PSEN1 and amyloidosis: Consistent with the increased levels of Aβ peptides in Spi1+/−;APP/PS1 mice, we detected a 1.76- and 2.59-fold increase in amyloid plaque burden in the cortex and hippocampus, respectively, in Spi1+/−;APP/PS1 mice compared to Spi1+/+;APP/PS1 mice (Fig. 1f, g).