BACH2 in human plasma cell fate decision. Homo sapiens

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. Overall design: Differential gene expression data between 3 conditions (RNAsequencing in triplicate) : Uncomitted, comitted, and BACH2-deficient B cells integrated with BACH2 ChipSequencing on human activated B cells versus BACH2 deficient B cells as control.

本研究报道了由BACH2转录因子调控的广谱转录组程序。我们采用适配性优异的B细胞分化体外模型，评估BACH2所调控的、介导浆细胞（Plasmocyte, PC）分化的转录组程序。在该模型中，我们将B细胞与抗B细胞抗原受体（anti-BCR）、CpG、CD40配体（CD40L）及白细胞介素2（IL2）共培养。该白细胞介素可通过直接抑制BACH2的表达，触发浆细胞分化。我们借助小干扰RNA（siRNA）人工下调BACH2的表达，发现无需添加IL2即可触发浆细胞分化。为解析BACH2被强制下调所诱导的全局转录变化，我们对活化B细胞与BACH2缺陷型B细胞（siBACH2）的染色质免疫沉淀测序（ChIP-Sequencing）数据进行了对比分析。结果显示，BACH2可结合人类基因组中超过3000个基因。我们将IL2诱导的分化细胞与siBACH2诱导的分化细胞进行RNA测序对比，发现二者共享一套庞大的共同转录组程序，且该程序参与调控B细胞命运。本研究证实BACH2是B细胞命运的守护者。
实验整体设计：本研究整合了三类条件下的差异基因表达数据（均进行三次生物学重复的RNA测序）：未分化B细胞、已分化B细胞及BACH2缺陷型B细胞，并以活化人B细胞与BACH2缺陷型B细胞的ChIP测序数据作为对照。