Sequential observation of mitochondrial distribution in mouse oocytes and embryos.
OBJECTIVE
The purpose of this study was to elucidate changes in the distribution of mitochondria through the cell cycle.


METHODS
Mouse oocytes and embryos were recovered sequentially from mice and stained with the vital fluorescent mitochondrial stain rhodamine 123. Mitochondrial staining pattern were classified into three types: aggregation (Ag), homogeneous (H), and perinuclear accumulation (PA).


RESULTS
Sequential observations revealed that mitochondria of oocytes and embryos grown in vivo translocated in the cytoplasm during the cell cycle, showing the H pattern before human chorionic gonadotropin (hCG) administration, the PA pattern 8-9 hr post-hCG, the H pattern again 10-14 hr post-hCG, and the PA pattern again 24 and 31-32 hr post-hCG following fertilization. In the two-cell stage, the Ag pattern was shown 35 hr post-hCG, the H pattern was observed 40 hr post-hCG, and the PA pattern was found 48 hr post-hCG. In the embryos cultured in vitro and showing developmental block, mitochondrial translocation was shown to be inhibited after they aggregated in the early two-cell stage (35 hr post-hCG). Moreover, the translocation of mitochondria was restored by the addition of superoxide dismutase or thioredoxin to the culture medium. Both of these enzymes have already been shown to have the ability to overcome developmental block.


CONCLUSIONS
The present study revealed that mitochondria translocated in the cell cycle and suggested that there is a close relationship between mitochondrial translocation and developmental arrest.
Tokura
T
T
Department of Gynecology and Obstetrics, Kyoto University Faculty of Medicine, Japan.
Noda
Y
Y
Goto
Y
Y
Mori
T
T
D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D002467:Cell Nucleus / Q000648:ultrastructure; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004622:Embryo, Mammalian / Q000648:ultrastructure*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000648:ultrastructure*; D009865:Oocytes / Q000648:ultrastructure*; D011247:Pregnancy; D020112:Rhodamine 123; D012235:Rhodamines; D013194:Staining and Labeling; D013482:Superoxide Dismutase / Q000494:pharmacology; D013879:Thioredoxins / Q000494:pharmacology
D006063:Chorionic Gonadotropin; D012235:Rhodamines; D020112:Rhodamine 123; D013879:Thioredoxins; D013482:Superoxide Dismutase