Studies on the role of APOE genotype and cognition in PD provide evidence that APOE may directly impact the pathological progression of αSyn in PD [9, 11, 22, 48, 49]; subsequently, in vivo investigations have demonstrated an APOE ε4 mediated exacerbation of αSyn pathology in murine models of synucleinopathy [9, 52]. This evidence concerns the gene APOE and synucleinopathy.