Otsuka-Kanazawa Saori, Ichii Osamu, Kon Yasuhiro
Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Mech Dev. 2015 Aug;137:23-32. doi: 10.1016/j.mod.2015.04.002. Epub 2015 Apr 16.
In general, mammalian males produce only spermatozoa in their testes and females produce only oocytes in their ovaries. However, newborn MRL/MpJ male mice produce oocytes within their testes. In this study, we examined the initiation and progression of oogenesis in fetal and neonatal MRL/MpJ mouse testes and evaluated the characteristics of testicular oocytes. Germ cells with positive reactions to oogenesis markers such as NOBOX oogenesis homeobox and synaptonemal complex protein 3 were observed in the MRL/MpJ fetal testes on embryonic day 18.5. These fetal testicular oocytes possessed maternal-specific methylation patterns of histone and DNA. The level of DNA methylation was still low in postnatal testicular oocytes at day 14 after birth. Additionally, the postnatal testicular oocytes contained both X and Y chromosomes and had the ability to fuse with sperm. These results suggest that some XY germ cells in fetal testes of MRL/MpJ mice enter meiosis prematurely, undergo oogenesis, and differentiate into oocytes. In addition, MRL/MpJ testicular oocytes have the ability to carry on oogenesis before and shortly after birth until they obtain some of the morphological, epigenetic, and functional characteristics of oocytes.
一般来说，哺乳动物雄性的睾丸仅产生精子，雌性的卵巢仅产生卵母细胞。然而，新生的MRL/MpJ雄性小鼠在其睾丸内产生卵母细胞。在本研究中，我们检查了胎儿和新生MRL/MpJ小鼠睾丸中卵子发生的起始和进程，并评估了睾丸卵母细胞的特征。在胚胎第18.5天的MRL/MpJ胎儿睾丸中观察到对卵子发生标记物如NOBOX卵子发生同源框和联会复合体蛋白3呈阳性反应的生殖细胞。这些胎儿睾丸卵母细胞具有母体特异性的组蛋白和DNA甲基化模式。出生后第14天的睾丸卵母细胞中DNA甲基化水平仍然较低。此外，出生后的睾丸卵母细胞含有X和Y染色体，并且具有与精子融合的能力。这些结果表明，MRL/MpJ小鼠胎儿睾丸中的一些XY生殖细胞过早进入减数分裂，进行卵子发生，并分化为卵母细胞。此外，MRL/MpJ睾丸卵母细胞在出生前和出生后不久具有进行卵子发生的能力，直到它们获得卵母细胞的一些形态、表观遗传和功能特征。
