A Proximal Centriole-Like Structure Is Present in Drosophila Spermatids and Can Serve as a Model to Study Centriole Duplication

Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
Genetics (Impact Factor: 5.96). 04/2009; 182(1):133-44. DOI: 10.1534/genetics.109.101709
Source: PubMed


Most animals have two centrioles in spermatids (the distal and proximal centrioles), but insect spermatids seem to contain only one centriole (Fuller 1993), which functionally resembles the distal centriole. Using fluorescent centriolar markers, we identified a structure near the fly distal centriole that is reminiscent of a proximal centriole (i.e., proximal centriole-like, or PCL). We show that the PCL exhibits several features of daughter centrioles. First, a single PCL forms near the proximal segment of the older centriole. Second, the centriolar proteins SAS-6, Ana1, and Bld10p/Cep135 are in the PCL. Third, PCL formation depends on SAK/PLK4 and SAS-6. Using a genetic screen for PCL defect, we identified a mutation in the gene encoding the conserved centriolar protein POC1, which is part of the daughter centriole initiation site (Kilburn et al. 2007) in Tetrahymena. We conclude that the PCL resembles an early intermediate structure of a forming centriole, which may explain why no typical centriolar structure is observed under electron microscopy. We propose that, during the evolution of insects, the proximal centriole was simplified by eliminating the later steps in centriole assembly. The PCL may provide a unique model to study early steps of centriole formation.

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Article: A Proximal Centriole-Like Structure Is Present in Drosophila Spermatids and Can Serve as a Model to Study Centriole Duplication

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    • "The procentrioles became displaced in S17 spermatids within the " centriole adjunct " (Fig. 3C; n 5 6) or at the edge of this material (Fig. 3D; n 5 5). As spermatid elongation proceed, Ana1- GFP recognized a small bulge close to the proximal region of the centriole and then a distinct dot [Blachon et al., 2009; Figs. 3E and 3F]. "
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    ABSTRACT: Male gametogenesis in insects is unusual in that the centrioles do not duplicate during the second meiosis and the differentiating spermatids inherit only one centriole. Here we showed that a distinct procentriole formed next the proximal region of the centriole in early S13 spermatids at the onion stage, confirming previous reports of a proximal centriole-like structure (PCL) at the proximal end of the spermatid centriole. However, the procentrioles of Drosophila spermatids do not behave like true procentrioles, but their development is blocked at an early stage before the assembly of a complete A-tubule set. Therefore, they may represent early frozen stages of procentriole assembly that do not develop further and eventually disappear in late spermatids. This article is protected by copyright. All rights reserved.
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    • "In embryos, coimmunolabeling of Root with the PNS neuron marker 22C10/Futsch showed that Root was expressed in both Ch and Es neurons (Fig. 2, B and C). By counterstaining endogenous Root or ectopic GFP-Root with the centriole markers Pericentrin-like protein (Plp; Galletta et al., 2014), Ana1 (Blachon et al., 2009), or Centrosomin (Cnn); the transition zone marker Chibby (Cby; Enjolras et al., 2012); or the cilium markers CG11356 (Enjolras et al., 2012) and 21A6/Eys (Lee et al., 2008; Park et al., 2013), we determined that Root localized to a prominent 10-to 15-µm–long structure within the dendrite of Ch neurons, consistent with the ciliary rootlet that extends from the proximal base of the basal body, along the length of the dendrite, and terminates within the neuron cell body (Fig. 2, A and D). In addition to the rootlet, Root localized to a focus, together with Cnn and Ana1, distal to the basal body, in an unknown structure that might be the ciliary dilation (asterisks in Fig. 2 D). "
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    • "The Cep135/Bld10p homologue in Drosophila is localized all along the centriole microtubules, not restricted to the proximal end. Importantly, Drosophila mutants that lack the Cep135/Bld10p homologue assemble cartwheels and centrioles, although the cartwheel appears to be unstable [42,45,64,65]. Instead, they have short centrioles and lack central pair microtubules in sperm flagella. "
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    ABSTRACT: The cartwheel is a subcentriolar structure consisting of a central hub and nine radially arranged spokes, located at the proximal end of the centriole. It appears at the initial stage of the centriole assembly process as the first ninefold symmetrical structure. The cartwheel was first described more than 50 years ago, but it is only recently that its pivotal role in establishing the ninefold symmetry of the centriole was demonstrated. Significant progress has since been made in understanding its fine structure and assembly mechanism. Most importantly, the central part of the cartwheel, from which the ninefold symmetry originates, is shown to form by self-association of nine dimers of the protein SAS-6. This finding, together with emerging data on other components of the cartwheel, has opened new avenues in centrosome biology.
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