To investigate the relationship between Aβ-related synaptic changes and tau spread across connected brain regions, we examined cerebrospinal fluid (CSF) levels of growth-associated protein 43 (GAP-43) in a cohort of 93 patients from the Alzheimer’s disease neuroimaging initiative (ADNI) dataset, covering the AD spectrum from cognitively normal to dementia as well as Aβ-negative cognitively normal controls. This evidence concerns the gene GAP43 and early-onset autosomal dominant Alzheimer disease.