Scatter plot of gene expression profiles as a function of age. Pairwise comparisons of age groups within each phenotypic class (control or PPT1 knockout) are shown. Each point represents a unique probe set, and Y- and X-axis values are expressed as the logarithm of expression intensity for each probe set. The data set includes all probe sets (a total of 5236) that passed filtering as described under "Materials and Methods". Note the increased scatter of data points with age in the PPT1 knockout with age as compared to the wild type mice.