Demethylating NR3C1, SLC6A4 and BDNF Using dCas9-Tet1: Applications in Understanding and Treating MDD and CM

Abstract

Major depressive disorder (MDD) is the most common psychiatric disorder, affecting one in six adults. Early-life experiences and environment shape the genome through epigenetic modifications, making individuals who experienced child maltreatment (CM) be more predisposed to develop MDD later on in life. This happens through the deregulation of the hypothalamus-pituitary-adrenal (HPA) axis as a result of the continuous stress response. Increased methylation levels in the promoter regions of NR3C1, SLC6A4 and BDNF genes, three genes which have been shown to have key functions in the regulation of the HPA axis, were found in cases of patients with CM and MDD. The downregulation of these genes leads to a decrease in glucocorticoid receptors, lower rates of serotonin uptake and neuroplasticity, all of which affect HPA axis activity and work in concert to form the well-known MDD symptoms. We propose the use of the catalytically inactive dCas9 protein fused with the Tet1 demethylating domain to selectively demethylate the promoter regions of the previously presented genes. Afterwards, using the Herpes simplex virus as a vector, we will transfect patients with the modified plasmid in order to increase the respective protein concentrations. In order to assess the methylation levels, we will use a combination of qRT-PCR, bisulfite pyrosequencing and other NGS techniques. We believe that this therapy will work better than current antidepressants, decreasing the number of anxious and depressive behaviors, as well as stopping future depressive episodes over a long-term period of time.