Analysis of genetic variations of protein tyrosine kinase fyn and their association with alcohol dependence in two independent cohorts

A Genome-Wide Association Study Reveals a BDNF-Centered Molecular Network Associated with Alcohol Dependence and Related Clinical Measures

At least 50% of factors predisposing to alcohol dependence (AD) are genetic and women affected with this disorder present with more psychiatric comorbidities, probably indicating different genetic factors involved. We aimed to run a genome-wide association study (GWAS) followed by a bioinformatic functional annotation of associated genomic regions in patients with AD and eight related clinical measures. A genome-wide significant association of rs220677 with AD (p-value = 1.33 × 10^-8 calculated with the Yates-corrected χ² test under the assumption of dominant inheritance) was discovered in female patients. Associations of AD and related clinical measures with seven other single nucleotide polymorphisms listed in previous GWASs of psychiatric and addiction traits were differently replicated in male and female patients. The bioinformatic analysis showed that regulatory elements in the eight associated linkage disequilibrium blocks define the expression of 80 protein-coding genes. Nearly 68% of these and of 120 previously published coding genes associated with alcohol phenotypes directly interact in a single network, where BDNF is the most significant hub gene. This study indicates that several genes behind the pathogenesis of AD are different in male and female patients, but implicated molecular mechanisms are functionally connected. The study also reveals a central role of BDNF in the pathogenesis of AD.

Saracatinib Fails to Reduce Alcohol-Seeking and Consumption in Mice and Human Participants

More effective treatments to reduce pathological alcohol drinking are needed. The glutamatergic system and the NMDA receptor (NMDAR), in particular, are implicated in behavioral and molecular consequences of chronic alcohol use, making the NMDAR a promising target for novel pharmacotherapeutics. Ethanol exposure upregulates Fyn, a protein tyrosine kinase that indirectly modulates NMDAR signaling by phosphorylating the NR2B subunit. The Src/Fyn kinase inhibitor saracatinib (AZD0530) reduces ethanol self-administration and enhances extinction of goal-directed ethanol-seeking in mice. However, less is known regarding how saracatinib affects habitual ethanol-seeking. Moreover, no prior studies have assessed the effects of Src/Fyn kinase inhibitors on alcohol-seeking or consumption in human participants. Here, we tested the effects of saracatinib on alcohol consumption and craving/seeking in two species, including the first trial of an Src/Fyn kinase inhibitor to reduce drinking in humans. Eighteen male C57BL/6NCrl mice underwent operant conditioning on a variable interval schedule to induce habitual responding for 10% ethanol/0.1% saccharin. Next, mice received 5 mg/kg saracatinib or vehicle 2 h or 30 min prior to contingency degradation to measure habitual responding. In the human study, 50 non-treatment seeking human participants who drank heavily and met DSM-IV criteria for alcohol abuse or dependence were randomized to receive 125 mg/day saracatinib (n = 33) or placebo (n = 17). Alcohol Drinking Paradigms (ADP) were completed in a controlled research setting: before and after 7-8 days of treatment. Each ADP involved consumption of a priming drink of alcohol (0.03 mg%) followed by ad libitum access (3 h) to 12 additional drinks (0.015 g%); the number of drinks consumed and craving (Alcohol Urge Questionnaire) were recorded. In mice, saracatinib did not affect habitual ethanol seeking or consumption at either time point. In human participants, no significant effects of saracatinib on alcohol craving or consumption were identified. These results in mice and humans suggest that Fyn kinase inhibition using saracatinib, at the doses tested here, may not reduce alcohol consumption or craving/seeking among those habitually consuming alcohol, in contrast to reports of positive effects of saracatinib in individuals that seek ethanol in a goal-directed manner. Nevertheless, future studies should confirm these negative findings using additional doses and schedules of saracatinib administration.

cAMP-Fyn signaling in the dorsomedial striatum direct pathway drives excessive alcohol use

