Figure 2

Hierarchical clustering of microarray data and identification of genes with similar transcriptional profiles. (A) Total of 1561 genes was clustered on the basis of their expression profiles across the sixteen time-points using TIGR MultiExperiment Viewer (MeV) software[17]. Each gene's expression values were standardized to have a median of zero and a standard deviation of one across the sixteen time points. The lighter colour in the cluster dendrogram is correlated with a higher expression level. Five distinct clusters were selected visually, and the node separating each cluster is shown in the distance tree. (B) An average expression profile of genes within each cluster. To obtain each profile, a sum of expression values across the sixteen time-points for each gene was standardized to 1. Next, time-course values for all genes in each cluster were summed, and the summed value for the sixteen time-points for each cluster was scaled to 1. (C) A sub-cluster of cluster I. (D) The name of each cluster and representative profile is shown in deferent colour.