Jennifer A. Rinker, B.S., M.A., Ph.D. - US grants

DESCRIPTION (provided by applicant): A growing body of literature has implicated aberrant changes in gene expression induced by drugs of abuse as possible mechanisms for long-term neuroplastic changes that likely contribute to the transition to dependence. Specifically, these changes in gene expression have been linked to the ability of drugs of abuse to induce posttranslation modifications to core histone proteins, thereby relaxing or compacting chromatin structure and increasing or decreasing gene expression, respectively. These posttranslational changes include: acetylation, phosphorylation, and methylation of histone amino acid residues. Examination of the epigenetic mechanisms of drug addiction has predominantly focused on the role of histone acetylation and phosphorylation, while histone methylation has received far less attention. Histone acetylation has been implicated in the regulation of acute responses to ethanol, development of tolerance, and withdrawal. A recent examination of the impact of cocaine on histone modifications demonstrated a role for ¿FosB, a transcription factor induced by a number of drugs of abuse, in suppressing the activity of histone methyltransferases, G9a and G9a-like protein (GLP), and consequently reducing methylation of histone H3 on lysine 9 (H3K9) in the nucleus accumbens (NAc). This effect resulted in reductions of dimethylated H3K9 (H3K9me2) and the activation of numerous genes involved in dendritic plasticity. Until recently, the impact of ethanol on histone methylation has received little attention, and no published reports have examined the impact of voluntary ethanol consumption on H3K9me2 in regions of the brain associated with the maintenance of drug taking behavior. Because ethanol, like cocaine, induces ¿FosB in discrete reward-related regions of the brain, it is reasonable to conceive that neuroplastic changes induced by excessive ethanol consumption might be mediated by changes in histone methylation. Therefore, the experiments outlined in this proposal are designed to test the hypothesis that ethanol consumption and the reinforcing effects of ethanol are mediated, in part, by the suppression of H3K9me2 in the NAc, and that the reinforcing effects and consumption of ethanol can be modulated by manipulating H3K9me2. We predict that ethanol consumption, in both binge-drinking and operant self- administration paradigms, will increase deltaFosB and decrease H3K9me2, G9a and GLP (Specific Aim 1). As well, we predict that regional overexpression of G9a and conditional suppression of G9a in the NAc will decrease and increase binge-like ethanol consumption, respectively (Specific Aim 2). Similarly, we predict that regional overexpression or suppression of G9a in the NAc will correspondingly alter the motivation to respond for ethanol reinforcers in an operant self-administration paradigm (Specific Aim 3). The predicted results would provide the first evidence that histone dimethylation is an epigenetic mechanism involved in binge-like ethanol consumption and operant self-administration of ethanol. Understanding these mechanisms may provide insight into more targeted treatments and prevention strategies for alcohol abuse and dependence disorders. PUBLIC HEALTH RELEVANCE: Binge-like and excessive alcohol consumption are major health concerns, as these types of behaviors can lead to a host of adverse health consequences, including the development of alcoholism, which costs billions of dollars in annual healthcare expenditures and other related costs. Repeated exposure to alcohol can cause neuroadaptive changes, i.e., epigenetic changes, in key circuitry in the brain, altering the neurobiological response to alcohol and possibly contributing to the transition to alcohol dependence. Results from the proposed research will help elucidate the mechanisms underlying alcohol-induced neuroplastic changes and provide insight into the development of more targeted treatment and prevention strategies.

ABSTRACT This is an application for a Mentored Research Scientist Development Award (K01) to support the career development and intensive training of Dr. Jennifer Rinker to facilitate her transition to an independent academic investigator in the alcohol research field. The candidate is an early-stage investigator transitioning from Postdoctoral Fellow to Assistant Professor. Dr. Rinker has extensive experience with in vivo pharmacology and chemogenetic manipulations to study the neural circuitry involved in alcohol use disorder, but has limited experience with slice electrophysiology and advanced molecular techniques to examine plasticity-related events. An intense and comprehensive training, mentoring and research plan has been developed that will provide training in advanced techniques to assess Kv7 channel involvement in alcohol dependence-induced changes in functional plasticity. Dr. Rinker's training will be supported by a firm institutional commitment to her career development and a strong mentoring team of leaders in the alcohol research field, each providing strategic guidance in both the development of this proposal and mentoring as her career progresses. The proposed research plan is a natural extension of the recent studies Dr. Rinker has been conducting in the mentor's laboratory, but is distinguished by its examination of Kv7 channels in discrete corticostriatal circuits in modulating the effects of dependence-induced ethanol consumption. The medial prefrontal cortex (mPFC) is a critical structure involved in imposing inhibitory control over reward-motivated behaviors and projects to the nucleus accumbens (NAc), an essential component of the mesolimbic reward pathway. Ethanol dependence is associated with elevated and uncontrolled drinking and is known to alter the plasticity and physiology of mPFC pyramidal neurons. Specifically, ethanol withdrawal results in the hyperexcitability of NAc-projecting mPFC neurons, the underlying mechanism of which remains unknown. Kv7 channels generate the M-current that critical regulates neuronal excitability by maintaining the membrane potential and dampening neuronal firing. These channels have been implicated in regulating ethanol consumption in the NAc, but their role in the corticostriatal circuits in dependent rodents remains unexplored. Thus, the overarching hypothesis of this proposal is that dependence-induced neuroadaptations in Kv7 channels in the corticostriatal circuitry (i.e., mPFC to NAc) drive the escalated and uncontrolled ethanol consumption in dependence. This proposal will test this hypothesis using a multifaceted approach incorporating subcellular analysis of protein expression and analysis of structural and functional plasticity using diolistic labeling and slice electrophysiology, respectively. Our results demonstrating involvement of Kv7 channels in heavy drinking and dependent mice suggests that continuing these studies will significantly advance our understanding of the cellular mechanisms underlying ethanol dependence. This opportunity will provide the candidate with comprehensive training and a solid foundation on which to build a successful and independent research program in the alcohol neuroscience field.