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Razuvaeva AV, Graziadio L, Palumbo V, Pavlova GA, Popova JV, Pindyurin AV, Bonaccorsi S, Somma MP, Gatti M. The Multiple Mitotic Roles of the ASPM Orthologous Proteins: Insight into the Etiology of ASPM-Dependent Microcephaly. Cells 2023; 12:cells12060922. [PMID: 36980263 PMCID: PMC10047693 DOI: 10.3390/cells12060922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/13/2023] [Accepted: 03/15/2023] [Indexed: 03/19/2023] Open
Abstract
The Drosophila abnormal spindle (asp) gene was discovered about 40 years ago and shown to be required for both mitotic and meiotic cell division. Subsequent studies showed that asp is highly conserved and that mutations in its human ortholog ASPM (Abnormal Spindle-like Microcephaly-associated; or MCPH5) are the most common cause of autosomal recessive primary microcephaly. This finding greatly stimulated research on ASPM and its fly and mouse (Aspm) orthologs. The three Asp orthologous proteins bind the microtubules (MTs) minus ends during cell division and also function in interphase nuclei. Investigations on different cell types showed that Asp/Aspm/ASPM depletion disrupts one or more of the following mitotic processes: aster formation, spindle pole focusing, centrosome-spindle coupling, spindle orientation, metaphase-to-anaphase progression, chromosome segregation, and cytokinesis. In addition, ASPM physically interacts with components of the DNA repair and replication machineries and is required for the maintenance of chromosomal DNA stability. We propose the working hypothesis that the asp/Aspm/ASPM genes play the same conserved functions in Drosophila, mouse, and human cells. Human microcephaly is a genetically heterogeneous disorder caused by mutations in 30 different genes that play a variety of functions required for cell division and chromosomal DNA integrity. Our hypothesis postulates that ASPM recapitulates the functions of most human microcephaly genes and provides a justification for why ASPM is the most frequently mutated gene in autosomal recessive primary microcephaly.
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Affiliation(s)
- Alyona V. Razuvaeva
- Department of Regulation of Genetic Processes, Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (A.V.R.); (J.V.P.); (A.V.P.)
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Lucia Graziadio
- IBPM CNR c/o Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy;
| | - Valeria Palumbo
- Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy; (V.P.); (S.B.)
| | - Gera A. Pavlova
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK;
| | - Julia V. Popova
- Department of Regulation of Genetic Processes, Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (A.V.R.); (J.V.P.); (A.V.P.)
- Laboratory of Bioengineering, Novosibirsk State Agrarian University, Novosibirsk 630039, Russia
| | - Alexey V. Pindyurin
- Department of Regulation of Genetic Processes, Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (A.V.R.); (J.V.P.); (A.V.P.)
| | - Silvia Bonaccorsi
- Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy; (V.P.); (S.B.)
| | - Maria Patrizia Somma
- IBPM CNR c/o Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy;
- Correspondence: (M.P.S.); (M.G.)
| | - Maurizio Gatti
- IBPM CNR c/o Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy;
- Correspondence: (M.P.S.); (M.G.)
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Wormser O, Levy Y, Bakhrat A, Bonaccorsi S, Graziadio L, Gatti M, AbuMadighem A, McKenney RJ, Okada K, El Riati S, Har-Vardi I, Huleihel M, Levitas E, Birk OS, Abdu U. Absence of SCAPER causes male infertility in humans and Drosophila by modulating microtubule dynamics during meiosis. J Med Genet 2020; 58:254-263. [PMID: 32527956 PMCID: PMC10405349 DOI: 10.1136/jmedgenet-2020-106946] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 04/22/2020] [Accepted: 04/25/2020] [Indexed: 12/25/2022]
Abstract
BACKGROUND Mutation in S-phase cyclin A-associated protein rin the endoplasmic reticulum (SCAPER) have been found across ethnicities and have been shown to cause variable penetrance of an array of pathological traits, including intellectual disability, retinitis pigmentosa and ciliopathies. METHODS Human clinical phenotyping, surgical testicular sperm extraction and testicular tissue staining. Generation and analysis of short spindle 3 (ssp3) (SCAPER orthologue) Drosophila CAS9-knockout lines. In vitro microtubule (MT) binding assayed by total internal reflection fluorescence microscopy. RESULTS We show that patients homozygous for a SCAPER mutation lack SCAPER expression in spermatogonia (SPG) and are azoospermic due to early defects in spermatogenesis, leading to the complete absence of meiotic cells. Interestingly, Drosophila null mutants for the ubiquitously expressed ssp3 gene are viable and female fertile but male sterile. We further show that male sterility in ssp3 null mutants is due to failure in both chromosome segregation and cytokinesis. In cells undergoing male meiosis, the MTs emanating from the centrosomes do not appear to interact properly with the chromosomes, which remain dispersed within dividing spermatocytes (SPCs). In addition, mutant SPCs are unable to assemble a normal central spindle and undergo cytokinesis. Consistent with these results, an in vitro assay demonstrated that both SCAPER and Ssp3 directly bind MTs. CONCLUSIONS Our results show that SCAPER null mutations block the entry into meiosis of SPG, causing azoospermia. Null mutations in ssp3 specifically disrupt MT dynamics during male meiosis, leading to sterility. Moreover, both SCAPER and Ssp3 bind MTs in vitro. These results raise the intriguing possibility of a common feature between human and Drosophila meiosis.
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Affiliation(s)
- Ohad Wormser
- The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Ygal Levy
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Anna Bakhrat
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza University of Rome, Rome, Italy
| | - Lucia Graziadio
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza University of Rome, Rome, Italy
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza University of Rome, Rome, Italy.,Istituto di Biologia e Patologia Molecolari Consiglio Nazionale delle Ricerche, Roma, Italy
| | - Ali AbuMadighem
- Shraga Segal Department of Microbiology, Immunology and Genetics, Ben-Gurion University of the Negev Faculty of Health Sciences, Beer-Sheva, Israel.,The Center of Advanced Research and Education in Reproduction (CARER), Ben-Gurion University of the Negev Faculty of Health Sciences, Beer-Sheva, Israel
| | - Richard J McKenney
- Department of Molecular and Cellular Biology, UC Davis, Davis, California, USA
| | - Kyoko Okada
- Department of Molecular and Cellular Biology, UC Davis, Davis, California, USA
| | - Saad El Riati
- Southern District, Clalit Health Services, Beer-Sheva, Israel
| | - Iris Har-Vardi
- The Center of Advanced Research and Education in Reproduction (CARER), Ben-Gurion University of the Negev Faculty of Health Sciences, Beer-Sheva, Israel.,Fertility and IVF Unit, Department of Obstetrics and Gynecology, Soroka University Medical Center, Beer-Sheva, Israel
| | - Mahmoud Huleihel
- Shraga Segal Department of Microbiology, Immunology and Genetics, Ben-Gurion University of the Negev Faculty of Health Sciences, Beer-Sheva, Israel.,The Center of Advanced Research and Education in Reproduction (CARER), Ben-Gurion University of the Negev Faculty of Health Sciences, Beer-Sheva, Israel
| | - Eliahu Levitas
- The Center of Advanced Research and Education in Reproduction (CARER), Ben-Gurion University of the Negev Faculty of Health Sciences, Beer-Sheva, Israel.,Fertility and IVF Unit, Department of Obstetrics and Gynecology, Soroka University Medical Center, Beer-Sheva, Israel
| | - Ohad S Birk
- The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel .,Genetics Institute, Soroka University Medical Center, Beer-Sheva, Israel
| | - Uri Abdu
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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Palumbo V, Tariq A, Borgal L, Metz J, Brancaccio M, Gatti M, Wakefield JG, Bonaccorsi S. Drosophila Morgana is an Hsp90-interacting protein with a direct role in microtubule polymerisation. J Cell Sci 2020; 133:jcs236786. [PMID: 31907206 PMCID: PMC6983718 DOI: 10.1242/jcs.236786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 12/17/2019] [Indexed: 12/25/2022] Open
Abstract
Morgana (Mora, also known as CHORD in flies) and its mammalian homologue, called CHORDC1 or CHP1, is a highly conserved cysteine and histidine-rich domain (CHORD)-containing protein that has been proposed to function as an Hsp90 co-chaperone. Morgana deregulation promotes carcinogenesis in both mice and humans while, in Drosophila, loss of mora causes lethality and a complex mitotic phenotype that is rescued by a human morgana transgene. Here, we show that Drosophila Mora localises to mitotic spindles and co-purifies with the Hsp90-R2TP-TTT supercomplex and with additional well-known Hsp90 co-chaperones. Acute inhibition of Mora function in the early embryo results in a dramatic reduction in centrosomal microtubule stability, leading to small spindles nucleated from mitotic chromatin. Purified Mora binds to microtubules directly and promotes microtubule polymerisation in vitro, suggesting that Mora directly regulates spindle dynamics independently of its Hsp90 co-chaperone role.
