Figure 8. Lsd1-null MII oocytes are mostly unfertilizable.

(a,b) Morphologically ‘normal' MII oocytes isolated from superovulated control and Lsd1 KO mice were activated with strontium chloride and scored for pronuclear (PN) formation after 7 h. (a) Representative images of the oocytes following strontium chloride exposure. Arrows indicate the pronuclei. Scale bars, 80 μm. (b) The percentages of oocytes with pronuclei are shown (mean±s.e.m. of three independent experiments). Statistical comparisons of values were made using unpaired t-test. **P<0.01. (c–e) Fully grown GV oocytes collected from control and Lsd1 KO mice were incubated in maturation medium for 1 h to induce GVBD and then further cultured for 24 h with or without the CDC25 phosphatase inhibitor BN82002 (BN), as indicated. After determining the meiotic stages, the oocytes were inseminated with sperm from wild-type males, and fertilization rates (judged by PN formation) were determined after 7 h. (c) Representative images of the oocytes 7 h after insemination. Arrows indicate the pronuclei. Scale bars, 80 μm. (d) The numbers of GV arrested (grey bar), MI (white bar), MII (black bar) and fragmented (yellow bar) oocytes were counted before insemination. The average proportion of oocytes at each stage from three experiments is plotted as a percentage of the total. (e) Fertilization rates. The numbers of fertilized eggs (those with pronuclei) were counted 7 h after insemination, and they were divided by the total numbers of MII oocytes to determine the fertilization rates (mean±s.e.m. from three experiments). Statistical comparisons of values were made using one-way ANOVA. **P<0.01.