCID: PMC10602034 DOI: 10.1101/2023.06.30.547255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
IgG is a key mediator of immune responses throughout the human body, and the structure of the conserved glycan on the Fc region has been identified as a key inflammatory switch regulating its downstream effects. In particular, the absence of terminal sialic acid has been shown to increase the affinity of IgG for activating Fc receptors, cascading the inflammatory response in a variety of diseases and conditions. Previously, we have shown that IgG sialylation is mediated by B cell-extrinsic processes. Here, we show that the FcRn-mediated recycling pathway within endothelial cells is a critical modulator of IgG sialylation. Building a deeper understanding of how IgG sialylation is regulated will drive the development of novel therapeutics which dynamically tune IgG functionality in vivo.
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Affiliation(s)
| | - Kalob M Reynero
- Department of Pathology, Case Western Reserve University; Cleveland, OH, 44124, USA
| | - Emily N Kukan
- Department of Pathology, Case Western Reserve University; Cleveland, OH, 44124, USA
| | - Megan D Long
- Department of Pathology, Case Western Reserve University; Cleveland, OH, 44124, USA
| | - Brian A Cobb
- Department of Pathology, Case Western Reserve University; Cleveland, OH, 44124, USA
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Zhou JY, Glendenning LM, Cavanaugh JM, McNeer SK, Goodman WA, Cobb BA. Intestinal Tr1 Cells Confer Protection against Colitis in the Absence of Foxp3+ Regulatory T Cell-Derived IL-10. Immunohorizons 2023; 7:456-466. [PMID: 37314833 PMCID: PMC10580124 DOI: 10.4049/immunohorizons.2200071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 05/16/2023] [Indexed: 06/15/2023] Open
Abstract
The intestinal mucosa is continually exposed to diverse microbial and dietary Ags, requiring coordinated efforts by specialized populations of regulatory T cells (Tregs) to maintain homeostasis. Suppressive mechanisms used by intestinal Tregs include the secretion of anti-inflammatory cytokines such as IL-10 and TGF-β. Defects in IL-10 signaling are associated with severe infantile enterocolitis in humans, and mice deficient in IL-10 or its receptors develop spontaneous colitis. To determine the requirement of Foxp3+ Treg-specific IL-10 for protection against colitis, we generated Foxp3-specific IL-10 knockout (KO) mice (IL-10 conditional KO [cKO] mice). Colonic Foxp3+ Tregs isolated from IL-10cKO mice showed impaired ex vivo suppressive function, although IL-10cKO mice maintained normal body weights and developed only mild inflammation over 30 wk of age (in contrast to severe colitis in global IL-10KO mice). Protection from colitis in IL-10cKO mice was associated with an expanded population of IL-10-producing type 1 Tregs (Tr1, CD4+Foxp3-) in the colonic lamina propria that produced more IL-10 on a per-cell basis compared with wild-type intestinal Tr1 cells. Collectively, our findings reveal a role for Tr1 cells in the gut, as they expand to fill a tolerogenic niche in conditions of suboptimal Foxp3+ Treg-mediated suppression and provide functional protection against experimental colitis.
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Affiliation(s)
- Julie Y. Zhou
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Leandre M. Glendenning
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Jill M. Cavanaugh
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Sarah K. McNeer
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Wendy A. Goodman
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Brian A. Cobb
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
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Alvarez CA, Qian E, Glendenning LM, Reynero KM, Kukan EN, Cobb BA. Acute and chronic lung inflammation drives changes in epithelial glycans. Front Immunol 2023; 14:1167908. [PMID: 37283757 PMCID: PMC10239862 DOI: 10.3389/fimmu.2023.1167908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 05/02/2023] [Indexed: 06/08/2023] Open
Abstract
Introduction Asthma is the most common chronic inflammatory disease and it is characterized by leukocyte infiltration and tissue remodeling, with the latter generally referring to collagen deposition and epithelial hyperplasia. Changes in hyaluronin production have also been demonstrated, while mutations in fucosyltransferases reportedly limit asthmatic inflammation. Methods Given the importance of glycans in cellular communication and to better characterize tissue glycosylation changes associated with asthma, we performed a comparative glycan analysis of normal and inflamed lungs from a selection of murine asthma models. Results We found that among other changes, the most consistent was an increase in fucose-α1,3-N-acetylglucosamine (Fuc-α1,3-GlcNAc) and fucose-α1,2-galactose (Fuc-α1,2-Gal) motifs. Increases in terminal galactose and N-glycan branching were also seen in some cases, whereas no overall change in O-GalNAc glycans was observed. Increased Muc5AC was found in acute but not chronic models, and only the more human-like triple antigen model yielded increased sulfated galactose motifs. We also found that human A549 airway epithelial cells stimulated in culture showed similar increases in Fuc-α1,2-Gal, terminal galactose (Gal), and sulfated Gal, and this matched transcriptional upregulation of the α1,2-fucosyltransferase Fut2 and the α1,3-fucosyltransferases Fut4 and Fut7. Conclusions These data suggest that airway epithelial cells directly respond to allergens by increasing glycan fucosylation, a known modification important for the recruitment of eosinophils and neutrophils.
