GAP43 and Alzheimer disease: To do so, we leveraged the data collected in two large cohorts dealing with AD pathophysiology, namely the pre-symptomatic PREVENT-AD cohort and the ROSMAP cohort and investigated whether SNPs in the PTPRS locus affected known biomarkers of AD, such as Amyloid, Aβ-42, p(181)Tau and synaptic integrity markers SNAP-25, SYT-1 and GAP-43.