Fyn kinase in the dorsomedial striatum (DMS) of rodents plays a central role in mechanisms underlying excessive alcohol intake. The DMS is comprised of medium spiny neurons (MSNs) that project directly (dMSNs) or indirectly (iMSNs) to the substantia nigra. Here, we examined the cell-type specificity of Fyn's actions in alcohol use. First, we knocked down Fyn selectively in DMS dMSNs or iMSNs of mice and measured the level of alcohol consumption. We found that downregulation of Fyn in dMSNs, but not in iMSNs, reduces excessive alcohol but not saccharin intake. D1Rs are coupled to Gαs/olf, which activate cAMP signaling. To examine whether Fyn's actions are mediated through cAMP signaling, DMS dMSNs were infected with GαsDREADD, and the activation of Fyn signaling was measured following CNO treatment. We found that remote stimulation of cAMP signaling in DMS dMSNs activates Fyn and promotes the phosphorylation of the Fyn substrate, GluN2B. In contract, remote activation of GαsDREADD in DLS dMSNs did not alter Fyn signaling. We then tested whether activation of GαsDREADD in DMS dMSNs or iMSNs alters alcohol intake and observed that CNO-dependent activation of GαsDREADD in DMS dMSNs but not iMSNs increases alcohol but not saccharin intake. Finally, we examined the contribution of Fyn to GαsDREADD-dependent increase in alcohol intake, and found that systemic administration of the Fyn inhibitor, AZD0503 blocks GαsDREADD-dependent increase in alcohol consumption. Our results suggest that the cAMP-Fyn axis in the DMS dMSNs is a molecular transducer of mechanisms underlying the development of excessive alcohol consumption.

Acute alcohol withdrawal and recovery in men lead to profound changes in DNA methylation profiles: a longitudinal clinical study

BACKGROUND AND AIMS

Withdrawal is a serious and sometimes life-threatening event in alcohol-dependent individuals. It has been suggested that epigenetic processes may play a role in this context. This study aimed to identify genes and pathways involved in such processes which hint to relevant mechanisms underlying withdrawal.

DESIGN

Cross-sectional case-control study and longitudinal within-cases study during alcohol withdrawal and after 2 weeks of recovery SETTING: Addiction medicine departments in two university hospitals in southern Germany.

PARTICIPANTS/CASES

Ninety-nine alcohol-dependent male patients receiving in-patient treatment and suffering from severe withdrawal symptoms during detoxification and 95 age-matched male controls.

MEASUREMENTS

Epigenome-wide methylation patterns were analyzed in patients during acute alcohol withdrawal and after 2 weeks of recovery, as well as in age-matched controls using Illumina EPIC bead chips. Methylation levels of patients and controls were tested for association with withdrawal status. Tests were adjusted for technical and batch effects, age, smoking and cell type distribution. Single-site analysis, as well as an analysis of differentially methylated regions and gene ontology analysis, were performed.

FINDINGS

We found pronounced epigenome-wide significant [false discovery rate (FDR) < 0.05] differences between patients during withdrawal and after 2 weeks [2876 cytosine-phosphate-guanine (CpG) sites], as well as between patients and controls (9845 and 6094 CpG sites comparing patients at time-point 1 and patients at time-point 2 versus controls, respectively). Analysis of differentially methylated regions and involved pathways revealed an over-representation of gene ontology terms related to the immune system response. Differences between patients and controls diminished after recovery (> 800 CpG sites less), suggesting a partial reversibility of alcohol- and withdrawal-related methylation.

CONCLUSIONS

Acute alcohol withdrawal in severely dependent male patients appears to be associated with extensive changes in epigenome-wide methylation patterns. In particular, genes involved in immune system response seem to be affected by this condition.

Genetic association between −93A/G polymorphism in the Fyn kinase gene and alcohol dependence in Spanish men

Background

Fyn tyrosine kinase is a member of the Scr family that phosphorylates the NR2A and NR2B subunits of the NMDA receptors reducing the inhibitory effects of ethanol and therefore may regulate the individual sensitivity to ethanol.

Objectives

To investigate whether there is any relationship between the polymorphism at position −93 of the Fyn kinase gene and the susceptibility to develop alcoholism.

