EFhd2/Swiprosin-1 is a common genetic determinator for sensation-seeking/low anxiety and alcohol addiction.

In many societies, the majority of adults regularly consume alcohol. However, only a small proportion develops alcohol addiction. Individuals at risk often show a high sensation-seeking/low-anxiety behavioural phenotype. Here we asked which role EF hand domain containing 2 (EFhd2; Swiprosin-1) plays in the control of alcohol addiction-associated behaviours. EFhd2 knockout (KO) mice drink more alcohol than controls and spontaneously escalate their consumption. This coincided with a sensation-seeking and low-anxiety phenotype. A reversal of the behavioural phenotype with ß-carboline, an anxiogenic inverse benzodiazepine receptor agonist, normalized alcohol preference in EFhd2 KO mice, demonstrating an EFhd2-driven relationship between personality traits and alcohol preference. These findings were confirmed in a human sample where we observed a positive association of the EFhd2 single-nucleotide polymorphism rs112146896 with lifetime drinking and a negative association with anxiety in healthy adolescents. The lack of EFhd2 reduced extracellular dopamine levels in the brain, but enhanced responses to alcohol. In confirmation, gene expression analysis revealed reduced tyrosine hydroxylase expression and the regulation of genes involved in cortex development, Eomes and Pax6, in EFhd2 KO cortices. These findings were corroborated in Xenopus tadpoles by EFhd2 knockdown. Magnetic resonance imaging (MRI) in mice showed that a lack of EFhd2 reduces cortical volume in adults. Moreover, human MRI confirmed the negative association between lifetime alcohol drinking and superior frontal gyrus volume. We propose that EFhd2 is a conserved resilience factor against alcohol consumption and its escalation, working through Pax6/Eomes. Reduced EFhd2 function induces high-risk personality traits of sensation-seeking/low anxiety associated with enhanced alcohol consumption, which may be related to cortex function.

Single nucleotide polymorphism in the neuroplastin locus associates with cortical thickness and intellectual ability in adolescents.

Despite the recognition that cortical thickness is heritable and correlates with intellectual ability in children and adolescents, the genes contributing to individual differences in these traits remain unknown. We conducted a large-scale association study in 1583 adolescents to identify genes affecting cortical thickness. Single-nucleotide polymorphisms (SNPs; n=54,837) within genes whose expression changed between stages of growth and differentiation of a human neural stem cell line were selected for association analyses with average cortical thickness. We identified a variant, rs7171755, associating with thinner cortex in the left hemisphere (P=1.12 × 10(-)(7)), particularly in the frontal and temporal lobes. Localized effects of this SNP on cortical thickness differently affected verbal and nonverbal intellectual abilities. The rs7171755 polymorphism acted in cis to affect expression in the human brain of the synaptic cell adhesion glycoprotein-encoding gene NPTN. We also found that cortical thickness and NPTN expression were on average higher in the right hemisphere, suggesting that asymmetric NPTN expression may render the left hemisphere more sensitive to the effects of NPTN mutations, accounting for the lateralized effect of rs7171755 found in our study. Altogether, our findings support a potential role for regional synaptic dysfunctions in forms of intellectual deficits.

Clusterin regulates ß-amyloid toxicity via Dickkopf-1-driven induction of the wnt-PCP-JNK pathway.

Although the mechanism of Aß action in the pathogenesis of Alzheimer's disease (AD) has remained elusive, it is known to increase the expression of the antagonist of canonical wnt signalling, Dickkopf-1 (Dkk1), whereas the silencing of Dkk1 blocks Aß neurotoxicity. We asked if clusterin, known to be regulated by wnt, is part of an Aß/Dkk1 neurotoxic pathway. Knockdown of clusterin in primary neurons reduced Aß toxicity and DKK1 upregulation and, conversely, Aß increased intracellular clusterin and decreased clusterin protein secretion, resulting in the p53-dependent induction of DKK1. To further elucidate how the clusterin-dependent induction of Dkk1 by Aß mediates neurotoxicity, we measured the effects of Aß and Dkk1 protein on whole-genome expression in primary neurons, finding a common pathway suggestive of activation of wnt-planar cell polarity (PCP)-c-Jun N-terminal kinase (JNK) signalling leading to the induction of genes including EGR1 (early growth response-1), NAB2 (Ngfi-A-binding protein-2) and KLF10 (Krüppel-like factor-10) that, when individually silenced, protected against Aß neurotoxicity and/or tau phosphorylation. Neuronal overexpression of Dkk1 in transgenic mice mimicked this Aß-induced pathway and resulted in age-dependent increases in tau phosphorylation in hippocampus and cognitive impairment. Furthermore, we show that this Dkk1/wnt-PCP-JNK pathway is active in an Aß-based mouse model of AD and in AD brain, but not in a tau-based mouse model or in frontotemporal dementia brain. Thus, we have identified a pathway whereby Aß induces a clusterin/p53/Dkk1/wnt-PCP-JNK pathway, which drives the upregulation of several genes that mediate the development of AD-like neuropathologies, thereby providing new mechanistic insights into the action of Aß in neurodegenerative diseases.

