IL-7R expression and IL-7 signaling confer a distinct phenotype on developing human B-lineage cells

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Precursor B cell production from bone marrow in mice and humans declines with age. Because the mechanisms behind are still unknown, we studied five precursor B cell subsets (ProB, PreBI, PreBII large, PreBII small, immature B) and their differentiation-stage characteristic gene expression profiles in healthy individual toddlers and middle-aged adults. Notably, the composition of the precursor B cell compartment did not change with age. The expression levels of several transcripts encoding V(D)J recombination factors were decreased in adults as compared with children: RAG1 expression was significantly reduced in ProB cells, and DNA-PKcs, Ku80, and XRCC4 were decreased in PreBI cells. In contrast, TdT was 3-fold upregulated in immature B cells of adults. Still, N-nucleotides, P-nucleotides, and deletions were similar for IGH and IGK junctions between children and adults. PreBII large cells in adults, but not in children, showed highly upregulated expression of the differentiation inhibitor, inhibitor of DNA binding 2 (ID2), in absence of changes in expression of the ID2-binding partner E2A. Further, we identified impaired Ig locus contraction in adult precursor B cells as a likely mechanism by which ID2-mediated blocking of E2A function results in reduced bone marrow B cell output in adults. The reduced B cell production was not compensated by increased proliferation in adult immature B cells, despite increased Ki67 expression. These findings demonstrate distinct regulatory mechanisms in B cell differentiation between adults and children with a central role for transcriptional regulation of ID2.

Section: Differences In Transcripts Essential In B Cell Commitment Ansupporting

confidence: 90%

Section: Dna Probe Preparation and Three-dimensional Immunofluorescenmentioning

confidence: 99%

Section: Differences In Transcripts Essential In B Cell Commitment Anmentioning

confidence: 99%

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Increased ID2 Levels in Adult Precursor B Cells as Compared with Children Is Associated with Impaired Ig Locus Contraction and Decreased Bone Marrow Output

Jensen

Rother

Brusletto

et al. 2013

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“…Microarray analysis remains one of the most powerful tools for the identification of such lineage relationships especially among blood cells and malignancies (34)(35)(36)(37)(38). In this study, we have used hierarchical clustering and principle component analysis to further understand the origins and relationships between isolated blood and skin DC and monocytic cell populations (Fig.…”

Section: Discussionmentioning

confidence: 99%

Identification of Lineage Relationships and Novel Markers of Blood and Skin Human Dendritic Cells

Harman

Bye

Nasr

et al. 2013

The lineage relationships and fate of human dendritic cells (DCs) have significance for a number of diseases including HIV where both blood and tissue DCs may be infected. We used gene expression profiling of human monocyte and DC subpopulations sorted directly from blood and skin to define the lineage relationships. We also compared these with monocyte-derived DCs (MDDCs) and MUTZ3 Langerhans cells (LCs) to investigate their relevance as model skin DCs. Hierarchical clustering analysis showed that myeloid DCs clustered according to anatomical origin rather than putative lineage. Plasmacytoid DCs formed the most discrete cluster, but ex vivo myeloid cells formed separate clusters of cells both in blood and in skin. Separate and specific DC populations could be determined within skin, and the proportion of CD14+ dermal DCs (DDCs) was reduced and CD1a+ DDCs increased during culture, suggesting conversion to CD1a+-expressing cells in situ. This is consistent with origin of the CD1a+ DDCs from a local precursor rather than directly from circulating blood DCs or monocyte precursors. Consistent with their use as model skin DCs, the in vitro–derived MDDC and MUTZ3 LC populations grouped within the skin DC cluster. MDDCs clustered most closely to CD14+ DDCs; furthermore, common unique patterns of C-type lectin receptor expression were identified between these two cell types. MUTZ3 LCs, however, did not cluster closely with ex vivo–derived LCs. We identified differential expression of novel genes in monocyte and DC subsets including genes related to DC surface receptors (including C-type lectin receptors, TLRs, and galectins).

“…Aberrant expression of various transcription factors can predispose developing B cells to leukemia (2). Development of B cell progenitors requires signaling through the IL-7R (3,4). Productive rearrangement of the IgH locus in pro-B cells permits expression of IgH protein and assembly with surrogate L chain components to promote cell surface expression of a pre-BCR.…”

mentioning

confidence: 99%

PU.1 Opposes IL-7–Dependent Proliferation of Developing B Cells with Involvement of the Direct Target Gene Bruton Tyrosine Kinase

Christie

Turkistany

et al. 2015

Deletion of genes encoding the E26 transformation-specific transcription factors PU.1 and Spi-B in B cells (CD19-CreΔPB mice) leads to impaired B cell development, followed by B cell acute lymphoblastic leukemia at 100% incidence and with a median survival of 21 wk. However, little is known about the target genes that explain leukemogenesis in these mice. In this study we found that immature B cells were altered in frequency in the bone marrow of preleukemic CD19-CreΔPB mice. Enriched pro–B cells from CD19-CreΔPB mice induced disease upon transplantation, suggesting that these were leukemia-initiating cells. Bone marrow cells from preleukemic CD19-CreΔPB mice had increased responsiveness to IL-7 and could proliferate indefinitely in response to this cytokine. Bruton tyrosine kinase (BTK), a negative regulator of IL-7 signaling, was reduced in preleukemic and leukemic CD19-CreΔPB cells compared with controls. Induction of PU.1 expression in cultured CD19-CreΔPB pro–B cell lines induced Btk expression, followed by reduced STAT5 phosphorylation and early apoptosis. PU.1 and Spi-B regulated Btk directly as shown by chromatin immunoprecipitation analysis. Ectopic expression of BTK was sufficient to induce apoptosis in cultured pro–B cells. In summary, these results suggest that PU.1 and Spi-B activate Btk to oppose IL-7 responsiveness in developing B cells.