Juliette Azimzadeh

Publications (11)90.01 Total impact

• Article: Analysis of ciliary assembly and function in planaria.

  Panteleimon Rompolas, Juliette Azimzadeh, Wallace F Marshall, Stephen M King
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  ABSTRACT: Planarians are free-living invertebrates that employ motile cilia for locomotion. Specifically, cilia that populate the ventral epithelium of the planarian body are highly conserved, with a 9+2 axoneme and a full complement of inner and outer arm dynein motors. The abundance of cilia on the planarian body, their unique accessibility, and high degree of conservation make this organism an attractive experimental model system for cilia biology. Moreover, planarians are genetically amenable and defects that compromise the function and structure of the cilia are not detrimental for their overall health, making them an ideal system for cilia gene loss-of-function studies. In this chapter, we provide information for introducing and maintaining planarians for experimental purposes in the laboratory and describe protocols for RNAi-induced gene knockdown studies. Furthermore, we elaborate on different imaging techniques used to analyze cilia physiology and structure, including live video microscopy, immunofluorescence analysis, and electron microscopy. Last, we provide assays for evaluating physical parameters of ciliary motility, including quantification of planarian gliding locomotion and measurement of ciliary beat frequency.
  Methods in enzymology 01/2013; 525:245-64. · 1.90 Impact Factor
• Article: Centrosome loss in the evolution of planarians.

  Juliette Azimzadeh, Mei Lie Wong, Diane Miller Downhour, Alejandro Sánchez Alvarado, Wallace F Marshall
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  ABSTRACT: The centrosome, a cytoplasmic organelle formed by cylinder-shaped centrioles surrounded by a microtubule-organizing matrix, is a hallmark of animal cells. The centrosome is conserved and essential for the development of all animal species described so far. Here, we show that planarians, and possibly other flatworms, lack centrosomes. In planarians, centrioles are only assembled in terminally differentiating ciliated cells through the acentriolar pathway to trigger the assembly of cilia. We identified a large set of conserved proteins required for centriole assembly in animals and note centrosome protein families that are missing from the planarian genome. Our study uncovers the molecular architecture and evolution of the animal centrosome and emphasizes the plasticity of animal cell biology and development.
  Science 01/2012; 335(6067):461-3. · 31.20 Impact Factor
• Article: Building the centriole.

  Juliette Azimzadeh, Wallace F Marshall
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  ABSTRACT: Centrioles are conserved microtubule-based organelles that lie at the core of the animal centrosome and play a crucial role in nucleating the formation of cilia and flagella in most eukaryotes. Centrioles have a complex ultrastructure with ninefold symmetry and a well-defined length. This structure is assembled from a host of proteins, including a variety of disease gene products. Over a century after the discovery of centrioles, the mechanisms underlying the assembly of these fascinating organelles, in particular the establishment of ninefold symmetry and the control of centriole length, are now starting to be uncovered.
  Current biology: CB 09/2010; 20(18):R816-25. · 10.99 Impact Factor
• Source

  Available from: Etienne Formstecher

  Article: hPOC5 is a centrin-binding protein required for assembly of full-length centrioles.

  Juliette Azimzadeh, Polla Hergert, Annie Delouvée, Ursula Euteneuer, Etienne Formstecher, Alexey Khodjakov, Michel Bornens
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  ABSTRACT: Centrin has been shown to be involved in centrosome biogenesis in a variety of eukaryotes. In this study, we characterize hPOC5, a conserved centrin-binding protein that contains Sfi1p-like repeats. hPOC5 is localized, like centrin, in the distal portion of human centrioles. hPOC5 recruitment to procentrioles occurs during G2/M, a process that continues up to the full maturation of the centriole during the next cell cycle and is correlated with hyperphosphorylation of the protein. In the absence of hPOC5, RPE1 cells arrest in G1 phase, whereas HeLa cells show an extended S phase followed by cell death. We show that hPOC5 is not required for the initiation of procentriole assembly but is essential for building the distal half of centrioles. Interestingly, the hPOC5 family reveals an evolutionary divergence between vertebrates and organisms like Drosophila melanogaster or Caenorhabditis elegans, in which the loss of hPOC5 may correlate with the conspicuous differences in centriolar structure.
  The Journal of Cell Biology 05/2009; 185(1):101-14. · 10.26 Impact Factor
• Article: Arabidopsis TONNEAU1 proteins are essential for preprophase band formation and interact with centrin.

  Juliette Azimzadeh, Philippe Nacry, Anna Christodoulidou, Stéphanie Drevensek, Christine Camilleri, Nardjis Amiour, François Parcy, Martine Pastuglia, David Bouchez
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  ABSTRACT: Plant cells have specific microtubule structures involved in cell division and elongation. The tonneau1 (ton1) mutant of Arabidopsis thaliana displays drastic defects in morphogenesis, positioning of division planes, and cellular organization. These are primarily caused by dysfunction of the cortical cytoskeleton and absence of the preprophase band of microtubules. Characterization of the ton1 insertional mutant reveals complex chromosomal rearrangements leading to simultaneous disruption of two highly similar genes in tandem, TON1a and TON1b. TON1 proteins are conserved in land plants and share sequence motifs with human centrosomal proteins. The TON1 protein associates with soluble and microsomal fractions of Arabidopsis cells, and a green fluorescent protein-TON1 fusion labels cortical cytoskeletal structures, including the preprophase band and the interphase cortical array. A yeast two-hybrid screen identified Arabidopsis centrin as a potential TON1 partner. This interaction was confirmed both in vitro and in plant cells. The similarity of TON1 with centrosomal proteins and its interaction with centrin, another key component of microtubule organizing centers, suggests that functions involved in the organization of microtubule arrays by the centrosome were conserved across the evolutionary divergence between plants and animals.
  The Plant Cell 09/2008; 20(8):2146-59. · 8.99 Impact Factor
• Source

  Available from: 218.4.189.15

  Article: Structure and duplication of the centrosome.

