Genes confirmed as differentially regulated between the 3 different undifferentiated ES cell lines, HM1, SHBl6.3 and IMT11. Ann = PCR annealing temperature, Cyc = number of PCR cycles used. Beta-actin was not used as a housekeeping control as the arrays noted it as variable. It was variable, but the variation in expression patterns between repeats was very high, such that array results for this gene could not be confirmed. 4 genes were confirmed; Mki67 and Scmh1 showed highest expression in IMT11 cells, Pter showed lower expression in SHBl6.3 cells than in the other two lines, while Hprt expression was absent from HM1 cells as expected.