Ozturk Saffet, Sozen Berna, Demir Necdet
Department of Histology and Embryology, School of Medicine, Akdeniz University, Campus, 07070, Antalya, Turkey.
J Assist Reprod Genet. 2015 Jan;32(1):137-46. doi: 10.1007/s10815-014-0362-5. Epub 2014 Nov 5.
Embryonic poly(A)-binding protein (EPAB) and poly(A)-binding protein, cytoplasmic 1 (PABPC1) bind poly(A) tails of mRNAs and mediate their translational regulation in germ cells and early preimplantation embryos. Although expression patterns and possible functions of the Epab and Pabpc1 genes have been examined in vertebrate germ cells and early embryos, their expression levels and cellular localizations in the postnatal mouse ovaries remained elusive.
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.
胚胎多聚腺苷酸结合蛋白（EPAB）和细胞质多聚腺苷酸结合蛋白1（PABPC1）结合mRNA的多聚腺苷酸尾，并在生殖细胞和植入前早期胚胎中介导其翻译调控。尽管已经在脊椎动物生殖细胞和早期胚胎中研究了Epab和Pabpc1基因的表达模式及可能的功能，但它们在出生后小鼠卵巢中的表达水平和细胞定位仍不清楚。
在本研究中，我们首先旨在通过定量实时聚合酶链反应（qRT-PCR）来表征Epab和Pabpc1基因在青春期前（1、2和3周龄）、青春期（4、5和6周龄）、青春期后（16周和18周龄）以及老年（52、60和72周龄）小鼠卵巢中的表达水平。
与后期发育阶段相比，Epab mRNA在青春期前卵巢中表达占主导。然而，除1周龄卵巢外，Pabpc1转录本在青春期前和青春期小鼠卵巢中的生成量高于其他发育阶段。在青春期前小鼠卵巢中，RNA原位杂交将Epab和Pabpc1转录本定位在所有卵泡阶段卵母细胞和颗粒细胞的细胞质中。同样，在从卵丘卵母细胞复合体（COC）获得的卵丘细胞和MII卵母细胞中检测到了Epab和Pabpc1基因表达。对出生后卵巢中的卵泡进行计数发现，与发育后期相比，青春期前卵巢中的卵泡总数更多。
因此，Epab和Pabpc1的表达在出生后卵巢发育阶段存在差异，且这两个基因均在颗粒细胞和卵母细胞中转录。这些发现表明，EPAB可能在早期卵子发生和卵泡发生过程中主要在mRNA的翻译调控中发挥作用，但PABPC1很可能在卵巢发育后期与EPAB蛋白一起发挥这些作用。
