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Spindle assembly checkpoint inactivation fails to suppress neuroblast tumour formation in aurA mutant Drosophila.

Caous R, Pascal A, Romé P, Richard-Parpaillon L, Karess R, Giet R - Nat Commun (2015)

Bottom Line: By contrast, disrupting the SAC in the aurA mutant does not prevent NB amplification, tumour formation or chromosome segregation.Thus, the NBs of aurA mutants present delayed mitosis, with accurate chromosome segregation occurring in a SAC-independent manner.We report here the existence of an Aurora A-dependent mechanism promoting efficient, timed cyclin B degradation.

View Article: PubMed Central - PubMed

Affiliation: Institut de Génétique et Développement de Rennes-Université de Rennes I-CNRS- UMR 6290, 2 avenue du Pr Léon Bernard, 35043 Rennes, France.

ABSTRACT
Tissue homeostasis requires accurate control of cell proliferation, differentiation and chromosome segregation. Drosophila sas-4 and aurA mutants present brain tumours with extra neuroblasts (NBs), defective mitotic spindle assembly and delayed mitosis due to activation of the spindle assembly checkpoint (SAC). Here we inactivate the SAC in aurA and sas-4 mutants to determine whether the generation of aneuploidy compromises NB proliferation. Inactivation of the SAC in the sas-4 mutant impairs NB proliferation and disrupts euploidy. By contrast, disrupting the SAC in the aurA mutant does not prevent NB amplification, tumour formation or chromosome segregation. The monitoring of Mad2 and cyclin B dynamics in live aurA NBs reveals that SAC satisfaction is not coupled to cyclin B degradation. Thus, the NBs of aurA mutants present delayed mitosis, with accurate chromosome segregation occurring in a SAC-independent manner. We report here the existence of an Aurora A-dependent mechanism promoting efficient, timed cyclin B degradation.

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Related in: MedlinePlus

SAC deletion prevents the amplification of sas-4 mutant NBs but not of aurA mutant NBs.(a) Examination of WT, sas-4, aurA, mad2, sas-4 mad2 and aurA mad2 mutant brain development. WT and mad2 mutant brains grew normally, whereas sas-4 and aurA mutant brains contained large numbers of NBs. SAC deletion impaired brain development in combination with sas-4, but not with aurA. The pan-NBs were counted by staining of the central brain region with an anti-deadpan antibody (red and lower monochrome panels). Staining for the neuronal marker prospero is shown in green. Staining for phosphorylated histone H3 (Ser10) is shown in blue. Scale bar, 50 μm. (b) Quantification of pan-NBs (±s.d.) in WT, sas-4, mad2 and sas-4 mad2 brain lobes. WT and mad2 brain lobes had 75.4±10.5 NBs per lobe (n=14) and 73.2±9.0 NBs per lobe (n=22), respectively. sas-4 lobes contained a larger number of NBs per lobe (126.2±16.2 NBs; n=18). The disruption of Mad2 in a sas-4 background decreased the growth rate and number of NBs (42.0±14.5, n=14). ***P<10−10 (Wilcoxon test). (c) Quantification of pan-NBs (±s.d.) in aurA and aurA mad2 brain lobes. The number of NBs in aurA brain lobes (1003.6±79.7, n=12) was high, even in the absence of Mad2 (1164.2±134.3, n=11). *P<3 × 10−3 (Wilcoxon test). (d) SAC deletion compromises spindle morphology in sas-4 but not aurA mutant NBs. Metaphase NBs from the indicated genotypes were stained for phosphorylated histone H3 (Ser10) (blue), tubulin (red and lower panels in monochrome). Many spindles in sas-4 brains were bipolar, but sas-4 mad2 mutant spindles were abnormal in shape. The aurA and aurA mad2 mutants had short bipolar spindles. Scale bar, 10 μm. (e) The ability of aurA mutant brains to develop tumours is not compromised by SAC deletion. WT, aurA, mad2 and aurA mad2 brains were labelled with H2A-GFP and transplanted into host flies to assess their tumorigenic potential15. The transplantation of aurA and aurA mad2 brain tissues induced tumour formation in 82% (41/50) and 80% (45/56) of cases. (f) The transplantation of H2A-GFP-labelled sas-4 brain tissues led to tumour formation (5.9%, 6/102) whereas the transplantation of sas-4 mad2 brain tissues did not (0%, 0/112). Scale bar, 0.5 mm.
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f1: SAC deletion prevents the amplification of sas-4 mutant NBs but not of aurA mutant NBs.(a) Examination of WT, sas-4, aurA, mad2, sas-4 mad2 and aurA mad2 mutant brain development. WT and mad2 mutant brains grew normally, whereas sas-4 and aurA mutant brains contained large numbers of NBs. SAC deletion impaired brain development in combination with sas-4, but not with aurA. The pan-NBs were counted by staining of the central brain region with an anti-deadpan antibody (red and lower monochrome panels). Staining for the neuronal marker prospero is shown in green. Staining for phosphorylated histone H3 (Ser10) is shown in blue. Scale bar, 50 μm. (b) Quantification of pan-NBs (±s.d.) in WT, sas-4, mad2 and sas-4 mad2 brain lobes. WT and mad2 brain lobes had 75.4±10.5 NBs per lobe (n=14) and 73.2±9.0 NBs per lobe (n=22), respectively. sas-4 lobes contained a larger number of NBs per lobe (126.2±16.2 NBs; n=18). The disruption of Mad2 in a sas-4 background decreased the growth rate and number of NBs (42.0±14.5, n=14). ***P<10−10 (Wilcoxon test). (c) Quantification of pan-NBs (±s.d.) in aurA and aurA mad2 brain lobes. The number of NBs in aurA brain lobes (1003.6±79.7, n=12) was high, even in the absence of Mad2 (1164.2±134.3, n=11). *P<3 × 10−3 (Wilcoxon test). (d) SAC deletion compromises spindle morphology in sas-4 but not aurA mutant NBs. Metaphase NBs from the indicated genotypes were stained for phosphorylated histone H3 (Ser10) (blue), tubulin (red and lower panels in monochrome). Many spindles in sas-4 brains were bipolar, but sas-4 mad2 mutant spindles were abnormal in shape. The aurA and aurA mad2 mutants had short bipolar spindles. Scale bar, 10 μm. (e) The ability of aurA mutant brains to develop tumours is not compromised by SAC deletion. WT, aurA, mad2 and aurA mad2 brains were labelled with H2A-GFP and transplanted into host flies to assess their tumorigenic potential15. The transplantation of aurA and aurA mad2 brain tissues induced tumour formation in 82% (41/50) and 80% (45/56) of cases. (f) The transplantation of H2A-GFP-labelled sas-4 brain tissues led to tumour formation (5.9%, 6/102) whereas the transplantation of sas-4 mad2 brain tissues did not (0%, 0/112). Scale bar, 0.5 mm.

