Parity-induced gene signature in total mammary cell suspensions. (A) Heat-map and cluster analysis of differential gene expression in total isolated mammary cells from age-matched virgin control and parous mice. Gene expression is presented as normalized Z-scores, defined as Z = (x-μ)/sd to allow visualization. A cut-off of P < 0.05 was applied. If multiple probe sets existed for the same gene, the probe set with the largest change in expression was selected. Four independent experiments were performed with 10 mice (five virgins; five parous) per experiment. (B) qPCR validation of pregnancy-induced gene-expression changes in total mammary cell suspensions. Fold changes are shown in relation to expression in cell suspensions from age-matched virgin control mice. Ct values were normalized to the reference gene Hprt. As control for luminal epithelial cell number, qPCR for Krt8 was performed. Data represent the mean ± SEM of four independent experiments with 10 mice (five virgins; five parous) per experiment.