Gene expression profiles of B cells and PCs generated in the 3-step culture system, of MBCs and BMPCs. The gene expression profile of purified B cells or PC populations (5 separate samples for each population) was determined with Affymetrix U133 Plus 2.0 microarrays. (A) An unsupervised hierarchical clustering was run with the 2000 probe sets with the highest SD (log transform, center genes and arrays, uncentered correlation, and average linkage). The dendrogram shows that all samples of a given population (D0 MBCs, D4 actBCs, D7 PBs, D10 PCs, and BMPCs) strongly cluster together (r ≥ 0.5) and that D7 PBs and D10 PCs are correlated together unlike other populations. (B) The probe sets differentially expressed between D0 MBCs + D4 actBCs and D7 PBS + D10 PCS + BMPCs were determined with a SAM-supervised analysis (Wilcoxon statistic, 2-fold ratio, 0% false discovery rate), identifying 459 unique genes with Ingenuity software. When a gene was assayed by several probe sets, the probe set with the highest variance was used. An unsupervised hierarchical clustering was run on this 459 unique gene list. The normalized expression value for each gene is indicated by a color: red represents high expression; green, low expression.