Mentions: We investigated the effects on fly viability and brain development of an absence of the SAC in aurA8839 flies (hereafter referred as aurA). Mad2 is a key component of the SAC apparatus and appears to have no other role in Drosophila14.


Spindle assembly checkpoint inactivation fails to suppress neuroblast tumour formation in aurA mutant Drosophila.

Caous R, Pascal A, Romé P, Richard-Parpaillon L, Karess R, Giet R - Nat Commun (2015)

SAC deletion prevents the amplification of sas-4 mutant NBs but not of aurA mutant NBs.(a) Examination of WT, sas-4, aurA, mad2, sas-4 mad2 and aurA mad2 mutant brain development. WT and mad2 mutant brains grew normally, whereas sas-4 and aurA mutant brains contained large numbers of NBs. SAC deletion impaired brain development in combination with sas-4, but not with aurA. The pan-NBs were counted by staining of the central brain region with an anti-deadpan antibody (red and lower monochrome panels). Staining for the neuronal marker prospero is shown in green. Staining for phosphorylated histone H3 (Ser10) is shown in blue. Scale bar, 50 μm. (b) Quantification of pan-NBs (±s.d.) in WT, sas-4, mad2 and sas-4 mad2 brain lobes. WT and mad2 brain lobes had 75.4±10.5 NBs per lobe (n=14) and 73.2±9.0 NBs per lobe (n=22), respectively. sas-4 lobes contained a larger number of NBs per lobe (126.2±16.2 NBs; n=18). The disruption of Mad2 in a sas-4 background decreased the growth rate and number of NBs (42.0±14.5, n=14). ***P<10−10 (Wilcoxon test). (c) Quantification of pan-NBs (±s.d.) in aurA and aurA mad2 brain lobes. The number of NBs in aurA brain lobes (1003.6±79.7, n=12) was high, even in the absence of Mad2 (1164.2±134.3, n=11). *P<3 × 10−3 (Wilcoxon test). (d) SAC deletion compromises spindle morphology in sas-4 but not aurA mutant NBs. Metaphase NBs from the indicated genotypes were stained for phosphorylated histone H3 (Ser10) (blue), tubulin (red and lower panels in monochrome). Many spindles in sas-4 brains were bipolar, but sas-4 mad2 mutant spindles were abnormal in shape. The aurA and aurA mad2 mutants had short bipolar spindles. Scale bar, 10 μm. (e) The ability of aurA mutant brains to develop tumours is not compromised by SAC deletion. WT, aurA, mad2 and aurA mad2 brains were labelled with H2A-GFP and transplanted into host flies to assess their tumorigenic potential15. The transplantation of aurA and aurA mad2 brain tissues induced tumour formation in 82% (41/50) and 80% (45/56) of cases. (f) The transplantation of H2A-GFP-labelled sas-4 brain tissues led to tumour formation (5.9%, 6/102) whereas the transplantation of sas-4 mad2 brain tissues did not (0%, 0/112). Scale bar, 0.5 mm.
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f1: SAC deletion prevents the amplification of sas-4 mutant NBs but not of aurA mutant NBs.(a) Examination of WT, sas-4, aurA, mad2, sas-4 mad2 and aurA mad2 mutant brain development. WT and mad2 mutant brains grew normally, whereas sas-4 and aurA mutant brains contained large numbers of NBs. SAC deletion impaired brain development in combination with sas-4, but not with aurA. The pan-NBs were counted by staining of the central brain region with an anti-deadpan antibody (red and lower monochrome panels). Staining for the neuronal marker prospero is shown in green. Staining for phosphorylated histone H3 (Ser10) is shown in blue. Scale bar, 50 μm. (b) Quantification of pan-NBs (±s.d.) in WT, sas-4, mad2 