• although growing oocytes derived from day-14 mice have normal size and morphology, oocytes show impaired growth from day 14 to day 21, resulting in a significantly decreased oocyte diameter at day 21
• in addition to smaller size, oocytes exhibit a thinner zona pellucida, enlarged perivitelline space, and increased granularity in the ooplasm
• oocytes from day-21 mice show large-scale accumulation of RNAs in the nucleus and blockage of cytoplasmic mRNA storage
• immunofluorescent staining of PABPN1 and SRSF2 shows absence of nuclear speckles in oocytes derived from day-21 mice
• growing oocytes from day-14 mice show an non-surrounded nucleoli (NSN) chromatin configuration, whereas all oocytes from day-21 mice fail to accomplish the NSN-to-SN (surrounded nucleoli) transition
• no nucleolus-like structures are formed in day-21 oocytes