Figure 3 Independent verification of microarray quantitation. Relative mRNA levels of the indicated genes (Mast = Mast/stem cell growth factor receptor) were measured using the TaqMan 5' nuclease fluorigenic quantitative PCR assay (9) in the same samples that were used to prepare probes for microarray hybridizations. Data from the TaqMan analysis were normalized to mRNA concentrations and plotted relative to the level at time zero, so that the results could be compared to those from the microarray hybridizations. In general, quantitation using the two methods gave very similar results (Ref. 10).