Methods

We studied the distribution of genotypes and alleles of the polymorphism −93A/G (137346 T/C) in the 5′ UTR region of the fyn gene in 207 male heavy drinkers (119 with alcohol dependence and 88 with alcohol abuse) and 100 control subjects from Castilla y León (Spain).

Results

The frequency of G allele carriers was higher in alcohol dependents than in alcohol abusers (47.9% vs 30.6%; p = 0.015; OR = 2.077; 95% CI 1.165–3.704).

Conclusion

Our results show that the −93G allele of Fyn kinase gene is associated with higher risk to develop alcohol dependence in Spanish men.

The Fyn kinase inhibitor, AZD0530, suppresses mouse alcohol self-administration and seeking

Fyn is a member of the Src family of protein tyrosine kinases (PTKs) that plays an important role not only in normal synaptic functions but also in brain pathologies including alcohol use disorder. We previously reported that repeated cycles of binge drinking and withdrawal activate Fyn in the dorsomedial striatum (DMS) of rodents, and that Fyn signaling in the DMS contributes to rat alcohol intake and relapse. Here, we used AZD0530, a CNS penetrable inhibitor of Src PTKs developed for the treatment of Alzheimer disease and cancer and tested its efficacy to suppress alcohol-dependent molecular and behavioral effects. We show that systemic administration of AZD0530 prevents alcohol-induced Fyn activation and GluN2B phosphorylation in the DMS of mice. We further report that a single dose of AZD0530 reduces alcohol operant self-administration and promotes extinction of alcohol self-administration without altering basal and dopamine D1 receptor-dependent locomotion. Together, our findings suggest that AZD0530, through its inhibitory actions on Fyn kinase, dampens alcohol seeking and drinking.

Src-dependent phosphorylation of μ-opioid receptor at Tyr336 modulates opiate withdrawal

Opiate withdrawal/negative reinforcement has been implicated as one of the mechanisms for the progression from impulsive to compulsive drug use. Increase in the intracellular cAMP level and protein kinase A (PKA) activities within the neurocircuitry of addiction has been a leading hypothesis for opiate addiction. This increase requires the phosphorylation of μ‐opioid receptor (MOR) at Tyr³³⁶ by Src after prolonged opiate treatment in vitro. Here, we report that the Src‐mediated MOR phosphorylation at Tyr³³⁶ is a prerequisite for opiate withdrawal in mice. We observed the recruitment of Src in the vicinity of MOR and an increase in phosphorylated Tyr³³⁶ (pY336) levels during naloxone‐precipitated withdrawal. The intracerebroventricular or stereotaxic injection of a Src inhibitor (AZD0530), or Src shRNA viruses attenuated pY336 levels, and several somatic withdrawal signs. This was also observed in Fyn^−/− mice. The stereotaxic injection of wild‐type MOR, but not mutant (Y336F) MOR, lentiviruses into the locus coeruleus of MOR^−/− mice restored somatic withdrawal jumping. Regulating pY336 levels during withdrawal might be a future target for drug development to prevent opiate addictive behaviors.

A Critical Review of Methods and Results in the Search for Genetic Contributors to Alcohol Sensitivity

Attributes of alcohol sensitivity are present before alcohol use disorders (AUDs) develop, they predict those adverse alcohol outcomes, are familial in nature, and many are heritable. Whether measured by alcohol challenges or retrospective reports of numbers of drinks required for effects, alcohol sensitivity reflects multiple phenotypes, including low levels of alcohol response and alcohol-related stimulation. Identification of genes that contribute to alcohol sensitivity could help identify individuals carrying risks for AUDs through their alcohol responses for whom early intervention might mitigate their vulnerability. Such genes could also improve understanding of biological underpinnings of AUDs, which could lead to new treatment approaches. However, the existing literature points to a wide range of genetic mechanisms that might contribute to alcohol responses, and few such genetic findings have been widely replicated. This critical review describes the potential impact of the diverse methods used to study sensitivity on the diversity of genetic findings that have been reported, places the genetic variants mentioned in the literature into broader categories rather than isolated results, and offers suggestions regarding how to advance the field by interpreting findings in light of the methods used to select research subjects and to measure alcohol sensitivity. To date, the most promising results have been for GABA, glutamate, opioid, dopamine, serotonin, and cholinergic system genes. The more gene variants that can be identified as contributors to sensitivity the better future gene screening platforms or polygenic scores are likely to be.

