Discovering the basis of the essential function of DNMT1 in wasp embryogenesis



 DESCRIPTION (provided by applicant): DNA methylation plays a crucial role in regulating genome function in a wide variety of biological contexts in humans and other eukaryotes. In humans, aberrations of methylation are implicated in many diseases, including cancers. Surprisingly, most of the cellular machinery required for methylation has been lost in the main invertebrate model systems, the worm C. elegans and the fly Drosophila. Thus, the powerful genetic tools available in those systems have not been brought to bear on the questions of the fundamental roles for DNA methylation in development and disease. The wasp Nasonia has many of the advantages of the invertebrate model systems (e.g., small, sequenced and annotated genome, fast development, powerful genetic tools). It possesses the full complement of eukaryotic DNA methyltransferases (DNMT1, 2, and 3), and the genome has significant levels of methylation at typical CpG sites. There are three DNMT1 paralogs (a, b, and c) in Nasonia. When DNMT1a is knocked down by RNAi, embryonic lethality results. This project aims to answer four questions about the roles of DNA methylation and DNMT1a. 1) Is DNA methylation dynamic in early wasp embryogenesis? 2) Do the patterns of methylation in the early embryo depend on DNMT1a function? 3) How does the loss of DNMT1a affect the expression of genes during early embryogenesis? 4) Are the genes whose methylation state is dependent on DNMT1a correlated with those whose mRNA expression levels change after DNMT1a RNAi? Questions 1 and 2 will be addressed with Whole Genome Bisulfite Sequence, and Question 3 will use an RNA-sequencing approach, and Question 4 will use a computational approach. Medical Relevance: The Nasonia embryo provides a simple, accessible and powerful model system to gain basic insights into the functions of DNMT1 enzymes and DNA methylation, topics that are of great relevance to human health. Of the main types of methylation found in eukaryotes, Nasonia appears to employ almost exclusively gene body methylation, which is increasingly recognized as a major aspect of the disease relevance of DNA methylation. Thus Nasonia presents a special opportunity to study the importance of gene body methylation in isolation from potential confounding effects of other modes of DNA methylation.