Fig. 2. Microarray analysis of gene expression during epithelial differentiation in rat metanephric mesenchyme. (A) Heatmap representation of all genes upregulated independently by Lif, NGAL and NHBF in a temporal sequence from day 0 (freshly isolated mesenchyme) to day 7 (differentiated renal epithelia). Average profiles (right) were deduced arithmetically and grouped into three classes based on the time point of peak expression (class A, day 1-2; class B, day 3-5; class C, day 7). Note that only genes upregulated by all three inducers were included in this analysis. (B) Correlation matrices comparing global gene expression at individual time points (day 0 to day 7) were calculated and hierarchical clustering identified time points of major shifts in gene expression (tree diagram). Pearson correlation coefficients R of neighboring time points (blue) illustrate the degree of change in global gene expression. Epithelial differentiation is depicted at the times of peak expression of each class of genes.