Cyclin B1 is a cell cycle protein involved in the G2/M transition and plays a vital role in the survival of postmitotic neurons.23 In healthy neurons, cyclin B1 degradation takes place in the proteasome after ubiquitylation via the complex/cyclosome (APC/C)‐cadherin 1 (Cdh1).24 In the pathophysiological situation of Alzheimer’s disease,25 experimental brain ischemia,26 traumatic brain injury,19 however, the affected brain regions aberrantly express cyclin B1. Here, CCNB1 is linked to early-onset autosomal dominant Alzheimer disease.