APP and Parkinson disease: Many of the miRNAs we were able to detect as differentially expressed in cell-free CSF and SER have been reported previously in studies examining brain tissue from patients with AD and PD [22], [24], [26], [29], [51], [52], [53], [54], or as miRNAs that target genes of particular interest- such as APP, BACE1 and α-synuclein [54], [55], [56].