To generate a single consensus estimate of expression across the panel of BXD strains, we computed the PC1 of three probe sets (1421087_at, 1460662_at and 1421086_at). We used this consensus Per3 eigengene to identify BXD strains with the lowest and highest expression. In the hippocampus, BXD2 and BXD22 have the lowest, and BXD28 and BXD42 have the highest expression of Per3 (Figure 2a). This genetic difference in transcript levels between the extreme strains was confirmed at the protein level by western blot analysis that showed lower PER3 level in BXD2 and BXD22 compared with BXD28 and BXD42 (Figure 2b,c).