  Juliette Azimzadeh, Michel Bornens
  Journal of Cell Science 08/2007; 120(Pt 13):2139-42. · 6.11 Impact Factor
• Article: Origin and evolution of the centrosome.

  Michel Bornens, Juliette Azimzadeh
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  ABSTRACT: In this brief account we specifically address the question of how the plasma membrane-associated basal body/axoneme of the unicellular ancestor of eukaryotes has evolved into the centrosome organelle through the several attempts to multicellularity. We propose that the connection between the flagellar apparatus and the nucleus has been a critical feature for leading to the centriole-based centrosome of metazoa, the Spindle Pole Body of fungi, or to the absence of any centrosome in seed plants. We further suggest that the evolution of this connection could be reflected in the evolution of the centrin proteins. We then review evidence showing that the evolution of the centrosome-based tubulin network has been correlated with the evolution of the cortical actin-based cleavage apparatus. Finally we argue that this coevolution had a major impact on the cell individuation process and on the evolution of multicellular organisms. We conclude that only the metazoan lineage evolved multicellularity without loosing the ancestral association of three basic cellular functions of the basal body/axoneme or the derived centrosome organelle, namely sensation, motion and division.
  Advances in experimental medicine and biology 02/2007; 607:119-29. · 1.09 Impact Factor
• Article: Gamma-tubulin is essential for microtubule organization and development in Arabidopsis.

  Martine Pastuglia, Juliette Azimzadeh, Magali Goussot, Christine Camilleri, Katia Belcram, Jean-Luc Evrard, Anne-Catherine Schmit, Philippe Guerche, David Bouchez
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  ABSTRACT: The process of microtubule nucleation in plant cells is still a major question in plant cell biology. gamma-Tubulin is known as one of the key molecular players for microtubule nucleation in animal and fungal cells. Here, we provide genetic evidence that in Arabidopsis thaliana, gamma-tubulin is required for the formation of spindle, phragmoplast, and cortical microtubule arrays. We used a reverse genetics approach to investigate the role of the two Arabidopsis gamma-tubulin genes in plant development and in the formation of microtubule arrays. Isolation of mutants in each gene and analysis of two combinations of gamma-tubulin double mutants showed that the two genes have redundant functions. The first combination is lethal at the gametophytic stage. Disruption of both gamma-tubulin genes causes aberrant spindle and phragmoplast structures and alters nuclear division in gametophytes. The second combination of gamma-tubulin alleles affects late seedling development, ultimately leading to lethality 3 weeks after germination. This partially viable mutant combination enabled us to follow dynamically the effects of gamma-tubulin depletion on microtubule arrays in dividing cells using a green fluorescent protein marker. These results establish the central role of gamma-tubulin in the formation and organization of microtubule arrays in Arabidopsis.
  The Plant Cell 07/2006; 18(6):1412-25. · 8.99 Impact Factor
• Chapter: The Centrosome in Evolution

  Juliette Azimzadeh, Michel Bornens
  06/2005: pages 93 - 122; , ISBN: 9783527603800
• Article: Forward and reverse genetics in Arabidopsis: isolation of cytoskeletal mutants.

  Martine Pastuglia, Juliette Azimzadeh, Christine Camilleri, David Bouchez
  Cell Biology International 02/2003; 27(3):249-50. · 1.48 Impact Factor
• Article: The Arabidopsis TONNEAU2 gene encodes a putative novel protein phosphatase 2A regulatory subunit essential for the control of the cortical cytoskeleton.

  Christine Camilleri, Juliette Azimzadeh, Martine Pastuglia, Catherine Bellini, Olivier Grandjean, David Bouchez
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  ABSTRACT: In Arabidopsis ton2 mutants, abnormalities of the cortical microtubular cytoskeleton, such as disorganization of the interphase microtubule array and lack of the preprophase band before mitosis, markedly affect cell shape and arrangement as well as overall plant morphology. We present the molecular isolation of the TON2 gene, which is highly conserved in higher plants and has a vertebrate homolog of unknown function. It encodes a protein similar in its C-terminal part to B" regulatory subunits of type 2A protein phosphatases (PP2As). We show that the TON2 protein interacts with an Arabidopsis type A subunit of PP2A in the yeast two-hybrid system and thus likely defines a novel subclass of PP2A subunits that are possibly involved in the control of cytoskeletal structures in plants.
  The Plant Cell 05/2002; 14(4):833-45. · 8.99 Impact Factor