Cell Cycle Regulation
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Our research focuses on cell cycle progression and the cytoskeleton in normal development and disease. We are particularly interested in the role played by microtubule organizing structures, such as the centrosome, cilia and flagella. The centrosome is the major microtubule organizer in animal cells, and is very often abnormal in cancer. Cilia and flagella are cellular projections which are indispensable in a variety of cellular and developmental processes including cell motility, propagation of morphogenic signals and sensory reception.
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Browsing Cell Cycle Regulation by Subject "Animals"
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- BLD10/CEP135 Is a Microtubule-Associated Protein that Controls the Formation of the Flagellum Central Microtubule PairPublication . Carvalho-Santos, Zita; Machado, Pedro; Alvarez-Martins, Inês; Gouveia, Susana M.; Jana, Swadhin C.; Duarte, Paulo; Amado, Tiago; Branco, Pedro; Freitas, Micael C.; Silva, Sara T.N.; Antony, Claude; Bandeiras, Tiago M.; Bettencourt-Dias, MónicaCilia and flagella are involved in a variety of processes and human diseases, including ciliopathies and sterility. Their motility is often controlled by a central microtubule (MT) pair localized within the ciliary MT-based skeleton, the axoneme. We characterized the formation of the motility apparatus in detail in Drosophila spermatogenesis. We show that assembly of the central MT pair starts prior to the meiotic divisions, with nucleation of a singlet MT within the basal body of a small cilium, and that the second MT of the pair only assembles much later, upon flagella formation. BLD10/CEP135, a conserved player in centriole and flagella biogenesis, can bind and stabilize MTs and is required for the early steps of central MT pair formation. This work describes a genetically tractable system to study motile cilia formation and provides an explanation for BLD10/CEP135's role in assembling highly stable MT-based structures, such as motile axonemes and centrioles.
- Centrioles: active players or passengers during mitosis?Publication . Debec, Alain; Sullivan, William; Bettencourt-Dias, MonicaCentrioles are cylinders made of nine microtubule (MT) triplets present in many eukaryotes. Early studies, where centrosomes were seen at the poles of the mitotic spindle led to their coining as "the organ for cell division". However, a variety of subsequent observational and functional studies showed that centrosomes might not always be essential for mitosis. Here we review the arguments in this debate. We describe the centriole structure and its distribution in the eukaryotic tree of life and clarify its role in the organization of the centrosome and cilia, with an historical perspective. An important aspect of the debate addressed in this review is how centrioles are inherited and the role of the spindle in this process. In particular, germline inheritance of centrosomes, such as their de novo formation in parthenogenetic species, poses many interesting questions. We finish by discussing the most likely functions of centrioles and laying out new research avenues.
- Differential regulation of transition zone and centriole proteins contributes to ciliary base diversityPublication . Jana, Swadhin Chandra; Mendonça, Susana; Machado, Pedro; Werner, Sascha; Rocha, Jaqueline; Pereira, António; Maiato, Helder; Bettencourt-Dias, MónicaCilia are evolutionarily conserved structures with many sensory and motility-related functions. The ciliary base, composed of the basal body and the transition zone, is critical for cilia assembly and function, but its contribution to cilia diversity remains unknown. Hence, we generated a high-resolution structural and biochemical atlas of the ciliary base of four functionally distinct neuronal and sperm cilia types within an organism, Drosophila melanogaster. We uncovered a common scaffold and diverse structures associated with different localization of 15 evolutionarily conserved components. Furthermore, CEP290 (also known as NPHP6) is involved in the formation of highly diverse transition zone links. In addition, the cartwheel components SAS6 and ANA2 (also known as STIL) have an underappreciated role in basal body elongation, which depends on BLD10 (also known as CEP135). The differential expression of these cartwheel components contributes to diversity in basal body length. Our results offer a plausible explanation to how mutations in conserved ciliary base components lead to tissue-specific diseases.
- Evolution: Tracing the origins of centrioles, cilia, and flagellaPublication . Carvalho-Santos, Zita; Azimzadeh, Juliette; Pereira-Leal, José B; Bettencourt-Dias, MónicaCentrioles/basal bodies (CBBs) are microtubule-based cylindrical organelles that nucleate the formation of centrosomes, cilia, and flagella. CBBs, cilia, and flagella are ancestral structures; they are present in all major eukaryotic groups. Despite the conservation of their core structure, there is variability in their architecture, function, and biogenesis. Recent genomic and functional studies have provided insight into the evolution of the structure and function of these organelles.
- Mapping molecules to structure: unveiling secrets of centriole and cilia assembly with near-atomic resolutionPublication . Jana, Swadhin Chandra; Marteil, Gaëlle; Bettencourt-Dias, MónicaCentrioles are microtubule (MT)-based cylinders that form centrosomes and can be modified into basal bodies that template the axoneme, the ciliary MT skeleton. These MT-based structures are present in all branches of the eukaryotic tree of life, where they have important sensing, motility and cellular architecture-organizing functions. Moreover, they are altered in several human conditions and diseases, including sterility, ciliopathies and cancer. Although the ultrastructure of centrioles and derived organelles has been known for over 50 years, the molecular basis of their remarkably conserved properties, such as their 9-fold symmetry, has only now started to be unveiled. Recent advances in imaging, proteomics and crystallography, allowed the building of 3D models of centrioles and derived structures with unprecedented molecular details, leading to a much better understanding of their assembly and function. Here, we cover progress in this field, focusing on the mechanisms of centriole and cilia assembly.
