Genetic properties of North African Drosophila melanogaster and comparison with European and Afrotropical populations

International audienc

Amygdala 14-3-3ζ as a Novel Modulator of Escalating Alcohol Intake in Mice

Alcoholism is a devastating brain disorder that affects millions of people worldwide. The development of alcoholism is caused by alcohol-induced maladaptive changes in neural circuits involved in emotions, motivation, and decision-making. Because of its involvement in these processes, the amygdala is thought to be a key neural structure involved in alcohol addiction. However, the molecular mechanisms that govern the development of alcoholism are incompletely understood. We have previously shown that in a limited access choice paradigm, C57BL/6J mice progressively escalate their alcohol intake and display important behavioral characteristic of alcohol addiction, in that they become insensitive to quinine-induced adulteration of alcohol. This study used the limited access choice paradigm to study gene expression changes in the amygdala during the escalation to high alcohol consumption in C57BL/6J mice. Microarray analysis revealed that changes in gene expression occurred predominantly after one week, i.e. during the initial escalation of alcohol intake. One gene that stood out from our analysis was the adapter protein 14-3-3ζ, which was up-regulated during the transition from low to high alcohol intake. Independent qPCR analysis confirmed the up-regulation of amygdala 14-3-3ζ during the escalation of alcohol intake. Subsequently, we found that local knockdown of 14-3-3ζ in the amygdala, using RNA interference, dramatically augmented alcohol intake. In addition, knockdown of amygdala 14-3-3ζ promoted the development of inflexible alcohol drinking, as apparent from insensitivity to quinine adulteration of alcohol. This study identifies amygdala 14-3-3ζ as a novel key modulator that is engaged during escalation of alcohol use

SIGNAL TRANSDUCTION IN ALCOHOL-PREFERRING AA AND ALCOHOL-AVOIDING ANA RAT LINES

AA and ANA rats are one of the earliest and well established rodent models for ethanol preference. Several candidate genes have been suggested to confer genetic susceptibility for alcoholism in these lines including mitogen-activated protein kinases, Akt/PKB and GSK-3 pathways. The aim of the study was to compare the protein levels and phopshorylation of ERK 1/2, Akt and GSK-3 in AA and ANA rats under basal condition and after acute ethanol challenge. Animals were injected with either ethanol (1.5 g/kg) or saline and killed 20 or 45 minutes after injection. Brains were frozen and dissected, nucleus accumbens (NAcc) and cingulate cortex (CCx) were extracted and subject to immunobloting with total and phosphospecifi c antibodies. Baseline differences in ERK 1/2 phopshorylation were discovered between AA and ANA lines. Intraperitoneal injection of ethanol (1.5 g/kg) induced a rapid and transient decrease in ERK 1/2 phosphorylation in both CCx and NAcc within 20 minutes which was already reverting towards control levels at the 45 minute time point. There was no change in the total ERK levels. Phosphorylation of both GSK-3 and Akt in CCx of AA rats was increased 45 minutes after ethanol injection, however no changes were found in NAcc. In ANA rats there were no statistically signifi cant changes in all structures. Thus, AA rats are more susceptible to acute effects of ethanol involving some of the mitogen-activated protein kinases, Akt/PKB and GSK-3 pathways, and these differences are more prominent in the CCx compared to the NAcc

Modulation of voluntary ethanol consumption by beta-arrestin 2

Beta-arrestin 2 is a multifunctional key component of the G protein-coupled receptor complex and is involved in micro-opiate and dopamine D2 receptor signaling, both of which are thought to mediate the rewarding effects of ethanol consumption. We identified elevated expression of the beta-arrestin 2 gene (Arrb2) in the striatum and the hippocampus of ethanol-preferring AA rats compared to their nonpreferring counterpart ANA line. Differential mRNA expression was accompanied by different levels of Arrb2 protein. The elevated expression was associated with a 7-marker haplotype in complete linkage disequilibrium, which segregated fully between the lines, and was unique to the preferring line. Furthermore, a single, distinct, and highly significant quantitative trait locus for Arrb2 expression in hippocampus and striatum was identified at the locus of this gene, providing evidence that genetic variation may affect a cis-regulatory mechanism for expression and regional control of Arrb2. These findings were functionally validated using mice lacking Arrb2, which displayed both reduced voluntary ethanol consumption and ethanol-induced psychomotor stimulation. Our results demonstrate that beta-arrestin 2 modulates acute responses to ethanol and is an important mediator of ethanol reward