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UBC Theses and Dissertations

Identification of M-RAS/RAS-2 expression patterns in Caenorhabditis elegans and characterization of M-RAS/RAS-2-null worms Gunaretnam, Erandika Prasadani


M-Ras is a member of the Ras superfamily of small-molecular weight-GTP binding proteins. It is a close relative of the oncoprotein p21Ras and shares 50% overall amino acid sequence identity. ras-2 is the Caenorhabditis elegans ortholog of the human M-Ras. It shows strong conservation of structure in worms and vertebrates. In mammals, endogenous M-Ras acts downstream of the EGF and FGF receptors to activate ERK (MAPK) signaling. The M-Ras is predominantly expressed in the mammalian central nervous system and the heart. Many human cancers including breast and colonic cancers exhibit dramatic elevations of M-Ras mRNA. Receptor tyrosine kinase /RasGTPase/ERK signaling pathway is evolutionary conserved. In C. elegans this highly conserved signaling pathway controls many biological processes including vulval induction. C. elegans is a good model system to understand the role of M-Ras in RTK/Ras/ERK pathway. To understand the expression patterns of RAS-2 in C. elegans, I generated a transgenic C. elegans that expresses GFP driven by the endogenous ras-2 promoter. To investigate the effect of over expressed or activated RAS-2, I also generated transgenic lines over expressing WT or activated RAS-2. I observed that RAS-2 is expressed in various tissues and organs of C. elegans including amphid sensory apparatus, proximal myoepithelial sheaths, spermatheca and in developing gonads. Based on the ras-2 expression patterns, I chose and performed appropriate behavioral assays to characterize ras-2 null worms. The phenotypic characterization and behavioral observations on ras-2 null worms revealed several phenotypes including smaller body size and faster locomotion. Furthermore, based on the behavioral assays, I found that ras-2 mutants have a normal ability to sense inputs and reproduce. To investigate the importance of RAS-2 in pathological signaling of activated LET-23 (EGFR) or activated LET-60 (p21Ras) which cause multivulval phenotype in C. elegans, I examined the different vulval phenotypes in crosses between ras-2 null worms and let-23 or let-60 activated mutants. This revealed that ras-2 null background do not suppresses multivulval phenotype caused by activated let-23 or let-60. However, the activated let-60 exhibits a higher frequency of protruding vulva in the absence of ras-2.

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