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Australin: a chromosomal passenger protein required specifically for Drosophila melanogaster male meiosis.

Gao S, Giansanti MG, Buttrick GJ, Ramasubramanyan S, Auton A, Gatti M, Wakefield JG - J. Cell Biol. (2008)

Bottom Line: Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust).We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC.Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oxford, OX1 3PS Oxford, England, UK.

ABSTRACT
The chromosomal passenger complex (CPC), which is composed of conserved proteins aurora B, inner centromere protein (INCENP), survivin, and Borealin/DASRA, localizes to chromatin, kinetochores, microtubules, and the cell cortex in a cell cycle-dependent manner. The CPC is required for multiple aspects of cell division. Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust). Although Borr is a passenger in all mitotic tissues studied, it is specifically replaced by Aust for the two male meiotic divisions. We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC. Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation. Furthermore, we show that the CPC is required earlier in cytokinesis than previously thought; cells lacking Aust do not initiate central spindle formation, accumulate anillin or actin at the cell equator, or undergo equatorial constriction.

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MT and chromatin organization in aust spermatocytes. (A) Wild-type and aust primary spermatocytes stained for α-tubulin (green) and DNA (blue). In mutant cells, chromosomes fail to align on the metaphase plate and are irregularly segregated during anaphase. Although meiotic spindle morphology appears normal, the central spindle is absent during both anaphase and telophase. (B) Wild-type and aust testes prepared to visualize chromosome morphology. In contrast to wild-type cells, aust spermatocytes in prometaphase I show separation of sister chromatids (arrows). (C) Wild-type and aust spermatocytes stained with antibodies to α-tubulin (green), phosphohistone H3 Ser10 (red), and DNA (blue). In both wild-type and aust cells, histone H3 is phosphorylated upon entry into meiosis I and II and dephosphorylated by telophase. Bars, 10 μm.
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fig7: MT and chromatin organization in aust spermatocytes. (A) Wild-type and aust primary spermatocytes stained for α-tubulin (green) and DNA (blue). In mutant cells, chromosomes fail to align on the metaphase plate and are irregularly segregated during anaphase. Although meiotic spindle morphology appears normal, the central spindle is absent during both anaphase and telophase. (B) Wild-type and aust testes prepared to visualize chromosome morphology. In contrast to wild-type cells, aust spermatocytes in prometaphase I show separation of sister chromatids (arrows). (C) Wild-type and aust spermatocytes stained with antibodies to α-tubulin (green), phosphohistone H3 Ser10 (red), and DNA (blue). In both wild-type and aust cells, histone H3 is phosphorylated upon entry into meiosis I and II and dephosphorylated by telophase. Bars, 10 μm.

Mentions: The defects observed in aust spermatids are the result of problems in chromosome segregation and cytokinesis (Fig. 1 and Table I). To analyze how these defects occur, we stained aust mutant testes preparations for DNA and α-tubulin and analyzed the first meiotic division (Fig. 7 A). Several distinct phenotypes in chromatin organization could be discerned. First, the number of chromosomal masses during prometaphase I appeared to vary between cells. Second, chromosomes often failed to align correctly on the metaphase plate. Third, chromosomes were often segregated inappropriately during anaphase. The defects in alignment and segregation can be explained by the well-characterized role of the CPC in rectifying inappropriate kinetochore–MT attachments (Hauf et al., 2003; Lens and Medema, 2003; Cimini et al., 2006; Knowlton et al., 2006) and by the lack of a robust checkpoint in D. melanogaster male meiosis, which allows spindles to proceed into anaphase in the presence of misattached chromosomes (Rebollo and Gonzalez, 2000).


Australin: a chromosomal passenger protein required specifically for Drosophila melanogaster male meiosis.

Gao S, Giansanti MG, Buttrick GJ, Ramasubramanyan S, Auton A, Gatti M, Wakefield JG - J. Cell Biol. (2008)

MT and chromatin organization in aust spermatocytes. (A) Wild-type and aust primary spermatocytes stained for α-tubulin (green) and DNA (blue). In mutant cells, chromosomes fail to align on the metaphase plate and are irregularly segregated during anaphase. Although meiotic spindle morphology appears normal, the central spindle is absent during both anaphase and telophase. (B) Wild-type and aust testes prepared to visualize chromosome morphology. In contrast to wild-type cells, aust spermatocytes in prometaphase I show separation of sister chromatids (arrows). (C) Wild-type and aust spermatocytes stained with antibodies to α-tubulin (green), phosphohistone H3 Ser10 (red), and DNA (blue). In both wild-type and aust cells, histone H3 is phosphorylated upon entry into meiosis I and II and dephosphorylated by telophase. Bars, 10 μm.
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Related In: Results  -  Collection

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fig7: MT and chromatin organization in aust spermatocytes. (A) Wild-type and aust primary spermatocytes stained for α-tubulin (green) and DNA (blue). In mutant cells, chromosomes fail to align on the metaphase plate and are irregularly segregated during anaphase. Although meiotic spindle morphology appears normal, the central spindle is absent during both anaphase and telophase. (B) Wild-type and aust testes prepared to visualize chromosome morphology. In contrast to wild-type cells, aust spermatocytes in prometaphase I show separation of sister chromatids (arrows). (C) Wild-type and aust spermatocytes stained with antibodies to α-tubulin (green), phosphohistone H3 Ser10 (red), and DNA (blue). In both wild-type and aust cells, histone H3 is phosphorylated upon entry into meiosis I and II and dephosphorylated by telophase. Bars, 10 μm.
Mentions: The defects observed in aust spermatids are the result of problems in chromosome segregation and cytokinesis (Fig. 1 and Table I). To analyze how these defects occur, we stained aust mutant testes preparations for DNA and α-tubulin and analyzed the first meiotic division (Fig. 7 A). Several distinct phenotypes in chromatin organization could be discerned. First, the number of chromosomal masses during prometaphase I appeared to vary between cells. Second, chromosomes often failed to align correctly on the metaphase plate. Third, chromosomes were often segregated inappropriately during anaphase. The defects in alignment and segregation can be explained by the well-characterized role of the CPC in rectifying inappropriate kinetochore–MT attachments (Hauf et al., 2003; Lens and Medema, 2003; Cimini et al., 2006; Knowlton et al., 2006) and by the lack of a robust checkpoint in D. melanogaster male meiosis, which allows spindles to proceed into anaphase in the presence of misattached chromosomes (Rebollo and Gonzalez, 2000).

Bottom Line: Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust).We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC.Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oxford, OX1 3PS Oxford, England, UK.

ABSTRACT
The chromosomal passenger complex (CPC), which is composed of conserved proteins aurora B, inner centromere protein (INCENP), survivin, and Borealin/DASRA, localizes to chromatin, kinetochores, microtubules, and the cell cortex in a cell cycle-dependent manner. The CPC is required for multiple aspects of cell division. Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust). Although Borr is a passenger in all mitotic tissues studied, it is specifically replaced by Aust for the two male meiotic divisions. We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC. Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation. Furthermore, we show that the CPC is required earlier in cytokinesis than previously thought; cells lacking Aust do not initiate central spindle formation, accumulate anillin or actin at the cell equator, or undergo equatorial constriction.

Show MeSH
Related in: MedlinePlus