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Association between p 34 cdc2 levels and meiotic arrest in pig oocytes during early growth

1995; Cambridge University Press; Volume: 3; Issue: 4 Linguagem: Inglês

10.1017/s0967199400002756

1469-8730

Yuji Hirao, Youki Tsuji, Takashi Miyano, Akira Okano, Masashi Miyake, Seishiro KATO, R. M. Moor,

DNA Repair Mechanisms

Summary The molecules involved in determining meiotic competence were determined in porcine oocytes isolated from preantral and antral follicles of different sizes. Oocytes isolated from preantral follicles had a mean diameter of 78 μm, contained diffuse filamentous chromatin in the germinal vesicle and were incapable of progressing from the G 2 to the M phase of the cycle even after 72 h in culture. Oocytes from early antral follicles had a mean diameter of 105 μm, showed a filamentous chromatin configuration and about half resumed meiosis but arrested at metaphase I (MI) when cultured. Oocytes from mid-antral (3–4 mm) and large antral follicles (5–6 mm) had mean oocyte diameters of 115 and 119 μm respectively, contained condensed chromatin around the nucleolus and progressed to metaphase II (MII) in 48% and 93% of instances respectively. Analysis of p 34 cdc2 , the catalytic subunit of maturation promoting factor (MPF), by immunoblotting indicates that the inability of small (78 μm) oocytes to resume meiosis is due, at least in part, to inadequate levels of the catalytic subunit of MPF. On the other hand, the inability of intermediate-sized (105 μm) oocytes from antral follicles to complete the first meiotic division by progressing beyond MI appears not to be limited by levels of p 34 cdc2 , which are maximal by this stage. We postulate that an inadequacy of molecules other than p 34 cdc2 limits progression of MI to MII; the acquisition of these molecules during the final stages of growth may be correlated with the formation of the perinucleolar chromatin rim in the germinal vesicle.