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Affiliation(s)
- Valeria Palumbo
- Dipartimento di Biologia e Biotecnologie Sapienza, Università di Roma, 00185 Rome, Italy
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Ammarah Tariq
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Lori Borgal
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Jeremy Metz
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Mara Brancaccio
- Dipartimento di Genetica, Biologia e Biochimica, Università di Torino, 10126 Torino, Italy
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie Sapienza, Università di Roma, 00185 Rome, Italy
- Istituto di Biologia e Patologia Molecolari del CNR, 00185 Rome, Italy
| | - James G Wakefield
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie Sapienza, Università di Roma, 00185 Rome, Italy
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Pavlova GA, Razuvaeva AV, Popova JV, Andreyeva EN, Yarinich LA, Lebedev MO, Pellacani C, Bonaccorsi S, Somma MP, Gatti M, Pindyurin AV. Publisher Correction: The role of Patronin in Drosophila mitosis. BMC Mol Cell Biol 2019; 20:24. [PMID: 31286886 PMCID: PMC6615211 DOI: 10.1186/s12860-019-0196-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
During production of the original article [1], there was a technical error that resulted in author corrections not being rendered in the PDF version of the article.
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Affiliation(s)
- Gera A Pavlova
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Alyona V Razuvaeva
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
- Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Julia V Popova
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Evgeniya N Andreyeva
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Lyubov A Yarinich
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
- Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Mikhail O Lebedev
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
- Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Claudia Pellacani
- IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy
| | - Silvia Bonaccorsi
- IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy
| | - Maria Patrizia Somma
- IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy
| | - Maurizio Gatti
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia.
- IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy.
| | - Alexey V Pindyurin
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia.
- Novosibirsk State University, Novosibirsk, 630090, Russia.
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Pavlova GA, Razuvaeva AV, Popova JV, Andreyeva EN, Yarinich LA, Lebedev MO, Pellacani C, Bonaccorsi S, Somma MP, Gatti M, Pindyurin AV. The role of Patronin in Drosophila mitosis. BMC Mol Cell Biol 2019; 20:7. [PMID: 31284878 PMCID: PMC6469034 DOI: 10.1186/s12860-019-0189-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Background The calmodulin-regulated spectrin-associated proteins (CAMSAPs) belong to a conserved protein family, which includes members that bind the polymerizing mcrotubule (MT) minus ends and remain associated with the MT lattice formed by minus end polymerization. Only one of the three mammalian CAMSAPs, CAMSAP1, localizes to the mitotic spindle but its function is unclear. In Drosophila, there is only one CAMSAP, named Patronin. Previous work has shown that Patronin stabilizes the minus ends of non-mitotic MTs and is required for proper spindle elongation. However, the precise role of Patronin in mitotic spindle assembly is poorly understood. Results Here we have explored the role of Patronin in Drosophila mitosis using S2 tissue culture cells as a model system. We show that Patronin associates with different types of MT bundles within the Drosophila mitotic spindle, and that it is required for their stability. Imaging of living cells expressing Patronin-GFP showed that Patronin displays a dynamic behavior. In prometaphase cells, Patronin accumulates on short segments of MT bundles located near the chromosomes. These Patronin “seeds” extend towards the cell poles and stop growing just before reaching the poles. Our data also suggest that Patronin localization is largely independent of proteins acting at the MT minus ends such as Asp and Klp10A. Conclusion Our results suggest a working hypothesis about the mitotic role of Patronin. We propose that Patronin binds the minus ends within MT bundles, including those generated from the walls of preexisting MTs via the augmin-mediated pathway. This would help maintaining MT association within the mitotic bundles, thereby stabilizing the spindle structure. Our data also raise the intriguing possibility that the minus ends of bundled MTs can undergo a limited polymerization. Electronic supplementary material The online version of this article (10.1186/s12860-019-0189-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Gera A Pavlova
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Alyona V Razuvaeva
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia.,Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Julia V Popova
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Evgeniya N Andreyeva
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Lyubov A Yarinich
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia.,Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Mikhail O Lebedev
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia.,Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Claudia Pellacani
- IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy
| | - Silvia Bonaccorsi
- IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy
| | - Maria Patrizia Somma
- IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy
| | - Maurizio Gatti
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia. .,IBPM CNR and Department of Biology and Biotechnology, Sapienza University of Rome, 00185, Rome, Italy.
| | - Alexey V Pindyurin
- Institute of Molecular and Cellular Biology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Novosibirsk, 630090, Russia.
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Pellacani C, Bucciarelli E, Renda F, Hayward D, Palena A, Chen J, Bonaccorsi S, Wakefield JG, Gatti M, Somma MP. Splicing factors Sf3A2 and Prp31 have direct roles in mitotic chromosome segregation. eLife 2018; 7:40325. [PMID: 30475206 PMCID: PMC6287947 DOI: 10.7554/elife.40325] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 11/14/2018] [Indexed: 12/26/2022] Open
Abstract
Several studies have shown that RNAi-mediated depletion of splicing factors (SFs) results in mitotic abnormalities. However, it is currently unclear whether these abnormalities reflect defective splicing of specific pre-mRNAs or a direct role of the SFs in mitosis. Here, we show that two highly conserved SFs, Sf3A2 and Prp31, are required for chromosome segregation in both Drosophila and human cells. Injections of anti-Sf3A2 and anti-Prp31 antibodies into Drosophila embryos disrupt mitotic division within 1 min, arguing strongly against a splicing-related mitotic function of these factors. We demonstrate that both SFs bind spindle microtubules (MTs) and the Ndc80 complex, which in Sf3A2- and Prp31-depleted cells is not tightly associated with the kinetochores; in HeLa cells the Ndc80/HEC1-SF interaction is restricted to the M phase. These results indicate that Sf3A2 and Prp31 directly regulate interactions among kinetochores, spindle microtubules and the Ndc80 complex in both Drosophila and human cells.
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Affiliation(s)
- Claudia Pellacani
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Roma, Italy
| | - Elisabetta Bucciarelli
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Roma, Italy
| | - Fioranna Renda
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza Università di Roma, Roma, Italy
| | - Daniel Hayward
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Antonella Palena
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Roma, Italy
| | - Jack Chen
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza Università di Roma, Roma, Italy
| | - James G Wakefield
- Biosciences/Living Systems Institute, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Maurizio Gatti
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Roma, Italy.,Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza Università di Roma, Roma, Italy
| | - Maria Patrizia Somma
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Roma, Italy
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7
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Graziadio L, Palumbo V, Cipressa F, Williams BC, Cenci G, Gatti M, Goldberg ML, Bonaccorsi S. Phenotypic characterization of diamond (dind), a Drosophila gene required for multiple aspects of cell division. Chromosoma 2018; 127:489-504. [PMID: 30120539 DOI: 10.1007/s00412-018-0680-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/01/2018] [Accepted: 08/03/2018] [Indexed: 01/04/2023]
Abstract
Many genes are required for the assembly of the mitotic apparatus and for proper chromosome behavior during mitosis and meiosis. A fruitful approach to elucidate the mechanisms underlying cell division is the accurate phenotypic characterization of mutations in these genes. Here, we report the identification and characterization of diamond (dind), an essential Drosophila gene required both for mitosis of larval brain cells and for male meiosis. Larvae homozygous for any of the five EMS-induced mutations die in the third-instar stage and exhibit multiple mitotic defects. Mutant brain cells exhibit poorly condensed chromosomes and frequent chromosome breaks and rearrangements; they also show centriole fragmentation, disorganized mitotic spindles, defective chromosome segregation, endoreduplicated metaphases, and hyperploid and polyploid cells. Comparable phenotypes occur in mutant spermatogonia and spermatocytes. The dind gene encodes a non-conserved protein with no known functional motifs. Although the Dind protein exhibits a rather diffuse localization in both interphase and mitotic cells, fractionation experiments indicate that some Dind is tightly associated with the chromatin. Collectively, these results suggest that loss of Dind affects chromatin organization leading to defects in chromosome condensation and integrity, which in turn affect centriole stability and spindle assembly. However, our results do not exclude the possibility that Dind directly affects some behaviors of the spindle and centrosomes.
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Affiliation(s)
- Lucia Graziadio
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy
| | - Valeria Palumbo
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy
| | - Francesca Cipressa
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.,Museo storico della fisica e centro di studi e ricerche Enrico Fermi, Rome, Italy
| | - Byron C Williams
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Giovanni Cenci
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.,Istituto Pasteur Fondazione Cenci Bolognetti, Rome, Italy
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.,Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Rome, Italy
| | - Michael L Goldberg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA.
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza, Università di Roma, Rome, Italy.
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8
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Bianchi FT, Tocco C, Pallavicini G, Liu Y, Vernì F, Merigliano C, Bonaccorsi S, El-Assawy N, Priano L, Gai M, Berto GE, Chiotto AMA, Sgrò F, Caramello A, Tasca L, Ala U, Neri F, Oliviero S, Mauro A, Geley S, Gatti M, Di Cunto F. Citron Kinase Deficiency Leads to Chromosomal Instability and TP53-Sensitive Microcephaly. Cell Rep 2017; 18:1674-1686. [PMID: 28199840 PMCID: PMC5318669 DOI: 10.1016/j.celrep.2017.01.054] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 12/16/2016] [Accepted: 01/22/2017] [Indexed: 11/16/2022] Open
Abstract
Mutations in citron (CIT), leading to loss or inactivation of the citron kinase protein (CITK), cause primary microcephaly in humans and rodents, associated with cytokinesis failure and apoptosis in neural progenitors. We show that CITK loss induces DNA damage accumulation and chromosomal instability in both mammals and Drosophila. CITK-deficient cells display "spontaneous" DNA damage, increased sensitivity to ionizing radiation, and defective recovery from radiation-induced DNA lesions. In CITK-deficient cells, DNA double-strand breaks increase independently of cytokinesis failure. Recruitment of RAD51 to DNA damage foci is compromised by CITK loss, and CITK physically interacts with RAD51, suggesting an involvement of CITK in homologous recombination. Consistent with this scenario, in doubly CitK and Trp53 mutant mice, neural progenitor cell death is dramatically reduced; moreover, clinical and neuroanatomical phenotypes are remarkably improved. Our results underscore a crucial role of CIT in the maintenance of genomic integrity during brain development.
