APP and Cognitive impairment: When overexpressed in human Aβ-forming amyloid precursor protein (APP) transgenic mouse models, Fyn accelerates synaptic and cognitive impairment (Chin et al., 2005). Furthermore, synaptic degeneration and memory loss are rescued when either Fyn is depleted or its activity is suppressed in an APP mutant background, such that no Aβ is produced (Kaufman et al., 2015; Chin et al., 2004).