Quantitative polymerase chain reaction validation of microarray analysis. Quantitative PCR analysis of 10 genes from (A) HEK293, (B) AtT20, (C) BV2, and (D) N18 cell lines. mRNA levels determined from qPCR analysis were plotted against the mRNA levels measured in the microarray analyses in figures 1, 3 and 6. The dashed lines indicate the threshold of statistical significance for the microarray data. Points that fall between 0 and this threshold indicate genes that were detected with the microarray analysis but failed to meet statistical significance. Lower critical threshold (Ct) values indicate high mRNA copy numbers.