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The twisted pharynx phenotype in C. elegans.

Axäng C, Rauthan M, Hall DH, Pilon M - BMC Dev. Biol. (2007)

Bottom Line: The pharynx of C. elegans is an epithelial tube whose development has been compared to that of the embryonic heart and the kidney and hence serves as an interesting model for organ development.We also describe the ultrastructure of pharyngeal tendinous organs that connect the pharyngeal basal lamina to that of the body wall, and show that these are pulled into a spiral orientation by twisted pharynges.The twisted pharynx is a useful and easy-to-score phenotype for genes required in extracellular adhesion or organ attachment, and perhaps forgenes required for cytoskeleton regulation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Chemical and Biological Engineering, Lundberg Laboratory, Chalmers University, Göteborg, Sweden. claes.axang@molbiotech.chalmers.se <claes.axang@molbiotech.chalmers.se>

ABSTRACT

Background: The pharynx of C. elegans is an epithelial tube whose development has been compared to that of the embryonic heart and the kidney and hence serves as an interesting model for organ development. Several C. elegans mutants have been reported to exhibit a twisted pharynx phenotype but no careful studies have been made to directly address this phenomenon. In this study, the twisting mutants dig-1, mig-4, mnm-4 and unc-61 are examined in detail and the nature of the twist is investigated.

Results: We find that the twisting phenotype worsens throughout larval development, that in most mutants the pharynx retains its twist when dissected away from the worm body, and that double mutants between mnm-4 and mutants with thickened pharyngeal domains (pha-2 and sma-1) have less twisting in these regions. We also describe the ultrastructure of pharyngeal tendinous organs that connect the pharyngeal basal lamina to that of the body wall, and show that these are pulled into a spiral orientation by twisted pharynges. Within twisted pharynges, actin filaments also show twisting and are longer than in controls. In a mini screen of adhesionmolecule mutants, we also identified one more twisting pharynx mutant, sax-7.

Conclusion: Defects in pharyngeal cytoskeleton length or its anchor points to the extracellular matrix are proposed as the actual source of the twisting force. The twisted pharynx is a useful and easy-to-score phenotype for genes required in extracellular adhesion or organ attachment, and perhaps forgenes required for cytoskeleton regulation.

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Related in: MedlinePlus

The anterior part of the intestine is twisted in a direction opposite to that of the pharynx. Wild-type (N2) and mnm-4 mutant adults expressing ajm-1::gfp reporter were photographed to reveal not only the twisting within the pharynx of the mutant, but also the opposite twist in its anterior intestine. The dashed line indicates the border between the pharynx (to the left) and intestine. The arrowheads follow a stretch of adherens junctions in the intestine of each animal.
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Figure 6: The anterior part of the intestine is twisted in a direction opposite to that of the pharynx. Wild-type (N2) and mnm-4 mutant adults expressing ajm-1::gfp reporter were photographed to reveal not only the twisting within the pharynx of the mutant, but also the opposite twist in its anterior intestine. The dashed line indicates the border between the pharynx (to the left) and intestine. The arrowheads follow a stretch of adherens junctions in the intestine of each animal.

Mentions: Besides the tendon contacts along its anterior length, the pharynx is alsoconnected directly to the body-wall at its extreme anterior end, at the lips [1]. This connection via the arcade cells is unlikely to allow any local displacement, since it involves many robust intercellular junctions between hypodermis, arcade cells and pharyngeal epithelium. Thus pharyngeal twist must be relative to its fixed orientation at the lips. Indeed, when the twist is visualized using ajm1:gfp in the mnm-4 background, the pharynx seems to have rotated at the posterior end around the terminal bulb passively dragging the intestine with it, such that the foremost intestinal cells twist in a direction opposite to the pharynx, hence relieving the tension induced by the pharyngeal twist (Fig. 6).


The twisted pharynx phenotype in C. elegans.

Axäng C, Rauthan M, Hall DH, Pilon M - BMC Dev. Biol. (2007)

The anterior part of the intestine is twisted in a direction opposite to that of the pharynx. Wild-type (N2) and mnm-4 mutant adults expressing ajm-1::gfp reporter were photographed to reveal not only the twisting within the pharynx of the mutant, but also the opposite twist in its anterior intestine. The dashed line indicates the border between the pharynx (to the left) and intestine. The arrowheads follow a stretch of adherens junctions in the intestine of each animal.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1904197&req=5

Figure 6: The anterior part of the intestine is twisted in a direction opposite to that of the pharynx. Wild-type (N2) and mnm-4 mutant adults expressing ajm-1::gfp reporter were photographed to reveal not only the twisting within the pharynx of the mutant, but also the opposite twist in its anterior intestine. The dashed line indicates the border between the pharynx (to the left) and intestine. The arrowheads follow a stretch of adherens junctions in the intestine of each animal.
Mentions: Besides the tendon contacts along its anterior length, the pharynx is alsoconnected directly to the body-wall at its extreme anterior end, at the lips [1]. This connection via the arcade cells is unlikely to allow any local displacement, since it involves many robust intercellular junctions between hypodermis, arcade cells and pharyngeal epithelium. Thus pharyngeal twist must be relative to its fixed orientation at the lips. Indeed, when the twist is visualized using ajm1:gfp in the mnm-4 background, the pharynx seems to have rotated at the posterior end around the terminal bulb passively dragging the intestine with it, such that the foremost intestinal cells twist in a direction opposite to the pharynx, hence relieving the tension induced by the pharyngeal twist (Fig. 6).

Bottom Line: The pharynx of C. elegans is an epithelial tube whose development has been compared to that of the embryonic heart and the kidney and hence serves as an interesting model for organ development.We also describe the ultrastructure of pharyngeal tendinous organs that connect the pharyngeal basal lamina to that of the body wall, and show that these are pulled into a spiral orientation by twisted pharynges.The twisted pharynx is a useful and easy-to-score phenotype for genes required in extracellular adhesion or organ attachment, and perhaps forgenes required for cytoskeleton regulation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Chemical and Biological Engineering, Lundberg Laboratory, Chalmers University, Göteborg, Sweden. claes.axang@molbiotech.chalmers.se <claes.axang@molbiotech.chalmers.se>

ABSTRACT

Background: The pharynx of C. elegans is an epithelial tube whose development has been compared to that of the embryonic heart and the kidney and hence serves as an interesting model for organ development. Several C. elegans mutants have been reported to exhibit a twisted pharynx phenotype but no careful studies have been made to directly address this phenomenon. In this study, the twisting mutants dig-1, mig-4, mnm-4 and unc-61 are examined in detail and the nature of the twist is investigated.

Results: We find that the twisting phenotype worsens throughout larval development, that in most mutants the pharynx retains its twist when dissected away from the worm body, and that double mutants between mnm-4 and mutants with thickened pharyngeal domains (pha-2 and sma-1) have less twisting in these regions. We also describe the ultrastructure of pharyngeal tendinous organs that connect the pharyngeal basal lamina to that of the body wall, and show that these are pulled into a spiral orientation by twisted pharynges. Within twisted pharynges, actin filaments also show twisting and are longer than in controls. In a mini screen of adhesionmolecule mutants, we also identified one more twisting pharynx mutant, sax-7.

Conclusion: Defects in pharyngeal cytoskeleton length or its anchor points to the extracellular matrix are proposed as the actual source of the twisting force. The twisted pharynx is a useful and easy-to-score phenotype for genes required in extracellular adhesion or organ attachment, and perhaps forgenes required for cytoskeleton regulation.

Show MeSH
Related in: MedlinePlus