Figure 3: Expression and activity of BCL6 in human and murine HSPCs.

(a) Gene expression profiles of single human HSPCs showing expression of the control gene B2M were investigated for expression of BCL6. Positive expression values defined as being 2 s.d.’s above the mean were observed in 11/183 single cells, with approximately equal proportions in each donor. (b) GSEA of BCL6 target genes in BCL6 transcript-positive cells compared with BCL6 transcript-negative cells in each donor showed an enrichment of target-gene expression in BCL6 transcript-negative cells (GSEA FDRs =0.212 and 0.025 for Donor 1 and 2, respectively). This corresponds to repression of target genes in BCL6 transcript-positive cells. (c) Transient Bcl6 expression within HSPCs was achieved by placing a floxed (yellow loxP sites) Bcl6 cDNA with IRES-GFP reporter under control of the of the promoter for the HSPC-specific gene, stem cell antigen-1 (Sca1). (d) Tracking of the GFP marker for Bcl6 transgene expression during haematopoietic development shows expression is restricted to HSPCs and not in Pro-B or mature B-cells. Images are representative of four independent experiments. For gating schema, see Supplementary Fig. 3.