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Affiliation(s)
- Federico Tommaso Bianchi
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy; Neuroscience Institute Cavalieri Ottolenghi, University of Turin, 10043 Orbassano (TO), Italy.
| | - Chiara Tocco
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy
| | - Gianmarco Pallavicini
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy; Neuroscience Institute Cavalieri Ottolenghi, University of Turin, 10043 Orbassano (TO), Italy
| | - Yifan Liu
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy
| | - Fiammetta Vernì
- Department of Biology and Biotechnology "Charles Darwin," Sapienza University, 00185 Rome, Italy
| | - Chiara Merigliano
- Department of Biology and Biotechnology "Charles Darwin," Sapienza University, 00185 Rome, Italy
| | - Silvia Bonaccorsi
- Department of Biology and Biotechnology "Charles Darwin," Sapienza University, 00185 Rome, Italy
| | - Nadia El-Assawy
- Department of Neurology and Neurorehabilitation, San Giuseppe Hospital, Istituto Auxologico Italiano IRCCS, 28824 Piancavallo (VB), Italy
| | - Lorenzo Priano
- Department of Neurology and Neurorehabilitation, San Giuseppe Hospital, Istituto Auxologico Italiano IRCCS, 28824 Piancavallo (VB), Italy; Department of Neuroscience, University of Torino, 10126 Torino, Italy
| | - Marta Gai
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy
| | - Gaia Elena Berto
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy; Neuroscience Institute Cavalieri Ottolenghi, University of Turin, 10043 Orbassano (TO), Italy
| | - Alessandra Maria Adelaide Chiotto
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy; Neuroscience Institute Cavalieri Ottolenghi, University of Turin, 10043 Orbassano (TO), Italy
| | - Francesco Sgrò
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy
| | - Alessia Caramello
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy
| | - Laura Tasca
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy; Neuroscience Institute Cavalieri Ottolenghi, University of Turin, 10043 Orbassano (TO), Italy
| | - Ugo Ala
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy
| | - Francesco Neri
- Human Genetics Foundation (HuGeF), via Nizza 52, 10126 Torino, Italy
| | | | - Alessandro Mauro
- Department of Neurology and Neurorehabilitation, San Giuseppe Hospital, Istituto Auxologico Italiano IRCCS, 28824 Piancavallo (VB), Italy; Department of Neuroscience, University of Torino, 10126 Torino, Italy
| | - Stephan Geley
- Division of Molecular Pathophysiology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Maurizio Gatti
- Department of Biology and Biotechnology "Charles Darwin," Sapienza University, 00185 Rome, Italy; Institute of Molecular Biology and Pathology (IBPM), CNR, 00185 Rome, Italy
| | - Ferdinando Di Cunto
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy; Neuroscience Institute Cavalieri Ottolenghi, University of Turin, 10043 Orbassano (TO), Italy.
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9
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Gai M, Bianchi FT, Vagnoni C, Vernì F, Bonaccorsi S, Pasquero S, Berto GE, Sgrò F, Chiotto AA, Annaratone L, Sapino A, Bergo A, Landsberger N, Bond J, Huttner WB, Di Cunto F. ASPM and CITK regulate spindle orientation by affecting the dynamics of astral microtubules. EMBO Rep 2017; 18:1870. [PMID: 28970373 DOI: 10.15252/embr.201745023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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10
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Renda F, Pellacani C, Strunov A, Bucciarelli E, Naim V, Bosso G, Kiseleva E, Bonaccorsi S, Sharp DJ, Khodjakov A, Gatti M, Somma MP. The Drosophila orthologue of the INT6 onco-protein regulates mitotic microtubule growth and kinetochore structure. PLoS Genet 2017; 13:e1006784. [PMID: 28505193 PMCID: PMC5448806 DOI: 10.1371/journal.pgen.1006784] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 05/30/2017] [Accepted: 04/27/2017] [Indexed: 12/01/2022] Open
Abstract
INT6/eIF3e is a highly conserved component of the translation initiation complex that interacts with both the 26S proteasome and the COP9 signalosome, two complexes implicated in ubiquitin-mediated protein degradation. The INT6 gene was originally identified as the insertion site of the mouse mammary tumor virus (MMTV), and later shown to be involved in human tumorigenesis. Here we show that depletion of the Drosophila orthologue of INT6 (Int6) results in short mitotic spindles and deformed centromeres and kinetochores with low intra-kinetochore distance. Poleward flux of microtubule subunits during metaphase is reduced, although fluorescence recovery after photobleaching (FRAP) demonstrates that microtubules remain dynamic both near the kinetochores and at spindle poles. Mitotic progression is delayed during metaphase due to the activity of the spindle assembly checkpoint (SAC). Interestingly, a deubiquitinated form of the kinesin Klp67A (a putative orthologue of human Kif18A) accumulates near the kinetochores in Int6-depleted cells. Consistent with this finding, Klp67A overexpression mimics the Int6 RNAi phenotype. Furthermore, simultaneous depletion of Int6 and Klp67A results in a phenotype identical to RNAi of just Klp67A, which indicates that Klp67A deficiency is epistatic over Int6 deficiency. We propose that Int6-mediated ubiquitination is required to control the activity of Klp67A. In the absence of this control, excess of Klp67A at the kinetochore suppresses microtubule plus-end polymerization, which in turn results in reduced microtubule flux, spindle shortening, and centromere/kinetochore deformation. INT6 is an evolutionarily conserved gene originally identified as the insertion site of the mouse mammary tumor virus that causes tumors in mice. INT6 is downregulated in many human cancers, suggesting that it acts as tumor suppressor gene. The INT6 protein is involved in several biological processes, including translation and ubiquitin-mediated protein degradation. We performed RNA interference (RNAi) against the Drosophila homologue of INT6 (Int6) and analyzed the effects of Int6 depletion on mitotic cell division. We found that loss of Int6 results in short spindles, delayed progression though metaphase and abnormally shaped centromeres/kinetochores. We also found that Int6-depleted cells fail to degrade the kinesin Klp67A. This protein, known to attenuate polymerization of microtubule (MTs) plus ends, accumulated at the kinetochores in Int6-depleted cells. We propose that this condition affects MT growth at the kinetochore, which in turn results in centromere/kinetochore deformation and delays satisfaction of the mitotic checkpoint.
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Affiliation(s)
- Fioranna Renda
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Claudia Pellacani
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Roma, Italy
| | - Anton Strunov
- Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk, Russia
- Institute of Cytology and Genetics, Siberian Branch of RAS, Novosibirsk, Russia
| | | | - Valeria Naim
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Giuseppe Bosso
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Elena Kiseleva
- Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk, Russia
- Institute of Cytology and Genetics, Siberian Branch of RAS, Novosibirsk, Russia
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - David J. Sharp
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Roma, Italy
- Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk, Russia
- * E-mail: (MPS); (MG)
| | - Maria Patrizia Somma
- Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Roma, Italy
- * E-mail: (MPS); (MG)
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11
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Gai M, Bianchi FT, Vagnoni C, Vernì F, Bonaccorsi S, Pasquero S, Berto GE, Sgrò F, Chiotto AM, Annaratone L, Sapino A, Bergo A, Landsberger N, Bond J, Huttner WB, Di Cunto F. ASPM and CITK regulate spindle orientation by affecting the dynamics of astral microtubules. EMBO Rep 2016; 17:1396-1409. [PMID: 27562601 DOI: 10.15252/embr.201541823] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 07/26/2016] [Indexed: 11/09/2022] Open
Abstract
Correct orientation of cell division is considered an important factor for the achievement of normal brain size, as mutations in genes that affect this process are among the leading causes of microcephaly. Abnormal spindle orientation is associated with reduction of the neuronal progenitor symmetric divisions, premature cell cycle exit, and reduced neurogenesis. This mechanism has been involved in microcephaly resulting from mutation of ASPM, the most frequently affected gene in autosomal recessive human primary microcephaly (MCPH), but it is presently unknown how ASPM regulates spindle orientation. In this report, we show that ASPM may control spindle positioning by interacting with citron kinase (CITK), a protein whose loss is also responsible for severe microcephaly in mammals. We show that the absence of CITK leads to abnormal spindle orientation in mammals and insects. In mouse cortical development, this phenotype correlates with increased production of basal progenitors. ASPM is required to recruit CITK at the spindle, and CITK overexpression rescues ASPM phenotype. ASPM and CITK affect the organization of astral microtubules (MT), and low doses of MT-stabilizing drug revert the spindle orientation phenotype produced by their knockdown. Finally, CITK regulates both astral-MT nucleation and stability. Our results provide a functional link between two established microcephaly proteins.