Targeting the intracellular signaling "STOP" and "GO" pathways for the treatment of alcohol use disorders

In recent years, research has identified the molecular and neural substrates underlying the transition of moderate "social" consumption of alcohol to the characteristic alcohol use disorder (AUD) phenotypes including excessive and compulsive alcohol use which we define in the review as the GO signaling pathways. In addition, growing evidence points to the existence of molecular mechanisms that keep alcohol consumption in check and that confer resilience for the development of AUD which we define herein as the STOP signaling pathways. In this review, we focus on examples of the GO and the STOP intracellular signaling pathways and discuss our current knowledge of how manipulations of these pathways may be used for the treatment of AUD.

Alcohol-dependent molecular adaptations of the NMDA receptor system

Phenotypes such as motivation to consume alcohol, goal-directed alcohol seeking and habit formation take part in mechanisms underlying heavy alcohol use. Learning and memory processes greatly contribute to the establishment and maintenance of these behavioral phenotypes. The N-methyl-d-aspartate receptor (NMDAR) is a driving force of synaptic plasticity, a key cellular hallmark of learning and memory. Here, we describe data in rodents and humans linking signaling molecules that center around the NMDARs, and behaviors associated with the development and/or maintenance of alcohol use disorder (AUD). Specifically, we show that enzymes that participate in the regulation of NMDAR function including Fyn kinase as well as signaling cascades downstream of NMDAR including calcium/calmodulin-dependent protein kinase II (CamKII), the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and the mammalian target of rapamycin complex 1 (mTORC1) play a major role in mechanisms underlying alcohol drinking behaviors. Finally, we emphasize the brain region specificity of alcohol's actions on the above-mentioned signaling pathways and attempt to bridge the gap between the molecular signaling that drive learning and memory processes and alcohol-dependent behavioral phenotypes. Finally, we present data to suggest that genes related to NMDAR signaling may be AUD risk factors.

The FKBP5 Gene Affects Alcohol Drinking in Knockout Mice and Is Implicated in Alcohol Drinking in Humans

FKBP5 encodes FK506-binding protein 5, a glucocorticoid receptor (GR)-binding protein implicated in various psychiatric disorders and alcohol withdrawal severity. The purpose of this study is to characterize alcohol preference and related phenotypes in Fkbp5 knockout (KO) mice and to examine the role of FKBP5 in human alcohol consumption. The following experiments were performed to characterize Fkpb5 KO mice. (1) Fkbp5 KO and wild-type (WT) EtOH consumption was tested using a two-bottle choice paradigm; (2) The EtOH elimination rate was measured after intraperitoneal (IP) injection of 2.0 g/kg EtOH; (3) Blood alcohol concentration (BAC) was measured after 3 h limited access of alcohol; (4) Brain region expression of Fkbp5 was identified using LacZ staining; (5) Baseline corticosterone (CORT) was assessed. Additionally, two SNPs, rs1360780 (C/T) and rs3800373 (T/G), were selected to study the association of FKBP5 with alcohol consumption in humans. Participants were college students (n = 1162) from 21–26 years of age with Chinese, Korean or Caucasian ethnicity. The results, compared to WT mice, for KO mice exhibited an increase in alcohol consumption that was not due to differences in taste sensitivity or alcohol metabolism. Higher BAC was found in KO mice after 3 h of EtOH access. Fkbp5 was highly expressed in brain regions involved in the regulation of the stress response, such as the hippocampus, amygdala, dorsal raphe and locus coeruleus. Both genotypes exhibited similar basal levels of plasma corticosterone (CORT). Finally, single nucleotide polymorphisms (SNPs) in FKBP5 were found to be associated with alcohol drinking in humans. These results suggest that the association between FKBP5 and alcohol consumption is conserved in both mice and humans.

