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Accelerated progression of chronic lymphocytic leukemia in E?-TCL1 mice expressing catalytically inactive RAG1.

ABSTRACT: Chronic lymphocytic leukemia (CLL) is a prevalent B-cell neoplasia that is often preceded by a more benign monoclonal CD5(+) B-cell lymphocytosis. We previously generated transgenic mice expressing catalytically inactive RAG1 (dominant-negative recombination activating gene 1 [dnRAG1] mice) that develop an early-onset indolent CD5(+) B-cell lymphocytosis attributed to a defect in secondary V(D)J rearrangements initiated to edit autoreactive B-cell receptor (BCR) specificity. Hypothesizing that CD5(+) B cells in these animals represent potential CLL precursors, we crossed dnRAG1 mice with CLL-prone E?-TCL1 mice to determine whether dnRAG1 expression in E?-TCL1 mice accelerates CLL onset. Consistent with this hypothesis, CD5(+) B-cell expansion and CLL progression occurred more rapidly in double-transgenic mice compared with E?-TCL1 mice. Nevertheless, CD5(+) B cells in the 2 mouse strains exhibited close similarities in phenotype, immunoglobulin gene usage, and mutation status, and expression of genes associated with immune tolerance and BCR signaling. Gene expression profiling further revealed a potential role for prolactin signaling in regulating BCR editing. These results suggest a model in which benign accumulation of CD5(+) B cells can be initiated through a failure to successfully edit autoreactive BCR specificity and may, in turn, progress to CLL upon introduction of additional genetic mutations.

SUBMITTER: Nganga VK

PROVIDER: S-EPMC3700393 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature

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Accelerated progression of chronic lymphocytic leukemia in Eμ-TCL1 mice expressing catalytically inactive RAG1.

Nganga Vincent K VK Palmer Victoria L VL Naushad Hina H Kassmeier Michele D MD Anderson Dirk K DK Perry Greg A GA Schabla Nathan M NM Swanson Patrick C PC

Blood 20130315 19

Chronic lymphocytic leukemia (CLL) is a prevalent B-cell neoplasia that is often preceded by a more benign monoclonal CD5(+) B-cell lymphocytosis. We previously generated transgenic mice expressing catalytically inactive RAG1 (dominant-negative recombination activating gene 1 [dnRAG1] mice) that develop an early-onset indolent CD5(+) B-cell lymphocytosis attributed to a defect in secondary V(D)J rearrangements initiated to edit autoreactive B-cell receptor (BCR) specificity. Hypothesizing that C ...[more]

PMID: 23502221

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Project description:B cell chronic lymphocytic leukemia (CLL) is often preceded by a benign monoclonal or oligoclonal CD5+ B cell lymphocytosis. We have generated transgenic mice expressing a catalytically inactive, dominant-negative recombination activating gene 1 (dnRAG1 mice) in the periphery. These animals develop an early-onset indolent CD5+ B cell lymphocytosis, caused in part by a defect in secondary V(D)J rearrangements initiated to alter autoreactive B cell receptor specificity. Hypothesizing that the CD5+ B cells accumulating in dnRAG1 mice represent a CLL precursor, we crossed dnRAG1 mice with CLL-prone Eµ-TCL1 mice to determine whether dnRAG1 expression in Eµ-TCL1 mice accelerates the onset of CLL-like disease. We find that CD5+ B cell expansion and CLL progression occurs more rapidly and uniformly in double-transgenic mice (DTG mice) compared to Eµ-TCL1 mice, but with similar phenotypic and leukemogenic features. To gain insight into genes or pathways responsible for CD5+ B cell accumulation in the transgenic mice, we performed comparative gene expression profiling studies using normal and CD5+ B cells isolated from wild-type and transgenic mice at either 12 weeks of age (pre-leukemia) or at CLL onset in DTG mice (using age-matched wild-type and single-transgenic mice as controls). These analyses confirm the upregulation of tolerogenic genes in CD5+ B cells and reveal a possible role for prolactin signaling in the regulation of receptor editing. This study suggests that a failure to remodel B cell antigen receptor genes in response to autoreactivity may promote the benign accumulation of CD5+ B cells, which may then be subjected to secondary genetic lesions that promote CLL progression. dnRAG1 mice were bred to Eµ-TCL1 mice to obtain cohorts of wild-type (WT), single-transgenic (dnRAG1 and Eµ-TCL1), and DTG mice. Splenic CD19+B220hiCD5- B cells from WT mice or CD19+CD5+ B cells from transgenic mice were purified using fluorescence activated cell sorting (FACS). Biotin end-labeled cDNA prepared from the sorted cells was hybridized to Mouse Gene 1.0 ST Arrays. These experiments were performed two independent times: once with a cohort of 12-week-old mice, and once with older mice (>34 weeks old) consisting of two ill DTG mice and their age-matched counterparts. At least two biological replicates were used where possible.

Project description:IL10 plays a dual role in supporting humoral immunity and inhibiting inflammatory conditions. B cells producing IL10 are thought to play a key regulatory role in maintaining self-tolerance and suppressing excessive inflammation during autoimmune and infectious diseases, primarily by inhibiting associated T cell responses. The extent to which B cells, through the provision of IL10, might function to sustain or inhibit autoantibody production is less clear. We previously described transgenic mice expressing catalytically inactive RAG1 (dnRAG1 mice), which show expansion of an IL10-compentent CD5+ B cell subset that phenotypically resembles B10 B cells, hypogammaglobulinemia, and a restricted B cell receptor repertoire with features indicative of impaired B cell receptor editing. We show here that B10-like B cells in dnRAG1 mice bind the membrane-associated autoantigen phosphatidylcholine (PtC), and that in vitro lipopolysaccharide (LPS) stimulation of dnRAG1 splenocytes induces a robust IgM response enriched in reactivity toward lupus-associated autoantigens. This outcome was correlated with detection of sIgMhi B cell populations that were distinct from, but in addition to, sIgMint populations observed after similar treatment of wild-type splenocytes. Loss of IL10 expression in dnRAG1 mice had no significant effect on B10-like B cell expansion or the frequency of PtC+ B cells. Compared to IL10+/+ dnRAG1 mice, levels of serum IgM, but not serum IgG, were highly elevated in some naïve IL10-/- dnRAG1 mice, and was correlated with a significant increase in serum BAFF levels. Differentiation of sIgMint B cells from LPS-stimulated dnRAG1 splenocytes was enhanced by loss of IL10 expression and IL10 blockade, but was suppressed by treatment with recombinant IL10. In vitro LPS-induced differentiation and antibody production was inhibited by treatment with JAK/STAT inhibitors or a synthetic corticosteroid, independent of IL10 expression and genotype. Taken together, these data suggest that IL10 expression in dnRAG1 mice maintains suppression of IgM levels in part by inhibiting BAFF production, and that regulatory B10-like B cells, through the provision of IL10, constrains B cell differentiation in response to mitogenic stimuli. Furthermore, autoantibody profiling raises a possible link between CD5+ B cell expansion, mitogenic stimulation, and autoantibodies associated with autoimmune complications observed in lupus and lupus-related disorders.

Dataset Information

Accelerated progression of chronic lymphocytic leukemia in E?-TCL1 mice expressing catalytically inactive RAG1.

Publications

Accelerated progression of chronic lymphocytic leukemia in Eμ-TCL1 mice expressing catalytically inactive RAG1.

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