Induction of DNA replication in germinal vesicles and in nuclei formed in maturing mouse oocytes by 6-DMAP treatment

Abstract

Immature mouse oocytes (germinal vesicle stage, GV), oocytes at different stages during maturation (prometaphase to anaphase I) and matured oocytes (metaphase II arrested) were cultured in 6-dimethylaminopurine (6-DMAP)-supplemented medium also containing bromodeoxyuridine for the assessment of DNA replication in these cells. Immature oocytes remained arrested at the GV stage and DNA replication was never detected in them. On the other hand, oocytes at the prometaphase to anaphase-telophase I stages responded to 6-DMAP treatment by forming nuclei which synthesised DNA. Mature (metaphase II) oocytes did not respond to 6-DMAP and their chromatin remained condensed. DNA synthesis could even be induced in GV-staged oocytes, but only when they were fused to freshly activated oocytes and incubated in 6-DMAP-supplemented medium.

Telomere lengths in human oocytes, cleavage stage embryos and blastocysts

“…Therefore, the interpretations of data are subject to potential errors because these factors cannot be quantified in human material. For analysis, GV stage oocytes were used as a standard, because such oocytes are arrested in the diplotene stage of meiotic prophase I, their DNA having already replicated, and further replication being inhibited at this stage (Fulka et al ., 1997; Whitmire et al ., 2002). In view of the expected variation in the stage of the mitotic cycle in blastomeres, all blastomeres would be predicted to contain between half and the same number of telomere signals as for GV oocytes (which we confirm in our results), assuming a similar extent of telomere clustering.…”