Drugs as instruments: a new framework for non-addictive psychoactive drug use

Most people who are regular consumers of psychoactive drugs are not drug addicts, nor will they ever become addicts. In neurobiological theories, non-addictive drug consumption is acknowledged only as a "necessary" prerequisite for addiction, but not as a stable and widespread behavior in its own right. This target article proposes a new neurobiological framework theory for non-addictive psychoactive drug consumption, introducing the concept of "drug instrumentalization." Psychoactive drugs are consumed for their effects on mental states. Humans are able to learn that mental states can be changed on purpose by drugs, in order to facilitate other, non-drug-related behaviors. We discuss specific "instrumentalization goals" and outline neurobiological mechanisms of how major classes of psychoactive drugs change mental states and serve non-drug-related behaviors. We argue that drug instrumentalization behavior may provide a functional adaptation to modern environments based on a historical selection for learning mechanisms that allow the dynamic modification of consummatory behavior. It is assumed that in order to effectively instrumentalize psychoactive drugs, the establishment of and retrieval from a drug memory is required. Here, we propose a new classification of different drug memory subtypes and discuss how they interact during drug instrumentalization learning and retrieval. Understanding the everyday utility and the learning mechanisms of non-addictive psychotropic drug use may help to prevent abuse and the transition to drug addiction in the future.

Genetic Variation in the Vesicular Monoamine Transporter 1 (VMAT1/SLC18A1) Gene and Alcohol Withdrawal Severity

BACKGROUND

Alcohol withdrawal (AW) can be a serious consequence of alcohol dependence and consists of various neurochemical adaptations in the brain. One such neuroadaptation occurs in the monoamine neurotransmitter system. Recently, a functional variant in the presynaptic vesicular monoamine transporter gene (VMAT1/SLC18A1-Thr136Ile-rs1390938) was found to significantly increase transport of monoamines into synaptic vesicles in vitro. We hypothesize that the alteration of magnitude of monoamine release contributes to severity of AW symptoms.

METHODS

Alcohol-dependent individuals (n = 609; European American n = 340; African American n = 216; other n = 53) were administered the Clinical Institute Withdrawal Assessment of Alcohol Scale, Revised (CIWA-Ar) questionnaire at the time of inpatient admission. Patients were subsequently genotyped for 12 single nucleotide polymorphism (SNP) markers in VMAT1. Association analyses were conducted on the combined sample and separated by ethnicity.

RESULTS

Single marker association tests revealed a significant association between 3 VMAT1 markers and CIWA-Ar scores in the EA sample. The minor alleles of rs1390938 (A) and rs952859 (C) were significantly associated with lower CIWA-Ar scores (p = 0.0006; p = 0.0007), whereas the minor allele of rs3779672 (G) was significantly associated with higher scores (p = 0.006). Additionally, these 3 SNPs were found in a haplotype block that was significantly associated with lower CIWA-Ar scores after haplotype analyses were run (p = 0.009).

CONCLUSIONS

This study shows that genetic variants in VMAT1, including the functional SNP rs1390938, contribute to the severity of AW in patients of European descent. Our data show for the first time a role of presynaptic neurotransmitter release in AW severity. This finding could contribute to identifying patients at risk for severe AW and shed light into the pathophysiology of AW and its treatment.