Interactive molecular networks obtained by computer-aided conversion of microarray data from brains of alcohol-drinking rats.

Lists of differentially expressed genes in a disease have become increasingly more comprehensive with improvements on all technical levels. Despite statistical cutoffs of 99% or 95% confidence intervals, the number of genes can rise to several hundreds or even thousands, which is barely amenable to a researcher's understanding. This report describes some ways of processing those data by mathematical algorithms. Gene lists obtained from 53 microarrays (two brain regions (amygdala and caudate putamen), three rat strains drinking alcohol or being abstinent) have been used. They resulted from analyses on Affymetrix chips and encompassed approximately 6 000 genes that passed our quality filters. They have been subjected to four mathematical ways of processing: (a) basic statistics, (b) principal component analysis, (c) hierarchical clustering, and (d) introduction into Bayesian networks. It turns out, by using the p-values or the log-ratios, that they best subdivide into brain areas, followed by a fairly good discrimination into the rat strains and the least good discrimination into alcohol-drinking vs. abstinent. Nevertheless, despite the fact that the relation to alcohol-drinking was the weakest signal, attempts have been made to integrate the genes related to alcohol-drinking into Bayesian networks to learn more about their inter-relationships. The study shows, that the tools employed here are extremely useful for (a) quality control of datasets, (b) for constructing interactive (molecular) networks, but (c) have limitations in integration of larger numbers into the networks. The study also shows that it is often pivotal to balance out the number of experimental conditions with the number of animals.

Variation of the genetic expression pattern after exposure to estradiol-17beta and 4-nonylphenol in male zebrafish (Danio rerio).

There is much concern about the increasing presence in the environment of synthetic chemicals that are able to disrupt the endocrine system. Among these compounds, 4-nonylphenol (4-NP) is one of the most studied xenoestrogens, due to its widespread accumulation in water sediment and consequent presence in fatty acid of aquatic organisms. Here, we have used a zebrafish microarray representing 16,399 genes to study the effects of 4-NP and estradiol-17beta (E2) in adult male zebrafish in order to elucidate the mechanism of action of 4-NP compared with that of E2. The microarray results showed that both 4-NP and E2 induced a strong expression of vitellogenin (VTG), the sex related precursor of the yolk proteins in oviparous vertebrates. Both treatments induced elevated protein turnover upregulating genes involved in proteolysis and those that are constituents of the ribosome. Many genes regulated by 4-NP and E2 are involved in energy metabolism, oxidative stress defense mechanisms, xenobiotic metabolism, and lipid metabolism. A different pattern of expression in the two treatments was found for genes involved in oxidative stress, since E2 seems to induce the mechanism of detoxification, while 4-NP seems to inhibit this protective mechanism of the cell. Overall, these findings demonstrate that the microarray approach can contribute significantly to the understanding of expression patterns induced by E2 and 4-NP in male zebrafish. The results also demonstrate that 4-NP is able to act through an alternative pattern to that of estradiol-17beta, modulating the expression of the same genes in a different manner.

BDNF Val66Met and reward-related brain function in adolescents: role for early alcohol consumption.

