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Drosophila roadblock and Chlamydomonas LC7: a conserved family of dynein-associated proteins involved in axonal transport, flagellar motility, and mitosis.

Bowman AB, Patel-King RS, Benashski SE, McCaffery JM, Goldstein LS, King SM - J. Cell Biol. (1999)

Bottom Line: The gene identified by robl encodes a 97-amino acid polypeptide that is 57% identical (70% similar) to the 105-amino acid Chlamydomonas outer arm dynein-associated protein LC7, also reported here.Furthermore, we demonstrate that members of this family of proteins are associated with both flagellar outer arm dynein and Drosophila and rat brain cytoplasmic dynein.We propose that roadblock/LC7 family members may modulate specific dynein functions.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Division of Cellular and Molecular Medicine, Department of Pharmacology, University of California San Diego, La Jolla, California 92093-0683, USA.

ABSTRACT
Eukaryotic organisms utilize microtubule-dependent motors of the kinesin and dynein superfamilies to generate intracellular movement. To identify new genes involved in the regulation of axonal transport in Drosophila melanogaster, we undertook a screen based upon the sluggish larval phenotype of known motor mutants. One of the mutants identified in this screen, roadblock (robl), exhibits diverse defects in intracellular transport including axonal transport and mitosis. These defects include intra-axonal accumulations of cargoes, severe axonal degeneration, and aberrant chromosome segregation. The gene identified by robl encodes a 97-amino acid polypeptide that is 57% identical (70% similar) to the 105-amino acid Chlamydomonas outer arm dynein-associated protein LC7, also reported here. Both robl and LC7 have homology to several other genes from fruit fly, nematode, and mammals, but not Saccharomyces cerevisiae. Furthermore, we demonstrate that members of this family of proteins are associated with both flagellar outer arm dynein and Drosophila and rat brain cytoplasmic dynein. We propose that roadblock/LC7 family members may modulate specific dynein functions.

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Severe mitotic defects were revealed in robl mutants examined by third instar larval brain squash analysis. Examples of typical wild-type mitotic figures are shown (designated by arrows): (A) a normal prometaphase figure, (B) a normal metaphase figure, and (C) a normal anaphase figure. Multiple abnormal mitotic figures are observed in roblz hemizygotes, including (designated by arrows): (D and E) aneuploid figures, (F) aneuploid figures with hypercondensed chromosomes, and (G) mutant anaphase figures with hypercondensed chromosomes disorganized around the presumptive poles. Mitotic figures are infrequently found in roblz homozygotes such as (designated by arrows): (H) a mutant anaphase structure with severe chromosome bridging, (I) another anaphase structure with a lagging chromosome and a single chromosome bridge, and (J) apparent telophase bridging. (K) The mitotic index of roblz hemizygotes is about five times that of wild type, the error bars indicate the SEM. roblz hemizygotes are late pupal lethal, when dissected from their pupal cases they show (L) rough pupal eyes. (M) A wild-type pupal eye is shown for comparison.
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Figure 7: Severe mitotic defects were revealed in robl mutants examined by third instar larval brain squash analysis. Examples of typical wild-type mitotic figures are shown (designated by arrows): (A) a normal prometaphase figure, (B) a normal metaphase figure, and (C) a normal anaphase figure. Multiple abnormal mitotic figures are observed in roblz hemizygotes, including (designated by arrows): (D and E) aneuploid figures, (F) aneuploid figures with hypercondensed chromosomes, and (G) mutant anaphase figures with hypercondensed chromosomes disorganized around the presumptive poles. Mitotic figures are infrequently found in roblz homozygotes such as (designated by arrows): (H) a mutant anaphase structure with severe chromosome bridging, (I) another anaphase structure with a lagging chromosome and a single chromosome bridge, and (J) apparent telophase bridging. (K) The mitotic index of roblz hemizygotes is about five times that of wild type, the error bars indicate the SEM. roblz hemizygotes are late pupal lethal, when dissected from their pupal cases they show (L) rough pupal eyes. (M) A wild-type pupal eye is shown for comparison.

Mentions: The first indication of a mitotic defect in robl mutants was the observation of a complete absence of the mitotically active tissues (imaginal tissues) in roblz homozygous larvae. Additionally, roblz hemizygous and robl animals that survive into late pupal stages, demonstrate rough pupal eyes (Fig. 7 L), missing bristles (data not shown), and reduced size of imaginal tissue (data not shown). These observations are consistent with a mitotic defect in Drosophila.


