Fig. 1: Mouse GVOs undergo an NSN-SN transition through an intermediate stage in late oogenesis.

a Representative images of the three types of chromatin configurations in mouse germinal vesicle oocytes (GVOs) stained with Hoechst 33342. Scale bar = 20 μm. b Representative images of EU staining of the different types of GVOs. INT-GVOs were further categorized into early, mid, and late depending on the formation of the perinucleolar ring. EU signal intensity was equally adjusted (EU adj.) to compare the EU signals of INT-GVOs. Scale bar = 10 μm. c Quantification of EU signal intensity in NSN-, INT-, and SN-GVOs. EU signals were normalized to NSN-GVOs. Each dot represents a single oocyte (n = 10 for NSN, n = 12 for INT, and n = 15 for SN; data are derived from three independent experiments). The box plot is showing the interquartile (box), median (horizontal line), minimum and maximum values (error bars). Statistical significance was calculated using one-way analysis of variance (ANOVA with Tukey’s multiple comparison test). d Representative immunofluorescence images of the three types of GVOs analyzed for DDX21 (n > 10 for each type from two independent experiments). Scale bar = 10 μm. e Hoechst 33342 staining of NSN-GVOs 0 h and 24 h after isolation, cultured in IVM media supplemented with IBMX. The asterisk indicates the position of the nucleolus. Scale bar = 20 μm. f Quantification of the transition of NSN-GVOs at different timepoints. NSN-GVOs were isolated, sorted, and cultured under maturation inhibiting conditions for 48 h (n = 42 NSN-GVOs from two independent experiments).