Induction of maturation in small Xenopus laevis oocytes.
The competence of Xenopus laevis oocytes in various stages of growth to respond to progesterone treatment was investigated. Full-grown (stage 6) oocytes undergo nuclear membrane dissolution and resume meiosis in response to progesterone exposure, while smaller oocytes (stages 3-5; less than 1100 micron in diameter) do not. The defect which prevents 750- to 1050-micron oocytes from responding to progesterone can be overcome by microinjecting cytoplasm withdrawn from a stage 6 oocyte. Germinal vesicle breakdown in these small oocytes occurs on a timetable similar to that of stage 6 oocytes exposed to progesterone and is accompanied by a twofold increase in protein synthesis as well as the activation of MPF. The results argue that a cytoplasmic factor(s) which probably first appears at late stage 5 is required for progesterone responsiveness. The identity and role of the factor(s) in the development of maturation competence and the regulation of maternal mRNA translation are discussed.
D000818:Animals; D003593:Cytoplasm / Q000502:physiology; D005786:Gene Expression Regulation; D006133:Growth Substances / Q000494:pharmacology; D016200:Maturation-Promoting Factor; D008540:Meiosis / Q000187:drug effects; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D009866:Oogenesis / Q000187:drug effects; D011374:Progesterone / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D013997:Time Factors; D014982:Xenopus laevis / Q000502:physiology
D006133:Growth Substances; D012333:RNA, Messenger; D011374:Progesterone; D016200:Maturation-Promoting Factor