Worm Breeder's Gazette 13(5): e1 (February 1, 1995)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

The Caenorhabditis elegans Small GTP-Binding Protein RhoA Is Enriched In The Nerve Ring And Sensory Neurons During Larval Development

Weining CHEN*#, and Louis LIM*+

* Glaxo-IMCB Group, Institute of Molecular and Cell Biology,
National University of Singapore, 10 Kent Ridge Crescent,
Singapore 0511 and + Institute of Neurology, 1 Wakefield Street, London

p21 Ras has been implicated in vulval differentiation in Caenorhabditis
elegans. We now describe the characteristics during nematode development
of the related p21 RhoA which has been ascribed a morphological role in
mammals. The cDNA encoding C. elegans RhoA, CeRhoA, was isolated from a
mixed stage cDNA library. The encoded sequence of 192 amino acids residues
displays a high level of identity with its homologues in other organisms
(e.g. 87.6% identity to human RhoA). Genomic Southern analysis indicates
the presence of a single Rho gene in C. elegans. Its 2 kb mRNA is
expressed at the highest levels during embryogenesis and decreases
gradually thereafter. However, the level of the 24 kD protein during
development as detected by the anti-CeRhoA antibody is high at the larval
stages but low in embryos. The GST/CeRhoA fusion protein expressed in E.
coli displays conserved biochemical activities, such as GTP-binding and
stimulation of its intrinsic GTPase activity by GAPs. Unlike its
counterpart in mammalian cells which is predominantly cytosolic, most of
CeRhoA is associated with the membrane and the cytoskeleton throughout
development. Indirect immunofluorescence analysis indicates an ubiquitous
expression of CeRhoA throughout development with a particular enrichment
at larval stages in the pharyngeal nerve ring as well as at the tip of the
head containing chemosensory and mechanosensory neurons. This suggests an
involvement of p21 RhoA in events underlying the postembryonic development
of the sensory circuitry in C. elegans.