Figure 3.

Stratification of epidermis through oriented divisions. (a) At early stages of embryonic development, progenitor cells of the epidermis divide with their spindle oriented parallel to the basement membrane. (b) As stratification and differentiation progresses, perpendicular oriented divisions begin to dominate, representing up to 70% of all divisions through these critical stages of embryogenesis. Perpendicular divisions generate a basal progenitor cell and a differentiating cell positioned in the suprabasal layer. These differential cell fate acquisitions define the ACDs of the epidermis.