PSEN1 and Alzheimer disease: AD transgenic mice including the well studied strain possessing both a chimeric mouse/human amyloid precursor protein with the Swedish mutations (K595N/M596L) (APPswe) and a mutant form of presenilin 1 with deletion of exon 9 (PS1ΔE9) appears to express APP not only in brain, but in muscle as well (Dr. David Borchelt, personal communication).