Variations between lines likely reflect the different promoters used, the effects of the distinct mutations or combinations of mutations, and the genetic backgrounds on which the transgenes have been maintained. PDAPP mice, for example, have been mostly studied on a highly mixed C57BL6/DBA/Swiss-Webster background. By contrast, Tg2576 mice are typically studied on a hybrid C57BL6/SJL background. Indeed, the Tg2576 transgene has been difficult to move off this background and leads to early death on an FVB/N background.21
