title: Bruton's Tyrosine Kinase Synergizes with Notch2 To Govern Marginal Zone B Cells in Nonobese Diabetic Mice.
abstract: Expansion of autoimmune-prone marginal zone (MZ) B cells has been implicated in type 1 diabetes. To test disease contributions of MZ B cells in NOD mice, Notch2 haploinsufficiency (Notch2(+/-)) was introduced but failed to eliminate the MZ, as it does in C57BL/6 mice. Notch2(+/-)/NOD have MZ B cell numbers similar to those of wild-type C57BL/6, yet still develop diabetes. To test whether BCR signaling supports Notch2(+/-)/NOD MZ B cells, Bruton's tyrosine kinase (Btk) deficiency was introduced. Surprisingly, MZ B cells failed to develop in Btk-deficient Notch2(+/-)/NOD mice. Expression of Notch2 and its transcriptional target, Hes5, was increased in NOD MZ B cells compared with C57BL/6 MZ B cells. Btk deficiency reduced Notch2(+/-) signaling exclusively in NOD B cells, suggesting that BCR signaling enhances Notch2 signaling in this autoimmune model. The role of BCR signaling was further investigated using an anti-insulin transgenic (Tg) BCR (125Tg). Anti-insulin B cells in 125Tg/Notch2(+/-)/NOD mice populate an enlarged MZ, suggesting that low-level BCR signaling overcomes reliance on Notch2. Tracking clonotypes of anti-insulin B cells in H chain-only VH125Tg/NOD mice showed that BTK-dependent selection into the MZ depends on strength of antigenic binding, whereas Notch2-mediated selection does not. Importantly, anti-insulin B cell numbers were reduced by Btk deficiency, but not Notch2 haploinsufficiency. These studies show that 1) Notch2 haploinsufficiency limits NOD MZ B cell expansion without preventing type 1 diabetes, 2) BTK supports the Notch2 pathway in NOD MZ B cells, and 3) autoreactive NOD B cell survival relies on BTK more than Notch2, regardless of MZ location, which may have important implications for disease-intervention strategies.
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, TN.|Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: James B
authors.initials: JB
authors.lastname: Case
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Rachel H
authors.initials: RH
authors.lastname: Bonami
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Lindsay E
authors.initials: LE
authors.lastname: Nyhoff
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Hannah E
authors.initials: HE
authors.lastname: Steinberg
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Allison M
authors.initials: AM
authors.lastname: Sullivan
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, TN.|Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Peggy L
authors.initials: PL
authors.lastname: Kendall
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D001323:Autoantibodies / Q000096:biosynthesis; D015551:Autoimmunity; D016175:B-Lymphocyte Subsets / Q000276:immunology* / Q000473:pathology; D002454:Cell Differentiation; D002470:Cell Survival / Q000276:immunology; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis; D007328:Insulin / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D051883:Receptor, Notch2 / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000276:immunology; D015398:Signal Transduction
chemical_list: D001323:Autoantibodies; D007143:Immunoglobulin Heavy Chains; D007328:Insulin; C497765:Notch2 protein, mouse; D051883:Receptor, Notch2; D011947:Receptors, Antigen, B-Cell; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse