Heroin addiction is a chronic brain disease that is characterized by compulsive drug intake despite the presence of negative consequences. Heroin addictions have a lifelong vulnerability to relapse, in part due to heightened motivation to seek the drug. Unfortunately, pharmacotherapies for heroin addiction remain limited and largely ineffective. In order to identify novel therapeutic targets to aid in the prevention of relapse, the molecular mechanism of behaviors leading to relapse, specifically motivation, must be better understood. It is known that drugs of abuse induce plasticity in key regions of the mesolimbic dopamine system, including the prefrontal cortex (PFC). Specifically, alterations within this region have been associated with the maladaptive behaviors associated with addiction, including motivation for drug reinforcers, which can be assed using a progressive ratio test in both the human condition and animal models of addiction. While many of the cellular adaptions induced by heroin have predominately focused on the neuronal cells within the PFC, our preliminary data, presented in Aim 1, has identified a dysregulation in glial cells, and specifically oligodendrocytes, following heroin self-administration, an animal model of addiction. I have shown that a transcription factor key in the regulation of oligodendrocyte progenitor cell (OPC) differentiation, Sox10, is upregulated in the PFC following heroin self-administration via chromatin remodeler BRG1. Furthermore, I have identified Sox10 as a critical mediator in a hallmark behavior associated with addiction, motivation to seek the drug. While these novel studies have added to our understanding of the role of glial transcripts in the addicted state, the changes that are occurring specifically in progenitor population, versus cells of the whole lineage, remain unknown. Therefore, I am proposing to examine cellular changes in a specific subtype of OPCs, NG2+ cells, which have distinct physiology properties from other glial cells. My central hypothesis in Aim 2 is that heroin induces transcriptomic changes within the NG2+ cells in the PFC compared to saline controls. I will determine the cell-type specific alterations in genes transcription in this subset of cells using genetic mouse models combined with viral-mediated gene transfer to selectively purify RNA from NG2 cells using Translating Ribosomal Affinity Purification (TRAP). The RNA will be analyzed for transcript changes using RNA-sequencing. Scientifically, this proposal will establish a critical role for NG2 cells in the heroin-addicted state. While these studies are underway, I will participate in a multifaceted Training Plan designed to develop the non-bench skills necessary to reach my ultimate goals of becoming a tenured faculty in an academic setting. In addition, Aim 3 was designed to aid in the identification of a well-funded postdoctoral mentor who continue to help me develop the skills necessary to transition from a postdoctoral scholar to an independent researcher at a research intensive institution, which will include receiving my own funding through a K99 award.
This proposal utilizes a preclinical model of substance abuse disorder to study changes in the brain induced by heroin that contribute to the addicted state, which is a topic highly relevant to public health. The project aims to examine the transcriptome of NG2 oligodendrocyte precursor cells in the prefrontal cortex, a brain structure critically involved in reward and motivation to seek drug. Examining the expression of genes within these cells will help identify novel pharmacotherapeutic targets aimed at normalizing or reversing heroin-induced neuroadaptations that underlie the addicted state.
| Werner, Craig T; Viswanathan, Rathipriya; Martin, Jennifer A et al. (2018) E3 Ubiquitin-Protein Ligase SMURF1 in the Nucleus Accumbens Mediates Cocaine Seeking. Biol Psychiatry 84:881-892 |
