Proteins consistently downregulated in prion disease compared to controls include those related to synapse formation and maintenance, such as SYP or RAC1, and to ATP biosynthesis, such as PKM, SDHA, VDAC2 SLC25A4, in all samples [Fig. 3A(i), B(i) and C(i)]. The gene discussed is SLC25A4; the disease is prion disease.