Dynamic changes in E protein activity orchestrate germinal center and plasma cell development [RNA-Seq]

Humoral immunity requires the generation of high-affinity antibodies, which involves the generation of germinal centres (GC) promoting class switch and affinity maturation of antigen-specific B cells, and the differentiation of long-lived plasma cells. This multi-layered process is tightly controlled by the activity of a transcriptional network including Bcl6, essential for the development of GC, and Blimp1, required for the differentiation of plasma cells. Here, we reveal an additional layer of complexity by demonstrating that dynamic changes in E-protein activity mediated by Id3 govern both GC and plasma cell differentiation. We show that down-regulation of Id3 expression in B cells in essential for releasing E2A and E2-2, the combined activity of which is required for both GC B cell and plasma cell differentiation. We demonstrate that this pathway controls the expression of multiple key factors required for antigen-induced B cell differentiation, including Blimp1, Xbp1, Mef2b and CXCR4 and is therefore critical for establishing the transcriptional network that controls GC B cell and plasma cell differentiation. Transcriptional profiling of wild type, Id3 knockout and E2A/E22 double knockout B cells using RNA sequencing体液免疫依赖高亲和力抗体的产生，这一过程涉及生发中心（germinal centres, GC）的形成——其可促进抗原特异性B细胞的类别转换与亲和力成熟，以及长寿命浆细胞的分化。这一多层级调控过程受到一套转录网络的严格管控，其中包括生发中心发育必需的Bcl6，以及浆细胞分化所需的Blimp1。本研究揭示了该过程的额外调控复杂性，证实由Id3介导的E蛋白活性动态变化可同时调控生发中心与浆细胞的分化。我们发现，B细胞中Id3表达的下调是释放E2A与E2-2的必要条件，而二者的协同活性对于生发中心B细胞及浆细胞的分化均不可或缺。本研究证明，该通路可调控抗原诱导的B细胞分化所需的多种关键因子，包括Blimp1、Xbp1、Mef2b与CXCR4，因此对于构建调控生发中心B细胞及浆细胞分化的转录网络至关重要。本研究通过RNA测序（RNA sequencing）技术，对野生型、Id3敲除型及E2A/E22双敲除型B细胞开展了转录组分析。