IL-6-PAD4 axis in the earliest phase of arthritis in knock-in gp130F759 mice, a model for rheumatoid arthritis.

Objective: Animal models for human diseases are especially valuable for clarifying molecular mechanisms before or around the onset. As a model for rheumatoid arthritis (RA), we utilise knock-in mice gp130F759. They have a Y759F mutation in gp130, a common receptor subunit for interleukin 6 (IL-6) family cytokines.

Anti-apoptotic roles for the mutant p53R248Q through suppression of p53-regulated apoptosis-inducing protein 1 in the RA-derived fibroblast-like synoviocyte cell line MH7A.

We previously reported that somatic mutations in the p53 gene accumulated at a higher frequency in AID(activation induced cytidine deaminase)(+) RA-FLS, which may result in the malfunction of p53, causing the tumor-like properties of RA-FLS. Among the p53 mutations identified from 3 sources of AID(+) RA-FLS, we focused on the p53R248Q mutation because it was reported to enhance the invasiveness of lung cancer cells and to have dominant-negative activity for pro-apoptotic molecules. We obtained cDNA encoding the p53R248Q mutant and introduced it into the MH7A RA-FLS cell line.

Transgenic overexpression of G5PR that is normally augmented in centrocytes impairs the enrichment of high-affinity antigen-specific B cells, increases peritoneal B-1a cells, and induces autoimmunity in aged female mice.

To investigate signals that control B cell selection, we examined expression of G5PR, a regulatory subunit of the serine/threonine protein phosphatase 2A, which suppresses JNK phosphorylation. G5PR is upregulated in activated B cells, in Ki67-negative centrocytes at germinal centers (GCs), and in purified B220(+)Fas(+)GL7(+) mature GC B cells following Ag immunization. G5PR rescues transformed B cells from BCR-mediated activation-induced cell death by suppression of late-phase JNK activation.

A pro-inflammatory role for A20 and ABIN family proteins in human fibroblast-like synoviocytes in rheumatoid arthritis.

Circuit of chronic inflammation in the joints of rheumatoid arthritis (RA) starts from the production of inflammatory cytokines by fibroblast-like synoviocytes (FLS) stimulated by TNFα produced by inflammatory cells mainly composed of macrophages. In this context, TNFα/NF-κB pathway plays an essential role for the transcription of pro-inflammatory cytokines. Here we show that the kinetics of pro-inflammatory cytokine genes induced by TNFα in FLS from RA was synchronized with that of A20, ABIN1, and ABIN3 that have been thought as negative regulators for NF-κB activation.

GANP suppresses the arginine methyltransferase PRMT5 regulating IL-4-mediated STAT6-signaling to IgE production in B cells.

Antigen (Ag)-driven B cells undergo antibody (Ab) affinity maturation and class switching in germinal center (GC) B cells. GANP is one of the molecules required for Ab affinity maturation. We herein found an increase of IgE in B cell ganp-deficient mice and studied the signal transduction pathway regulated by GANP.

The immature B-cell subpopulation with low RAG1 expression is increased in the autoimmune New Zealand Black mouse.

Receptor editing is believed to play a critical role in immunological tolerance by altering the specificity of autoreactive B cells that emerge in the bone marrow. To study whether receptor editing is altered in autoimmune disease, recombination activation gene 1 (rag1) transcription in B cells from New Zealand Black (NZB) mice was examined by introducing a GFP gene at the rag1 locus. Female NZB(RAG1-GFP) mice generated autoantibodies and glomerular immune complexes.

Protein phosphatase subunit G5PR that regulates the JNK-mediated apoptosis signal is essential for the survival of CD4 and CD8 double-positive thymocytes.

Early T lineage cells are selected in the thymus by the specific recognition of peptide components presented by MHC molecules on the surface of thymic epithelial cells and dendritic cells. As a potential regulator of the apoptotic and survival signals, the protein phosphatase 2A-component G5PR regulates Bim phosphorylation in B-cells. Here, we studied whether G5PR is involved in the regulation of the similar apoptotic pathway for cell survival during the selection of thymocytes.

NF-kappaB is dispensable for normal lymphocyte development in bone marrow but required for protection of progenitors from TNFalpha.

Levels of the nuclear factor-kappa B (NF-kappaB)/Rel family of proteins are carefully modulated in differentiating lymphocytes, where these transcription factors are thought to be important for survival and fate decisions. In contrast, gene-targeting experiments have not revealed clear roles for these transcription factors in lymphopoiesis within bone marrow. Inhibition of NF-kappaB by introduction of mutated I kappa B alpha, a 'superinhibitor' of NF-kappaB, into hematopoietic stem cells or early progenitors suppressed B as well as T lymphopoiesis following transplantation into immunodeficient mice.

BCR-crosslinking induces a transcription of protein phosphatase component G5PR that is required for mature B-cell survival.

BCR-crosslinking triggers activation-induced cell death (AICD) selectively in the restricted stage of B-cell differentiation. We examined the transcription of a protein phosphatase subunit G5PR in immature and mature B-cells, because absence of this factor augmented cell sensitivity to AICD, associated with increased activation of JNK and Bim. BCR-crosslinking-induced G5pr transcription in AICD-resistant mature splenic IgM(lo)IgD(hi) B-cells but not in AICD susceptible immature IgM(hi)IgD(lo) B-cells.

