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The DHC1b (DHC2) isoform of cytoplasmic dynein is required for flagellar assembly.

Pazour GJ, Dickert BL, Witman GB - J. Cell Biol. (1999)

Bottom Line: The deletion also results in a massive redistribution of raft subunits from a peri-basal body pool (Cole, D.G., D.R.Natl.These results indicate that DHC1b is a cytoplasmic dynein essential for flagellar assembly, probably because it is the motor for retrograde IFT.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.

ABSTRACT
Dyneins are microtubule-based molecular motors involved in many different types of cell movement. Most dynein heavy chains (DHCs) clearly group into cytoplasmic or axonemal isoforms. However, DHC1b has been enigmatic. To learn more about this isoform, we isolated Chlamydomonas cDNA clones encoding a portion of DHC1b, and used these clones to identify a Chlamydomonas cell line with a deletion mutation in DHC1b. The mutant grows normally and appears to have a normal Golgi apparatus, but has very short flagella. The deletion also results in a massive redistribution of raft subunits from a peri-basal body pool (Cole, D.G., D.R. Diener, A.L. Himelblau, P.L. Beech, J.C. Fuster, and J.L. Rosenbaum. 1998. J. Cell Biol. 141:993-1008) to the flagella. Rafts are particles that normally move up and down the flagella in a process known as intraflagellar transport (IFT) (Kozminski, K.G., K.A. Johnson, P. Forscher, and J.L. Rosenbaum. 1993. Proc. Natl. Acad. Sci. USA. 90:5519-5523), which is essential for assembly and maintenance of flagella. The redistribution of raft subunits apparently occurs due to a defect in the retrograde component of IFT, suggesting that DHC1b is the motor for retrograde IFT. Consistent with this, Western blots indicate that DHC1b is present in the flagellum, predominantly in the detergent- and ATP-soluble fractions. These results indicate that DHC1b is a cytoplasmic dynein essential for flagellar assembly, probably because it is the motor for retrograde IFT.

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The location and morphology of the Golgi complex is  the same in wild-type (a) and dhc1b (b) cells.
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Figure 5: The location and morphology of the Golgi complex is the same in wild-type (a) and dhc1b (b) cells.

Mentions: Previous work (Vaisberg et al., 1996) showed that the mammalian DHC1b isoform was localized to the Golgi apparatus and that microinjection of DHC1b antibodies caused the Golgi complex to disperse. To determine if deletion of the DHC1b gene affected Golgi apparatus structure or positioning in Chlamydomonas, we compared wild-type and mutant cell bodies by electron microscopy. The organization of the mutant cell body was very similar to that of the wild-type parent. In both cell types, the Golgi stacks were located on the opposite side of the nucleus from the flagella, and were composed of four to eight cisternae (Fig. 5). We also did not detect defects in cell structures that presumably are dependent upon the Golgi apparatus for their formation. For example, Golgi complexes in green algae function in the formation of cell wall precursors (for review see Domozych, 1991). Cell walls in the mutant cell appear morphologically normal by electron microscopy. In addition, the cells do not lyse in the presence of 0.5% Triton X-100, indicating that the cell walls are structurally intact (data not shown).


The DHC1b (DHC2) isoform of cytoplasmic dynein is required for flagellar assembly.

Pazour GJ, Dickert BL, Witman GB - J. Cell Biol. (1999)

The location and morphology of the Golgi complex is  the same in wild-type (a) and dhc1b (b) cells.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132917&req=5

Figure 5: The location and morphology of the Golgi complex is the same in wild-type (a) and dhc1b (b) cells.
Mentions: Previous work (Vaisberg et al., 1996) showed that the mammalian DHC1b isoform was localized to the Golgi apparatus and that microinjection of DHC1b antibodies caused the Golgi complex to disperse. To determine if deletion of the DHC1b gene affected Golgi apparatus structure or positioning in Chlamydomonas, we compared wild-type and mutant cell bodies by electron microscopy. The organization of the mutant cell body was very similar to that of the wild-type parent. In both cell types, the Golgi stacks were located on the opposite side of the nucleus from the flagella, and were composed of four to eight cisternae (Fig. 5). We also did not detect defects in cell structures that presumably are dependent upon the Golgi apparatus for their formation. For example, Golgi complexes in green algae function in the formation of cell wall precursors (for review see Domozych, 1991). Cell walls in the mutant cell appear morphologically normal by electron microscopy. In addition, the cells do not lyse in the presence of 0.5% Triton X-100, indicating that the cell walls are structurally intact (data not shown).

Bottom Line: The deletion also results in a massive redistribution of raft subunits from a peri-basal body pool (Cole, D.G., D.R.Natl.These results indicate that DHC1b is a cytoplasmic dynein essential for flagellar assembly, probably because it is the motor for retrograde IFT.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.

ABSTRACT
Dyneins are microtubule-based molecular motors involved in many different types of cell movement. Most dynein heavy chains (DHCs) clearly group into cytoplasmic or axonemal isoforms. However, DHC1b has been enigmatic. To learn more about this isoform, we isolated Chlamydomonas cDNA clones encoding a portion of DHC1b, and used these clones to identify a Chlamydomonas cell line with a deletion mutation in DHC1b. The mutant grows normally and appears to have a normal Golgi apparatus, but has very short flagella. The deletion also results in a massive redistribution of raft subunits from a peri-basal body pool (Cole, D.G., D.R. Diener, A.L. Himelblau, P.L. Beech, J.C. Fuster, and J.L. Rosenbaum. 1998. J. Cell Biol. 141:993-1008) to the flagella. Rafts are particles that normally move up and down the flagella in a process known as intraflagellar transport (IFT) (Kozminski, K.G., K.A. Johnson, P. Forscher, and J.L. Rosenbaum. 1993. Proc. Natl. Acad. Sci. USA. 90:5519-5523), which is essential for assembly and maintenance of flagella. The redistribution of raft subunits apparently occurs due to a defect in the retrograde component of IFT, suggesting that DHC1b is the motor for retrograde IFT. Consistent with this, Western blots indicate that DHC1b is present in the flagellum, predominantly in the detergent- and ATP-soluble fractions. These results indicate that DHC1b is a cytoplasmic dynein essential for flagellar assembly, probably because it is the motor for retrograde IFT.

Show MeSH
Related in: MedlinePlus