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Affiliation(s)
- Carlos A. Alvarez
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Emily Qian
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, United States
- Hathaway Brown High School, Beachwood, OH, United States
| | - Leandre M. Glendenning
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Kalob M. Reynero
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Emily N. Kukan
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Brian A. Cobb
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, United States
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Glendenning LM, Zhou JY, Reynero KM, Cobb BA. Divergent Golgi trafficking limits B cell-mediated IgG sialylation. J Leukoc Biol 2022; 112:1555-1566. [PMID: 35726710 PMCID: PMC9701147 DOI: 10.1002/jlb.3ma0522-731r] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 05/19/2022] [Indexed: 01/04/2023] Open
Abstract
The degree of α2,6-linked sialylation on IgG glycans is associated with a variety of inflammatory conditions and is thought to drive IgG anti-inflammatory activity. Previous findings revealed that ablation of β-galactoside α2,6-sialyltransferase 1 (ST6Gal1) in B cells failed to alter IgG sialylation in vivo, yet resulted in the loss of B cell surface α2,6 sialylation, suggesting divergent pathways for IgG and cell surface glycoprotein glycosylation and trafficking. Employing both B cell hybridomas and ex vivo murine B cells, we discovered that IgG was poorly sialylated by ST6Gal1 and highly core fucosylated by α1,6-fucosyltransferase 8 (Fut8) in cell culture. In contrast, cell surface glycoproteins on IgG-producing cells showed the opposite pattern by flow cytometry, with high α2,6 sialylation and low α1,6 fucosylation. Paired studies further revealed that ex vivo B cell-produced IgG carried significantly less sialylation compared with IgG isolated from the plasma of matched animals, providing evidence that IgG sialylation increases after release in vivo. Finally, confocal analyses demonstrated that IgG poorly localized to subcellular compartments rich in sialylation and ST6Gal1, and strongly to regions rich in fucosylation and Fut8. These findings support a model in which IgG subcellular trafficking diverges from the canonical secretory pathway by promoting Fut8-mediated core fucosylation and limiting exposure to and modification by ST6Gal1, providing a mechanism for why B cell-expressed ST6Gal1 is dispensable for IgG sialylation in vivo.
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Affiliation(s)
- Leandre M. Glendenning
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH 44106, USA
| | - Julie Y. Zhou
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH 44106, USA
| | - Kalob M. Reynero
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH 44106, USA
| | - Brian A. Cobb
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH 44106, USA
- To whom correspondence should be sent
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Oswald DM, Lehoux SD, Zhou JY, Glendenning LM, Cummings RD, Cobb BA. ST6Gal1 in plasma is dispensable for IgG sialylation. Glycobiology 2022; 32:803-813. [PMID: 35746897 DOI: 10.1093/glycob/cwac039] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 06/08/2022] [Accepted: 06/13/2022] [Indexed: 11/13/2022] Open
Abstract
The glycosylation of IgG has attracted increased attention due to the impact of N-glycan modifications at N297 on IgG function, acting primarily through modulation of Fc domain conformation and Fcγ receptor binding affinities and signaling. However, the mechanisms regulating IgG glycosylation and especially α2,6-sialylation of its N-glycan remain poorly understood. We observed previously that IgG is normally sialylated in mice with B cells lacking the sialyltransferase ST6Gal1. This supported the hypothesis that IgG may be sialylated outside of B cells, perhaps through the action of hepatocyte-released plasma ST6Gal1. Here we demonstrate that this model is incorrect. Animals lacking hepatocyte expressed ST6Gal1 retain normal IgG α2,6-sialylation, despite the lack of detectable ST6Gal1 in plasma. Moreover, we confirmed that B cells were not a redundant source of IgG sialylation. Thus, while α2,6-sialylation is lacking in IgG from mice with germline ablation of ST6Gal1, IgG α2,6-sialylation is normal in mice lacking ST6Gal1 in either hepatocytes or B cells. These results indicate that IgG α2,6-sialylation arises after release from a B cell, but is not dependent on plasma-localized ST6Gal1 activity.
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Affiliation(s)
- Douglas M Oswald
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH, USA
| | - Sylvain D Lehoux
- Beth Israel Deaconess Medical Center, Harvard Medical School Center for Glycoscience, National Center for Functional Glycomics, Boston, MA, USA
| | - Julie Y Zhou
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH, USA
| | - Leandre M Glendenning
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH, USA
| | - Richard D Cummings
- Beth Israel Deaconess Medical Center, Harvard Medical School Center for Glycoscience, National Center for Functional Glycomics, Boston, MA, USA
| | - Brian A Cobb
- Case Western Reserve University School of Medicine, Department of Pathology, Cleveland, OH, USA
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