Myeloid lineage switch of Pax5 mutant but not wild-type B cell progenitors by C/EBP  and GATA factors

Abstract

The developmental potential of hematopoietic progenitors is restricted early on to either the erythromyeloid or lymphoid lineages. The broad developmental potential of Pax5−/− pro‐B cells is in apparent conflict with such a strict separation, although these progenitors realize the myeloid and erythroid potential with lower efficiency compared to the lymphoid cell fates. Here we demonstrate that ectopic expression of the transcription factors C/EBPα, GATA1, GATA2 and GATA3 strongly promoted in vitro macrophage differentiation and myeloid colony formation of Pax5−/− pro‐B cells. GATA2 and GATA3 expression also resulted in efficient engraftment and myeloid development of Pax5−/− pro‐B cells in vivo. The myeloid transdifferentiation of Pax5−/− pro‐B cells was accompanied by the rapid activation of myeloid genes and concomitant repression of B‐lymphoid genes by C/EBPα and GATA factors. These data identify the Pax5−/− pro‐B cells as lymphoid progenitors with a latent myeloid potential that can be efficiently activated by myeloid transcription factors. The same regulators were unable to induce a myeloid lineage switch in Pax5+/+ pro‐B cells, indicating that Pax5 dominates over myeloid transcription factors in B‐lymphocytes.

Chronic lymphocytic leukemia: Time to go past genomics?

“…In normal Blymphopoiesis, PAX5 accomplishes a dual function by activating Bcell commitment genes while concomitantly repressing non-B-lineage genes. PAX5 locks B-cell differentiation as PAX5-deficient cells are able to trans-differentiate in T and myeloid cells [122,123]. Furthermore Pax5 heterozygous mice show an accumulation of IL7-dependant proB cells and develop B-ALL when challenged by infections [124].…”

Pax5 inducesV-to-DJrearrangements and locus contraction of theimmunoglobulin heavy-chaingene

“…The retrovirus M-Pax5-iCD2 as well as the parental virus MiCD2 (Heavey et al 2003) express a human CD2 indicator protein, which facilitated FACS sorting of the infected cells prior to PCR quantification of IgH rearrangements (Fig. 7A).…”

“…A human Pax5 cDNA was inserted upstream of the IRES-hCD2t gene of the retroviral vector MiCD2, which results in expression of a C-terminally truncated (t) human (h) CD2 indicator protein (Heavey et al 2003). The M-Pax5-iCD2 virus was generated and used for infection of Pax5 −/− and Pax5 −/− RAG2 −/− pro-B cells as described (Heavey et al 2003).…”

“…The M-Pax5-iCD2 virus was generated and used for infection of Pax5 −/− and Pax5 −/− RAG2 −/− pro-B cells as described (Heavey et al 2003). Pax5 expression was verified by Western blot analysis of infected pro-B cells.…”

Antagonistic effect of CCAAT enhancer-binding protein-α and Pax5 in myeloid or lymphoid lineage choice in common lymphoid progenitors

“…2, although at a slightly lower level than in CLPs, C͞EBP␣ up-regulation was observed in IL-2R␤TG proB cells upon IL-2 stimulation in the same fashion as in IL-2R␤TG CLPs. Because it has been shown that the removal of Pax5 enables proB cells to differentiate into macrophages (22) in the presence of ectopic C͞EBP␣ (22,23), we hypothesized that Pax5 expression might be critically involved in this lineage conversion in proB cells from lymphoid to myeloid lineage. Therefore, we next examined Pax5 expression in IL-2R␤TG CLPs and proB cells after IL-2 stimulation.…”