Wapl mRNA injection in GV oocytes prevents the increase in cohesin levels observed upon Wapl depletion. Wapl depletion in oocytes using Zp3-Cre does not affect meiotic recombination, but leads to an increase in DNA breaks in mature oocytes. (A) Representative images of pro-metaphase I chromosome spreads of Wapl^fl/fl, Wapl^Δ/Δ, and Wapl^Δ/Δ oocytes injected with Wapl mRNA. Centromeres are shown in red, Smc3 in gray, and DNA in blue. Scale is the same in all images; scale bar, 10 µm. (B) Quantification of Smc3 fluorescence intensity per bivalent in relation to CREST fluorescence intensity in Wapl^fl/fl, Wapl^Δ/Δ, and Wapl^Δ/Δ oocytes injected with Wapl mRNA. Approximately 10 oocytes were analyzed per condition. (C) Representative images of pachytene Wapl^fl/fl and Wapl^Δ/Δ oocytes isolated from 17.5 d Wapl^fl/fl and Wapl^fl/fl (Tg)Zp3-Cre female embryos. Chromosome spreads were stained with anti-MLH1 antibody to visualize recombination foci (magenta) and with anti-Sycp1 antibody to visualize synaptonemal complex (green). Scale is the same in all images; scale bar, 10 µm. (D) Number MLH1 foci was quantified in Wapl^fl/fl and Wapl^Δ/Δ oocytes. The number of pachytene oocytes analyzed is indicated in the figure. P value is 0.054 (Mann-Whitney test), indicating the difference observed is not significant. (E) Representative images of in situ fixed Wapl^fl/fl and Wapl^Δ/Δ GV-oocytes in SN state (mature, SN). DNA is shown in blue and γH2AX in gray. Scale is the same in all images; scale bar, 10 µm. (F) Number γH2AX foci was quantified in Wapl^fl/fl and Wapl^Δ/Δ oocytes. The number of oocytes analyzed is indicated in the figure. P value is <0.0001 (****, unpaired t test), indicating the difference observed is significant.