Inter-strain, age-independent gene-expression changes. (a) A heat-map view of genes differentially expressed in hippocampus with either S8 compared to SR1, or S10 compared to SR1 is shown. Columns indicate fold change in gene expression between young S8 and SR1, young S10 and SR1, old S8 and SR1 and old S10 and SR1, respectively. Bright red and bright green indicate genes that met the most stringent criteria for an increased or decreased expression level change, including a WSRR p < 0.01. A gene is colored orange or light green if it was increased or decreased with an average WSRR p < 0.05 in all comparison files. Boxes, numbers and examples of genes with the pattern of change are as follows: group 1, genes differentially expressed between both young and old S8 and S10 mice compared to SR1, example gene is melanoma antigen, 80 kDa; group 2, genes differentially expressed in 3/4 comparisons of young and old S8 and S10 compared to SR1, example gene is decorin; group 3, genes differentially expressed in either young and old S8 versus SR1 or young and old S10 versus SR1, example gene is heat shock 70 kD protein 5; group 4, genes differentially expressed in any single comparison group of S8 or S10 to SR1, example gene is protein phosphatase 1-1A (differences unique to a single age and strain); group 5, genes with inconsistent expression differences, example genes are RAN binding protein 9, glutathione S-transferase a4 and kinesin family member 5b. Genes differentially expressed in both retina and hippocampus are indicated by an asterisk. Gene-expression differences confirmed by qRT-PCR are indicated by the symbol ‡. Line graphs in the last column represent the signal intensity on the y-axis and the time point of collection on the x-axis. S8 is indicated by a red line, S10 by a blue line, SR1 by a green line and B6J by a black line. (b) Heat-map view and line graphs of exemplars from each group representing differentially expressed genes in the retina between S8 versus SR1 and S10 versus SR1 mice is shown. Analysis and representation of the data is similar as described for (a).