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Affiliation(s)
- Marta Gai
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Federico T Bianchi
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Cristiana Vagnoni
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Fiammetta Vernì
- Department of Biology and Biotechnologies "C. Darwin", Sapienza, Università di Roma, Rome, Italy
| | - Silvia Bonaccorsi
- Department of Biology and Biotechnologies "C. Darwin", Sapienza, Università di Roma, Rome, Italy
| | - Selina Pasquero
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Gaia E Berto
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Francesco Sgrò
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Alessandra Ma Chiotto
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Laura Annaratone
- Department of Medical Sciences, University of Turin, Turin, Italy
| | - Anna Sapino
- Department of Medical Sciences, University of Turin, Turin, Italy
| | - Anna Bergo
- San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Nicoletta Landsberger
- San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Jacqueline Bond
- Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, Leeds, UK
| | - Wieland B Huttner
- Max-Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Ferdinando Di Cunto
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
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Palumbo V, Pellacani C, Heesom K, Rogala K, Deane C, Mottier-Pavie V, Gatti M, Bonaccorsi S, Wakefield J. Misato Controls Mitotic Microtubule Generation by Stabilizing the TCP-1 Tubulin Chaperone Complex. Curr Biol 2015. [PMCID: PMC4718965 DOI: 10.1016/j.cub.2015.07.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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Palumbo V, Pellacani C, Heesom KJ, Rogala KB, Deane CM, Mottier-Pavie V, Gatti M, Bonaccorsi S, Wakefield JG. Misato Controls Mitotic Microtubule Generation by Stabilizing the TCP-1 Tubulin Chaperone Complex [corrected]. Curr Biol 2015; 25:1777-83. [PMID: 26096973 PMCID: PMC4510148 DOI: 10.1016/j.cub.2015.05.033] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 04/14/2015] [Accepted: 05/15/2015] [Indexed: 12/17/2022]
Abstract
Mitotic spindles are primarily composed of microtubules (MTs), generated by polymerization of α- and β-Tubulin hetero-dimers [1, 2]. Tubulins undergo a series of protein folding and post-translational modifications in order to fulfill their functions [3, 4]. Defects in Tubulin polymerization dramatically affect spindle formation and disrupt chromosome segregation. We recently described a role for the product of the conserved misato (mst) gene in regulating mitotic MT generation in flies [5], but the molecular function of Mst remains unknown. Here, we use affinity purification mass spectrometry (AP-MS) to identify interacting partners of Mst in the Drosophila embryo. We demonstrate that Mst associates stoichiometrically with the hetero-octameric Tubulin Chaperone Protein-1 (TCP-1) complex, with the hetero-hexameric Tubulin Prefoldin complex, and with proteins having conserved roles in generating MT-competent Tubulin. We show that RNAi-mediated in vivo depletion of any TCP-1 subunit phenocopies the effects of mutations in mst or the Prefoldin-encoding gene merry-go-round (mgr), leading to monopolar and disorganized mitotic spindles containing few MTs. Crucially, we demonstrate that Mst, but not Mgr, is required for TCP-1 complex stability and that both the efficiency of Tubulin polymerization and Tubulin stability are drastically compromised in mst mutants. Moreover, our structural bioinformatic analyses indicate that Mst resembles the three-dimensional structure of Tubulin monomers and might therefore occupy the TCP-1 complex central cavity. Collectively, our results suggest that Mst acts as a co-factor of the TCP-1 complex, playing an essential role in the Tubulin-folding processes required for proper assembly of spindle MTs. Misato interacts biochemically with the Tubulin Chaperone Protein-1 (TCP-1) complex Misato stabilizes the TCP-1 complex, possibly by filling its Tubulin-folding cavity Loss of Misato or TCP-1 complex subunits leads to similar mitotic phenotypes In the absence of Misato, Tubulin is unstable and unable to efficiently polymerize
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Affiliation(s)
- Valeria Palumbo
- Dipartimento di Biologia e Biotecnologie, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Rome, Italy; Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Claudia Pellacani
- Dipartimento di Biologia e Biotecnologie, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Rome, Italy
| | - Kate J Heesom
- Proteomics Facility, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Kacper B Rogala
- Department of Statistics, University of Oxford, South Parks Road, Oxford OX1 3TG, UK
| | - Charlotte M Deane
- Department of Statistics, University of Oxford, South Parks Road, Oxford OX1 3TG, UK
| | - Violaine Mottier-Pavie
- Dipartimento di Biologia e Biotecnologie, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Rome, Italy
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Rome, Italy; Istituto di Biologia e Patologia Molecolari del CNR c/o Sapienza Università di Roma, 00185 Rome, Italy; Institute of Molecular and Cellular Biology SD RAS, Novosibirsk 630090, Russia
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Rome, Italy.
| | - James G Wakefield
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.
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14
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Mengoli V, Bucciarelli E, Lattao R, Piergentili R, Gatti M, Bonaccorsi S. The analysis of mutant alleles of different strength reveals multiple functions of topoisomerase 2 in regulation of Drosophila chromosome structure. PLoS Genet 2014; 10:e1004739. [PMID: 25340516 PMCID: PMC4207652 DOI: 10.1371/journal.pgen.1004739] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Accepted: 09/08/2014] [Indexed: 12/14/2022] Open
Abstract
Topoisomerase II is a major component of mitotic chromosomes but its role in the assembly and structural maintenance of chromosomes is rather controversial, as different chromosomal phenotypes have been observed in various organisms and in different studies on the same organism. In contrast to vertebrates that harbor two partially redundant Topo II isoforms, Drosophila and yeasts have a single Topo II enzyme. In addition, fly chromosomes, unlike those of yeast, are morphologically comparable to vertebrate chromosomes. Thus, Drosophila is a highly suitable system to address the role of Topo II in the assembly and structural maintenance of chromosomes. Here we show that modulation of Top2 function in living flies by means of mutant alleles of different strength and in vivo RNAi results in multiple cytological phenotypes. In weak Top2 mutants, meiotic chromosomes of males exhibit strong morphological abnormalities and dramatic segregation defects, while mitotic chromosomes of larval brain cells are not affected. In mutants of moderate strength, mitotic chromosome organization is normal, but anaphases display frequent chromatin bridges that result in chromosome breaks and rearrangements involving specific regions of the Y chromosome and 3L heterochromatin. Severe Top2 depletion resulted in many aneuploid and polyploid mitotic metaphases with poorly condensed heterochromatin and broken chromosomes. Finally, in the almost complete absence of Top2, mitosis in larval brains was virtually suppressed and in the rare mitotic figures observed chromosome morphology was disrupted. These results indicate that different residual levels of Top2 in mutant cells can result in different chromosomal phenotypes, and that the effect of a strong Top2 depletion can mask the effects of milder Top2 reductions. Thus, our results suggest that the previously observed discrepancies in the chromosomal phenotypes elicited by Topo II downregulation in vertebrates might depend on slight differences in Topo II concentration and/or activity. Type II topoisomerases (Topo II) are enzymes that disentangle DNA molecules during essential cellular processes such as DNA replication, chromosome condensation and mitotic cell division. Topo II is a major component of mitotic chromosomes and it is a well known target for cancer chemotherapy. Topo II inhibitors block the Topo II enzymatic activity leading to extensive DNA damage, which ultimately kills the cancer cell. Thus, investigating the role of Topo II in the assembly and structural maintenance of chromosomes is not only relevant to understand chromosome biology but might also have a translational impact on cancer therapy. Here we used Drosophila as model system to analyze the effect of Topo II depletion on chromosome stability. We show that the chromosomal phenotypes of mutant flies vary with the amount of residual Topo II, ranging from site-specific chromosome breaks, variations in chromosome number (aneuploidy and poliploidy) and dramatic defects in chromosome morphology. The chromosomal phenotypes observed in flies recapitulate all phenotypes seen in Topo II-depleted vertebrate chromosomes, reconciling the phenotypic discrepancies reported in previous studies. In addition, our finding that the Topo II dependent phenotypes vary with the residual amount of the enzyme provides useful information on the possible outcome of cancer therapy with Topo II inhibitors.
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Affiliation(s)
- Valentina Mengoli
- Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Elisabetta Bucciarelli
- Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Ramona Lattao
- Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Roberto Piergentili
- Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Maurizio Gatti
- Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russia
- * E-mail: (MG); (SB)
| | - Silvia Bonaccorsi
- Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- * E-mail: (MG); (SB)
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15
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Gatti M, Bucciarelli E, Lattao R, Pellacani C, Mottier-Pavie V, Giansanti MG, Somma MP, Bonaccorsi S. The relative roles of centrosomal and kinetochore-driven microtubules in Drosophila spindle formation. Exp Cell Res 2012; 318:1375-80. [DOI: 10.1016/j.yexcr.2012.05.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Revised: 04/29/2012] [Accepted: 05/02/2012] [Indexed: 11/17/2022]
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16
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Lattao R, Bonaccorsi S, Gatti M. Giant meiotic spindles in males from Drosophila species with giant sperm tails. Development 2012. [DOI: 10.1242/dev.081554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Abstract
The spindle is a highly dynamic molecular machine that mediates precise chromosome segregation during cell division. Spindle size can vary dramatically, not only between species but also between different cells of the same organism. However, the reasons for spindle size variability are largely unknown. Here we show that variations in spindle size can be linked to a precise developmental requirement. Drosophila species have dramatically different sperm flagella that range in length from 0.3 mm in D. persimilis to 58.3 mm in D. bifurca. We found that males of different species exhibit striking variations in meiotic spindle size, which positively correlate with sperm length, with D. bifurca showing 30-fold larger spindles than D. persimilis. This suggests that primary spermatocytes of Drosophila species manufacture and store amounts of tubulin that are proportional to the axoneme length and use these tubulin pools for spindle assembly. These findings highlight an unsuspected plasticity of the meiotic spindle in response to the selective forces controlling sperm length.
