APP and familial Alzheimer disease: For example, oligodendrocyte loss and myelin abnormalities are observed by 6 months of age, prior to the onset of amyloid pathology, in mouse models of familial Alzheimer's disease that overexpress human mutations in the amyloid precursor and presenilin 1 proteins, either alone (APP/PS1 mice; Behrendt et al., 2013; Dong et al., 2018) or in combination with the MAPTP301L mutation (3xTg mice; Desai et al., 2010; Desai et al., 2009).