Mutations in the Drosophila melanogaster gene three rows permit aspects of mitosis to continue in the absence of chromatid segregation
Abstract
We have cloned the three rows (thr) gene, by a combination of chromosome microdissection and P element tagging. We describe phenotypes of embryos homozygous for mutations at the thr locus. Maternal mRNA and protein appear to be sufficient to allow 14 rounds of mitosis in embryos homozygous for thr mutations. However, a small percentage of cells in syncytial blastoderm stage thr embryos sink into the interior of the embryo as if they have failed to divide properly. Following cellularisation all cells complete mitosis 14 normally. All cells become delayed at mitosis 15 with their chromosomes remaining aligned on the spindle in a metaphase-like configuration, even though both cyclins A and B have both been degraded. As cyclin B degradation occurs at the metaphase-anaphase transition, subsequent to the microtubule integrity checkpoint, the delay induced by mutations at the thr locus defines a later point in mitotic progression. Chromosomes in the cells of thr embryos do not undertake anaphase separation, but remain at the metaphase plate. Subsequently they decondense. A subset of nuclei go on to replicate their DNA but there is no further mitotic division.
Additional Information
© 1993 by Company of Biologists. (Received 10 May 1993 - Accepted 28 May 1993) We are extremely grateful for the assistance of Fiona Cullen who made sequencing almost bearable. We thank Christiane Nusslein-Volhard for pointing out to D.M.G. in 1984 that thr was likely to be a mitotic mutant. We also thank Alfonso Martinez-Arias for drawing our attention to the dysgenic thr alleles. We are especially grateful to Sarah Bray for providing the marked CyO ftz-lacZ balancer and for the previously unpublished thr^(SJB22) allele. In the course of this work we became aware that the laboratories of Robert Saint and Christian Lehner were carrying out similar experiments. They have been extremely helpful in generously exchanging data prior to publication. Flies were obtained from the Tübingen and Bloomington stock centers. Finally we thank our colleagues in the lab. Their robust criticism is always enlightening. The work was supported by the Cancer Research Campaign and the Wellcome Trust. A.V.P. holds a Wellcome Trust studentship.Attached Files
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Additional details
- Eprint ID
- 105594
- Resolver ID
- CaltechAUTHORS:20200928-145945750
- Cancer Research Campaign
- Wellcome Trust
- Created
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2020-09-28Created from EPrint's datestamp field
- Updated
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2020-10-01Created from EPrint's last_modified field