title: Expression of a non-DNA-binding Ikaros isoform exclusively in B cells leads to autoimmunity but not leukemogenesis.
abstract: Ikaros is a transcriptional regulator whose function is essential for B cell development. It is expressed in the hematopoietic stem cell (HSC) through the mature B cell stage. Using genetically engineered mice in which the endogenous Ikaros gene is disrupted, it has been shown that a lack of Ikaros leads to a block in B cell development and that its severe diminution results in a hyperresponsive B cell compartment. Ikaros expression within the HSC has led to speculation as to whether the role of Ikaros in B cell biology is largely accomplished prior to B cell specification. In addition, widespread expression of Ikaros in hematopoietic cells leads to the possibility that some or all of the observed defects are not B cell autonomous. In this report, we demonstrate that over-expression of a dominant interfering Ikaros isoform exclusively in B cells has profound effects on mature B cell function. We provide evidence that continued high-level expression of Ikaros is essential for homeostasis of peripheral lymphocytes and maintenance of B cell tolerance. We also show that deregulation of Ikaros activity does not rapidly result in B cell leukemogenesis as it does with 100% penetrance within the T cell lineage.
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
authors.forename: Heather
authors.initials: H
authors.lastname: Wojcik
authors.forename: Erin
authors.initials: E
authors.lastname: Griffiths
authors.forename: Sarah
authors.initials: S
authors.lastname: Staggs
authors.forename: James
authors.initials: J
authors.lastname: Hagman
authors.forename: Susan
authors.initials: S
authors.lastname: Winandy
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000096:biosynthesis*; D001327:Autoimmune Diseases / Q000235:genetics* / Q000276:immunology; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D051740:Ikaros Transcription Factor / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D015448:Leukemia, B-Cell / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology
chemical_list: D001323:Autoantibodies; D004268:DNA-Binding Proteins; C497239:IKZF1 protein, human; D020033:Protein Isoforms; D051740:Ikaros Transcription Factor; D004247:DNA