Cell cycle-dependent dynamics of cytoskeleton involving mitochondrial redistribution in hamster embryos

Mitochondria-cytoskeleton interactions were studied in the hamster embryos during interphase and M phase of the cell cycle. Two-cell embryos were cultured for 1 h with nocodazole, cytochalasin D or in a combination of both inhibitors and then centrifuged at 10,000 × g for 2 min. The control embryos were only centrifuged with no inhibitor treatment. Centrifuged embryos were fluorescently stained to examine the distribution of active mitochondria and nuclear configuration. In the control 2-cell embryos, most mitochondria were accumulated at the perinuclear region with some at the cell cortex. Neither each inhibitor nor centrifugation did affect the distribution of mitochondria in interphase blastomeres. However, mitochondria were spun down towards the centrifugal pole in 71% (n = 41) of the interphase blastomeres treated with centrifugation following a combination of nocodazole plus cytochalasin D, suggesting that both microtubules and microfilaments may involve in mitochondrial redistribution during interphase of the cell cycle. In contrast, when M-phase blastomeres were treated with all drug treatments applied, including cytochalasin D, mitochondria had been usually dislocated in a unipolar cluster, suggesting that microfilaments, not microtubules, may involve in the mitochondrial redistribution during M phase of the cell cycle. The data indicate that microfilaments function in mitochondrial redistribution regardless of the stages of the cell cycle and that microtubules may strongly associate with mitochondria during the interphase but dissociate from them during the M phase.