Additional file 11.
Aging effects in gene expression (mRNA) and DNAm data. Due to space limitations, I can only report results for the direct approach of matching each individual CpG to its corresponding gene symbol. Using publicly available gene expression data (Additional file 2), I do not find a significant relationship between age effects on messenger RNA levels and age effects on DNAm levels in (A) blood, (C) brain, (E) kidney, (G) muscle, and (I) CD8 T cells. For each data modality, I estimated 'pure’ age effect using a meta-analysis method that conditioned on data (as described in Additional file 2). The y-axis reports a signed logarithm (base 10) of the meta-analysis P-value, that is, a high positive (negative) value indicates that the gene expression level increases (decreases) with age. Gene expression data and CpG data were matched according to gene symbol as described in . Each point in the scatter plots corresponds to a CpG (x-axis) and the corresponding gene symbol (y-axis). Genes corresponding to the positively related and negatively related clock CpGs are colored in red and blue, respectively. (B,D,F,H,J,L) Mean age effect (y-axis) across gene groups defined by their corresponding CpG. (K,L) Aging effects on DNAm levels (x-axis) do not affect genes known to be differentially expressed between naive CD8 T cells and CD8 memory cells. The y-axis reports the signed logarithm of the Student t-test P-value of differential expression.
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Horvath Genome Biology 2013 14:R115 doi:10.1186/gb-2013-14-10-r115