Generation and characterization of Oct4-HS-RG and Oct4-HS-CR transgenic mice. A, Schematic of the Oct4-HS-RG and Oct4-HS-CR gene constructs. cHS4 = chicken hypersensitive site 4; SS = endoplasmic reticulum signal peptide; pA = bovine growth hormone polyadenylation signal. B, C, Oct4-HS-RGtg/+ E13.5 testis. Left panels, H2B-mCherry; center panels, EGFP-GPI; right panels, composite images. B, Four cords with germ cells (arrowheads). Scale bar = 100 μm. C, Arrow indicates a germ cell in anaphase. Scale bar = 50 μm. D, Oct4-HS-CRtg/+ E12.5 testis; composite. Scale bar = 100 μm. E, Oct4-HS-CRtg/+ E12.5 ovary; composite. Scale bar = 100 μm. F, Frames at different hours from a time-lapse video of an Oct4-HS-RGtg/+ E11.5 gonad. Arrowhead indicates a cell that undergoes mitosis during the video.