title: IFN regulatory factor 4 and 8 promote Ig light chain kappa locus activation in pre-B cell development.
abstract: Previous studies have shown that B cell development is blocked at the pre-B cell stage in IFN regulatory factor (IRF)4 (pip) and IRF8 (IFN consensus sequence binding protein) double mutant mice (IRF4,8(-/-)). In this study, the molecular mechanism by which IRF4,8 regulate pre-B cell development was further investigated. We show that IRF4,8 function in a B cell intrinsic manner to control pre-B cell development. IRF4,8(-/-) mice expressing a Bcl-2 transgene fail to rescue pre-B cell development, suggesting that the defect in B cell development in IRF4,8(-/-) mice is not due to a lack of survival signal. IRF4,8(-/-) pre-B cells display a high proliferation index that may indirectly inhibit the L chain rearrangement. However, forced cell cycle exit induced by IL-7 withdrawal fails to rescue the development of IRF4,8(-/-) pre-B cells, suggesting that cell cycle exit by itself is not sufficient to rescue the development of IRF4,8(-/-) pre-B cells and that IRF4,8 may directly regulate the activation of L chain loci. Using retroviral mediated gene transduction, we show that IRF4 and IRF8 function redundantly to promote pre-B cell maturation and the generation of IgM(+) B cells. Molecular analysis indicates that IRF4, when expressed in IRF4,8(-/-) pre-B cells, induces kappa germline transcription, enhances V(D)J rearrangement activity at the kappa locus, and promotes L chain rearrangement and transcription. Chromatin immunoprecipitation assay further reveals that IRF4 expression leads to histone modifications and enhanced chromatin accessibility at the kappa locus. Thus, IRF4,8 control pre-B cell development, at least in part, by promoting the activation of the kappa locus.
authors.affiliation: Department of Genetics, Cell Biology, and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA.
authors.forename: Shibin
authors.initials: S
authors.lastname: Ma
authors.forename: Anna
authors.initials: A
authors.lastname: Turetsky
authors.forename: Long
authors.initials: L
authors.lastname: Trinh
authors.forename: Runqing
authors.initials: R
authors.lastname: Lu
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation / Q000276:immunology*; D005434:Flow Cytometry; D007145:Immunoglobulin kappa-Chains / Q000276:immunology / Q000378:metabolism*; D047468:Immunoprecipitation; D050835:Interferon Regulatory Factors / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D016133:Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D007145:Immunoglobulin kappa-Chains; D050835:Interferon Regulatory Factors