Grant: Discovery Grants Program - Individual

Epigenetics, meaning above genetics, was first conceptualized to explain how different cell types can develop from the same genetic material. Epigenetic gene expression changes are often mediated by chromatin modification. While the field of epigenetics has its origin in developmental biology, there is some evidence that changing environmental conditions can also induce chromatin modifications that alter the transcriptional output of specific cells to facilitate adaptation of adult animals to their environment. But many questions remain. How does the environment induce epigenetic changes? What tissues and genes are affected by a given environmental exposure? How do these epigenetic changes in transcription output mediate the response of the organism? My research program investigates epigenetic mechanisms involved in mediating responses to different types of toxic environmental exposure (TEE) in the fruit fly, Drosophila melanogaster. We showed previously that the conserved epigenetic regulator G9a is required for tolerance of several different TEEs in Drosophila, including bacteria, virus, oxidative stress, heat, and cold. Using comparative transcriptome analysis, we found that G9a might mediate TEE tolerance through similar mechanisms in different systems, including flies, mouse, and human cells, suggesting that G9a-mediated TEE tolerance is evolutionarily conserved. In this proposal I describe experiments designed to further dissect the molecular mechanisms underlying G9a-dependent TEE tolerance in flies. Aim 1 - understanding G9a-mediated epigenetic mechanisms in adaptations to TEE. In Aim 1.1 we will use Drosophila genetic tools and tissue-specific epigenome analysis to identify G9a target genes in the fat body (FB), a tissue that we demonstrated to be critical for G9a-mediated DCV and OS tolerance. In Aim 1.2 we will explore the mechanisms of G9a-mediated heat and cold resistance. In Aim 1.3, we will functionally validate candidate G9a-dependent TEE response genes to identify the mechanisms through which G9a confers tolerance. Aim 2 - understanding how G9a is regulated and recruited to different TEE response genes. In Drosophila, the factors that interact with G9a to regulate its function are unknown. While Aim 1 seeks to identify downstream epigenetic targets of G9a in the FB, the goal of this aim is to discover specific upstream factors that regulate G9a activity in the FB during different types of TEEs. To do so, we created and validated a novel transgenic system to perform tissue specific proximity labelling with the modified biotin ligase Turbo-ID. We will employ this system to identify G9a protein interactors during different TEEs. Identified G9a interaction partners will be functionally validated to understand how G9a is regulated and recruited to different TEE response genes. Impact - One potential outcome of this work would be to identify a conserved mechanism of TEE resistance involving G9a and H3K9 methylation.