E4.5 chimeric embryos stained for tdTomato and DAPI.   Quantification of donor cells' contribution in E4.5 blastocysts, Mann-Whitney test, data represent mean ± SD; Ronin fl/del n embryos = 26, Ronin del/del n embryos = 27.   Diapause embryos stained for tdTomato and DAPI.   Quantification of donor cells' contribution in diapause embryos, unpaired Student's t test, data represent mean ± SD, Ronin fl/del n embryos = 4, Ronin del/del n embryos = 12.   E5.5 chimeric embryos stained for tdTomato and DAPI.   Quantification of donor cells' contribution in E5.5 embryos, unpaired Student's t test, data represent mean ± SD, Ronin fl/del n embryos = 21, Ronin del/del n embryos = 15.   Reactivated E5.5 chimeric embryos stained for tdTomato and DAPI.   Quantification of donor cells' contribution in reactivated E5.5 embryos, Mann-Whitney test, data represent mean ± SD, Ronin fl/del n embryos = 17, Ronin del/del n embryos = 12.   