Elsevier

Developmental Biology

Volume 256, Issue 2, 15 April 2003, Pages 290-301
Developmental Biology

Regular article
The role of the ELAV homologue EXC-7 in the developmentof the Caenorhabditis elegans excretory canals

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Abstract

The exc mutations of Caenorhabditis elegans alter the position and shape of the apical cytoskeleton in polarized epithelial cells. Mutants in exc-7 form small cysts throughout the tubular excretory canals that regulate organismal osmolarity. We have cloned the exc-7 gene, the closest nematode homologue to the neural RNA-binding protein ELAV. EXC-7 is expressed in the canal for a short time midway through embryogenesis. Cysts in exc-7 mutants do not develop until several hours later, beginning at the time of hatching. We find that the first larval period is when the canal completes the majority of its outgrowth, and adds new apical cytoskeleton at a rapid rate. Ultrastructural studies show that exc-7 mutant defects resemble loss of βH-spectrin (encoded by sma-1) at the distal ends of the excretory canals. In addition, exc-7 mutants exhibit synergistic excretory canal defects with mutations in sma-1, and EXC-7 binds sma-1 mRNA. These data imply that EXC-7 protein may affect expression of sma-1 and other genes to effect proper development of the excretory canals.

Keywords

ELAV
RNA-binding
Epithelial polarity
Spectrin
Excretory canals
Apical cytoskeleton

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1

Present address: RIKEN, Center for Developmental Biology, 2-2 Minatojima-Minamimachi, Chuo-Ku, Kobe 650-0047, Japan.