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. 2018 Sep 10;28(17):2837-2844.e3.
doi: 10.1016/j.cub.2018.06.062. Epub 2018 Aug 16.

Absence of the Spindle Assembly Checkpoint Restores Mitotic Fidelity upon Loss of Sister Chromatid Cohesion

Rui D Silva  1 , Mihailo Mirkovic  2 , Leonardo G Guilgur  2 , Om S Rathore  1 , Rui Gonçalo Martinho  3 , Raquel A Oliveira  4
Affiliations

Absence of the Spindle Assembly Checkpoint Restores Mitotic Fidelity upon Loss of Sister Chromatid Cohesion

Rui D Silva et al. Curr Biol. .

Abstract

The fidelity of mitosis depends on cohesive forces that keep sister chromatids together. This is mediated by cohesin that embraces sister chromatid fibers from the time of their replication until the subsequent mitosis [1-3]. Cleavage of cohesin marks anaphase onset, where single chromatids are dragged to the poles by the mitotic spindle [4-6]. Cohesin cleavage should only occur when all chromosomes are properly bio-oriented to ensure equal genome distribution and prevent random chromosome segregation. Unscheduled loss of sister chromatid cohesion is prevented by a safeguard mechanism known as the spindle assembly checkpoint (SAC) [7, 8]. To identify specific conditions capable of restoring defects associated with cohesion loss, we screened for genes whose depletion modulates Drosophila wing development when sister chromatid cohesion is impaired. Cohesion deficiency was induced by knockdown of the acetyltransferase separation anxiety (San)/Naa50, a cohesin complex stabilizer [9-12]. Several genes whose function impacts wing development upon cohesion loss were identified. Surprisingly, knockdown of key SAC proteins, Mad2 and Mps1, suppressed developmental defects associated with San depletion. SAC impairment upon cohesin removal, triggered by San depletion or artificial removal of the cohesin complex, prevented extensive genome shuffling, reduced segregation defects, and restored cell survival. This counterintuitive phenotypic suppression was caused by an intrinsic bias for efficient chromosome biorientation at mitotic entry, coupled with slow engagement of error-correction reactions. Thus, in contrast to SAC's role as a safeguard mechanism for mitotic fidelity, removal of this checkpoint alleviates mitotic errors when sister chromatid cohesion is compromised.

Keywords: Drosophila; SAN; aneuploidy; cohesin; mitosis; separation anxiety; sister chromatid cohesion; spindle assembly checkpoint.

