Epab and Pabpc1 are differentially expressed in the postnatal mouse ovaries

In the present study, we first aimed to characterize expression levels of the Epab and Pabpc1 genes in the prepubertal (1-, 2-, and 3-week old), pubertal (4-, 5-, and 6-week old), postpubertal (16-week and 18-week old), and aged (52-, 60-, and 72-week old) mouse ovaries by using quantitative real-time polymerase chain reaction (qRT-PCR). Epab mRNA was predominantly expressed in the prepubertal ovaries when compared to later developmental periods. However, Pabpc1 transcript was highly generated in the prepubertal and pubertal mouse ovaries except for 1-week old ovary than those of other developmental terms. In the prepubertal mouse ovaries, RNA in situ hybridization localized both Epab and Pabpc1 transcripts in the cytoplasm of oocytes and granulosa cells of all follicular stages. Consistently, Epab and Pabpc1 gene expression were detected in the cumulus cells and MII oocytes obtained from cumulus oocyte complexes (COCs). Ovarian follicle counting in the postnatal ovaries revealed that total number of follicles was higher in the prepubertal ovaries in comparison with later stages of development. As a result, Epab and Pabpc1 expression exhibit differences at postnatal ovary development stages and both genes are transcribed in the granulosa cells and oocytes. These findings suggest that EPAB may predominantly play roles in translational regulation of the mRNAs during early oogenesis and folliculogenesis, but PABPC1 most likely perform these roles in the later terms of ovarian development along with EPAB protein.