Reporter gene insertions reveal a strictly B lymphoid-specific expression pattern of Pax5 in support of its B cell identity function.

The transcription factor Pax5 is essential for B cell commitment and development. Although the detail Pax5 expression pattern within the hemopoietic system is still largely unknown, we previously reported that Pax5 is monoallelically transcribed in pro-B and mature B cells. In this study, we have investigated the expression of Pax5 at single-cell resolution by inserting a GFP or human Cd2 indicator gene under the translational control of an internal ribosomal entry sequence into the 3' untranslated region of Pax5.

Reporter gene insertions reveal a strictly B lymphoid-specific expression pattern of Pax5 in support of its B cell identity function.

The transcription factor Pax5 is essential for B cell commitment and development. Although the detailed Pax5 expression pattern within the hemopoietic system is still largely unknown, we previously reported that Pax5 is monoallelically transcribed in pro-B and mature B cells. In this study, we have investigated the expression of Pax5 at single-cell resolution by inserting a GFP or human cd2 indicator gene under the translational control of an internal ribosomal entry site element into the 3' untranslated region of Pax5.

Transcriptional regulation in early B cell development.

Transcription factors and signalling molecules are important for both lineage commitment and lineage-specific regulation. The B cell specification factor Pax5 plays a dual role in B lineage commitment. Simultaneously, it potentiates and limits lineage choice by activating genes that are required for the B cell program while repressing lineage-inappropriate genes; more than 100 of the latter have now been identified.

Locus 'decontraction' and centromeric recruitment contribute to allelic exclusion of the immunoglobulin heavy-chain gene.

Allelic exclusion of immunoglobulin genes ensures the expression of a single antibody molecule in B cells through mostly unknown mechanisms. Large-scale contraction of the immunoglobulin heavy-chain (Igh) locus facilitates rearrangements between Igh variable (V(H)) and diversity gene segments in pro-B cells. Here we show that these long-range interactions are mediated by 'looping' of individual Igh subdomains.

Analysis of Notch1 function by in vitro T cell differentiation of Pax5 mutant lymphoid progenitors.

Signaling through the Notch1 receptor is essential for T cell development in the thymus. Stromal OP9 cells ectopically expressing the Notch ligand Delta-like1 mimic the thymic environment by inducing hemopoietic stem cells to undergo in vitro T cell development. Notch1 is also expressed on Pax5-/- pro-B cells, which are clonable lymphoid progenitors with a latent myeloid potential.

Pax5 induces V-to-DJ rearrangements and locus contraction of the immunoglobulin heavy-chain gene.

The subnuclear location and chromatin state of the immunoglobulin heavy-chain (IgH) locus have been implicated in the control of VDJ recombination. VH-to-DJH rearrangement of distal, but not proximal V(H) genes, furthermore, depends on the B-lineage commitment factor Pax5 (BSAP). He e we demonstrate that ectopic Pax5 expression from the Ikaros promote induces proximal rather than distal VH-DJH rearrangements in Ik(Pax5/+) thymocytes, thus recapitulating the loss-of-function phenotype of Pax5-/- pro-B cells.