Distinct cerebrospinal fluid DNA methylation signatures linked to Alzheimer's disease

Alzheimers disease (AD) accounts for more than 60% of the dementia cases and currently there is no curative treatment for it. With the emergence of potentially disease modifying treatments, early diagnosis is key to identify patient groups that would benefit from such treatments, aiming to prevent severe cognitive decline. We previously identified a set of DNA methylation signatures that allow for accurate diagnosis of AD in cortical neurons and brain tissue, even before clinical manifestation of the disease [1]. Here we investigate 11 of these signature regions via targeted next-generation sequencing in cell-free DNA (cfDNA) isolated from cerebrospinal fluid (CSF) of AD patients homozygous for APOE4 (n=4) and sporadic AD (n=5) cases compared to age-matched control samples (n=5). Our analyses demonstrated that 6/11 of the tested DNA methylation signatures that had initially been identified in cortical neurons and brain tissue were also validated in cfDNA. The remainder of the tested regions either showed opposite trends (3/11) or did not result in any differences (2/11) between control and AD cases. Thus, this presents a direct approach allowing to test for these DNA methylation signatures in CSF-derived cfDNA, and bypasses the need to generate induced pluripotent stem cell-derived cortical neurons from patients.