Scatter plot of gene expression profiles at 3, 5 and 8 months of age. Each point represents a unique probe set. Y- and X-axis values are expressed as the logarithm of expression intensity for each probe set. (A, C, E) Groupwise comparisons between wild-type and PPT1 knockout at 3, 5, and 8 months for all probe sets (5236) that passed filtering as described under "Materials and Methods". (B, D, F) Groupwise comparison between wild-type and PPT1 knockout mice showing only those probe sets selected by SAM (significance) analysis (total of 267). The scatter plot indicates an increasing number of gene expression changes with time in the knockout mice.