Whereas M1-WT mice showed little change in the expression of APO-E, serpinA3N, clusterin α-chain, and galectin-1 at 16 and 18 w.p.i., M1-PD mice showed a significant increase in all four of these prion disease biomarkers in the hippocampus and/or cortex (Fig. 2 C and D and SI Appendix, Fig. S6 C and D). This evidence concerns the gene APOE and prion disease.