Figure 2

Three-dimensional principal component analysis. Global relationships between the expression patterns of individual animals were visualized using the 7,951 differentially expressed features meeting the initial filtering criteria (p < 0.05 and at least +/- 1.5 relative fold change). Each sphere represents the expression from one animal. Animals of the same sex and age have the same color and are labelled by age in weeks (ArrayTrack). Females are indicated by black vertices or whiskers, males have none. Together, these data illustrate the relatively high reproducibility between biological replicates (n = 5) in a discrete and continuous linear pattern from young to old animals. It also suggests clear sex- and age-dependent differences in liver gene expression, with males and females exhibiting diverging profiles beginning at 2 weeks with greatest differences observed at 21 and 52 weeks before converging again at 104 weeks.