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Distinct mutants of retrograde intraflagellar transport (IFT) share similar morphological and molecular defects.

Piperno G, Siuda E, Henderson S, Segil M, Vaananen H, Sassaroli M - J. Cell Biol. (1998)

Bottom Line: Each of these mutants was significantly defective for the retrograde velocity of particles and the frequency of bidirectional transport but not for the anterograde velocity of particles, as revealed by a novel method of analysis of IFT that allows tracking of single particles in a sequence of video images.Furthermore, each mutant was defective for the same four subunits of a 17S complex that was identified earlier as the IFT complex A.The occurrence of the same set of phenotypes, as the result of a mutation in any one of three loci, suggests the hypothesis that complex A is a portion of the IFT particles specifically involved in retrograde intraflagellar movement.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Anatomy, Mount Sinai School of Medicine, New York, 10029, USA. Piperno@msvax.mssm.edu

ABSTRACT
A microtubule-based transport of protein complexes, which is bidirectional and occurs between the space surrounding the basal bodies and the distal part of Chlamydomonas flagella, is referred to as intraflagellar transport (IFT). The IFT involves molecular motors and particles that consist of 17S protein complexes. To identify the function of different components of the IFT machinery, we isolated and characterized four temperature-sensitive (ts) mutants of flagellar assembly that represent the loci FLA15, FLA16, and FLA17. These mutants were selected among other ts mutants of flagellar assembly because they displayed a characteristic bulge of the flagellar membrane as a nonconditional phenotype. Each of these mutants was significantly defective for the retrograde velocity of particles and the frequency of bidirectional transport but not for the anterograde velocity of particles, as revealed by a novel method of analysis of IFT that allows tracking of single particles in a sequence of video images. Furthermore, each mutant was defective for the same four subunits of a 17S complex that was identified earlier as the IFT complex A. The occurrence of the same set of phenotypes, as the result of a mutation in any one of three loci, suggests the hypothesis that complex A is a portion of the IFT particles specifically involved in retrograde intraflagellar movement.

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The deformation of  the flagellar shape caused by  fla15 was correlated with the accumulation of cytoplasmic matrix. (a and b) Electron micrographs. (a) Longitudinal section  cut through the central pair microtubules. The cytoplasm accumulated between the outer doublet microtubules and the  flagellar membrane in a section  of the axoneme. (b) Longitudinal section cut through the cytoplasm accumulated in the bulge  of the flagellar membrane. Bar,  0.1 μm.
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Figure 3: The deformation of the flagellar shape caused by fla15 was correlated with the accumulation of cytoplasmic matrix. (a and b) Electron micrographs. (a) Longitudinal section cut through the central pair microtubules. The cytoplasm accumulated between the outer doublet microtubules and the flagellar membrane in a section of the axoneme. (b) Longitudinal section cut through the cytoplasm accumulated in the bulge of the flagellar membrane. Bar, 0.1 μm.

Mentions: Electron microscopy of fla15, fla16, and fla17-1 revealed that the bulge of the flagellar membrane contained amorphous material that was concentrated between the flagellar membrane and the outer doublet microtubules (Fig. 3) and was indistinguishable from cytoplasm. Axonemal substructures, such as the central pair complex, radial spokes, and dynein arms, had normal morphology in both cross and longitudinal sections. Therefore, mutations in FLA15, FLA16, and FLA17 affected the flagellar shape but not the axonemal structure.


Distinct mutants of retrograde intraflagellar transport (IFT) share similar morphological and molecular defects.

Piperno G, Siuda E, Henderson S, Segil M, Vaananen H, Sassaroli M - J. Cell Biol. (1998)

The deformation of  the flagellar shape caused by  fla15 was correlated with the accumulation of cytoplasmic matrix. (a and b) Electron micrographs. (a) Longitudinal section  cut through the central pair microtubules. The cytoplasm accumulated between the outer doublet microtubules and the  flagellar membrane in a section  of the axoneme. (b) Longitudinal section cut through the cytoplasm accumulated in the bulge  of the flagellar membrane. Bar,  0.1 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132975&req=5

Figure 3: The deformation of the flagellar shape caused by fla15 was correlated with the accumulation of cytoplasmic matrix. (a and b) Electron micrographs. (a) Longitudinal section cut through the central pair microtubules. The cytoplasm accumulated between the outer doublet microtubules and the flagellar membrane in a section of the axoneme. (b) Longitudinal section cut through the cytoplasm accumulated in the bulge of the flagellar membrane. Bar, 0.1 μm.
Mentions: Electron microscopy of fla15, fla16, and fla17-1 revealed that the bulge of the flagellar membrane contained amorphous material that was concentrated between the flagellar membrane and the outer doublet microtubules (Fig. 3) and was indistinguishable from cytoplasm. Axonemal substructures, such as the central pair complex, radial spokes, and dynein arms, had normal morphology in both cross and longitudinal sections. Therefore, mutations in FLA15, FLA16, and FLA17 affected the flagellar shape but not the axonemal structure.

Bottom Line: Each of these mutants was significantly defective for the retrograde velocity of particles and the frequency of bidirectional transport but not for the anterograde velocity of particles, as revealed by a novel method of analysis of IFT that allows tracking of single particles in a sequence of video images.Furthermore, each mutant was defective for the same four subunits of a 17S complex that was identified earlier as the IFT complex A.The occurrence of the same set of phenotypes, as the result of a mutation in any one of three loci, suggests the hypothesis that complex A is a portion of the IFT particles specifically involved in retrograde intraflagellar movement.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Anatomy, Mount Sinai School of Medicine, New York, 10029, USA. Piperno@msvax.mssm.edu

ABSTRACT
A microtubule-based transport of protein complexes, which is bidirectional and occurs between the space surrounding the basal bodies and the distal part of Chlamydomonas flagella, is referred to as intraflagellar transport (IFT). The IFT involves molecular motors and particles that consist of 17S protein complexes. To identify the function of different components of the IFT machinery, we isolated and characterized four temperature-sensitive (ts) mutants of flagellar assembly that represent the loci FLA15, FLA16, and FLA17. These mutants were selected among other ts mutants of flagellar assembly because they displayed a characteristic bulge of the flagellar membrane as a nonconditional phenotype. Each of these mutants was significantly defective for the retrograde velocity of particles and the frequency of bidirectional transport but not for the anterograde velocity of particles, as revealed by a novel method of analysis of IFT that allows tracking of single particles in a sequence of video images. Furthermore, each mutant was defective for the same four subunits of a 17S complex that was identified earlier as the IFT complex A. The occurrence of the same set of phenotypes, as the result of a mutation in any one of three loci, suggests the hypothesis that complex A is a portion of the IFT particles specifically involved in retrograde intraflagellar movement.

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