clk-1 encodes an enzyme involved in the biosynthesis of ubiquinone (UQ), a redox active lipid that is found in all cellular membranes, including in the mitochondrial respiratory chain. In the nematode Caenorhabditis elegans clk-1 mutants display slow and deregulated physiological rates, including slow embryonic and post-embryonic development, retarded germline development, slow behaviours, and an increased lifespan. clk-1 slow germline development phenotype was previously linked to clk-1 altered ROS metabolism and its effect on lipid oxidization and the let-60/ras pathway. I have taken a genetic suppressor approach to further investigate the causes of the slow germline development phenotype of the clk-1 mutants. / Through this approach one mutant that suppresses the germline phenotype of clk-1 was identified. This suppressor, gsc-1(qm216), restored clk-1 germline development to slightly faster rates than wild type worms. This effect was specific to clk-1 and gsc-1 did not speed germline development rates in wild type worms. Furthermore, this effect appeared to be additive to lowering cholesterol levels but not to increasing cytoplasmic ROS levels. gsc-1 by itself appeared to have a deleterious effect on brood size and to increase lifespan. Neither of these effects were additive to the clk-1 phenotype and were therefore believed to affect similar mechanisms. The genetic mapping of gsc-1 precisely located the mutation to the center of chromosome II and linked it tightly to the lin-5 mutation. However, none of the transgenic lines managed to complement the gsc-1 mutation and its identity was not discovered. / In addition, to determine the role of reactive oxygen species (ROS) in the Clk phenotype, I have been analyzing all clk mutants (clk-1 to -10), by increasing ROS levels through the disruption of sod-1 and sod-2 genes, and scoring Clk phenotypes. I found that, although several clk mutants appear to have altered ROS levels, the phenomenon does not apply to all clk worms and does not correlate with lifespan. The disruption of either sod-1 or -2 affects growth and embryonic viability: sod-2 tends to exacerbate the mutant phenotypes, while sod-1 shows both weakly enhancing or weakly suppressing effects. Interestingly, only one mutant, clk-4, and only one phenotype of this mutant, slow post-embryonic development, is suppressed by sod-2 (but not sod-1). Furthermore, disrupting the expression of the sod-1 gene has only moderate or no effect on the lifespan of wild type worms, while sod-2 was shown to extend lifespan. On the whole, our results suggest that low superoxide levels do not participate in extending lifespan and are not the common process inducing the Clk phenotype in these mutants. Yet, several of the mutants analyzed have a dramatically increased lifespan and specifically behave like mutants which affect mitochondrial electron transport such as isp-1. Thus, our findings suggest that electron transport has a crucial role in longevity and developmental rates that is independent of superoxide generation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.100781 |
| Date | January 2006 |
| Creators | Camp, Darius. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Biology.) |
| Rights | © Darius Camp, 2006 |
| Relation | alephsysno: 002599347, proquestno: AAIMR32677, Theses scanned by UMI/ProQuest. |
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