Wapl predominantly controls chromatin-associated levels of Scc1-cohesin in mouse oocytes. (A) Representative images of pro-metaphase I spreads of Wapl^fl/fl and Wapl^Δ/Δ oocytes. Centromeres are shown in red, Smc3, Scc1, and Rec8 in gray, and DNA in blue. Scale bar, 10 µm; inset scale bar, 5 µm. (B) Quantification of Smc3, Smc1α, Rec8, and Scc1 fluorescence intensities per bivalent in relation to CREST fluorescence intensities in Wapl^fl/f and Wapl^Δ/Δ oocytes. This ratio of fluorescent intensities is presented in arbitrary units (AU). For Smc3 and Rec8 quantifications, three Wapl^fl/fl and three Wapl^fl/fl (Tg)Zp3-Cre littermate females were analyzed. For Smc1α quantifications, two Wapl^fl/fl and two Wapl^fl/fl (Tg)Zp3-Cre littermate females were analyzed. For Scc1 quantifications, two Wapl^fl/fl and two Wapl^fl/fl (Tg)Zp3-Cre littermate females were analyzed. The total number of oocytes analyzed per condition is indicated in the figure. Fluorescence intensities are shown in a whisker plot graph indicating the median, first and third quartiles, and minimum and maximum values. P values are <0.0001 (Welch’s t test). (C) Quantification of chiasma-like structures per bivalent in Wapl^fl/fl and Wapl^Δ/Δ oocytes. Error bars show SEM of three independent experiments (10 oocytes per condition, per experiment). Representative images of bivalent chromosome structure are shown, with Rec8 in gray, centromeres in red, and DNA in blue. The white arrowheads indicate the structures that we classified as chiasma-like structures. Scale bar, 5 µm.