Correlation between retroviral integration and gene activity in CD34⁺ cells. The bars show the percentage of distribution of expression values from Affymetrix HG-U133A microarrays of cytokine-stimulated CD34⁺ cells. To correlate retroviral integration and gene activity, expression values from the CD34⁺ cell microarrays were divided into 4 classes: absent (black), low (below the 25th percentile in a normalized distribution; blue), intermediate (between the 25th and the 75th percentiles; yellow) and high (above the 75th percentile; red). (A) The first 2 bars (all genes) show the distribution of the more than 16 000 genes on the microarray of CB- or BM-derived CD34⁺ cells activated in the same conditions used for transduction with RV vectors; the other 2 bars represent the expression values of genes targeted by all RV integrations (RV all) or by integration hot spots (RV hot spots), derived from a weighted mean of the CB and BM microarray values. (B) The first bar (all genes) shows the distribution of the more than 16 000 genes on the microarray of CB-derived CD34⁺ cells activated in the same conditions used for transduction with LV vectors; the other 2 bars represent the expression values of genes targeted by all LV integrations (LV all) or by integration hot spots (LV hot spots). The n values indicate the number of probesets analyzed for each group of genes.