Role of the Fyn -93A>G polymorphism (rs706895) in acute rejection after liver transplantation

The tyrosine kinase Fyn phosphorylates tyrosine residues on key targets involved in early T-cell signal transduction. T-cell signal transduction is one essential step for acute transplant rejection. The aim of this study was to evaluate the association of Fyn -93A>G single nucleotide polymorphism (SNP) (rs706895) with the susceptibility to acute rejection episodes in liver transplantation. In total, 72 liver transplant recipients with one biopsy proven acute rejection (S-BPAR), 56 with multiple BPAR (M-BPAR), 105 without BPAR (No-BPAR), and 145 healthy controls were enrolled in this case-control study. The SNP was genotyped by polymerase chain reaction-allele specific restriction enzyme analysis (PCR-ASRA) and was analyzed for a recessive and a dominant model. The Fyn -93G allele exhibits in healthy controls a statistically significant lower frequency than in liver recipients (18% vs. 24%; p=0.046) or in liver recipients with BPAR (18% vs. 27%; p=0.017). However, the genotype and allele frequencies of the Fyn -93A>G SNP demonstrate no significant differences between recipients with acute rejection episodes (S-BPAR and M-BPAR) and No-BPAR recipients. Thus our results provide no evidence that the Fyn -93A>G SNP contributes to the susceptibility to acute liver transplant rejection in a Caucasian population.

Alcohol consumption mediates the relationship between ADH1B and DSM-IV alcohol use disorder and criteria

OBJECTIVE

A single nucleotide variation in the alcohol dehydrogenase 1B (ADH1B) gene, rs1229984, produces an ADH1B enzyme with faster acetaldehyde production. This protective variant is associated with lower alcohol consumption and lower risk for alcohol use disorders (AUDs). Based on the premise that faster ADH1B kinetics decreases alcohol consumption, we formally tested if the association between ADH1B variant rs1229984 and AUDs occurs through consumption. We also tested whether the association between rs1229984 and each of the 11 Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), AUD criteria occurs through consumption.

METHOD

A total of 1,130 lifetime drinkers from an Israeli household sample were assessed with a structured interview and genotyped for rs1229984 (protective allele frequency = 0.28). Logistic regression evaluated the association between rs1229984 and each phenotype (AUDs, 11 individual DSM-IV criteria). For phenotypes significantly related to rs1229984, the effect through consumption was tested with logistic regression and bootstrapping.

RESULTS

ADH1B rs1229984 was significantly associated with AUDs and six criteria, with odds ratios ranging from 1.32 to 1.96. The effect through consumption was significant for these relationships, explaining 23%-74% of the total ADH1B effect.

CONCLUSIONS

This is the first study to show that ADH1B rs1229984 is related to 6 of the 11 DSM-IV AUD criteria and that alcohol consumption explained a significant proportion of these associations and the association of ADH1B with AUDs. Better understanding of the relationship between ADH1B and the DSM-IV AUD criteria, including effects through consumption, will enhance our understanding of the etiologic model through which AUDs can occur.

Extracellular signal-regulated protein kinases 1 and 2 activation by addictive drugs: a signal toward pathological adaptation

Addiction is a chronic and relapsing psychiatric disorder that is thought to occur in vulnerable individuals. Synaptic plasticity evoked by drugs of abuse in the so-called neuronal circuits of reward has been proposed to underlie behavioral adaptations that characterize addiction. By increasing dopamine in the striatum, addictive drugs alter the balance of dopamine and glutamate signals converging onto striatal medium-sized spiny neurons (MSNs) and activate intracellular events involved in long-term behavioral alterations. Our laboratory contributed to the identification of salient molecular changes induced by administration of addictive drugs to rodents. We pioneered the observation that a common feature of addictive drugs is to activate, by a double tyrosine/threonine phosphorylation, the extracellular signal-regulated kinases 1 and 2 (ERK1/2) in the striatum, which control a plethora of substrates, some of them being critically involved in cocaine-mediated molecular and behavioral adaptations. Herein, we review how the interplay between dopamine and glutamate signaling controls cocaine-induced ERK1/2 activation in MSNs. We emphasize the key role of N-methyl-D-aspartate receptor potentiation by D1 receptor to trigger ERK1/2 activation and its subsequent nuclear translocation where it modulates both epigenetic and genetic processes engaged by cocaine. We discuss how cocaine-induced long-term synaptic and structural plasticity of MSNs, as well as behavioral adaptations, are influenced by ERK1/2-controlled targets. We conclude that a better knowledge of molecular mechanisms underlying ERK1/2 activation by drugs of abuse and/or its role in long-term neuronal plasticity in the striatum may provide a new route for therapeutic treatment in addiction.

