ArtΔ/Δ MSCs show an attenuated transcriptional response to serum withdrawal. (a) Schematic showing experimental design for comparative gene expression analysis. RNA was isolated from duplicate cultures representing either WT (blue) or ArtΔ/Δ (red) MSCs cultured in either normal (solid line with filled nuclei) or serum starvation (dashed line with open nuclei) media. All samples were analyzed by hybridization to Affymetrix GeneChip Mouse 430 2.0 microarrays. Relative fold change (RFC) in transcription levels was determined for serum-starved cells versus corresponding controls in WT and in ArtΔ/Δ samples. Using a threshold of threefold or greater RFC, WT and ArtΔ/Δ data were comparatively analyzed and results were categorized as unique to WT cells (blue), unique to ArtΔ/Δ cells (red) or common to both (overlap). In total, 157 genes were identified with a threefold or greater RFC in WT or ArtΔ/Δ or both. Number of genes identified in each category is indicated on the Venn diagram. (b) RFC data for each of the 157 genes in (a). Shown are RFC data for each gene in WT cells (blue bars) and in ArtΔ/Δ cells (red bars). Negative RFC values indicate lower expression in serum-starved cells relative to control; positive RFC values indicate elevated expression in serum-starved cells relative to controls. (c) RFC for genes common to both WT and ArtΔ/Δ cells from (a). Plotted are RFC for WT (blue) and ArtΔ/Δ (red) cells as in (b).