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Chromosome Segregation in Control Spermatocytes

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posted on 30.12.2011, 10:47 by Elena Rebollo, Salud Llamazares, José Reina, Cayetano Gonzalez
Contribution of Noncentrosomal Microtubules to Spindle Assembly in Drosophila Spermatocytes. PLoS Biol 2(1): e8. doi:10.1371/journal.pbio.0020008 Copyright: © 2004 Rebollo et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We then decided to study in more detail the extent to which the anastral spindles organised in cells with membrane-bound centrosomes can mediate successful cell division. To this end, we produced transgenic flies carrying a GFP–α-tubulin fusion together with a His2AvD–YFP (yellow fluorescent protein) strain so that both chromosomes and microtubules could be visualised in the same cell (Figure 5; Video S5). In asp cells, during prometaphase, the bivalents do not move to the extent that they do in control cells (data not shown). As mentioned before, congression occurs (Figure 5; Video S6), but orientation is rarely bipolar. Homologue chromosomes separate at the onset of anaphase, but they barely move, remaining near the center of the spindle. Moreover, they tend to cosegregate (Video S7) and end up included in the same daughter nucleus. All together, these abnormalities result in high levels of aneuploidy in agreement with previous genetic analysis data (Ripoll et al. 1985). In contrast, in half (52%) of the anastral spindles assembled following transient colcemid treatment, homologue chromosomes could be seen to segregate from one another (Figure 5; Video S8). Anaphase in these cells is not complete, however, because only the chromosome-to-pole movement (anaphase A) is observed. The further separation achieved in wild-type cells by the extension of the spindle (anaphase B) is very limited in these cells.

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