Indeed the Alzheimer Aß peptide, the proteolytic product of the PS1 based γ-secretase enzyme on the APP protein and the key player in AD pathogenesis, also induces abnormal spindle structure and chromosome mis-segregation, including human trisomy 21 and mouse trisomy 16 in transgenic mice, transfected cells, and cell-free Xenopus egg extracts [22]–[24], [25]–[28]. The gene discussed is APP; the disease is Alzheimer disease.