Cluster analysis to compare the fold changes in gene expression in cells treated by A23187. Cluster analysis allowed to directly compare the fold changes in gene expression for each one the three cell lines respectively (C: control B lymphoblasts; D: daughter's B lymphoblasts; S: Scott B lymphoblasts). Ratios determining the fold changes in gene expression due to treatment for 48 hours with 200 nM A23187 were examined for each one of the three cell types. The hierachical clustering of the selected genes (fold change of gene expression >2 with a P-value of <0.02 in at least one of the three cell types, see additional file 1) was performed. Without changing their respective hierarchical order, the genes were then grouped by functional category. Differential gene expression in A23187-treated versus non-treated cells is color coded as indicated at the bottom of the figure (fold-changes < 0.5 [see Additional file 1] correspond here to <-1/0.5, i.e. <-2). (A) Cluster analysis of up-regulated genes. (B) Cluster analysis of down-regulated genes. For selected genes represented on the U95Av2 GeneChips by more than one Probe Set ID [see Additional file 1], data corresponding to a single Probe Set ID were used for the cluster analysis and the gene lists in Tables 2 and 3.