An IRF4-MYC-mTORC1 integrated pathway controls cell growth and the proliferative capacity of activated B cells during B cell differentiationin vivo

Abstract

Cell division is an essential component of B cell differentiation to antibody-secreting plasma cells, with critical reprogramming occurring during the initial stages of B cell activation. However, a complete understanding of the factors that coordinate early reprogramming events in vivo remain to be determined. In this study, we examined the initial reprogramming by IRF4 in activated B cells using an adoptive transfer system and mice with a B cell-specific deletion of IRF4. IRF4-deficient B cells responding to influenza, NP-Ficoll and LPS divided, but stalled during the proliferative response. Gene expression profiling of IRF4-deficient B cells at discrete divisions revealed IRF4 was critical for inducing MYC target genes, oxidative phosphorylation, and glycolysis. Moreover, IRF4-deficient B cells maintained an inflammatory gene expression signature. Complementary chromatin accessibility analyses established a hierarchy of IRF4 activity and identified networks of dysregulated transcription factor families in IRF4-deficient B cells, including E-box binding bHLH family members. Indeed, B cells lacking IRF4 failed to fully induce Myc after stimulation and displayed aberrant cell cycle distribution. Furthermore, IRF4-deficient B cells showed reduced mTORC1 activity and failed to initiate the B cell-activation unfolded protein response and grow in cell size. Myc overexpression in IRF4-deficient was sufficient to overcome the cell growth defect. Together, these data reveal an IRF4-MYC-mTORC1 relationship critical for controlling cell growth and the proliferative response during B cell differentiation.

B cell‐intrinsic changes with age do not impact antibody‐secreting cell formation but delay B cell participation in the germinal centre reaction

“…IRF4 is a transcription factor lowly expressed in naïve cells, absent in GC B cells and upregulated in plasma cells (Willis et al, 2014). In particular, IRF4 has been shown to be important for regulating the proliferative capacity of B cells during activation and is required for early GC B cells formation in a B cell-intrinsic manner (Patterson et al, 2021;Willis et al, 2014). Thus, the lower expression of IRF4 by B cells from older donors may result in early proliferative defects, as previously reported (Blaeser et al, 2008) and contribute to the reduced early GC response, as we observed in our mouse The SW HEL adoptive transfer system allowed us to compare the function of B cells from young or aged donor mouse in responding to vaccination in vivo in a young environment.…”

Strong Basal/Tonic TCR Signals Are Associated with Negative Regulation of Naive CD4+ T Cells

“…RNA sequencing and assay for transposase-accessible chromatin with sequencing libraries RNA sequencing (RNA-seq) libraries were prepared from 1 × 10 5 CD4 1 CD44 lo RFP À population AD cells from the spleen and lymph nodes of Nur77-GFP Foxp3-IRES-RFP mice. Cells were sorted directly into RLT lysis buffer (Qiagen) with 1% 2-ME, sequenced, quality checked, and mapped to the mm10 genome as previously described (18). Genes expressed at 3 reads per million in all samples of one group were considered expressed.…”

“…Genes expressed at 3 reads per million in all samples of one group were considered expressed. Assay for transposase-accessible chromatin with sequencing (ATAC-seq) libraries were prepared from 2 × 10 4 CD4 1 CD44 lo RFP À population AD cells from the spleen and lymph nodes of Nur77-GFP Foxp3-IRES-RFP mice, sequenced, and mapped to the mm10 genome as previously described (18).…”

Novel mechanism ofMYCderegulation in Multiple Myeloma

“…Although it is expressed in normal plasma cells, its transcription level steadily increases throughout MM progression 27,34,37,38 . Several studies in B cell malignancies, including MM, describe the binding of IRF4 to the MYC promoter and the creation of an autoregulatory feedback loop deregulating these two genes [39][40][41] . However, this is the first description of how binding of cMAF and IRF4 to a small non-coding regulatory region, changed the chromatin conformation and led to MYC activation in nontranslocated cell lines.…”