FIG. 5.

Cycling progenitor cells give rise to new Foxl2-expressing cells. A) Example of BrdU lineage tracing and data collection. In this series, pregnant females were injected with BrdU at E12.5, chased with thymidine 2 h later, and dissected after the indicated trace durations. Gonads were stained with antibodies against BrdU (magenta) and FOXL2 (green); white color indicates overlap between the markers. BrdU/FOXL2 double-positive cells (circles) were counted relative to the total number of FOXL2-positive cells and expressed as a percentage. Original magnification ×40; bar = 20 μm. B) Quantification of BrdU results. Embryonic stages listed above the bars indicate when BrdU was injected (n = 4–12 images per time point, from two to four independent gonad samples). Error bars indicate SEM. Embryos pulsed at E11.5 or E12.5 showed significantly higher proportions of BrdU/FOXL2 double-positive cells in 48-h traces relative to 24-h traces, but those injected at E13.5–E14.5 did not, suggesting that the number of new cells entering the population was proportionally much lower at later stages. *P < 0.001; n/s, not significant.