Here I show that the so-called core components of NMD are not all essential genes, since flies that lack the function of Upf3 are viable, in contrast to flies that lack the function of Upf1 and Upf2. By removing the <i>upf1 </i>and <i>upf2 </i>maternal contribution during oogenesis, I demonstrate that Upf1 and Upf2 are required during embryogenesis, as was the case in mice and zebrafish, exemplifying the fly as a valuable NMD model system for vertebrates. In addition, <i>upf1 </i>and <i>upf2</i> mutant eggs exhibit a specific dorsal appendage phenotype, possibly the result of developmental perturbation. I have observed that <i>upf1 </i>and <i>upf2,</i> but not <i>upf3</i>, mutant cell clones are unable to grow, suggesting that <i>upf1 </i>and <i>upf2 </i>mutant cells do not proliferate and, in addition, undergo apoptosis. This supported the hypothesis that Upf1 and Upf2 have Upf3-independent functions that are essential for cell and organism viability, and that NMD is not required for the development of an organism. NMD target gene expression levels were analysed using qPCR. My results suggested that potential NMD targets can be separated into distinct groups depending on which NMD factors are most important for mediating their degradation. In adult flies, genes with known PTCs required Upf2 and Upf3, but not Smg1 for their full degradation by NMD, whereas targets with as yet unidentified NMD-inducing features were fully stabilised only in <i>upf2 </i>mutants. These results suggest that Smg1 is a weak inducer of the pathway, rather than a core component, and that Upf3 is only essential for NMD of specific target mRNAs. In embryos, Upf1 and Upf2 were essential for NMD whereas Smg1 and Upf3 had only moderate effects.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:596225 |
| Date | January 2010 |
| Creators | Avery, P. S. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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