Mechanisms of Transcriptome Aging Figure 5. Aging in mouse tail skin leads to an aberrantly weak inflammatory signature with decreased expression of Lyz1, Lyz2, Clec7a, Cd48, Tyrobp and Mpeg1. Gene expression profiles associated with aging in mouse tail skin (first two columns in chart) were aligned with 28 other aging profiles from a panel of mouse tissues. All profiles were generated from datasets that included young and old mice, where the same Affymetrix Mouse Genome 430 2.0 array platform was used to generate each dataset (see Methods and Table S2 for further detail). The chart lists in rank-order the top 50 genes increased by aging across all profiles (based upon the total number of significant (age-increased) results among all profiles for a given gene). Colors within the chart denote the estimated 2-year fold change (old/young) for a given gene (row) and profile (column) (see color scale), while up and down-triangles denote significant aging effects (comparison-wise P,0.05). Several alternative versions of this chart with different gene-ranking schemes are shown in Figure S10. doi:10.1371/journal.pone.0033204.g005 mice (Figures 1 and 7) [31]. In human skin, females exhibit an age- related increase in the expression of transcripts associated with T- cells, macrophages, DC, monocytes and neutrophils, while males exhibit decreased expression of transcripts associated with T- and B-cells (Figures 1 and 2). This sexually dimorphic pattern parallels that observed in the human central nervous system, with heightened inflammatory gene expression with aging in females as compared to males [21]. It is possible that anti-inflammatory PLoS ONE | www.plosone.org 8 March 2012 | Volume 7 | Issue 3 | e33204