spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online November 11, 2004
doi: 10.1242/10.1242/dev.01433

Development 131, 5947-5958 (2004)
Published by The Company of Biologists 2004
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplementary Material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in Development
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bénard, C. Y.
Right arrow Articles by Hekimi, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bénard, C. Y.
Right arrow Articles by Hekimi, S.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

mau-2 acts cell-autonomously to guide axonal migrations in Caenorhabditis elegans

Claire Y. Bénard, Hania Kébir, Shin Takagi and Siegfried Hekimi*

Department of Biology, McGill University, 1205 Dr Penfield Avenue, Montreal, Quebec H3A 1B1, Canada



View larger version (50K):

[in a new window]
  		Fig. 1. Phenotype of maternally rescued mau-2 animals. (A) Detail of the dorsal cord and the vulval muscles in young adult worms carrying the reporter unc-31::gfp used to visualize the nervous system and the vulval muscles. The dorsal cord is normal in the wild type (a), defasciculated in mau-2(qm5) mutants as indicated by the arrow (b), and normal in maternally rescued mau-2(qm5) animals (c). The vm1 vulval muscles (black asterisks) are normal in the wild type (e), and at least one of the vm1 is abnormally placed in mau-2(qm5) mutants and in maternally rescued mau-2(qm5) animals, as indicated by the arrow (f). (B) Quantification of the phenotype in maternally rescued mau-2(qm5) animals, compared with the wild type and mau-2(qm5) mutants (n=50-200). Both the placement of the soma and the projection of the axon of the AVM neurone are completely maternally rescued. The axon of HSN could not be scored in mau-2 mutants (red asterisk), as tph-1::gfp is not expressed in HSNs for unknown reasons, while it is still expressed in the NSMs (Sze et al., 2000Go).

 


View larger version (95K):

[in a new window]
  		Fig. 2. Positional cloning of mau-2. (A) Genetic markers used to map mau-2. (B) Cosmids and subclones of C09H6 used for rescue assays (rescuing clones in bold). (C) Genomic structure of mau-2 and the lesions of the four mau-2 alleles. (D) An alignment of the predicted amino acid sequence of C. elegans MAU-2 with its homologues from D. melanogaster (CG4203-PA), F. rubripes (SINFRUP00000081396), M. musculus (NP_083269) and H. sapiens (KIAA0892). Identical residues in all five species are shown in dark grey; identical residues in three or four species are shown in light grey. The mau-2(qm4) mutation affects the conserved Gly residue (indicated by an asterisk). The C. elegans protein is about 25% identical to the vertebrate and the fly proteins. The sequence in the fish is 95% identical to human MAU-2, and the mouse sequence is more than 99% identical to human MAU-2.

 


View larger version (39K):

[in a new window]
  		Fig. 3. The expression pattern of mau-2. (A) MAU-2 protein level in the wild type (N2) and in the four mau-2 mutant alleles. No MAU-2 protein is detected in the deletion and nonsense alleles, but a reduced level is detected in the mis-sense allele qm4 (arrowhead). A band is detected in transgenic worms carrying wild-type copies of the gene mau-2 [mau-2(qm160); qmEx[mau-2(+)]]. Total protein extract loaded per lane is 50 µg. (B) Northern analysis of mau-2 at all developmental stages (E, embryos; L1-L4, larval stages; A, young adults) and at the adult stage in mutant backgrounds. Total RNA extract loaded per lane is 10 µg. (C) Western analysis of MAU-2 at all developmental stages and at the adult stage in mutant backgrounds. Total protein extract loaded per lane is. (D) Western analysis of MAU-2 at three larval stages, comparing the MAU-2 level in the wild-type and maternally rescued worms. m+z+ worms were of the genotype dpy-5(e61) mau-2(+); m–z–, dpy-5(e61) mau-2(qm5) derived from a dpy-5(e61) mau-2(qm5) mutant hermaphrodites; and m+z–, dpy-5(e61) mau-2(qm5) derived from dpy-5(e61) mau-2(qm5)/++ hermaphrodites. In each lane, 400 worms loaded. For the late L4 stage worms, the double band both for MAU-2 and tubulin is a migration artefact.

