The role of H3K27me2 in regulating Culex pipiens diapause

Baylor University, Waco TX

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Abstract

PROJECT SUMMARY Insects go through various evolutionary processes to survive in extreme environments and climates. Diapause is one of the most effective means that many insects adapted for a temperate environment. Our objective is to determine whether H3K27me2 regulates diapause traits including extended lifespan, fat accumulation, and enhanced stress resistance in the northern house mosquito, Cx. pipiens. We have three specific goals for this project: 1) To establish the link between diapause-relevant genes and H3K27me2 loss in fat body tissues. We will identify the genetic targets of the H3K27me2 and evaluate the genes’ putative roles in diapause traits using three functional assays: ChIP- seq, RNA-seq, and RNA interference (RNAi). 2) To identify and characterize the genes that are activated by H3K27me2 loss to generate the overwintering fat storage and consumption. We will identify dozens of specific types of lipids in the fat body cells during the overwintering periods using SSNMR and FTIR methods. Second, we will use KEGG Mapper to predict higher-level biochemical and functional pathways that are differentially expressed in fat body tissues exposed to the diapause-inducing condition. 3) To define the roles of the histone demethylase (UTX) and the histone methyltransferases (E(z) and ESC) in regulating H3K27me2 in order to understand the mechanisms that extend the lifespan of diapausing mosquitoes. We will characterize the role of utx, e(z) and esc in modulating H3K27 methylation and lifespan of diapausing females of Cx. pipiens. This will be achieved by knocking down the expression of these genes or by injecting chemical inhibitors that target the encoded proteins. We will monitor the impact on the H3K27 methylation levels and on the survival rates of the treated Cx. pipiens. Histone methylation is potentially a powerful target for breaking or reversing diapause-associated physiological changes. Like other epigenetic modifications, histone methylation is reversible, and thus by altering the activity of the enzyme that regulates these modifications, it may be possible to develop a novel control strategy to delay or prevent the onset of overwintering diapause in these mosquitoes and thus cause significant population loss during the winter season.