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Affiliation(s)
- Ramona Lattao
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biologia e Biotecnologie “Charles Darwin” Sapienza, Università di Roma, 00185, Italy
| | - Silvia Bonaccorsi
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biologia e Biotecnologie “Charles Darwin” Sapienza, Università di Roma, 00185, Italy
| | - Maurizio Gatti
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biologia e Biotecnologie “Charles Darwin” Sapienza, Università di Roma, 00185, Italy
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18
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Abstract
Preparations of Drosophila testes fixed with paraformaldehyde can be stained for F-actin according to the protocol described here. This staining procedure is particularly suitable for staining the male fusome and the cytokinetic contractile ring.
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Abstract
This protocol describes paraformaldehyde fixation of Drosophila testes. The procedure preserves F-actin-containing structures because it does not involve the use of methanol. Thus, it is particularly suitable for contractile ring and fusome visualization. However, it does not preserve cell morphology and microtubules as efficiently as methanol-acetone fixation and does not permit clear detection of the Y loops.
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Abstract
Fixed Drosophila testis preparations can be immunostained with a variety of antibodies. This article describes a general procedure for immunostaining. The concentration of the primary antibody will vary with both the type of antibody and the type of incubation and should be determined empirically each time.
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Abstract
This protocol describes two techniques for methanol-acetone fixation of Drosophila melanogaster testis squashes. The first method results in very good preservation of cell morphology. Fixed cells viewed by phase-contrast optics show most of the structural details that can be seen in live material. This allows analysis of unstained fixed preparations and selection of the most suitable ones for immunostaining. Remarkably, the Y loops, which are usually faint and labile in living preparations, become clearly apparent after this type of fixation. Moreover, this fixation method results in excellent microtubule preservation for immunostaining with antitubulin antibodies. The main disadvantage of this technique is poor preservation of chromosome structure. In most instances, the chromosomes do not show a distinct morphology and tend to coalesce into one or more masses of chromatin. The second technique for methanol-acetone fixation described here has proved to be particularly suitable for γ-tubulin and centrosomin immunostaining. It results in preparations having the same characteristics as those obtained with the first method.
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Pimpinelli S, Bonaccorsi S, Fanti L, Gatti M. Immunostaining of mitotic chromosomes from Drosophila larval brain. Cold Spring Harb Protoc 2011; 2011:2011/9/pdb.prot065524. [PMID: 21880821 DOI: 10.1101/pdb.prot065524] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Good mitotic chromosome preparations are essential for the immunolocalization of chromosomal proteins. Although methanol/acetic acid fixation techniques preserve chromosome morphology very well, they remove a substantial fraction of chromosomal proteins. We have developed fixation/immunostaining procedures, described here, that are suitable for the immunolocalization of proteinaceous components of metaphase chromosomes from larval Drosophila brain cells. These procedures result in good chromosomal quality with minimal removal of proteins.
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Abstract
We generated FM7a and CyO balancer chromosomes bearing a Tubby1 (Tb1) dominant transgene. Flies heterozygous for these FM7a and CyO derivatives exhibit a phenotype undistinguishable from that elicited by the Tb1 mutation associated with the TM6B balancer. We tested two of these Tb-bearing balancers (FM7-TbA and CyO-TbA) for more than 30 generations and found that the Tb1 transgene they carry is stable. Thus, these new Tb-tagged balancers are particularly useful for balancing lethal mutations and distinguish homozygous mutant larvae from their heterozygous siblings.
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Affiliation(s)
- Ramona Lattao
- Dipartimento di Biologia e Biotecnologie “Charles Darwin” and Istituto di Biologia e Patologia Molecolari del CNR, Sapienza, Università di Roma, Rome, Italy
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Mottier-Pavie V, Cenci G, Vernì F, Gatti M, Bonaccorsi S. Phenotypic analysis of misato function reveals roles of noncentrosomal microtubules in Drosophila spindle formation. Development 2011. [DOI: 10.1242/dev.065730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Bonaccorsi S, Giansanti MG, Cenci G, Gatti M. Preparation of meiotic chromosomes from larval and pupal Drosophila testes. Cold Spring Harb Protoc 2011; 2011:prot5579. [PMID: 21363943 DOI: 10.1101/pdb.prot5579] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Bonaccorsi S, Giansanti MG, Cenci G, Gatti M. Preparation of meiotic chromosomes from adult Drosophila testes. Cold Spring Harb Protoc 2011; 2011:prot5578. [PMID: 21363942 DOI: 10.1101/pdb.prot5578] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
INTRODUCTIONSeveral techniques have been developed for the preparation of Drosophila male meiotic chromosomes. All of these techniques allow a clear visualization of chromosomes, but not of other cellular structures such as the cytoskeleton and the spindle. The protocol described here is particularly useful for the analysis of adult testes.
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Mottier-Pavie V, Cenci G, Vernì F, Gatti M, Bonaccorsi S. Phenotypic analysis of misato function reveals roles of noncentrosomal microtubules in Drosophila spindle formation. J Cell Sci 2011; 124:706-17. [PMID: 21285248 DOI: 10.1242/jcs.072348] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mitotic spindle assembly in centrosome-containing cells relies on two main microtubule (MT) nucleation pathways, one based on centrosomes and the other on chromosomes. However, the relative role of these pathways is not well defined. In Drosophila, mutants without centrosomes can form functional anastral spindles and survive to adulthood. Here we show that mutations in the Drosophila misato (mst) gene inhibit kinetochore-driven MT growth, lead to the formation of monopolar spindles and cause larval lethality. In most prophase cells of mst mutant brains, asters are well separated, but collapse with progression of mitosis, suggesting that k-fibers are essential for maintenance of aster separation and spindle bipolarity. Analysis of mst; Sas-4 double mutants showed that mitotic cells lacking both the centrosomes and the mst function form polarized MT arrays that resemble monopolar spindles. MT regrowth experiments after cold exposure revealed that in mst; Sas-4 metaphase cells MTs regrow from several sites, which eventually coalesce to form a single polarized MT array. By contrast, in Sas-4 single mutants, chromosome-driven MT regrowth mostly produced robust bipolar spindles. Collectively, these results indicate that kinetochore-driven MT formation is an essential process for proper spindle assembly in Drosophila somatic cells.
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Affiliation(s)
- Violaine Mottier-Pavie
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Roma, Italy
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Pimpinelli S, Bonaccorsi S, Fanti L, Gatti M. Fluorescent in situ hybridization (FISH) of mitotic chromosomes from Drosophila larval brain. Cold Spring Harb Protoc 2010; 2010:pdb.prot5391. [PMID: 20194460 DOI: 10.1101/pdb.prot5391] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The fluorescent in situ hybridization (FISH) technique permits fine mapping of both middle and highly repetitive DNA sequences along Drosophila melanogaster heterochromatin. Best results are obtained when this technique is coupled with DAPI staining and digital recording of fluorescent signals. For example, if digital images of the FISH signals and DAPI fluorescence are detected separately using a charge-coupled device (CCD) camera, they can then be pseudocolored and merged using suitable computer programs. This allows precise overlapping of the DAPI banding (which is identical to the Hoechst 33258 banding) and the FISH signals, facilitating the assignment of the repetitive sequence under study to specific regions of the cytological map of D. melanogaster heterochromatin. This article describes FISH procedures that are routinely used with larval brain squashes, including preparation of slides, preparation of biotin- and digoxigenin-labeled probes, hybridization, and detection.
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Ferretti R, Palumbo V, Di Savino A, Velasco S, Sbroggiò M, Sportoletti P, Micale L, Turco E, Silengo L, Palumbo G, Hirsch E, Teruya-Feldstein J, Bonaccorsi S, Pandolfi PP, Gatti M, Tarone G, Brancaccio M. Morgana/chp-1, a ROCK inhibitor involved in centrosome duplication and tumorigenesis. Dev Cell 2010; 18:486-95. [PMID: 20230755 DOI: 10.1016/j.devcel.2009.12.020] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 11/04/2009] [Accepted: 12/28/2009] [Indexed: 11/19/2022]
Abstract
Centrosome abnormalities lead to genomic instability and are a common feature of many cancer cells. Here we show that mutations in morgana/chp-1 result in centrosome amplification and lethality in both Drosophila and mouse, and that the fly centrosome phenotype is fully rescued by the human ortholog of morgana. In mouse cells, morgana forms a complex with Hsp90 and ROCK I and II, and directly binds ROCK II. Morgana downregulation promotes the interaction between ROCK II and nucleophosmin (NPM), leading to an increased ROCK II kinase activity, which results in centrosome amplification. Morgana(+/-) primary cells and mice display an increased susceptibility to neoplastic transformation. In addition, tumor tissue array histochemical analysis revealed that morgana is underexpressed in a large fraction of breast and lung human cancers. Thus, morgana/chp-1 appears to prevent both centrosome amplification and tumorigenesis.
