APP and ABri amyloidosis: Third, in knock-in model mice (FDD-KI and FBD-KI) for familial Danish dementia (FDD) and familial British dementia (FBD), neuronal defects occur only when sufficient levels of APP are supplied (Tamayev et al., 2011; Yao et al., 2019) and, more surprisingly, Aβ accumulation itself appears to be much less involved in these types of dementia than hitherto considered (Tamayev et al., 2012; Yao et al., 2019).