A Unified Taxonomy for Ciliary Dyneins

Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA.
Cytoskeleton (Impact Factor: 3.12). 10/2011; 68(10):555-65. DOI: 10.1002/cm.20533
Source: PubMed


The formation and function of eukaryotic cilia/flagella require the action of a large array of dynein microtubule motor complexes. Due to genetic, biochemical, and microscopic tractability, Chlamydomonas reinhardtii has become the premier model system in which to dissect the role of dyneins in flagellar assembly, motility, and signaling. Currently, 54 proteins have been described as components of various Chlamydomonas flagellar dyneins or as factors required for their assembly in the cytoplasm and/or transport into the flagellum; orthologs of nearly all these components are present in other ciliated organisms including humans. For historical reasons, the nomenclature of these diverse dynein components and their corresponding genes, mutant alleles, and orthologs has become extraordinarily confusing. Here, we unify Chlamydomonas dynein gene nomenclature and establish a systematic classification scheme based on structural properties of the encoded proteins. Furthermore, we provide detailed tabulations of the various mutant alleles and protein aliases that have been used and explicitly define the correspondence with orthologous components in other model organisms and humans.

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    • "No functional studies of LRRC56 members have been previously reported. Based on current nomenclature for dynein-related proteins in Chlamydomonas with LRRs, this gene is now formally designated DLU2 [Hom et al., 2011]. For continuity, and to retain an association with its role in outer arm dynein assembly, we will refer to the locus as the ODA8 locus and the encoded protein as ODA8. "
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    ABSTRACT: The Chlamydomonas reinhardtii oda8 mutation blocks assembly of flagellar outer dynein arms, and interacts genetically with oda5 and oda10, which encode axonemal proteins thought to aid dynein binding onto axonemal docking sites. We positionally cloned ODA8 and identified the gene product as the algal homolog of vertebrate LRRC56. Its flagellar localization depends on ODA5 and ODA10, consistent with genetic interaction studies, but phylogenomics suggests that LRRC56 homologs play a role in intraflagellar transport (IFT)-dependent assembly of outer row dynein arms, not axonemal docking. ODA8 distribution between cytoplasm and flagella is similar to that of IFT proteins and about half of flagellar ODA8 is in the soluble matrix fraction. Dynein extracted in vitro from wild type axonemes will rebind efficiently to oda8 mutant axonemes, without rebinding of ODA8, further supporting a role in dynein assembly or transport, not axonemal binding. Assays comparing preassembled outer dynein arm complexes from the cytoplasm of wild type and mutant strains show that dynein in oda8 mutant cytoplasm has not properly preassembled and cannot bind normally onto oda axonemes. We conclude that ODA8 plays an important role in formation and transport of mature dynein complexes during flagellar assembly. This article is protected by copyright. All rights reserved.
    Full-text · Article · Dec 2014 · Cytoskeleton
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    • "To our knowledge, this is the first evidence in any eukaryote for the existence of a heterodimer of dynein heavy chains able to move along microtubules. So far, all reported cytoplasmic and IFT dynein complexes function as homodimers of heavy chains (Vale, 2003; Hom et al., 2011; Schiavo et al., 2013). Heterodimers (or even heterotrimers) of dynein heavy chains are active in the axoneme but they are attached on microtubule doublets and do not proceed along them as does the IFT dynein (DiBella and King, 2001). "
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    ABSTRACT: Cilia and flagella are assembled by intraflagellar transport (IFT) of protein complexes that bring tubulin and other precursors to the incorporation site at their distal tip. Anterograde transport is driven by kinesin whereas retrograde transport is ensured by a specific dynein. In the protist Trypanosoma brucei, two distinct genes encode fairly different heavy chains (∼40% identity) termed DHC2.1 and DHC2.2 that form a heterodimer and are both essential for retrograde IFT. The stability of each heavy chain relies on the presence of the dynein light IC DLI1 (XBX-1/D1bLIC). The presence of both heavy chains and of DLI1 at the base of the flagellum depends on the intermediate dynein chain DIC5 (FAP133/WDR34). In the IFT140(RNAi) mutant, an IFT-A protein essential for retrograde transport, the IFT dynein components are found at a high concentration at the flagellar base but fail to penetrate the flagellar compartment. We propose a model by which the IFT dynein particle is assembled in the cytoplasm, reaches the base of the flagellum and associated to the IFT machinery in a manner dependent of the IFT-A complex.
    Full-text · Article · Jul 2014 · Molecular Biology of the Cell
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    • "To confirm whether Bug22 is a flagellar protein in Chlamydomonas, Bug22–HA-expressing cells were fractionated into cell body and flagellar fractions and subjected to immunoblot analysis. Compared with intraflagellar transport (IFT) proteins, represented by IFT139 and the outer dynein arm protein IC2 (previously known as IC69) (Hom et al., 2011), Bug22 was even more enriched in the flagella (Fig. 2D). Flagellar fractionation followed by SDS-PAGE and immunoblot analysis showed that Bug22 was exclusively localized to the axonemal fraction (Fig. 2E). "
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    ABSTRACT: Eukaryotic flagella and cilia may exhibit planar or non-planar beating, the mechanism underlying which is unknown. Chlamydomonas flagella beat in approximately the same plane either in asymmetric ciliary or symmetric flagellar waveforms. Each B tubule of number 1, 5 and 6 doublets of the flagellar axoneme possesses a beak-like structure. The number 5 and 6 beak structures are implicated in conversion of ciliary motion into flagellar motion. Here, we show that a null mutant of Bug22 converts asymmetric ciliary waveform into symmetric flagellar waveforms in three dimensions. Bug22 is localized approximately to the proximal half to two-thirds of the flagellum, similar to localization of beak-like structures. However, Bug22 associates with axonemal microtubules without apparent preference for any doublets shown by immunogold labeling. Interestingly, bug22 lacks all beak-like structures. We propose that one function of Bug22 is to regulate the anchoring of the beak-like structures to the doublet microtubules and confines flagellar beating in a plane.
    Full-text · Article · Nov 2013 · Journal of Cell Science
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