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Affiliation(s)
- Roberta Ferretti
- Dipartimento di Genetica, Biologia e Biochimica, Università di Torino, 10126 Torino, Italy
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Pimpinelli S, Bonaccorsi S, Fanti L, Gatti M. Chromosome banding of mitotic chromosomes from Drosophila larval brain. Cold Spring Harb Protoc 2010; 2010:pdb.prot5390. [PMID: 20194459 DOI: 10.1101/pdb.prot5390] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The classical chromosome-banding techniques developed for mammalian chromosomes do not differentiate the euchromatic arms of Drosophila mitotic chromosomes. However, some of these techniques produce a sharp and highly reproducible banding of Drosophila heterochromatin. For example, the use of quinacrine-, Hoechst-, and N-banding differentiates Drosophila heterochromatin into 61 cytological entities, allowing precise localization of heterochromatic breakpoints. These banding techniques can also be successfully used to differentiate mitotic heterochromatin of various Drosophila and mosquito species. Here we present protocols routinely used in our laboratories for chromosome banding, including the use of Hoechst, 4',6-diamidino-2-phenylindole (DAPI), quinacrine, and Giemsa stains.
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Pimpinelli S, Bonaccorsi S, Fanti L, Gatti M. Preparation and orcein staining of mitotic chromosomes from Drosophila larval brain. Cold Spring Harb Protoc 2010; 2010:pdb.prot5389. [PMID: 20194458 DOI: 10.1101/pdb.prot5389] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this protocol, larval brains from Drosophila are incubated in vitro with colchicine, treated with hypotonic solution, fixed, and squashed in aceto-orcein. This procedure provides a large number of well-spread metaphase figures (200-400 per brain) that can be analyzed for chromosome morphology, the presence of chromosome aberrations, and the degree of ploidy.
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Wainman A, Creque J, Williams B, Williams EV, Bonaccorsi S, Gatti M, Goldberg ML. Roles of the Drosophila NudE protein in kinetochore function and centrosome migration. J Cell Sci 2009; 122:1747-58. [PMID: 19417004 DOI: 10.1242/jcs.041798] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We examined the distribution of the dynein-associated protein NudE in Drosophila larval brain neuroblasts and spermatocytes, and analyzed the phenotypic consequences of a nudE null mutation. NudE can associate with kinetochores, spindles and the nuclear envelope. In nudE mutant brain mitotic cells, centrosomes are often detached from the poles. Moreover, the centrosomes of mutant primary spermatocytes do not migrate from the cell cortex to the nuclear envelope, establishing a new role for NudE. In mutant neuroblasts, chromosomes fail to congress to a tight metaphase plate, and cell division arrests because of spindle assembly checkpoint (SAC) activation. The targeting of NudE to mitotic kinetochores requires the dynein-interacting protein Lis1, and surprisingly Cenp-meta, a Drosophila CENP-E homolog. NudE is non-essential for the targeting of all mitotic kinetochore components tested. However, in the absence of NudE, the 'shedding' of proteins off the kinetochore is abrogated and the SAC cannot be turned off, implying that NudE regulates dynein function at the kinetochore.
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Affiliation(s)
- Alan Wainman
- Instituto Pasteur Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Sapienza, Università di Roma, 00185 Rome, Italy
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Giansanti MG, Bucciarelli E, Bonaccorsi S, Gatti M. Drosophila SPD-2 is an essential centriole component required for PCM recruitment and astral-microtubule nucleation. Curr Biol 2008; 18:303-9. [PMID: 18291647 DOI: 10.1016/j.cub.2008.01.058] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Revised: 01/04/2008] [Accepted: 01/24/2008] [Indexed: 12/12/2022]
Abstract
SPD-2 is a C. elegans centriolar protein required for both centriole duplication and pericentriolar material (PCM) recruitment [1-4]. SPD-2 is conserved in Drosophila (DSpd-2) and is a component of the fly centriole [5-7]. The analysis of a P element-induced hypomorphic mutation has shown that DSpd-2 is primarily required for PCM recruitment at the sperm centriole but is dispensable for both centriole duplication and aster formation [5]. Here we show that null mutations carrying early stop codons in the DSpd-2 coding sequence suppress astral microtubule (MT) nucleation in both neuroblasts (NBs) and spermatocytes. These mutations also disrupt proper Miranda localization in dividing NBs, as previously observed in mutants lacking astral MTs [8-10]. Spermatocyte analysis revealed that DSpd-2 is enriched at both the centrioles and the PCM and is required for the maintenance of cohesion between the two centrioles but not for centriole duplication. We found that DSpd-2 localization at the centrosome requires the wild-type activity of Asl but is independent of the function of D-PLP, Cnn, gamma-tubulin, DGrip91, and D-TACC. Conversely, DSpd-2 mutants displayed normal centrosomal accumulations of Asl and D-PLP, strongly reduced amounts of Cnn, gamma-tubulin, and DGrip91, and diffuse localization of D-TACC. These results indicate that DSpd-2 functions in a very early step of the PCM recruitment pathway.
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Affiliation(s)
- Maria Grazia Giansanti
- Dipartimento di Genetica e Biologia Molecolare, Università di Roma La Sapienza, P.le A. Moro 5, 00185 Roma, Italy
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Bonaccorsi S, Mottier V, Giansanti MG, Bolkan BJ, Williams B, Goldberg ML, Gatti M. The Drosophila Lkb1 kinase is required for spindle formation and asymmetric neuroblast division. Development 2008; 134:2183-93. [PMID: 17507418 DOI: 10.1242/dev.02848] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have isolated lethal mutations in the Drosophila lkb1 gene (dlkb1), the homolog of C. elegans par-4 and human LKB1 (STK11), which is mutated in Peutz-Jeghers syndrome. We show that these mutations disrupt spindle formation, resulting in frequent polyploid cells in larval brains. In addition, dlkb1 mutations affect asymmetric division of larval neuroblasts (NBs); they suppress unequal cytokinesis, abrogate proper localization of Bazooka, Par-6, DaPKC and Miranda, but affect neither Pins/Galphai localization nor spindle rotation. Most aspects of the dlkb1 phenotype are exacerbated in dlkb1 pins double mutants, which exhibit more severe defects than those observed in either single mutant. This suggests that Dlkb1 and Pins act in partially redundant pathways to control the asymmetry of NB divisions. Our results also indicate that Dlkb1 and Pins function in parallel pathways controlling the stability of spindle microtubules. The finding that Dlkb1 mediates both the geometry of stem cell division and chromosome segregation provides novel insight into the mechanisms underlying tumor formation in Peutz-Jeghers patients.
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Affiliation(s)
- Silvia Bonaccorsi
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma La Sapienza, P.le A. Moro 5, 00185 Roma, Italy
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Giansanti MG, Bonaccorsi S, Kurek R, Farkas RM, Dimitri P, Fuller MT, Gatti M. The Class I PITP Giotto Is Required for Drosophila Cytokinesis. Curr Biol 2006; 16:195-201. [PMID: 16431372 DOI: 10.1016/j.cub.2005.12.011] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2005] [Revised: 11/03/2005] [Accepted: 12/02/2005] [Indexed: 10/25/2022]
Abstract
Phosphatidylinositol transfer proteins (PITPs) are highly conserved polypeptides that bind phosphatidylinositol or phosphatidylcholine monomers, facilitating their transfer from one membrane compartment to another . Although PITPs have been implicated in a variety of cellular functions, including lipid-mediated signaling and membrane trafficking, the precise biological roles of most PITPs remain to be elucidated . Here we show for the first time that a class I PITP is involved in cytokinesis. We found that giotto (gio), a Drosophila gene that encodes a class I PITP, serves an essential function required for both mitotic and meiotic cytokinesis. Neuroblasts and spermatocytes from gio mutants both assemble regular actomyosin rings. However, these rings fail to constrict to completion, leading to cytokinesis failures. Moreover, gio mutations cause an abnormal accumulation of Golgi-derived vesicles at the equator of spermatocyte telophases, suggesting that Gio is implicated in membrane-vesicle fusion. Consistent with these results, we found that Gio is enriched at the cleavage furrow, the ER, and the spindle envelope. We propose that Gio mediates transfer of lipid monomers from the ER to the equatorial membrane, causing a specific local enrichment in phosphatidylinositol. This change in membrane composition would ultimately facilitate vesicle fusion, allowing membrane addition to the furrow and/or targeted delivery of proteins required for cytokinesis.
