Quantification of oocyte-specific transcripts in follicle-enclosed oocytes during antral development and maturation in vitro.
Oocyte cytoplasmic maturation is influenced by the quantity of synthesized RNA and proteins accumulated and stored during growth. Transcriptional repression and degradation of transcripts occur during oocyte nuclear maturation, and prolonged transcriptional arrest might compromise RNA stores for early development. RNA quantification of key genes in oocytes might be valuable when setting up in vitro cultures that lack the normal hormonal interplay found in vivo. This study quantifies gene expression levels in relation to follicle culture time and time of oocyte maturation in a mouse model. RNA levels of Gdf-9, Bmp-15, Mater, Zar-1, Npm-2 and Fgf-8 were measured in germinal vesicle oocytes along fixed times during in vitro follicle development. For all genes, the highest mRNA levels were detected in oocytes in the pre-antral follicle stage. Antrum formation was associated with a progressive shutdown in transcription leading to mRNA values lower than those in vivo preovulatory oocytes by extending period of in vitro culture. In contrast to in vitro-matured oocytes, the in vivo oocytes from 22- and 29-day-old prepubertal animals obtained after pregnant mare's serum gonadotrophin and human chorionic gonadotrophin priming did not down-regulate transcripts upon maturation stimulus except for Mater. These findings show that oocyte gene expression patterns under in vitro conditions can, at certain times, mimic what is reported to occur under in vivo conditions. Moreover, they also show that meiotically competent oocytes kept in a prolonged transcriptionally inactive stage express altered levels of key transcripts compared with in vivo in both immature and mature oocytes.
Sánchez
Flor
F
Follicle Biology Laboratory, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium. fsanchez@vub.ac.be
Adriaenssens
Tom
T
Romero
Sergio
S
Smitz
Johan
J
D000818:Animals; D000941:Antigens / Q000235:genetics; D055430:Bone Morphogenetic Protein 15 / Q000235:genetics; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004527:Egg Proteins / Q000235:genetics; D005260:Female; D051524:Fibroblast Growth Factor 8 / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics; D006064:Gonadotropins, Equine / Q000494:pharmacology; D055429:Growth Differentiation Factor 9 / Q000235:genetics; D006736:Horses; D006801:Humans; D051379:Mice; D018832:Molecular Chaperones / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D056489:Nucleoplasmins; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006080:Ovarian Follicle / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics
D000941:Antigens; D055430:Bone Morphogenetic Protein 15; D006063:Chorionic Gonadotropin; D004527:Egg Proteins; C496457:Fgf8 protein, mouse; C525898:Gdf9 protein, mouse; D006064:Gonadotropins, Equine; D055429:Growth Differentiation Factor 9; D018832:Molecular Chaperones; C416503:Nalp5 protein, mouse; D009687:Nuclear Proteins; D056489:Nucleoplasmins; D010750:Phosphoproteins; D012333:RNA, Messenger; C471630:Zar1 protein, mouse; D051524:Fibroblast Growth Factor 8