Transcriptional Landscape of B cell Early Activation. Mus musculus

The physiological responses to B cell receptors (BCR) and Toll-like receptors (TLRs) so vital to immunity are well known but the transcriptional signatures and regulatory mechanisms that initiate activation and release cells from quiescence remain unclear. Here, we show that BCR- or TLR-mediated activation of B cells involves a large shared transcriptional signature and a smaller subset of distinct signal-specific transcriptional responses. Signal-specific transcription is observable within 2 hours of ligand exposure; suggesting different modes of activation begin soon after ligand binding and long before the well-documented BCR and TLR-dependent physiological responses occur. Ligand-specific differences in regulatory mechanisms including RNA Pol II recruitment, activating (H3K4me3) and repressing (H3K27me3) histone marks, transcription factor binding sites in responsive gene promoters, and miRNA expression were observed. These results begin to define the transcriptional landscape of early B cell activation revealing more ligand-specific regulation and character than occurs much earlier than previously expected. Overall design: CD43- mouse resting B cells were stimulated with ligands against the B cell receptor and TLR4 (LPS). RNA-sequencing was performed to describe differential transcription and ChIP-sequencing was performed to describe regulatory mechanism responses.