Figure 1. Unsupervised analysis of epicardial gene expression.

A self organizing map was used as an unsupervised analysis tool to simplify complex expression information. B) x-axis are relative normalized expression of epicardium samples, y-axis are relative normalized expression of muscle samples. The four resulting clusters represent generally different expression patters rather than their absolute expression values. Cluster 1 contains genes that were higher in the epicardial samples than in the muscle controls. Clusters 2 and 3 contains genes that were similar in expression in epicardium and muscle. Cluster 4 contains genes that were higher in the muscle controls than in the epicardial samples. B) Starting from Cluster 1, we applied conditions as described in Materials and Methods to select 197 epicardial signature genes shown as a heat map. The top four rows are epicardial samples, and the lower four rows are muscle control samples, where green colour represents upregulation and red colour represents downregulation of a given gene.