FKBP5 moderates alcohol withdrawal severity: human genetic association and functional validation in knockout mice

Alcohol withdrawal is associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction. The FKBP5 gene codes for a co-chaperone, FK506-binding protein 5, that exerts negative feedback on HPA axis function. This study aimed to examine the effects of single-nucleotide polymorphisms (SNPs) of the FKBP5 gene in humans and the effect of Fkbp5 gene deletion in mice on alcohol withdrawal severity. We genotyped six FKBP5 SNPs (rs3800373, rs9296158, rs3777747, rs9380524, rs1360780, and rs9470080) in 399 alcohol-dependent inpatients with alcohol consumption 48 h before admission and recorded scores from the Clinical Institute Withdrawal Assessment-Alcohol revised (CIWA-Ar). Fkbp5 gene knockout (KO) and wild-type (WT) mice were assessed for alcohol withdrawal using handling-induced convulsions (HICs) following both acute and chronic alcohol exposure. We found the minor alleles of rs3800373 (G), rs9296158 (A), rs1360780 (T), and rs9470080 (T) were significantly associated with lower CIWA-Ar scores whereas the minor alleles of rs3777747 (G) and rs9380524 (A) were associated with higher scores. The haplotype-based analyses also showed an association with alcohol withdrawal severity. Fkbp5 KO mice showed significantly greater HICs during withdrawal from chronic alcohol exposure compared with WT controls. This study is the first to show a genetic effect of FKBP5 on the severity of alcohol withdrawal syndrome. In mice, the absence of the Fkbp5 gene enhances sensitivity to alcohol withdrawal. We suggest that FKBP5 variants may trigger different adaptive changes in HPA axis regulation during alcohol withdrawal with concomitant effects on withdrawal severity.

Integrating GWASs and human protein interaction networks identifies a gene subnetwork underlying alcohol dependence

Despite a significant genetic contribution to alcohol dependence (AD), few AD-risk genes have been identified to date. In the current study, we aimed to integrate genome-wide association studies (GWASs) and human protein interaction networks to investigate whether a subnetwork of genes whose protein products interact with one another might collectively contribute to AD. By using two discovery GWAS data sets of the Study of Addiction: Genetics and Environment (SAGE) and the Collaborative Study on the Genetics of Alcoholism (COGA), we identified a subnetwork of 39 genes that not only was enriched for genes associated with AD, but also collectively associated with AD in both European Americans (p < 0.0001) and African Americans (p = 0.0008). We replicated the association of the gene subnetwork with AD in three independent samples, including two samples of European descent (p = 0.001 and p = 0.006) and one sample of African descent (p = 0.0069). To evaluate whether the significant associations are likely to be false-positive findings and to ascertain their specificity, we examined the same gene subnetwork in three other human complex disorders (bipolar disorder, major depressive disorder, and type 2 diabetes) and found no significant associations. Functional enrichment analysis revealed that the gene subnetwork was enriched for genes involved in cation transport, synaptic transmission, and transmission of nerve impulses, all of which are biologically meaningful processes that may underlie the risk for AD. In conclusion, we identified a gene subnetwork underlying AD that is biologically meaningful and highly reproducible, providing important clues for future research into AD etiology and treatment.

