Figure 6.
Short-Term Low-Dose UV Exposure Accelerates p53∗/wt Colonization
(A) Protocol: AhcreERT-p53∗/wt or -RYFP mice were exposed to a sub-erythema dose of UVB daily, 4 days per week for 2 weeks (red lines), after which labeling was induced (green arrow) and UV exposure continued; sample collection is indicated by blue arrows.
(B) Rendered confocal z stacks showing representative clones in epidermal whole mounts. Green indicates YFP in YFP panels and GFP in p53∗/wt panels; blue, DAPI. Scale bars, 20 μm. Basal, immediate suprabasal cells and basement membrane are indicated by closed and open arrows and dotted line, respectively.
(C and D) Average percentage of EdU-labeled basal cells at the 6-week time point in induced AhcreERT-p53∗/wt (D) or AhcreERT-RYFP (C) IFE. Samples were taken from UV-irradiated (purple circles) or adjacent unexposed areas (ctl, black circles). Values are mean from 5 fields per mouse. Red line indicates mean. n = 4 mice per condition. ∗p < 0.05 by paired t test. Percentage EdU in UV-irradiated epidermis in (D) was quantified in p53∗/wt clone area.
(E and F) Projected area of labeled UV irradiated and adjacent unirradiated IFE. Values are percentage from 6 fields. n = 4 mice per time point. (E) RYFP (purple, UV; black, unirradiated). (F) p53∗/wt (purple, UV; green, unirradiated).
(G) Schematic illustration of the effect of UV on clone behavior. UV increases the rate of cell division in both p53wt/wt and p53∗/wt cells but accelerates IFE colonization by mutant cells as p53∗/wt progenitors retain a bias in fate, generating more progenitor than differentiating daughters.