Use of DNA probes and modified extracellular vesicles as therapeutic tools to alter DNA methylation in the brain

About This Grant

PROJECT SUMMARY Chronic exposure to stress and its hormone cortisol is associated with psychiatric disorders such as depression, anxiety, and bipolar disorder. Studies have suggested that these disorders develop, in part, due to the ability of stress and cortisol to cause epigenetic changes that in turn lead to persistent changes in the function of genes that are critical for brain function and neurodevelopment. These stress-associated epigenetic changes are important because they represent environmental risk factors that work in conjunction with genetics to precipitate psychiatric symptoms. Unfortunately, there are very few effective medications that can reverse or attenuate the epigenetic changes caused by environmental stressors. Recently, we have developed a novel tool that can potentially alleviate the effects of stress on gene dysregulation. We found that a simple fragment of modified, single-stranded (ss) DNA probe designed against specific locations in the genome can cause epigenetic changes to occur. We tested this tool on a candidate stress response gene that we have previously shown to undergo cortisol- and stress-induced epigenetic changes. Application of our ssDNA probe against a crucial regulatory region of this gene in neuronal cells caused the reversal of much of the epigenetic change brought about by cortisol exposure. In addition, we also engineered lipid-based extracellular vesicles (EVs) capable of packaging and delivering the ssDNA probe to the brain. We found that expressing brain-derived proteins on the surface of these EVs can increase their targeting efficiency to the brain. Combined, these approaches constitute a potentially powerful translational tool for treating psychiatric disorders. To apply this technology in an animal model, we propose the following two aims. In Aim 1, we will test whether epigenetic changes in the brain of stressed mice can be reversed by injecting EVs carrying the ssDNA probe. We will use EVs that we have previously demonstrated to show increased uptake efficiency in the brain. EV-injected animals will be assessed for reversal of epigenetic changes as well as other molecular changes in gene expression, protein levels, and protein function. In Aim 2, we will further engineer EVs by performing a survey of cell surface proteins of different brain regions. Brain regions such as the hippocampus, amygdala, hypothalamus, and cortex are all impacted by stress and highly relevant to psychiatric disorders. By expressing surface proteins that are specific to each brain region, we anticipate steering the uptake of EVs to any brain region of interest. Stressed animals will be tested as in Aim 1 but this time incorporating the engineered EVs. Since the ssDNA probes and EVs are easy to manufacture, a successful completion of the aims can lead to the development of a powerful therapeutic tool that can be customized to any gene and brain region of interest to reverse stress-induced epigenetic changes in the brain.