Figure 1.

Differential gene expression in control vs. +21 fibroblasts. Results from supervised hierarchical clustering of the U95A microarray data are shown; with statistical criteria for selecting the genes indicated at the top (ANOVA, see Methods). Genes (probe sets) are on the x-axis and samples are on the y-axis, with expression indicated by the color scale from 0 (blue) to 5 (red), relative to the experiment mean. A, Data from early passage cells. As shown in the panel on the right, in which genes not on chromosome 21 have been blacked out, the set of over-expressed genes is enriched in genes on chromosome 21 and no genes on chromosome 21 are in the under-expressed set. B, Data from late passage cells. The MX1 gene is markedly over-expressed as the +21 fibroblasts become senescent. See Tables 2 and 3 for the complete lists of differentially expressed genes.