- A mechanism for the elimination of the female gamete centrosome in Drosophila melanogasterPublication . Pimenta-Marques, A.; Bento, I.; Lopes, C. A. M.; Duarte, P.; Jana, S. C.; Bettencourt-Dias, M.An important feature of fertilization is the asymmetric inheritance of centrioles. In most species it is the sperm that contributes the initial centriole, which builds the first centrosome that is essential for early development. However, given that centrioles are thought to be exceptionally stable structures, the mechanism behind centriole disappearance in the female germ line remains elusive and paradoxical. We elucidated a program for centriole maintenance in fruit flies, led by Polo kinase and the pericentriolar matrix (PCM): The PCM is down-regulated in the female germ line during oogenesis, which results in centriole loss. Perturbing this program prevents centriole loss, leading to abnormal meiotic and mitotic divisions, and thus to female sterility. This mechanism challenges the view that centrioles are intrinsically stable structures and reveals general functions for Polo kinase and the PCM in centriole maintenance. We propose that regulation of this maintenance program is essential for successful sexual reproduction and defines centriole life span in different tissues in homeostasis and disease, thereby shaping the cytoskeleton.
- PLK4 trans-Autoactivation Controls Centriole Biogenesis in SpacePublication . Lopes, Carla A.M.; Jana, Swadhin Chandra; Cunha-Ferreira, Inês; Zitouni, Sihem; Bento, Inês; Duarte, Paulo; Gilberto, Samuel; Freixo, Francisco; Guerrero, Adán; Francia, Maria; Lince-Faria, Mariana; Carneiro, Jorge; Bettencourt-Dias, MónicaCentrioles are essential for cilia and centrosome assembly. In centriole-containing cells, centrioles always form juxtaposed to pre-existing ones, motivating a century-old debate on centriole biogenesis control. Here, we show that trans-autoactivation of Polo-like kinase 4 (PLK4), the trigger of centriole biogenesis, is a critical event in the spatial control of that process. We demonstrate that centrioles promote PLK4 activation through its recruitment and local accumulation. Though centriole removal reduces the proportion of active PLK4, this is rescued by concentrating PLK4 to the peroxisome lumen. Moreover, while mild overexpression of PLK4 only triggers centriole amplification at the existing centriole, higher PLK4 levels trigger both centriolar and cytoplasmatic (de novo) biogenesis. Hence, centrioles promote their assembly locally and disfavor de novo synthesis. Similar mechanisms enforcing the local concentration and/or activity of other centriole components are likely to contribute to the spatial control of centriole biogenesis under physiological conditions.
- Polo-like kinase 4 controls centriole duplication but does not directly regulate cytokinesisPublication . Holland, A. J.; Fachinetti, D.; Da Cruz, S.; Zhu, Q.; Vitre, B.; Lince-Faria, M.; Chen, D.; Parish, N.; Verma, I. M.; Bettencourt-Dias, M.; Cleveland, D. W.Centrioles organize the centrosome, and accurate control of their number is critical for the maintenance of genomic integrity. Centrioles duplicate once per cell cycle, and duplication is coordinated by Polo-like kinase 4 (Plk4). We previously demonstrated that Plk4 accumulation is autoregulated by its own kinase activity. However, loss of heterozygosity of Plk4 in mouse embryonic fibroblasts has been proposed to cause cytokinesis failure as a primary event, leading to centrosome amplification and gross chromosomal abnormalities. Using targeted gene disruption, we show that human epithelial cells with one inactivated Plk4 allele undergo neither cytokinesis failure nor increase in centrosome amplification. Plk4 is shown to localize exclusively at the centrosome, with none in the spindle midbody. Substantial depletion of Plk4 by small interfering RNA leads to loss of centrioles and subsequent spindle defects that lead to a modest increase in the rate of cytokinesis failure. Therefore, Plk4 is a centriole-localized kinase that does not directly regulate cytokinesis.
- Revisiting the role of the mother centriole in centriole biogenesisPublication . Rodrigues-Martins, A; Riparbelli, M; Callaini, G; Glover, D M; Bettencourt-Dias, MCentrioles duplicate once in each cell division cycle through so-called templated or canonical duplication. SAK, also called PLK4 (SAK/PLK4), a kinase implicated in tumor development, is an upstream regulator of canonical biogenesis necessary for centriole formation. We found that overexpression of SAK/PLK4 could induce amplification of centrioles in Drosophila embryos and their de novo formation in unfertilized eggs. Both processes required the activity of DSAS-6 and DSAS-4, two molecules required for canonical duplication. Thus, centriole biogenesis is a template-free self-assembly process triggered and regulated by molecules that ordinarily associate with the existing centriole. The mother centriole is not a bona fide template but a platform for a set of regulatory molecules that catalyzes and regulates daughter centriole assembly.
- A structural road map to unveil basal body composition and assemblyPublication . Jana, Swadhin C; Machado, Pedro; Bettencourt-Dias, MónicaThe Basal Body (BB) acts as the template for the axoneme, the microtubule‐basedstructure of cilia and flagella. Although several proteins were recently implicatedin both centriole and BB assembly and function, their molecular mechanisms are stillpoorly characterized. In this issue of The EMBO journal, Li and coworkersdescribe for the first time the near‐native structure of the BB at 33 Åresolution obtained by Cryo‐Electron Microscopy analysis of wild‐type (WT) isolatedChlamydomonas BBs. They identified several uncharacterized non‐tubulinstructures and variations along the length of the BB, which likely reflect thebinding and function of numerous macromolecular complexes. These complexes areexpected to define BB intrinsic properties, such as its characteristic structure andstability. Similarly to the high‐resolution structures of ribosome and nuclear porecomplexes, this study will undoubtedly contribute towards the future analysis ofcentriole and BB biogenesis, maintenance and function.