Expression of membrane markers, transcription factors, and B-cell subset-specific genes in normal BM tissue. (A) B cells of the BM were defined by flow cytometry as CD19⁺, CD45⁺, and CD3⁻ and were additionally divided by surface marker expression of CD10, CD20, CD27, CD38, and CD34, published in detail previously.⁴⁴  The data quality of the differentiating B-cell subset compartments was validated as illustrated by normalized histograms of (A) the mean fluorescence intensities (MFIs) CD markers based on merged MFC reanalysis of pure sorted populations resulting from 7 independent sorting procedures. Broken lines represent MFI values for each sorted B-cell subset. (B) Principal component analysis of the MFI values for each sorted cell in all samples. The cells are coded with a color according to their original subset. The dots represent mean values for each sorted B-cell subset. (C) The most variable probe sets were used in unsupervised hierarchical clustering analysis of the surface markers (MME = CD10, CD34, CD38, CD27; PTPRC = CD45; MS4A = CD20, CD19) used for FACS. (D) B-cell differentiation–specific genes (n = 45), summarized from a literature review of transcriptional regulation of B lymphopoiesis. The colors at the top of panel D indicate the relative gene expression for each sample, with blue representing high and brown representing low.