| Summary: | Thesis (Ph.D.)--Memorial University of Newfoundland, 2010. Biochemistry Includes bibliographical references DNA methylation is a critical component of gene control, and is maintained by a family of of enzymes called the DNA methyltransferases. Methylation of CpG sequences promotes the formation of stably condensed, repressed chromatin. This process is important during development where DNA methylation is thought to have a role in lineage determination, X-chromosome inactivation, imprinting, and silencing of endogenous parasitic elements. -- Our aim is to examine the role of methylation in gene silencing during vertebrate development using the zebrafish as a model. To this end we have identified and isolated a number of de novo DNA methytransferase (dnmt3) gene sequences from the zebrafish (Danio redo) and determined the relative expression levels of each during a variety of developmental stages. The zebrafish has six de novo DNA methyltransferase genes as opposed to the three found in mammals. In order to characterize the roles of the dnmt genes we have performed knockdown analysis by morpholino injection. In addition we have treated embryos with a methylation blocker, 5-aza-2'-deoxycytidine in order to examine effects of overall methylation disruption. Based on results from both of these approaches, we conclude that normal methylation is critical to notochord differentiation and development. Other processes where methylation may be relevant include heart, and central nervous system (CNS) development. Preliminary microarray experiments suggest a number of genes that are directly or indirectly regulated by methylation that may be pursued for further investigations of DNA methylation. -- This work will not only allow us to use the zebrafish to examine the role of methylation in vertebrate development, but also develop it as a well-suited model for examining diseases related to abnormal methylation.
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