Project description:The molecular circuits that direct early T-dependent B cell responses and alternative cell-fate decisions remain poorly understood. Here, we show that either B cell receptor (BCR) or CD40 signals promoted mTORC1-dependent translation of the transcription factor Bach2. Transient up-regulation of Bach2 protein restrained activated B cell expansion and differentiation into plasma cell while promoting the germinal center (GC) and memory B cell fates at the pre-GC stage. However, enforced Bach2 expression facilitated memory B cell generation versus other cell fates. Mechanistically, Bach2 limited access of AP-1 factors and formed a reciprocal repression loop with IRF4. BCR and CD40 signals also down-regulated Bach2 transcript in antigen-activated B cells, and diversified its abundance in various effector populations, predisposing Bach2 protein expression and subsequent cell-fate choices during memory recall and GC reaction. Thus signaling-induced differential dynamics of Bach2 protein and mRNA in activated B cell control their cell-fate outcomes and imprint the fate of their descendant effector cells.
Project description:The molecular circuits that direct early T-dependent B cell responses and alternative cell-fate decisions remain poorly understood. Here, we show that either B cell receptor (BCR) or CD40 signals promoted mTORC1-dependent translation of the transcription factor Bach2. Transient up-regulation of Bach2 protein restrained activated B cell expansion and differentiation into plasma cell while promoting the germinal center (GC) and memory B cell fates at the pre-GC stage. However, enforced Bach2 expression facilitated memory B cell generation versus other cell fates. Mechanistically, Bach2 limited access of AP-1 factors and formed a reciprocal repression loop with IRF4. BCR and CD40 signals also down-regulated Bach2 transcript in antigen-activated B cells, and diversified its abundance in various effector populations, predisposing Bach2 protein expression and subsequent cell-fate choices during memory recall and GC reaction. Thus signaling-induced differential dynamics of Bach2 protein and mRNA in activated B cell control their cell-fate outcomes and imprint the fate of their descendant effector cells.
Project description:We report here the broad transcriptomic program regulated by BACH2 transcription factor. We used a well suited in vitro model of B cell differentiation to evaluate transcriptomic program governed by BACH2 leading to Plasmocyte (PC) differentiation. In this model B cells were cultured with anti-BCR, CpG, CD40L and Interleukin-2 (IL2). This Interleukin triggers PC differentiation by directly repressing BACH2 expression. We artificially inhibit BACH2 expression by siRNA and found that this condition is sufficient to trigger PC differentiation without IL2. To understand global changes induced by enforced BACH2 downregulation we compared Chip-Sequencing data between activated B Cells and BACH2 deficient B cells (siBACH2). We found that BACH2 binds more than 3000 genes across the human genome. RNAsequencing comparing IL2 drivent committed cells and siBACH2 committed cells highlighs a large common trasncriptional program shared by both conditions and involved in B cell destiny. This study provides evidence that BACH2 is a guardian of B cell fate.
Project description:To unveil cell fate decision pathways during osteoclast differentiation at single-cell resolution, we performed single-cell RNA sequencing (scRNA-seq) on the osteoclast culture system, in parallel with bulk RNA-seq and proteome analyses
Project description:The transcriptional repressors BCL6 and BACH2 are crucial regulators of germinal center (GC) B-cell fate, and are known to interact and repress transcription of PRDM1, a key driver of plasma cell differentiation. How these factors cooperate is not fully understood. Herein we show that while GC formation is only minimally impaired in Bcl6+/- or Bach2+/- mice, double heterozygous Bcl6+/-Bach2+/- mice exhibit profound reduction in GC formation. Splenic B-cells from Bcl6+/- Bach2+/- mice display accelerated plasmacytic differentiation and high expression of key plasma cell genes such as Prdm1, Xbp1 and CD138. ChIP-seq revealed that in B-cells BACH2 is mostly bound to genes together with its heterodimer partner MAFK. The BACH2-MAFK complex binds to sets of genes known to be involved in the GC response, 60% of which are also targets of BCL6. Approximately 30% of BACH2 peaks overlap with BCL6 including cis-regulatory sequences of the PRDM1 gene. BCL6 also modulates BACH2 protein stability and their protein levels are positively correlated in GC B-cells. Therefore, BCL6 and BACH2 cooperate to orchestrate gene expression patterning in GC B cells through both transcriptional and biochemical mechanisms, which collectively determine the proper initiation and timing of terminal differentiation. ChIP-seq using P18 antibodies in OCI-Ly7 cells