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Affiliation(s)
- Maria Grazia Giansanti
- Dipartimento di Genetica e Biologia Molecolare, Istituto Pasteur-Fondazione Cenci Bolognetti, Istituto di Biologia e Patologia Molecolari del CNR, Università di Roma La Sapienza, P.le A. Moro 5, 00185 Roma, Italy
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Abramov YA, Kogan GL, Tolchkov EV, Rasheva VI, Lavrov SA, Bonaccorsi S, Kramerova IA, Gvozdev VA. Eu-heterochromatic rearrangements induce replication of heterochromatic sequences normally underreplicated in polytene chromosomes of Drosophila melanogaster. Genetics 2005; 171:1673-81. [PMID: 16020783 PMCID: PMC1456094 DOI: 10.1534/genetics.105.044461] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In polytene chromosomes of D. melanogaster the heterochromatic pericentric regions are underreplicated (underrepresented). In this report, we analyze the effects of eu-heterochromatic rearrangements involving a cluster of the X-linked heterochromatic (Xh) Stellate repeats on the representation of these sequences in salivary gland polytene chromosomes. The discontinuous heterochromatic Stellate cluster contains specific restriction fragments that were mapped along the distal region of Xh. We found that transposition of a fragment of the Stellate cluster into euchromatin resulted in its replication in polytene chromosomes. Interestingly, only the Stellate repeats that remain within the pericentric Xh and are close to a new eu-heterochromatic boundary were replicated, strongly suggesting the existence of a spreading effect exerted by the adjacent euchromatin. Internal rearrangements of the distal Xh did not affect Stellate polytenization. We also demonstrated trans effects exerted by heterochromatic blocks on the replication of the rearranged heterochromatin; replication of transposed Stellate sequences was suppressed by a deletion of Xh and restored by addition of Y heterochromatin. This phenomenon is discussed in light of a possible role of heterochromatic proteins in the process of heterochromatin underrepresentation in polytene chromosomes.
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Affiliation(s)
- Yuri A Abramov
- Isituto di Biologia e Patologia Molecolari del CNR, Universitá di Roma La Sapienza, Rome, Italy I-00185
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Vernì F, Somma MP, Gunsalus KC, Bonaccorsi S, Belloni G, Goldberg ML, Gatti M. Feo, the Drosophila homolog of PRC1, is required for central-spindle formation and cytokinesis. Curr Biol 2005; 14:1569-75. [PMID: 15341744 DOI: 10.1016/j.cub.2004.08.054] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2004] [Revised: 07/09/2004] [Accepted: 07/13/2004] [Indexed: 10/26/2022]
Abstract
We performed a functional analysis of fascetto (feo), a Drosophila gene that encodes a protein homologous to the Ase1p/PRC1/MAP65 conserved family of microtubule-associated proteins (MAPs). These MAPs are enriched at the spindle midzone in yeast and mammals and at the fragmoplast in plants, and are essential for the organization and function of these microtubule arrays. Here we show that the Feo protein is specifically enriched at the central-spindle midzone and that its depletion either by mutation or by RNAi results in aberrant central spindles. In Feo-depleted cells, late anaphases showed normal overlap of the antiparallel MTs at the cell equator, but telophases displayed thin MT bundles of uniform width instead of robust hourglass-shaped central spindles. These thin central spindles exhibited diffuse localizations of both the Pav and Asp proteins, suggesting that these spindles comprise improperly oriented MTs. Feo-depleted cells also displayed defects in the contractile apparatus that correlated with those in the central spindle; late anaphase cells formed regular contractile structures, but these structures did not constrict during telophase, leading to failures in cytokinesis. The phenotype of Feo-depleted telophases suggests that Feo interacts with the plus ends of central spindle MTs so as to maintain their precise interdigitation during anaphase-telophase MT elongation and antiparallel sliding.
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Affiliation(s)
- Fiammetta Vernì
- Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari del Consiglio Nazionale delle Ricerche, Dipartimento di Genetica e Biologia Molecolare, Università di Roma La Sapienza, P. le A. Moro 5, 00185 Roma, Italy
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Abstract
The mechanisms underlying completion of cytokinesis are still poorly understood. Here, we show that the Drosophila orthologue of mammalian Citron kinases is essential for the final events of the cytokinetic process. Flies bearing mutations in the Drosophila citron kinase (dck) gene were defective in both neuroblast and spermatocyte cytokinesis. In both cell types, early cytokinetic events such as central spindle assembly and contractile ring formation were completely normal. Moreover, cytokinetic rings constricted normally, leading to complete furrow ingression. However late telophases of both cell types displayed persistent midbodies associated with disorganized F actin and anillin structures. Similar defects were observed in dck RNA interference (RNAi) telophases, which, in addition to abnormal F actin and anillin rings, also displayed aberrant membrane protrusions at the cleavage site. Together, these results indicate that mutations in the dck gene result in morphologically abnormal intercellular bridges and in delayed resolution of these structures, suggesting that the wild-type function of dck is required for abscission at the end of cytokinesis. The phenotype of Dck-depleted cells is different from those observed in most Drosophila cytokinesis mutants but extraordinarily similar to that caused by anillin RNAi, suggesting that Dck and anillin are in the same pathway for completion of cytokinesis.
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Affiliation(s)
- Valeria Naim
- Istituto di Biologia e Patologia Molecolari del Consiglio Nazionale Delle Ricerche, Dipartimento di Genetica e Biologia Molecolare, Universitá La Sapienza, 00185 Rome, Italy
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Piergentili R, Bonaccorsi S, Raffa GD, Pisano C, Hackstein JHP, Mencarelli C. Autosomal control of the Y-chromosome kl-3 loop of Drosophila melanogaster. Chromosoma 2004; 113:188-96. [PMID: 15338233 DOI: 10.1007/s00412-004-0308-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2004] [Revised: 07/07/2004] [Accepted: 07/12/2004] [Indexed: 10/26/2022]
Abstract
The Y chromosome of Drosophila melanogaster carries a limited number of loci necessary for male fertility that possess a series of unconventional features that still hinder a definition of their biological role: they have extremely large sizes; accommodate huge amounts of repetitive DNA; and develop prominent, lampbrush-like loops that bind a number of non-Y-encoded proteins. To obtain insight into the functional role of the loop-forming fertility factors, we characterized four autosomal male-sterile mutations that identify two loci we named loop unfolding protein-1 (lup-1) and loop unfolding protein-2 (lup-2). Biochemical and ultrastructural analysis revealed that neither of them impairs the synthesis of the putative dynein subunit encoded by the ORF localized within the kl-3 fertility factor. However, the stability of four dynein heavy chains is simultaneously affected in each mutant, together with the regular assembly of the axonemal dynein arms that are either absent or strongly reduced. These results indicate that the synthesis of the kl-3-encoded dynein can be uncoupled from the formation of the corresponding loop and suggest that this structure does not simply represent the cytological counterpart of a huge transcription unit, but must be regarded as a complex organelle serving some additional function necessary for male fertility.
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Affiliation(s)
- Roberto Piergentili
- Dipartimento di Genetica e Biologia Molecolare, Universita' di Roma La Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy
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Giansanti MG, Farkas RM, Bonaccorsi S, Lindsley DL, Wakimoto BT, Fuller MT, Gatti M. Genetic dissection of meiotic cytokinesis in Drosophila males. Mol Biol Cell 2004; 15:2509-22. [PMID: 15004238 PMCID: PMC404041 DOI: 10.1091/mbc.e03-08-0603] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We have used Drosophila male meiosis as a model system for genetic dissection of the cytokinesis mechanism. Drosophila mutants defective in meiotic cytokinesis can be easily identified by their multinucleate spermatids. Moreover, the large size of meiotic spindles allows characterization of mutant phenotypes with exquisite cytological resolution. We have screened a collection of 1955 homozygous mutant male sterile lines for those with multinucleate spermatids, and thereby identified mutations in 19 genes required for cytokinesis. These include 16 novel loci and three genes, diaphanous, four wheel drive, and pebble, already known to be involved in Drosophila cytokinesis. To define the primary defects leading to failure of cytokinesis, we analyzed meiotic divisions in male mutants for each of these 19 genes. Examination of preparations stained for tubulin, anillin, KLP3A, and F-actin revealed discrete defects in the components of the cytokinetic apparatus, suggesting that these genes act at four major points in a stepwise pathway for cytokinesis. Our results also indicated that the central spindle and the contractile ring are interdependent structures that interact throughout cytokinesis. Moreover, our genetic and cytological analyses provide further evidence for a cell type-specific control of Drosophila cytokinesis, suggesting that several genes required for meiotic cytokinesis in males are not required for mitotic cytokinesis.
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Affiliation(s)
- Maria Grazia Giansanti
- Istituto Pasteur Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari del CNR, Dipartimento di Genetica e Biologia Molecolare, Universitá La Sapienza, 00185 Rome, Italy
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Gandhi R, Bonaccorsi S, Wentworth D, Doxsey S, Gatti M, Pereira A. The Drosophila kinesin-like protein KLP67A is essential for mitotic and male meiotic spindle assembly. Mol Biol Cell 2004; 15:121-31. [PMID: 13679514 PMCID: PMC307533 DOI: 10.1091/mbc.e03-05-0342] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2003] [Revised: 08/20/2003] [Accepted: 08/28/2003] [Indexed: 11/11/2022] Open
Abstract
We have performed a mutational analysis together with RNA interference to determine the role of the kinesin-like protein KLP67A in Drosophila cell division. During both mitosis and male meiosis, Klp67A mutations cause an increase in MT length and disrupt discrete aspects of spindle assembly, as well as cytokinesis. Mutant cells exhibit greatly enlarged metaphase spindle as a result of excessive MT polymerization. The analysis of both living and fixed cells also shows perturbations in centrosome separation, chromosome segregation, and central spindle assembly. These data demonstrate that the MT plus end-directed motor KLP67A is essential for spindle assembly during mitosis and male meiosis and suggest that the regulation of MT plus-end polymerization is a key determinant of spindle architecture throughout cell division.
