title: Chromatin configurations in the germinal vesicle of mammalian oocytes.
abstract: In all the studied mammalian species, chromatin in the germinal vesicle (GV) is initially decondensed with the nucleolus not surrounded by heterochromatin (the NSN configuration). During oocyte growth, the GV chromatin condenses into perinucleolar rings (the SN configuration) or other corresponding configurations with or without the perinucleolar rings, depending on species. During oocyte maturation, the GV chromatin is synchronized in a less condensed state before germinal vesicle breakdown (GVBD) in species that has been minutely studied. Oocytes may also take on a SN/corresponding configuration during early atresia, but they undergo GVBD at the advanced stage of atresia. As not all the species show the SN configuration while in all the species, gene transcription always stops at the late stage of oocyte growth, it is suggested that not the formation of perinucleolar rings but a thorough condensation of GV chromatin is essential for transcriptional repression. The GV chromatin configuration is highly correlated with oocyte competence; oocytes must end the NSN configuration before they gain the full meiotic competence, and they must take on the SN/corresponding configurations and stop gene transcription before they acquire the competence for early embryonic development. While factors inhibiting follicle atresia tend to synchronize oocytes in a chromatin configuration toward maturation, factors inducing follicle atresia tend to synchronize oocytes in a chromatin configuration reminiscent of early atresia. Furthermore, although condensation of GV chromatin is associated with transcriptional repression, both processes may not be associated with histone deacetylation during oocyte growth.
authors.affiliation: Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, Shandong Province 271018, Peolple's Republic of China. tanjh@sdau.edu.cn
authors.forename: Jing-He
authors.initials: JH
authors.lastname: Tan
authors.forename: Hui-Li
authors.initials: HL
authors.lastname: Wang
authors.forename: Xing-Shen
authors.initials: XS
authors.lastname: Sun
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.forename: Hong-Shu
authors.initials: HS
authors.lastname: Sui
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002843:Chromatin / Q000235:genetics*; D005260:Female; D006570:Heterochromatin / Q000235:genetics; D006801:Humans; D008322:Mammals; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D002843:Chromatin; D006570:Heterochromatin