Overall transcriptional response of HCT-8 cells to TcdA and TcdB. A. A heatmap shows the number of differentially expressed probe sets at 2 h, 6 h, and 24 h. The color scale represents the fold change (binary log scale) of genes relative to untreated cells at the same time point. "A, 2 hr" indicates the gene expression of cells after 2 h of TcdA treatment. TcdA and TcdB concentration is 100 ng/ml. B. The correlation of transcriptional profiles between TcdA and TcdB at the indicated time points are displayed in a correlation matrix. The values represent the Pearson correlation coefficient calculated from the fold change of all the probe sets within the microarray. C. The number of differentially expressed genes used to identify enriched GO categories was determined from a linear model (Methods).