(A) Overall correlation of gene expression profiles between different cell types. A high correlation coefficient was observed between the DP-DF and Mx-ORS populations, consistent with their mesenchymal versus epithelial characters. Intriguingly, the least similar populations were the Mx and DP, which are strongly engaged in reciprocal exchange of signaling necessary for the maintenance of both compartments. Inset: Dendrogram outlining the correlation of gene expression between the populations.
(B,C) The Venn diagram demonstrates the degree of similarity based on absolute present calls. Probe-sets were considered present only if they were called present in both replicates. Note that for each cell type, ~200–400 probe-sets showed selective hybridization under these criteria, while ~2/3 of all present probe-sets were represented in at least four or all five of the fractions and ~4,000 genes (~6,000 probe-sets) were expressed and unchanged in all five populations (“Molecular backbone”). When all five fractions were cross-compared, ~150–300 genes (“Molecular signatures”) scored as being upregulated by ≥ 2× selectively in only cell type. The lists show array predictions for differential expression of mRNAs encoding some established, defining markers for each cell type, when compared against an adjacent or related cell population. The total number of mRNAs that show at least a 2× difference between the two cell populations is provided at the top, and the fold difference in specific mRNA levels is given next to each marker. DF, dermal fraction; DP, dermal papilla; Mc, melanocytes; Mx, matrix; ORS, outer root sheath.