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Sequencing of p53 genes from Mytilus edulis and Mytilus trossulus for use in environmental effects monitoring of primary treated effluent Muttray, Annette Friederike


This thesis describes the sequencing and potential use of a genetic biomarker for coastal environmental effects monitoring of municipal effluents. The Blue Mussel {Mytilus edulis) and the Bay Mussel (Mytilus trossulus) are currently investigated for their use in municipal effluent effects monitoring. Both can develop a disease of the haemolymph, called haemic neoplasia or leukemia, albeit at different prevalences. The p53 gene is a tumor suppressor gene that is fundamental in cell cycle control and apoptosis. It is mutated or differentially expressed in about 50% of all human cancers and has been implicated in leukemia development in clams. Thus, the p53 gene family was chosen as potential biomarkers for haemic neoplasia in Mytilus spp. During this study, the p53 mRNA sequences of both Mytilus species were elucidated and analyzed in detail using several databases. Sequences show 99.8% similarity on the protein level, but are only 96.5% similar at the DNA level, and differ especially in their 3 untranslated regions, which are important in the regulation of post-transcriptional events. Future studies are required to show potential linkages of p53 gene family expression patterns with haemic neoplasia in the mussels. During this study, an additional gene sequence was discovered and is submitted as a Mytilin C antimicrobial peptide precursor in M. trossulus. These peptides occur in the haemolymph and haemocytes of mussels and prevent microbial infections of the open circulatory system. This thesis also reviews the current state of knowledge on the use of molecular biomarkers for monitoring effects of endocrine disrupting compounds and surfactants and reviews iri-depth the fate and effects of one group of surfactants, linear alkylbenzene sulfonates (LAS). LAS were identified as a major cause of toxicity in the effluent of one treatment plant in the Greater Vancouver Regional District, and have been shown to enhance the effects of endocrine disrupting compounds. Based on our current knowledge about increased prevalence of haemic neoplasia in other bivalves in polluted areas, clam p53 gene family expression patterns, as well as environmental carcinogenesis involving the endocrine and p53 systems in humans, it is suggested that the p53 gene family is a good candidate for development of a molecular biomarker.

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