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.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
1 This work was supported by the National Institute of Allergy and Infectious Diseases grants P01 AI125180 and RO1 AI123733 to J.M.B., RO1 AI148471 to C.D.S., T32 GM0008490 to A.K.K. and J.R.R., and F31 AI138391 to M.J.P.
Abbreviations
- actB
- activated B cell
- ASC
- antibody-secreting plasma cell
- ATAC-seq
- assay for transposase accessible chromatin-sequencing
- CI
- confidence interval
- Ctrl
- CD45.2+Cd19+/+Irf4fl/fl
- CTV
- CellTrace Violet
- DAR
- differentially accessible region
- DEG
- differentially expressed genes
- FDR
- false discovery rate
- FSC-A
- forward scatter area
- gMFI
- geometric mean fluorescence intensity
- GSEA
- gene set enrichment analysis
- IRF4cKO
- CD45.2+Cd19Cre/+Irf4fl/fl
- MDN
- mean division number
- mTOR
- mammalian target of rapamycin
- nB
- naïve B cell
- NES
- normalized enrichment score
- OXPHOS
- oxidative phosphorylation
- pS6
- phosporylated S6
- RPKM
- reads per kilobase million
- scRNA-seq
- single cell RNA-sequencing
- t-SNE
- t-stochastic neighbor embedded
- UPR
- unfolded protein response