Myelin Gene Expression: Implications for Alcohol Abuse and Dependence

Acute behavioral responses to ethanol have predictive value for determining an individual\u27s risk of long-term drinking behavior. Although the neurobiology of alcohol abuse is complex, prior studies from our laboratory demonstrated differential myelin-associated gene expression (MAGE) in medial prefrontal cortex (PFC) as one potential mechanism influencing acute ethanol behaviors between C57BL/6J (B6) and DBA/2J (D2) mice. Our laboratory and others have also shown MAGE is reduced in PFC of alcoholics. Herein, I have extended these findings through expression profiling of PFC into chronic models of ethanol self-administration from non-human primates and mice. Together, these results suggest that regulation of MAGE may be relevant to behavioral phenotypes witnessed in alcoholism. The pathogenesis of alcoholism progresses through multiple stages of drug exposure and withdrawal, however, genetic predisposition is also a major contributing factor for this disease. Therefore, I tested the hypothesis that not only does ethanol have direct effects on MAGE, but also variation in basal MAGE within the PFC is a molecular endophenotype underlying ethanol behavioral sensitivity. Bioinformatics of basal MAGE across the BXD recombinant inbred panel (n=29), derived from B6 and D2 mice, revealed a densely correlated myelin gene network associated with several ethanol behavioral phenotypes. Literature association tools identified Fyn kinase as potential regulator of MAGE. Fyn knockout mice are known to be more sensitive to the sedative-hypnotic properties of ethanol in the loss of righting reflex (LORR) paradigm. Microarray analysis of Fyn knockout mice revealed a significant decrease in MAGE, suggesting MAGE may be an underlying factor for LORR. In support of this premise, microarray analysis of genetic variance in LORR across Inbred Long Sleep and Inbred Short Sleep mice, as well as congenics for the Lore5 quantitative trait locus, also demonstrated an inverse relationship between MAGE and duration of LORR. The hypothesis was further investigated using cuprizone to model demyelination in B6 mice and test them in a battery of acute ethanol behaviors. Cuprizone-treated mice had a significantly greater duration in LORR (p \u3c 0.01), demonstrating that myelin is an important contributor to the genetic variance in LORR. Thus, through genetic, genomic, and pharmacological tools I have ‘molecularly triangulated’ a myelin gene network as a contributing factor influencing acute ethanol behavioral sensitivity. The ability of myelin to alter acute ethanol sensitivity may warrant a prospective study of myelin in humans as a predictive molecular phenotype for an individual’s risk of developing alcohol dependence. Additionally, further genomic dissection of MAGE architecture and associated networks may aid in developing novel pharmacotherapies for an alcohol use disorder. Supported by NIAAA grants F31 AA018615 to SP