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Figures

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Graphical abstract
Figure 1
Figure 1
SAC Inhibition Modifies san RNAi-Induced Adult Wing Developmental Defects (A) Tissue-specific RNAi in the pouch of the larvae wing imaginal using the nubbin-Gal4 driver and the upstream activating sequence (UAS)/Gal4 system. (B) Adult wings of wild-type Drosophila (Oregon R) or Drosophila expressing a control RNAi (mCherry RNAi) or expressing RNAi for san in the larvae wing imaginal discs. (C) Representative adult Drosophila wing phenotypes co-expressing san RNAi with mCherry RNAi, mad2 RNAi, or mps1 RNAi in the larvae wing imaginal discs. (D) Adult wing phenotypic classes scored during the screen: class 1 (wild-type wings); class 2 (weak wing developmental defects); class 3 (san RNAi-like wing phenotype); class 4 (highly abnormal wings); and class 5 (absence or vestigial adult wings). Additional examples of the scored phenotypic classes are shown in [10]. (E) Quantification of Drosophila wing phenotypes expressing individual RNAi transgenes for control (mCherry), mad2, or mps1 (gray bars) or co-expressing san RNAi with control (mCherry) RNAi, mad2 RNAi, or mps1 RNAi (black bars) in the larvae wing imaginal discs, from the described screen. (F) Candidate gene analysis for enhancers/supressors of san RNAi. Quantification of Drosophila wing phenotypes expressing individual RNAi transgenes for control (mCherry), bubR1, mad1, fzy, and cdc23 (gray bars) or co-expressing san RNAi with control (mCherry) RNAi, bubR1 RNAis, mad1 RNAis, fzy RNAi, and cdc23 RNAi (black bars) in the larvae wing imaginal discs. bubR1 RNAi1, bubR1 RNAi2, mad1 RNAi1, and mad1 RNAi2 correspond to the TRiP RNAis GL00236, GLV21065, GLV21088, and HMC03671, respectively. The average phenotypic class of control and san RNAi and control RNAi (E and F) is the same. Phenotypic quantification of adult wings is mean ± SD of three independent experiments and is based on the classes described in (D) (∗∗∗p < 0.0001; one-way ANOVA with Bonferroni’s multiple comparison test; n represents the total number of scored flies). See also Figure S1, Table S1, and Data S1.
Figure 2
Figure 2
Inhibition of the SAC in Wing Imaginal Discs Alleviates Mitotic Errors Caused by Premature Loss of Cohesin (A) Images from movies of the wing disc pouch in the control, san RNAi, and san and mad2 RNAi strains. Strains contained HisH2Av-RFP (red) and Cid-EGFP (green). Times are relative to NEBD. The scale bar represents 5 μm. (B) Quantification of mitotic duration in control, san RNAi, or san and mad2 RNAi strains. The duration of mitosis was measured from nuclear envelope breakdown (NEBD) to nuclear envelope formation (NEF) using H2Av-RFP channel. Images were taken every 2 min. Each dot represents an individual cell and lines represent mean ± SD (n = 71/5 for control, 77/5 for san RNAi, and 124/5 for san+mad2 RNAi; n = number of cells and number of independent discs). (C) Images from movies of the wing disc from strains surviving solely on TEV-cleavable Rad21 (Rad21TEV) with and without heat-shock-induced TEV protease cleavage, in strains wild-type or homozygous mutant for the mad2 gene. Strains also expressed HisH2Av-RFP (red) for visualization of mitotic duration and phenotype. Times are relative to NEBD. The scale bar represents 5 μm. (D) Quantification of mitotic duration of the no TEV control upon TEV-protease-mediated cleavage of Rad21TEV, upon TEV-protease-mediated cleavage of Rad21TEV in a mad2 mutant background, and in a mad2 mutant without cohesin cleavage but after heat shock. The duration of mitosis was measured from NEBD to NEF using H2AvD-mRFP1. Images were taken every 2 or 3 min. Each dot represents an individual cell, and lines represent mean ± SD (n = 27/4 for Rad21TEV − TEV [no heat shock (HS)], 46/8 for Rad21TEV + TEV, 46/4 for Rad21TEV+TEV in a mad2P background, and 60/4 for mad2P after HS; n = number of cells and number of independent discs). (E) Representative images of mitotic cells from san RNAi undergoing mitosis with normal and defective mitotic exit. The scale bar represents 5 μm and applies to all images. Graph represents the quantification of mitotic defects observed in the different experimental conditions as mean ± SEM of errors of individual discs (n ≥ 4 independent discs corresponding to over 50 cells analyzed per experimental condition). (F) Quantification of centromere (cid-EGFP-labeled) segregation assymetry in the different experimental conditions; graph represents segregation symmetry index per cell calculated as the area of pole A (with higher area) divided by area of pole B (lower area), as illustrated on the left (n ≥ 4 independent discs corresponding to over 50 cells analyzed per experimental condition). Statistical analysis was performed using one-way ANOVA test. See also Figure S2 and Videos S1 and S2.