Changes in reward processing have been identified as one important pathogenetic mechanism in alcohol addiction. The nonsynonymous single nucleotide polymorphism in the brain-derived neurotrophic factor (BDNF) gene (rs6265/Val66Met) modulates the central nervous system activity of neurotransmitters involved in reward processing such as serotonin, dopamine, and glutamate. It was identified as crucial for alcohol consumption in healthy adults and, in rats, specifically related to the function in the striatum, a region that is commonly involved in reward processing. However, studies in humans on the association of BDNF Val66Met and reward-related brain functions and its role for alcohol consumption, a significant predictor of later alcohol addiction, are missing. Based on an intermediate phenotype approach, we assessed the early orientation toward alcohol and alcohol consumption in 530 healthy adolescents that underwent a monetary incentive delay task during functional magnetic resonance imaging. We found a significantly lower response in the putamen to reward anticipation in adolescent Met carriers with high versus low levels of alcohol consumption. During reward feedback, Met carriers with low putamen reactivity were significantly more likely to orient toward alcohol and to drink alcohol 2 years later. This study indicates a possible effect of BDNF Val66Met on alcohol addiction-related phenotypes in adolescence.

αCaMKII controls the establishment of cocaine's reinforcing effects in mice and humans.

Although addiction develops in a considerable number of regular cocaine users, molecular risk factors for cocaine dependence are still unknown. It was proposed that establishing drug use and memory formation might share molecular and anatomical pathways. Alpha-Ca(2+)/calmodulin-dependent protein kinase-II (αCaMKII) is a key mediator of learning and memory also involved in drug-related plasticity. The autophosphorylation of αCaMKII was shown to accelerate learning. Thus, we investigated the role of αCaMKII autophosphorylation in the time course of establishing cocaine use-related behavior in mice. We found that αCaMKII autophosphorylation-deficient αCaMKII(T286A) mice show delayed establishment of conditioned place preference, but no changes in acute behavioral activation, sensitization or conditioned hyperlocomotion to cocaine (20 mg kg(-1), intraperitoneal). In vivo microdialysis revealed that αCaMKII(T286A) mice have blunted dopamine (DA) and blocked serotonin (5-HT) responses in the nucleus accumbens (NAcc) and prefrontal cortex after acute cocaine administration (20 mg kg(-1), intraperitoneal), whereas noradrenaline responses were preserved. Under cocaine, the attenuated DA and 5-HT activation in αCaMKII(T286A) mice was followed by impaired c-Fos activation in the NAcc. To translate the rodent findings to human conditions, several CAMK2A gene polymorphisms were tested regarding their risk for a fast establishment of cocaine dependence in two independent samples of regular cocaine users from Brazil (n=688) and Switzerland (n=141). A meta-analysis across both samples confirmed that CAMK2A rs3776823 TT-allele carriers display a faster transition to severe cocaine use than C-allele carriers. Together, these data suggest that αCaMKII controls the speed for the establishment of cocaine's reinforcing effects.

Genetic risk for nicotine dependence in the cholinergic system and activation of the brain reward system in healthy adolescents.

Genetic variation in a genomic region on chromosome 15q25.1, which encodes the alpha5, alpha3, and beta4 subunits of the cholinergic nicotinic receptor genes, confers risk to smoking and nicotine dependence (ND). Neural reward-related responses have previously been identified as important factors in the development of drug dependence involving ND. Applying an imaging genetics approach in two cohorts (N=487; N=478) of healthy non-smoking adolescents, we aimed to elucidate the impact of genome-wide significant smoking-associated variants in the CHRNA5-CHRNA3-CHRNB4 gene cluster on reward-related neural responses in central regions such as the striatum, orbitofrontal and anterior cingulate cortex (ACC), and personality traits related to addiction. In both samples, carriers of the rs578776 GG compared with AG/AA genotype showed a significantly lower neural response to reward outcomes in the right ventral and dorsal ACC but not the striatum or the orbitofrontal cortex. Rs578776 was unrelated to neural reward anticipation or reward magnitude. Significantly higher scores of anxiety sensitivity in GG compared with AG/AA carriers were found only in sample 1. Associations with other personality traits were not observed. Our findings suggest that the rs578776 risk variant influences susceptibility to ND by dampening the response of the ACC to reward feedback, without recruiting the striatum or orbitofrontal cortex during feedback or anticipation. Thus, it seems to have a major role in the processing of and behavioral adaptation to changing reward outcomes.