Molecular tools to elucidate factors regulating alcohol use

Highlights

• TRAP simplifies sequestration of mRNA targeted for translation.

• TRAP can profile mRNA expression by cell type or subcellular compartment.

• Viral CRISPR techniques can manipulate gene expression in a restricted fashion.

• FLEX can target genetic manipulation by cell type via Cre recombination.

Abstract

Alcohol use disorder (AUD) is a pervasive societal problem, marked by high levels of alcohol intake and recidivism. Despite these common disease traits, individuals diagnosed with AUD display a range of disordered drinking and alcohol-related behaviors. The diversity in disease presentation, as well as the established polygenic nature of the disorder and complex neurocircuitry, speaks to the variety of neurochemical changes resulting from alcohol intake that may differentially regulate alcohol-related behaviors. Investigations into the molecular adaptations responsible for maladaptive alcohol-related behavioral outcomes require an ever-evolving set of molecular tools to elucidate with increasing precision how alcohol alters behavior through neurochemical changes. This review highlights recent advances in molecular methodology, addressing how incorporation of these cutting-edge techniques not only may enhance current knowledge of the molecular bases of AUD, but also may facilitate identification of improved treatment targets that may be therapeutic in specific subpopulations of AUD individuals.

Introduction

Alcohol use disorder (AUD) is a chronic condition characterized by loss of control over alcohol intake and high levels of relapse, in spite of individuals’ desire to maintain sobriety. The progressive and pervasive nature of this disorder, with escalation of alcohol intake over time and chronic recidivism, suggests alcohol consumption generates neuroadaptations that promote high alcohol drinking and persist long after the cessation of alcohol intake. AUD is a complex mental illness encompassing multiple disease phenotypes (Salvatore, Gottesman, & Dick, 2015) and genotypes (Hart & Kranzler, 2015) under a common diagnosis, with low penetrance of individual mutations across the AUD population. The polygenic nature of AUD not only contributes to behavioral variation within the diagnosis, but also likely restricts the efficacy of any individual pharmacological target to treat all AUD individuals. Together, these features implicate a variety of molecular neuroadaptations that may support divergent patterns of alcohol abuse and relapse. Systematic elucidation of the molecular changes resulting from alcohol consumption, as well as determination of their functional relevance, is crucial not only to provide greater knowledge about mechanisms underlying disordered alcohol use, but also to identify novel medication targets with the greatest potential to treat subsets of AUD patients. For treatments to succeed, however, understanding the specificity of individual molecular changes at the neuronal, brain region, and circuit levels, as well as their functional impact on behavior, is essential. This review addresses the evolution of methods to investigate and manipulate the molecular composition of neurons with increasing precision, with a focus on how recent advances in molecular tools may enhance our current state of understanding of the molecular bases of AUD.