Figure 3
Figure 3
Inhibition of the SAC in Syncytial Blastoderm Embryos Alleviates Mitotic Errors Caused by Premature Loss of Cohesin (A) Embryos surviving solely on Rad21TEV either non-injected (up) or injected with 5 mg/mL TEV protease (middle and bottom panels). Embryos are derived from females that are wild-type or homozygous mutant for mad2 gene and express HisH2Av-RFP (red) and Cid-EGFP (green). Images were taken every 30 s, and times are relative to NEBD. The scale bar represents 10 μm. (B) Quantification of mitotic duration in un-injected embryos and embryos injected with TEV protease in strains containing solely Rad21TEV and wild-type or mutant for mad2. The duration of mitosis was measured from NEBD to NEF using HisH2Av-RFP. Images were taken every 30 s. Each dot represents a single mitosis, and lines represent mean ± SD (n = 20/4 for Rad21TEV no TEV, 40/8 for Rad21TEV + TEV, and 55/11 for Rad21TEV+TEV in a mad2P background; n = number of mitosis and number of independent embryos). (C) Quantification of segregation asymmetry in control, cohesin cleavage, and cohesin cleavage in mad2 mutant background. Each value was quantified by normalizing the area of pole A (with higher area) and the area of pole B (lower area); (n = 46/5 for Rad21TEV no TEV, 60/6 for Rad21TEV + TEV, and 60/6 for Rad21TEV+TEV in a mad2P background; n = number of telophases and number of independent embryos); statistical analysis was performed using one-way ANOVA test. (D) Relative area of lagging centromeres in control, Rad21TEV + TEV protease, and Rad21TEV + TEV protease in a mad2 mutant background; statistical analysis was performed using one-way ANOVA test. (E) Kymographs of HisH2Av-RFP and Cid-EGFP of cells entering mitosis in control, cohesin cleavage, and cohesin cleavage in mad2 mutant background. Arrow points to centromere separation and arrowhead to the shuffling onset. The scale bars represent 5 min and 5 μm. (F) Quantification of time for chromosome shuffling onset upon TEV-mediated cohesin cleavage, relative to NEBD. Each dot represents a single dividing nuclei from >10 independent embryos. See also Figures S3 and S4 and Videos S3 and S4.
Figure 4
Figure 4
Inhibition of the SAC Suppresses Imaginal Wing Disc Apoptosis Caused by Premature Loss of Cohesin (A) Images of cleaved caspase-3 (CC3) immunofluorescence in controls (Rad21TEV without TEV and mad2P after HS), Rad21TEV + TEV protease, and Rad21TEV + TEV protease in mad2 mutant background after HS. The scale bar represents 100 μm. (B) Quantification of CC3-positive area of the entire wing disc, in the indicated experimental conditions; n ≥ 5 independent discs per experimental condition; statistical analysis was performed using one-way ANOVA test. (C) Representative images of CC3 immunofluorescence in control, san RNAi, and san and mad2 double RNAi. Scale bar indicates 100 μm. (D) Quantification of CC3-positive area of the wing disc pouch, in control, san, and san and mad2 RNAi; n ≥ 4 independent discs per experimental condition; multiple comparison analysis was perform using a one-way ANOVA test.
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References

    1. Michaelis C., Ciosk R., Nasmyth K. Cohesins: chromosomal proteins that prevent premature separation of sister chromatids. Cell. 1997;91:35–45. - PubMed
    1. Guacci V., Koshland D., Strunnikov A. A direct link between sister chromatid cohesion and chromosome condensation revealed through the analysis of MCD1 in S. cerevisiae. Cell. 1997;91:47–57. - PMC - PubMed
    1. Haering C.H., Farcas A.M., Arumugam P., Metson J., Nasmyth K. The cohesin ring concatenates sister DNA molecules. Nature. 2008;454:297–301. - PubMed
    1. Uhlmann F., Wernic D., Poupart M.A., Koonin E.V., Nasmyth K. Cleavage of cohesin by the CD clan protease separin triggers anaphase in yeast. Cell. 2000;103:375–386. - PubMed
    1. Uhlmann F., Lottspeich F., Nasmyth K. Sister-chromatid separation at anaphase onset is promoted by cleavage of the cohesin subunit Scc1. Nature. 1999;400:37–42. - PubMed

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