Shugoshin‐1 (Sgo1) haploinsufficient (∓) mice, a model of chromosome instability (CIN) with chromosomal and centrosomal cohesinopathy, spontaneously exhibited a major feature of AD pathology; amyloid beta accumulation that colocalized with phosphorylated Tau, beta‐secretase 1 (BACE), and mitotic marker phospho‐Histone H3 (p‐H3) in the brain. Here, BACE1 is linked to Alzheimer disease.