Novel exc Genes Involved in Formation of the Tubular Excretory Canals of Caenorhabditis elegans

ABSTRACTThe excretory canals of Caenorhabditis elegans are a model for understanding the maintenance of apical morphology in narrow single-celled tubes. Light and electron microscopy shows that mutants in exc-2 start to form canals normally, but these swell to develop large fluid-filled cysts that lack a complete terminal web at the apical surface, and accumulate filamentous material in the canal lumen. Here, whole-genome sequencing and gene rescue show that exc-2 encodes intermediate filament protein IFC-2. EXC-2/IFC-2 protein, fluorescently tagged via CRISPR/Cas9, is located at the apical surface of the canals independently of other intermediate filament proteins. EXC-2 is also located in several other tissues, though the tagged isoforms are not seen in the larger intestinal tube. Tagged EXC-2 binds via pulldown to intermediate filament protein IFA-4, which is also shown to line the canal apical surface. Overexpression of either protein results in narrow but shortened canals. These results are consistent with a model whereby three intermediate filaments in the canals, EXC-2, IFA-4, and IFB-1, restrain swelling of narrow tubules in concert with actin filaments that guide the extension and direction of tubule outgrowth, while allowing the tube to bend as the animal moves.Article SummaryThe C. elegans excretory canals form a useful model for understanding formation of narrow tubes. exc-2 mutants start to form normal canals that then swell into fluid-filled cysts. We show that exc-2 encodes a large intermediate filament (IF) protein previously not thought to be located in the canals. EXC-2 is located at the apical (luminal) membrane, binds to another IF protein, and appears to be one of three IF proteins that form a flexible meshwork to maintain the thin canal diameter. This work provides a genetically useful model for understanding the interactions of IF proteins with other cytoskeletal elements to regulate tube size and growth.

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Review for "The connectome of the Caenorhabditis elegans pharynx"

10.1002/cne.24932/v1/review1 ◽

2020 ◽

Author(s):

Sreekanth Chalasani

Keyword(s):

Caenorhabditis Elegans

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The glycomes of Caenorhabditis elegans and other model organisms

Biochemical Society Symposium ◽

10.1042/bss0690117 ◽

2002 ◽

Vol 69 ◽

pp. 117-134 ◽

Cited By ~ 47

Author(s):

Stuart M. Haslam ◽

David Gems ◽

Howard R. Morris ◽

Anne Dell

Keyword(s):

Caenorhabditis Elegans ◽

Current Knowledge ◽

Structural Data ◽

Model Organisms ◽

Entire Genome ◽

C Elegans ◽

The Face ◽

Area Of Concern ◽

Nematode Worm

There is no doubt that the immense amount of information that is being generated by the initial sequencing and secondary interrogation of various genomes will change the face of glycobiological research. However, a major area of concern is that detailed structural knowledge of the ultimate products of genes that are identified as being involved in glycoconjugate biosynthesis is still limited. This is illustrated clearly by the nematode worm Caenorhabditis elegans, which was the first multicellular organism to have its entire genome sequenced. To date, only limited structural data on the glycosylated molecules of this organism have been reported. Our laboratory is addressing this problem by performing detailed MS structural characterization of the N-linked glycans of C. elegans; high-mannose structures dominate, with only minor amounts of complex-type structures. Novel, highly fucosylated truncated structures are also present which are difucosylated on the proximal N-acetylglucosamine of the chitobiose core as well as containing unusual Fucα1–2Gal1–2Man as peripheral structures. The implications of these results in terms of the identification of ligands for genomically predicted lectins and potential glycosyltransferases are discussed in this chapter. Current knowledge on the glycomes of other model organisms such as Dictyostelium discoideum, Saccharomyces cerevisiae and Drosophila melanogaster is also discussed briefly.

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