High cerebrospinal tau levels are associated with the rs242557 tau gene variant and low cerebrospinal β-amyloid in Parkinson disease

Cerebrospinal fluid (CSF) tau and phospho-tau levels have been associated with certain tau gene variants and low CSF amyloid-β (Aβ) levels in Alzheimer disease (AD), constituting potential biomarkers of molecular mechanisms underlying neurodegeneration. We aimed to assess whether such CSF-genetic endophenotypes are also present in Parkinson disease (PD). CSF tau, phospho-tau and Aβ levels were obtained from 38 PD patients (19 with dementia) using specific ELISA techniques. All cases were genotyped for a series of tau gene polymorphisms (rs1880753, rs1880756, rs1800547, rs1467967, rs242557, rs2471738 and rs7521). The A-allele rs242557 polymorphism was the only tau gene variant significantly associated with higher CSF tau and phospho-tau levels, under both dominant and dose-response model. This association depended on the presence of dementia, and was only observed in individuals with low (<500. pg/mL) CSF Aβ levels. Such genetic-CSF endophenotypes are probably a reflection of the presence of AD-like molecular changes in part of PD patients in the setting of dementia.