During meiosis, a single round of DNA replication is followed by two rounds of chromosome segregation, called meiosis I and meiosis II. At meiosis I, homologous chromosomes recombine and then segregate to opposite poles, while the sister chromatids segregate from each other at meoisis II. In vertebrates, immature oocytes are arrested at the PI (prophase of meiosis I). The resumption of meiosis is stimulated by progesterone, which carries the oocyte through two consecutive M-phases (MI and MII) to a second arrest at MII. The key activity driving meiotic progression is the MPF (maturation-promoting factor), a heterodimer of CDC2 (cell division cycle 2 kinase) and cyclin B. In PI-arrested oocytes, MPF is initially inactive and is activated by the dual-specificity CDC25C phosphatase as the result of new synthesis of Mos induced by progesterone. MPF activation mediates the transition from the PI arrest to MI. The subsequent decrease in MPF levels, required to exit from MI into interkinesis, is induced by a negative feedback loop, where CDC2 brings about the activation of the APC (anaphase-promoting complex), which mediates destruction of cyclin B. Re-activation of MPF for MII requires re-accumulation of high levels of cyclin B as well as the inactivation of the APC by newly synthesized Emi2 and other components of the CSF (cytostatic factor), such as cyclin E or high levels of Mos. CSF antagonizes the ubiquitin ligase activity of the APC, preventing cyclin B destruction and meiotic exit until fertilization occurs. Fertilization triggers a transient increase in cytosolic free Ca2+, which leads to CSF inactivation and cyclin B destruction through the APC. Then eggs are released from MII into the first embryonic cell cycle.
kegg.pathway:hsa04114
RO:0002162
)
BFO:0000051
)
ncbigene:8881
ncbigene:805
ncbigene:801
ncbigene:3479
ncbigene:27330
ncbigene:5535
ncbigene:5533
ncbigene:9748
ncbigene:5534
ncbigene:3480
ncbigene:64682
ncbigene:387778
ncbigene:3710
ncbigene:27127
ncbigene:728622
ncbigene:63928
ncbigene:51434
ncbigene:51433
ncbigene:286151
ncbigene:8243
ncbigene:9985
ncbigene:6300
ncbigene:8945
ncbigene:5613
ncbigene:6500
ncbigene:23291
ncbigene:51806
ncbigene:109
ncbigene:108
ncbigene:5347
ncbigene:107
ncbigene:9978
ncbigene:10734
ncbigene:5241
ncbigene:7529
ncbigene:815
ncbigene:699
ncbigene:816
ncbigene:817
ncbigene:818
ncbigene:5566
ncbigene:5567
ncbigene:5568
ncbigene:26271
ncbigene:151648
ncbigene:9232
ncbigene:810
ncbigene:996
ncbigene:995
ncbigene:89869
ncbigene:991
ncbigene:7534
ncbigene:7533
ncbigene:808
ncbigene:891
ncbigene:7532
ncbigene:7531
ncbigene:898
ncbigene:10744
ncbigene:114
ncbigene:115
ncbigene:112
ncbigene:113
ncbigene:111
ncbigene:245711
ncbigene:983
ncbigene:9700
ncbigene:10393
ncbigene:3630
ncbigene:51529
ncbigene:5604
ncbigene:196883
ncbigene:6196
ncbigene:6197
ncbigene:8454
ncbigene:5501
ncbigene:5500
ncbigene:5499
ncbigene:64506
ncbigene:5595
ncbigene:29882
ncbigene:4085
ncbigene:29945
ncbigene:5594
ncbigene:6195
ncbigene:10971
ncbigene:8697
ncbigene:3708
ncbigene:3709
ncbigene:6790
ncbigene:5516
ncbigene:9126
ncbigene:5515
ncbigene:5518
ncbigene:367
ncbigene:5519
ncbigene:25847
ncbigene:4342
ncbigene:9088
ncbigene:1017
ncbigene:246184
ncbigene:5532
ncbigene:5530
ncbigene:5525
ncbigene:9134
ncbigene:9133
ncbigene:5529
ncbigene:10459
ncbigene:5528
ncbigene:5527
ncbigene:5526
ncbigene:11261
ncbigene:163688