Cutting edge: double-stranded DNA breaks in the IgV region gene were detected at lower frequency in affinity-maturation impeded GANP-/- mice.

Double-stranded DNA breaks (DSBs) at the IgV region (IgV) genes might be involved in somatic hypermutation and affinity-maturation of the B cell receptor in response to T cell-dependent Ag. By ligation-mediated PCR, we studied IgV DSBs that occurred in mature germinal center B cells in response to nitrophenyl-chicken gamma-globulin in a RAG1-independent, Ag-dependent, and IgV-selective manner. We quantified their levels in GANP-deficient B cells that have impaired generation of high-affinity Ab.

Protein phosphatase subunit G5PR is needed for inhibition of B cell receptor-induced apoptosis.

B cell receptor (BCR) cross-linking induces B cell proliferation and sustains survival through the phosphorylation-dependent signals. We report that a loss of the protein phosphatase component G5PR increased the activation-induced cell death (AICD) and thus impaired B cell survival. G5PR associates with GANP, whose expression is up-regulated in mature B cells of the peripheral lymphoid organs.

Early lymphoid progenitors in mouse and man are highly sensitive to glucocorticoids.

Glucocorticoids are extensively used in anti-inflammatory therapy and may contribute to the normal regulation of lymphopoiesis. This study utilized new information about the early stages of lymphopoiesis in mouse and man to determine precisely which cell types are hormone sensitive. Cycling B lineage precursors were depleted in dexamethasone-treated mice, while mature, non-dividing CD45R(Hi) CD19(Hi) lymphocytes, myeloid progenitors and stem cells with the potential for lymphocyte generation on transplantation were spared.

Adiponectin, a fat cell product, influences the earliest lymphocyte precursors in bone marrow cultures by activation of the cyclooxygenase-prostaglandin pathway in stromal cells.

Adiponectin, an adipocyte-derived hormone, is attracting considerable interest as a potential drug for diabetes and obesity. Originally cloned from human s.c.

Unique properties of fetal lymphoid progenitors identified according to RAG1 gene expression.

RAG1/GFP knockin mice were exploited to isolate and characterize fetal lymphoid progenitors. CD11b and IL-7Ralpha are expressed in a developmental stage-dependent fashion, revealing how substantial numbers of early lymphoid progenitors were discarded or neglected in previous studies. The myeloerythroid potential of fetal progenitors in clonal assays declined in synchrony with activation of the RAG1 locus but was not completely extinguished.

Lymphoid lineage cells in adult murine bone marrow diverge from those of other blood cells at an early, hormone-sensitive stage.

Advances in cell sorting and GFP knock-in technology have made it possible to identify rare hematopoietic cells in murine bone marrow that are undergoing lymphocyte fate specification. Steroid hormones also represent important research tools for investigating relationships between different categories of lympho-hematopoietic precursors. By selectively blocking entry into and progression within lymphoid lineages, the hormones probably have a major influence on numbers of lymphocytes that are produced under normal circumstances.

A developing picture of lymphopoiesis in bone marrow.

The earliest progenitors of lymphocytes are extremely rare and typically present among very complex populations of hematopoietic cells. Additionally, it is difficult to know how cells with any given set of characteristics are developmentally related to stem cells and maturing lymphoid precursors. However, it is now possible to divide bone marrow into progressively smaller fractions and exploit well-defined culture systems to determine which ones contain cells that can turn into lymphocytes.

Nature or nurture? Steady-state lymphocyte formation in adults does not recapitulate ontogeny.

Substantial progress has been made in determining developmental relationships between lymphocyte precursors and those corresponding to other blood cell lineages. Indeed, exploitation of RAG1/GFP knock-in mice has recently made it possible to chart the entire sequence of lymphocyte differentiation events in adult bone marrow and thymus. However, the differentiation pathways proposed for fetal life are very different from this model.

Transcription from the RAG1 locus marks the earliest lymphocyte progenitors in bone marrow.

Viable Lin(-) CD27(+) c-kit(Hi) Sca-1(Hi) GFP(+) cells recovered from heterozygous RAG1/GFP knockin mice progressed through previously defined stages of B, T, and NK cell lineage differentiation. In contrast to the GFP(-) cohort, there was minimal myeloid or erythroid potential in cells with an active RAG1 locus. Partial overlap with TdT(+) cells suggested that distinctive early lymphocyte characteristics are not synchronously acquired.

Paracrine regulation of fat cell formation in bone marrow cultures via adiponectin and prostaglandins.

Adiponectin, an adipocyte-derived hormone, was recently shown to have potential therapeutic applications in diabetes and obesity because of its influence on glucose and lipid metabolism. We found that brown fat in normal human bone marrow contains this protein and used marrow-derived preadipocyte lines and long-term cultures to explore potential roles in hematopoiesis. Recombinant adiponectin blocked fat cell formation in long-term bone marrow cultures and inhibited the differentiation of cloned stromal preadipocytes.