Finally, miR-29c-3p, miR15a-5p, and let-7i-5p were found as three differential expressed miRNAs in CSF of AD patients that could all be related to AD relevant targets such as APP (amyloid precursor protein) and BACE1 (Beta-secretase 1), implying that miRNA is actively involved in key pathogenetic AD processes [184]. Here, BACE1 is linked to Alzheimer disease.