 


View larger version (89K):

[in a new window]
  		Fig. 4. The expression pattern of a functional mau-2::gfp reporter. (A) A translational reporter containing 6 kb of sequence upstream of mau-2 and the entire mau-2 gene. (B) mau-2::gfp is ubiquitously expressed in embryos from late gastrulation until the twofold stage. At the threefold stage of embryogenesis, mau-2::gfp expression is restricted to the nervous system. (C) mau-2::gfp is expressed in the nervous system in larvae and adults, and is visible in virtually all neuronal cell bodies and processes in head and tail ganglia, as well as in neurones that are isolated on the body wall.

 


View larger version (30K):

[in a new window]
  		Fig. 5. mau-2 functions cell autonomously for the guidance of AVM. (A) Constructs used to express mau-2(+) in different tissues. The expression of each transgene was monitored with gfp. Rescue of the locomotion, egg laying and larval development are indicated. (B) Phenotype of the axon of AVM in mau-2(qm160)-expressing mau-2(+) in different tissues. AVM guidance was examined with mec-4::gfp. Four independent transgenic lines were scored (n>200 for each construct). Light grey indicates that the axon projected anteriorly; dark grey, posteriorly. The AVM guidance defect observed in mau-2 is rescued by expression of mau-2(+) in the nervous system and in the mechanosensory neurones alone. Error bars indicate standard error of the proportion. The effect of expressing mau-2(+) under these different promoters was also examined in the mau-2(+) background. The transgenic animals were completely wild type for locomotion and egg-laying, as well as for the guidance of the AVM axon (n>137 transgenic animals from three lines scored for each construct, data not shown).

 


View larger version (49K):

[in a new window]
  		Fig. 6. The action of mau-2 is independent of that of slt-1 to guide AVM ventrally. (A) AVM was visualized with mec-4::gfp. Anterior is towards the right, ventral at the bottom. (a) A wild-type AVM axon in which the axon first projects ventrally and then turns anteriorly. The axon of AVM fails to migrate ventrally (b-d): the axon of AVM projects anteriorly in mau-2 and slt-1 single mutants (b), or posteriorly in mau-2 single mutant (c), and dorsally in mau-2;slt-1 double mutants and in mau-2(qm160) misexpressing SLT-1 under the myo-3 promoter (d,e). (e) The axon of AVM projects dorsally (past the dorsoventral position of the neurone ALM) and, although not in the plane of focus here, then turns anteriorly, migrating alone for a distance and finally joining the axon of ALM. A short anterior branch is also present. Arrows and arrowheads in a-e indicate AVM and ALM, respectively. (B) Phenotype of the axon of AVM in mau-2;slt-1 double mutants and in mau-2(qm160) animals misexpressing SLT-1 (kyIs218 and kyIs209 are integrated myo-3::slt-1 transgenes). Light grey indicates that the AVM axon projected anteriorly; dark grey, posteriorly; black, dorsally. The mau-2;slt-1 double mutants exhibit an enhancement of the ventral guidance defect compared with the single mutants, and display a novel phenotype (dorsal projection; n=170-300). Error bars indicate standard error of the proportion. (C) The function of mau-2 appears to be acting in parallel to those of slt-1 and unc-6 to guide the axon of AVM. The AVM neurone is shown in the right-hand panel. Its cell body rests at the boundary between the ventral muscle quadrant and the lateral hypodermis. The axon of AVM normally projects ventrally (towards the bottom), along the ventral muscle quadrant, and then turns anteriorly (towards the right). The broken arrows indicate that the axon of AVM can project abnormally (anteriorly, posteriorly or dorsally) in some mutant situations. Loss of function of unc-6, slt-1 or mau-2 results in abnormal anteriorly projecting AVM axons; loss of function of unc-6 or mau-2 can also result in posteriorly oriented axons. When the activity of both mau-2 and slt-1 are altered, the axon of AVM can project dorsally. It appears that three mechanisms (unc-6-mediated attraction, slt-1-mediated repulsion and that involving mau-2) are partially redundant to guide AVM ventrally. Scale bars: 5 µm.

 

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?



© The Company of Biologists Ltd 2004