Figure 10. Model for the relationship between cell cycle and differentiation in human epidermis.
Stem cells within the basal layer (SC; yellow) by division give rise to actively cycling cells that proliferate rapidly (ACC; pink). ACC lose adherence to the basement membrane, block mitosis, initiate terminal differentiation, migrate into suprabasal layers and continue DNA replication (red). Some of them undergo endomitosis in peribasal layers and become binucleate. Suprabasal keratinocytes lose mitotic cyclins A and B and reinitiate DNA replication in the absence of nuclear division (endoreduplication; punctuated red), the nuclei becoming polyploid. Endomitosis and endoreduplication are different forms of endoreplication.
doi:10.1371/journal.pone.0015701.g010