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Affiliation(s)
- Rita Gandhi
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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Cosentino S, Cacopardo B, Celesia B, Vinciguerra G, Zagami A, Vinci G, Boscia V, Ricifari L, Bonaccorsi S, Nunnari A. [Multiple osteo-articular involvement due to methicillin-resistant Staphylococcus aureus septicaemia: clinical and therapeutic evaluation]. Infez Med 2003; 6:39-43. [PMID: 12732825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
Here we report a rare case of septic spondilodiskitis by methicillin-resistant Staphylococcus aureus, complicated by the atypical involvement of two articular sites such as manubrio-clavicular joints and right wrist. The source of the septic process was identified in hand's eczematous lesions and paronychia. A first therapeutical attempt performed by combining teicoplanin with netilmicin or rifampicin was useless. A new course with vancomycin instead of teicoplanin favoured the prompt remission of symptoms. Following 10 weeks of continuous treatment, we observed the complete disappearance of all radiological signs of vertebral damage. Though rarely, polyarthritis may complicate a Staphylococcus aureus bacteraemia. An adequate chemio-antibiotic course may lead to definitive recovery and avoid surgery.
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Affiliation(s)
- S. Cosentino
- Istituto di Malattie Infettive, Universita di Catania, Italy
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44
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Abstract
A large body of work indicates that chromosomes play a key role in the assembly of both a centrosomal and centrosome-containing spindles. In animal systems, the absence of chromosomes either prevents spindle formation or allows the assembly of a metaphase-like spindle that fails to evolve into an ana-telophase spindle. Here, we show that Drosophila secondary spermatocytes can assemble morphologically normal spindles in the absence of chromosomes. The Drosophila mutants fusolo and solofuso are severely defective in chromosome segregation and produce secondary spermatocytes that are devoid of chromosomes. The centrosomes of these anucleated cells form robust asters that give rise to bipolar spindles that undergo the same ana-telophase morphological transformations that characterize normal spindles. The cells containing chromosome-free spindles are also able to assemble regular cytokinetic structures and cleave normally. In addition, chromosome-free spindles normally accumulate the Aurora B kinase at their midzones. This suggests that the association of Aurora B with chromosomes is not a prerequisite for its accumulation at the central spindle, or for its function during cytokinesis.
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Giansanti MG, Bonaccorsi S, Bucciarelli E, Gatti M. Drosophila male meiosis as a model system for the study of cytokinesis in animal cells. Cell Struct Funct 2001; 26:609-17. [PMID: 11942616 DOI: 10.1247/csf.26.609] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Drosophila male meiosis offers unique opportunities for mutational dissection of cytokinesis. This system allows easy and unambiguos identification of mutants defective in cytokinesis through the examination of spermatid morphology. Moreover, cytokinesis defects and protein immunostaining can be analyzed with exquisite cytological resolution because of the large size of meiotic spindles. In the past few years several mutations have been isolated that disrupt meiotic cytokinesis in Drosophila males. These mutations specify genes required for the assembly, proper constriction or disassembly of the contractile ring. Molecular characterization of these genes has identified essential components of the cytokinetic machinery, highlighting the role of the central spindle during cytokinesis. This structure appears to be both necessary and sufficient for signaling cytokinesis. In addition, many data indicate that the central spindle microtubules cooperatively interact with elements of the actomyosin contractile ring, so that impairment of either of these structures prevents the formation of the other.
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Affiliation(s)
- M G Giansanti
- Istituto Pasteur-Fondazione Cenci Bolognetti, Universita' Roma La Sapienza, Italy.
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46
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Abstract
Abnormal spindle (Asp) is a 220-kD microtubule-associated protein from Drosophila that has been suggested to be involved in microtubule nucleation from the centrosome. Here, we show that Asp is enriched at the poles of meiotic and mitotic spindles and localizes to the minus ends of central spindle microtubules. Localization to these structures is independent of a functional centrosome. Moreover, colchicine treatment disrupts Asp localization to the centrosome, indicating that Asp is not an integral centrosomal protein. In both meiotic and mitotic divisions of asp mutants, microtubule nucleation occurs from the centrosome, and γ-tubulin localizes correctly. However, spindle pole focusing and organization are severely affected. By examining cells that carry mutations both in asp and in asterless, a gene required for centrosome function, we have determined the role of Asp in the absence of centrosomes. Phenotypic analysis of these double mutants shows that Asp is required for the aggregation of microtubules into focused spindle poles, reinforcing the conclusion that its function at the spindle poles is independent of any putative role in microtubule nucleation. Our data also suggest that Asp has a role in the formation of the central spindle. The inability of asp mutants to correctly organize the central spindle leads to disruption of the contractile ring machinery and failure in cytokinesis.
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Affiliation(s)
- James G. Wakefield
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma “La Sapienza,” 00185 Rome, Italy
| | - Silvia Bonaccorsi
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma “La Sapienza,” 00185 Rome, Italy
| | - Maurizio Gatti
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma “La Sapienza,” 00185 Rome, Italy
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47
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Abstract
Drosophila neuroblasts are stem cells that divide asymmetrically to produce another large neuroblast and a smaller ganglion mother cell (GMC). During neuroblast division, several cell fate determinants, such as Miranda, Prospero and Numb, are preferentially segregated into the GMC, ensuring its correct developmental fate. The accurate segregation of these determinants relies on proper orientation of the mitotic spindle within the dividing neuroblast, and on the correct positioning of the cleavage plane. In this study we have analyzed the role of centrosomes and astral microtubules in neuroblast spindle orientation and cytokinesis. We examined neuroblast division in asterless (asl) mutants, which, although devoid of functional centrosomes and astral microtubules, form well-focused anastral spindles that undergo anaphase and telophase. We show that asl neuroblasts assemble a normal cytokinetic ring around the central spindle midzone and undergo unequal cytokinesis. Thus, astral microtubules are not required for either signaling or positioning cytokinesis in Drosophila neuroblasts. Our results indicate that the cleavage plane is dictated by the positioning of the central spindle midzone within the cell, and suggest a model on how the central spindle attains an asymmetric position during neuroblast mitosis. We have also analyzed the localization of Miranda during mitotic division of asl neuroblasts. This protein accumulates in morphologically regular cortical crescents but these crescents are mislocalized with respect to the spindle orientation. This suggests that astral microtubules mediate proper spindle rotation during neuroblast division.
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Affiliation(s)
- M G Giansanti
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Universita' di Roma La Sapienza, P.le Aldo Moro 5, Italy
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48
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Abstract
During late anaphase and telophase, animal cells develop a bundle of antiparallel, interdigitating microtubules between the two daughter nuclei. Recent data indicate that this structure, called the central spindle, plays an essential role during cytokinesis. Studies in Drosophila and on vertebrate cells strongly suggest that the molecular signals for cytokinesis specifically emanate from the central spindle midzone. Moreover, the analysis of Drosophila mutants defective in cytokinesis has revealed a cooperative interaction between the central spindle microtubules and the contractile ring: when either of these structures is perturbed, the proper assembly of the other is disrupted. Based on these results we propose a model for the role of the central spindle during cytokinesis. We suggest that the interaction between central spindle microtubules and cortical actin filaments leads to two early events crucial for cytokinesis: the positioning of the contractile ring, and the stabilization of the plus ends of the interdigitating microtubules that comprise the central spindle. The latter event would provide the cell with a specialized microtubule scaffold that could mediate the translocation of plus-end-directed molecular motors to the cell's equator. Among the cargoes transported by these motors could be proteins involved in the regulation and execution of cytokinesis.
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Affiliation(s)
- M Gatti
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma "La Sapienza," P. A. Mozo 5, 00185 Roma, Italy.
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49
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Tolchkov EV, Rasheva VI, Bonaccorsi S, Westphal T, Gvozdev VA. The size and internal structure of a heterochromatic block determine its ability to induce position effect variegation in Drosophila melanogaster. Genetics 2000; 154:1611-26. [PMID: 10747057 PMCID: PMC1461014 DOI: 10.1093/genetics/154.4.1611] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In the In(1LR)pn2a rearrangement, the 1A-2E euchromatic segment is transposed to the vicinity of X heterochromatin (Xh), resulting in position effect variegation (PEV) of the genes in the 2BE region. Practically the whole X-linked heterochromatin is situated adjacent to variegated euchromatic genes. Secondary rearrangements showing weakening or reversion of PEV were obtained by irradiation of the In(1LR)pn2a. These rearrangements demonstrate a positive correlation between the strength of PEV of the wapl locus and the sizes of the adjacent heterochromatic blocks carrying the centromere. The smallest PEV-inducing fragment consists of a block corresponding to approximately 10% of Xh and containing the entire XR, the centromere, and a very proximal portion of XL heterochromatin. Heterochromatic blocks retaining the entire XR near the 2E region, but lacking the centromere, show no PEV. Reversion of PEV was also observed as a result of an internal rearrangement of the Xh blocks where the centromere is moved away from the eu-heterochromatin boundary but the amount of X heterochromatin remaining adjacent to 2E is unchanged. We propose a primary role of the X pericentromeric region in PEV induction and an enhancing effect of the other blocks, positively correlated with their size.
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Affiliation(s)
- E V Tolchkov
- Department of Molecular Genetics of Animals, Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
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50
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Affiliation(s)
- S Bonaccorsi
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Universita' di Roma 'La Sapienza', P. le Aldo Moro 5, 00185 Rome, Italy
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