Pearson correlation clustering of involution specific genes. (a) One hundred and three upregulated probe sets identified through SOM clustering were clustered with the Pearson correlation clustering program of GeneSpring (Silicon Genetics). The colours (see colour bar) represent a relative measure for the expression, with 1 representing the median, the red colour upregulated and blue downregulated gene expression. The resulting gene tree was grouped into 10 clusters of similarly expressed genes (shown bracketed at the right) and their average expression patterns are shown on the right as graphs (red lines) with standard deviations (blue lines) (DMT®; Affymetrix). Note that the y-axes represent only arbitrary expression levels and are not scaled identically between graphs. (b) Sixteen downregulated genes were clustered by using the software mentioned above and their average expression (red line) and standard deviations (blue lines) are shown in the graph on the right (DMT®; Affymetrix). Abbreviations: vir, virgin; preg, pregnancy; lac, lactation; inv, involution.