Biomedical subjects

M Zernicka-Goetz

Publications and source records attributed to M Zernicka-Goetz.

21 records · Page 2Linked to original sources

PubMed1993

Okadaic acid affects spindle organization in metaphase II-arrested rat oocytes.

We used okadaic acid (OA), a potent phosphatase inhibitor, to study the role of phosphatases in the organization of the spindle microtubules in metaphase II-arrested rat oocytes. OA induced a dramatic elongation of the spindle and disorganization of the metaphase plate. Biochemical analysis revealed some dramatic changes after OA treatment: increased histone H1 kinase activity, a burst of protein phosphorylation, and inhibition of protein synthesis. The latter effect alone cannot be responsible for the changes in the spindle structure since inhibition of protein synthesis with puromycin had no such effect. To identify the targets of OA among the proteins associated with the spindle, meiotic spindles of OA-treated and control oocytes were purified. After OA treatment some proteins gained and others lost their association with the spindle. A few proteins that lost their affinity for the spindle also underwent hyperphosphorylation after OA treatment. These results suggest that hyperphosphorylation of some proteins associated with the spindle alters their affinity to microtubules and thus stabilizes them.

Animals↗

PubMed1993

Full activation of the rat oocyte by protein synthesis inhibition requires protein phosphatase activity.

The rat oocyte provides an interesting system in which to dissect the control mechanisms involved in the transition between a meiotic M phase and a mitotic interphase. In this study, we show that in rat oocytes activated parthenogenetically by puromycin, okadaic acid (a potent inhibitor of protein phosphatases 1 and 2A) induced an increase in histone H1 kinase activity suggesting that MPF was reactivated. However, the inhibition of phosphatases 1 and 2A shortly after second polar body extrusion did not allow the formation of a metaphase-like spindle, although microtubule polymerization was not inhibited. Instead, the chromatin remained condensed as a single mass and a large aster formed around it.

Animals↗

PubMed1991

Spontaneous and induced activation of rat oocytes.

Ovulated rat oocytes undergo spontaneous activation during in vitro culture. After extrusion of the second polar body, they do not enter interphase but are arrested again in next metaphase-like stage (M III arrest). The present study demonstrates that puromycin and chloral hydrate can trigger transition to interphase of metaphase II and spontaneously (incompletely) activated rat oocytes. The response of oocytes to these activators depends on their stage at the time of application of a stimulus. Metaphase II oocytes enter interphase at 86.8% when treated with puromycin and in 28.7% after chloral hydrate activation. Oocytes activated with chloral hydrate at the time of spontaneously induced anaphase II enter interphase at 64.8%, but after reaching the stage of telophase II their capability to shift to interphase is again low (28.8%). Finally, M III oocytes cannot be forced to enter interphase by either chloral hydrate or puromycin treatment. This study shows that resumption of the second meiotic division and transition to interphase--the two processes that normally occur in succession as a response to oocyte activatin--can be experimentally separated.

Animals↗