and sas-4 mad2 brain lobes. WT and mad2 brain lobes had 75.4±10.5 NBs per lobe (n=14) and 73.2±9.0 NBs per lobe (n=22), respectively. sas-4 lobes contained a larger number of NBs per lobe (126.2±16.2 NBs; n=18). The disruption of Mad2 in a sas-4 background decreased the growth rate and number of NBs (42.0±14.5, n=14). ***P<10−10 (Wilcoxon test). (c) Quantification of pan-NBs (±s.d.) in aurA and aurA mad2 brain lobes. The number of NBs in aurA brain lobes (1003.6±79.7, n=12) was high, even in the absence of Mad2 (1164.2±134.3, n=11). *P<3 × 10−3 (Wilcoxon test). (d) SAC deletion compromises spindle morphology in sas-4 but not aurA mutant NBs. Metaphase NBs from the indicated genotypes were stained for phosphorylated histone H3 (Ser10) (blue), tubulin (red and lower panels in monochrome). Many spindles in sas-4 brains were bipolar, but sas-4 mad2 mutant spindles were abnormal in shape. The aurA and aurA mad2 mutants had short bipolar spindles. Scale bar, 10 μm. (e) The ability of aurA mutant brains to develop tumours is not compromised by SAC deletion. WT, aurA, mad2 and aurA mad2 brains were labelled with H2A-GFP and transplanted into host flies to assess their tumorigenic potential15. The transplantation of aurA and aurA mad2 brain tissues induced tumour formation in 82% (41/50) and 80% (45/56) of cases. (f) The transplantation of H2A-GFP-labelled sas-4 brain tissues led to tumour formation (5.9%, 6/102) whereas the transplantation of sas-4 mad2 brain tissues did not (0%, 0/112). Scale bar, 0.5 mm.
Mentions: We investigated the effects on fly viability and brain development of an absence of the SAC in aurA8839 flies (hereafter referred as aurA). Mad2 is a key component of the SAC apparatus and appears to have no other role in Drosophila14.

Bottom Line: By contrast, disrupting the SAC in the aurA mutant does not prevent NB amplification, tumour formation or chromosome segregation.Thus, the NBs of aurA mutants present delayed mitosis, with accurate chromosome segregation occurring in a SAC-independent manner.We report here the existence of an Aurora A-dependent mechanism promoting efficient, timed cyclin B degradation.

View Article: PubMed Central - PubMed

Affiliation: Institut de Génétique et Développement de Rennes-Université de Rennes I-CNRS- UMR 6290, 2 avenue du Pr Léon Bernard, 35043 Rennes, France.

ABSTRACT
Tissue homeostasis requires accurate control of cell proliferation, differentiation and chromosome segregation. Drosophila sas-4 and aurA mutants present brain tumours with extra neuroblasts (NBs), defective mitotic spindle assembly and delayed mitosis due to activation of the spindle assembly checkpoint (SAC). Here we inactivate the SAC in aurA and sas-4 mutants to determine whether the generation of aneuploidy compromises NB proliferation. Inactivation of the SAC in the sas-4 mutant impairs NB proliferation and disrupts euploidy. By contrast, disrupting the SAC in the aurA mutant does not prevent NB amplification, tumour formation or chromosome segregation. The monitoring of Mad2 and cyclin B dynamics in live aurA NBs reveals that SAC satisfaction is not coupled to cyclin B degradation. Thus, the NBs of aurA mutants present delayed mitosis, with accurate chromosome segregation occurring in a SAC-independent manner. We report here the existence of an Aurora A-dependent mechanism promoting efficient, timed cyclin B degradation.

Show MeSH
Related in: MedlinePlus