Localization of mitotic arrest deficient 1 (MAD1) in mouse oocytes during the first meiosis and its functions as a spindle checkpoint protein.
The present study was designed to investigate the localization of mitotic arrest deficient 1 (MAD1) in mouse oocytes during meiotic maturation and its relationship with kinetochores, chromosomes, and microtubules. Oocytes at various stages during the first meiosis were fixed and immunostained for MAD1, kinetochores, microtubules, and chromosomes. The stained oocytes were examined by confocal microscopy. Some oocytes were treated with nocodazole or Taxol before examination. The anti-MAD1 antibody was injected into the oocytes at the germinal vesicle (GV) stage for examination of chromosome alignment and spindle formation. It was found that MAD1 was present in the oocytes from the GV to prometaphase I stages around the nuclei. When the oocytes reached the metaphase I (M-I) to metaphase II (M-II) stages, MAD1 was mainly localized at the spindle poles. However, MAD1 relocated to the vicinity of the chromosomes when spindles were disassembled by nocodazole or cooling, and the relocated MAD1 moved back to the spindle poles during spindle recovery. Taxol treatment did not affect the MAD1 localization. Although anti-MAD1 antibody injection did not affect nuclear maturation, significantly higher proportions of injected oocytes had misaligned chromosomes when the oocytes reached the M-I to M-II stages. The results of the present study indicate that MAD1 is present in mouse oocytes at all stages during the first meiosis and that it participates in spindle checkpoint during meiosis. However, MAD1 could not check misaligned chromosomes during spindle recovery after the spindles were destroyed by drug or cooling, which caused some chromosomes to scatter in the oocytes.
Zhang
Dong
D
State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China.
Li
Ming
M
Ma
Wei
W
Hou
Yi
Y
Li
Yong-Hai
YH
Li
Shi-Wen
SW
Sun
Qing-Yuan
QY
Wang
Wei-Hua
WH
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics; D002478:Cells, Cultured; D033481:Chromosomes, Mammalian / Q000235:genetics / Q000378:metabolism; D005260:Female; D018386:Kinetochores / Q000187:drug effects / Q000378:metabolism; D008540:Meiosis; D051379:Mice; D008815:Mice, Inbred Strains; D008845:Microinjections; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D017239:Paclitaxel / Q000494:pharmacology; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism*
D000906:Antibodies; D018797:Cell Cycle Proteins; C501385:Mad1l1 protein, mouse; D009687:Nuclear Proteins; D017239:Paclitaxel; D015739:Nocodazole