PCNA and Parkinson disease: A bioinformatics profiling of mRNA transcripts in multiple single nuclei using a human normal aging, AD, and Parkinson’s disease-associated Lewy body dementia (PD-LBD) brains dataset suggests the presence of cell cycle regulatory mRNA transcripts such as G2/M-phase marker cyclin B and S-phase marker proliferating cell nuclear antigen (PCNA) in excitatory neurons [158].