Functional classification of differentially expressed genes. Genes are broadly grouped into selected, known functional categories: apoptosis regulators (A), cell-cycle control (B), and transcription factors (C). The X-axis refers to the signal log ratio (SLR), representing the log₂ of the average change in the expression level of a transcript between ET and donor MK pools. Positive/negative SLRs denote increases/decreases in expression in ET MKs, and an SLR of 1 corresponds to a 2-fold change. (D) Expression of selected genes was also monitored by quantitative RT-PCR (gray histograms) as well as by the array (black histograms). On the x-axis, RT-PCR values are expressed as log₂ of the RQ (relative quantity) in order to allow comparison with the microarray SLRs.