Figure 4.

Ooep protects oocytes from DNA DSB-induced apoptosis and meiosis delay

A: Postnatal day 5 (P5) ovaries from WT and Ooep^tm/tm females were subjected to the same cisplatin treatment. TUNEL examination showed that the numbers of apoptotic germ cells (DDX4⁺TUNEL⁺, arrowheads) were higher in Ooep^tm/tm ovaries than in WT ovaries. B: HE staining revealed that ovaries from 4-week-old Ooep^tm/tm females contained more primordial and primary follicles than those from WT females (left panel). At 16-week old, Ooep^tm/tm ovaries contained less primordial and primary follicles than WT ovaries (right panel). Ten ovarian sections were examined for each animal and five females were used at each stage. C: The germinal vesicle breakdown (GVBD) of Ooep^tm/tm oocytes was delayed compared to the WT oocytes under normal conditions. There was a 4-h difference in the timing of 50%-GVBD between the two samples. More than 80 oocytes were used in each sample. D: Kinetics of the first polar body extrusion (PBE) in WT and Ooep^tm/tm GV oocytes under normal conditions. Ooep^tm/tm oocytes displayed 2-h delay in reaching 50%-PBE. More than 50 oocytes were used in each sample. E: mRNA expression of Ooep declined with maternal aging in GV oocytes. Fourteen single GV oocytes from two females were examined at each stage. Data are presented as mean±SEM. *: P<0.05, **: P<0.01, ***: P<0.001.