PSEN1 and Alzheimer disease: In zebrafish with a knockout of PSEN1, a risk gene for AD, adult fish exhibit anxiety-like behaviors, a contrast to mice with PSEN1 knockout, which do not show changes in memory capabilities or anxiety-like behaviors (Saura et al., 2004; Sundvik et al., 2013; Soto-Faguás et al., 2021).