Drosophila roadblock and Chlamydomonas LC7: a conserved family of dynein-associated proteins involved in axonal transport, flagellar motility, and mitosis.

Bowman AB, Patel-King RS, Benashski SE, McCaffery JM, Goldstein LS, King SM - J. Cell Biol. (1999)

Severe mitotic defects were revealed in robl mutants examined by third instar larval brain squash analysis. Examples of typical wild-type mitotic figures are shown (designated by arrows): (A) a normal prometaphase figure, (B) a normal metaphase figure, and (C) a normal anaphase figure. Multiple abnormal mitotic figures are observed in roblz hemizygotes, including (designated by arrows): (D and E) aneuploid figures, (F) aneuploid figures with hypercondensed chromosomes, and (G) mutant anaphase figures with hypercondensed chromosomes disorganized around the presumptive poles. Mitotic figures are infrequently found in roblz homozygotes such as (designated by arrows): (H) a mutant anaphase structure with severe chromosome bridging, (I) another anaphase structure with a lagging chromosome and a single chromosome bridge, and (J) apparent telophase bridging. (K) The mitotic index of roblz hemizygotes is about five times that of wild type, the error bars indicate the SEM. roblz hemizygotes are late pupal lethal, when dissected from their pupal cases they show (L) rough pupal eyes. (M) A wild-type pupal eye is shown for comparison.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199740&req=5

Figure 7: Severe mitotic defects were revealed in robl mutants examined by third instar larval brain squash analysis. Examples of typical wild-type mitotic figures are shown (designated by arrows): (A) a normal prometaphase figure, (B) a normal metaphase figure, and (C) a normal anaphase figure. Multiple abnormal mitotic figures are observed in roblz hemizygotes, including (designated by arrows): (D and E) aneuploid figures, (F) aneuploid figures with hypercondensed chromosomes, and (G) mutant anaphase figures with hypercondensed chromosomes disorganized around the presumptive poles. Mitotic figures are infrequently found in roblz homozygotes such as (designated by arrows): (H) a mutant anaphase structure with severe chromosome bridging, (I) another anaphase structure with a lagging chromosome and a single chromosome bridge, and (J) apparent telophase bridging. (K) The mitotic index of roblz hemizygotes is about five times that of wild type, the error bars indicate the SEM. roblz hemizygotes are late pupal lethal, when dissected from their pupal cases they show (L) rough pupal eyes. (M) A wild-type pupal eye is shown for comparison.
Mentions: The first indication of a mitotic defect in robl mutants was the observation of a complete absence of the mitotically active tissues (imaginal tissues) in roblz homozygous larvae. Additionally, roblz hemizygous and robl animals that survive into late pupal stages, demonstrate rough pupal eyes (Fig. 7 L), missing bristles (data not shown), and reduced size of imaginal tissue (data not shown). These observations are consistent with a mitotic defect in Drosophila.

Bottom Line: The gene identified by robl encodes a 97-amino acid polypeptide that is 57% identical (70% similar) to the 105-amino acid Chlamydomonas outer arm dynein-associated protein LC7, also reported here.Furthermore, we demonstrate that members of this family of proteins are associated with both flagellar outer arm dynein and Drosophila and rat brain cytoplasmic dynein.We propose that roadblock/LC7 family members may modulate specific dynein functions.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Division of Cellular and Molecular Medicine, Department of Pharmacology, University of California San Diego, La Jolla, California 92093-0683, USA.

ABSTRACT
Eukaryotic organisms utilize microtubule-dependent motors of the kinesin and dynein superfamilies to generate intracellular movement. To identify new genes involved in the regulation of axonal transport in Drosophila melanogaster, we undertook a screen based upon the sluggish larval phenotype of known motor mutants. One of the mutants identified in this screen, roadblock (robl), exhibits diverse defects in intracellular transport including axonal transport and mitosis. These defects include intra-axonal accumulations of cargoes, severe axonal degeneration, and aberrant chromosome segregation. The gene identified by robl encodes a 97-amino acid polypeptide that is 57% identical (70% similar) to the 105-amino acid Chlamydomonas outer arm dynein-associated protein LC7, also reported here. Both robl and LC7 have homology to several other genes from fruit fly, nematode, and mammals, but not Saccharomyces cerevisiae. Furthermore, we demonstrate that members of this family of proteins are associated with both flagellar outer arm dynein and Drosophila and rat brain cytoplasmic dynein. We propose that roadblock/LC7 family members may modulate specific dynein functions.

Show MeSH
Related in: MedlinePlus