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First published online December 20, 2005
doi: 10.1242/10.1242/dev.02193

Development 133, 343-350 (2006)
Published by The Company of Biologists 2006
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Centrosome destined to decay in starfish oocytes

Yukako Shirato1,2,*, Miwa Tamura1,2, Mitsuki Yoneda3 and Shin-ichi Nemoto1,2,{dagger}

1 Department of Biology, Faculty of Science, Ochanomizu University, Bunkyo, Tokyo 112-8610, Japan.
2 Tateyama Marine Laboratory, Marine and Coastal Research Center, Ochanomizu University, Koh-yatsu, Umi-no-Hoshi, Tateyama, Chiba 294-0301, Japan.
3 Takiyama 5-7-7, Higashikurume, Tokyo 203-0033, Japan.

{dagger} Author for correspondence (e-mail: snemo{at}cc.ocha.ac.jp)

Accepted 1 November 2005

In contrast to the somatic cell cycle, duplication of the centrioles does not occur in the second meiotic cycle. Previous studies have revealed that in starfish each of the two centrosomes in fully-grown immature oocytes consists of two centrioles with different destinies: one survives and retains its reproductive capacity, and the other is lost after completion of meiosis. In this study, we investigated whether this heterogeneity of the meiotic centrioles is already determined before the re-initiation of meiosis. We prepared a small fragment of immature oocyte containing the four centrioles and fused it electrically with a mature egg in order to transfer two sets of the premeiotic centrioles into the mature cytoplasm. Two asters were present in this conjugate, and in each of them only a single centriole was detected by electron microscopy. In the first mitosis of the conjugate artificially activated without sperm, two division poles formed, each of which doubled in each subsequent round of mitosis. These results indicate that only two of the four premeiotic centrioles survived in the mature cytoplasm and that they retained their reproductive capacity, which suggests that the heterogeneity of the maternal centrioles is determined well before re-initiation of meiosis, and that some factor in the mature cytoplasm is responsible for suppressing the reproductive capacity of the centrioles destined to decay.

Key words: Centrioles, Centrosomes, Centrosome regulation, Centrosome duplication, Electrofusion, Maturation division, Meiosis, Starfish






© The Company of Biologists Ltd 2006