Eric L. Greer
My lab is interested in how non-genetic information can be transmitted across generations. An increasing number of complex phenotypes, such as physical appearance, energy metabolism, psychological state, and longevity, have recently been shown to be regulated, in part, by heritable epigenetic information. Epigenetics describes how gene expression changes occur without changes to the DNA sequence. Proteins, RNA molecules, or chemical modifications to histones or DNA can induce these epigenetic changes. How this information, which is not directly coded in our DNA, is passed from generation to generation is still unknown. Understanding the molecular determinants of stable epigenetic memory will provide insight into how environmental changes can affect the health and lifespan of not only the individual who experiences them, but also of their progeny. Our goals are to identify epigenetic inheritance phenotypes and to elucidate the mechanisms behind their transmission across generations.
We have previously identified chromatin-modifying enzymes that regulate complex transgenerational phenotypes in C. elegans, including longevity and fertility. Mutation of a histone H3 lysine 4 (H3K4) trimethylation complex regulates worm lifespan in both the generation in which the mutation occurs and in subsequent generations lacking the mutation. More recent work focuses on understanding how deletion of the C. elegans H3K4me2 demethylase, spr-5, leads to inherited accumulation of the euchromatic H3K4me2 mark and a progressive decline in fertility in successive generations. We identified and characterized chromatin modifying enzymes which regulate the transgenerational epigenetic inheritance of information in spr-5 mutant worms. We also identified a novel form of DNA modifications in Metazoa, methylation of adenines (6mA), which increases transgenerationally in spr-5 mutant worms. We identified enzymes which demethylate and potentially methylate adenines and regulate the epigenetic inheritance of information in C. elegans. Therefore 6mA may be responsible for stable transgenerational epigenetic inheritance.
We are working to further characterize this DNA methylation which was previously thought to occur only in prokaryotes and ancient eukaryotes. We are also examining 6mA's conservation in other species including mammals. Future studies will focus on experimentally testing our working model of epigenetic inheritance and 1) identification of the molecules that are inherited to regulate these transgenerational phenotypes, 2) how environmental cues alter an organism's epigenetic landscape, and 3) determining how an epigenetic mark can be stably maintained or removed. We will address these questions using a combination of genetic, genomic and biochemical approaches in C. elegans and mammalian systems.
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