Fyn-dependent gene networks in acute ethanol sensitivity

Studies in humans and animal models document that acute behavioral responses to ethanol are predisposing factor for the risk of long-term drinking behavior. Prior microarray data from our laboratory document strain- and brain region-specific variation in gene expression profile responses to acute ethanol that may be underlying regulators of ethanol behavioral phenotypes. The non-receptor tyrosine kinase Fyn has previously been mechanistically implicated in the sedative-hypnotic response to acute ethanol. To further understand how Fyn may modulate ethanol behaviors, we used whole-genome expression profiling. We characterized basal and acute ethanol-evoked (3 g/kg) gene expression patterns in nucleus accumbens (NAC), prefrontal cortex (PFC), and ventral midbrain (VMB) of control and Fyn knockout mice. Bioinformatics analysis identified a set of Fyn-related gene networks differently regulated by acute ethanol across the three brain regions. In particular, our analysis suggested a coordinate basal decrease in myelin-associated gene expression within NAC and PFC as an underlying factor in sensitivity of Fyn null animals to ethanol sedation. An in silico analysis across the BXD recombinant inbred (RI) strains of mice identified a significant correlation between Fyn expression and a previously published ethanol loss-of-righting-reflex (LORR) phenotype. By combining PFC gene expression correlates to Fyn and LORR across multiple genomic datasets, we identified robust Fyn-centric gene networks related to LORR. Our results thus suggest that multiple system-wide changes exist within specific brain regions of Fyn knockout mice, and that distinct Fyn-dependent expression networks within PFC may be important determinates of the LORR due to acute ethanol. These results add to the interpretation of acute ethanol behavioral sensitivity in Fyn kinase null animals, and identify Fyn-centric gene networks influencing variance in ethanol LORR. Such networks may also inform future design of pharmacotherapies for the treatment and prevention of alcohol use disorders.

Alcohol use disorders and perceived drinking norms: ethnic differences in Israeli adults

OBJECTIVE

Individuals' perceptions of drinking acceptability in their society (perceived injunctive drinking norms) are widely assumed to explain ethnic group differences in drinking and alcohol use disorders (AUDs), but this has never been formally tested. Immigrants to Israel from the former Soviet Union (FSU) are more likely to drink and report AUD symptoms than other Israelis. We tested perceived drinking norms as a mediator of differences between FSU immigrants and other Israelis in drinking and AUDs.

METHOD

Adult household residents (N = 1,349) selected from the Israeli population register were assessed with a structured interview measuring drinking, AUD symptoms, and perceived drinking norms. Regression analyses were used to produce odds ratios (OR) and risk ratios (RR) and 95% confidence intervals (CI) to test differences between FSU immigrants and other Israelis on binary and graded outcomes. Mediation of FSU effects by perceived drinking norms was tested with bootstrapping procedures.

RESULTS

FSU immigrants were more likely than other Israelis to be current drinkers (OR = 2.39, CI [1.61, 3.55]), have higher maximum number of drinks per day (RR = 1.88, CI [1.64, 2.16]), have any AUD (OR = 1.75, CI [1.16, 2.64]), score higher on a continuous measure of AUD (RR = 1.44, CI [1.12, 1.84]), and perceive more permissive drinking norms (p < .0001). For all four drinking variables, the FSU group effect was at least partially mediated by perceived drinking norms.

CONCLUSIONS

This is the first demonstration that drinking norms mediate ethnic differences in AUDs. This work contributes to understanding ethnic group differences in drinking and AUDs, potentially informing etiologic research and public policy aimed at reducing alcohol-related harm.

Tau phosphorylation pathway genes and cerebrospinal fluid tau levels in Alzheimer's disease

Alzheimer's disease (AD) is characterized by the presence in the brain of amyloid plaques, consisting predominately of the amyloid β peptide (Aβ), and neurofibrillary tangles, consisting primarily of tau. Hyper-phosphorylated-tau (p-tau) contributes to neuronal damage, and both p-tau and total-tau (t-tau) levels are elevated in AD cerebrospinal fluid (CSF) compared to cognitively normal controls. Our hypothesis was that increased ratios of CSF phosphorylated-tau levels relative to total-tau levels correlate with regulatory region genetic variation of kinase or phosphatase genes biologically associated with the phosphorylation status of tau. Eighteen SNPs located within 5' and 3' regions of 5 kinase and 4 phosphatase genes, as well as two SNPs within regulatory regions of the MAPT gene were chosen for this analysis. The study sample consisted of 101 AD patients and 169 cognitively normal controls. Rs7768046 in the FYN kinase gene and rs913275 in the PPP2R4 phosphatase gene were both associated with CSF p-tau and t-tau levels in AD. These SNPs were also differentially associated with either CSF t-tau (rs7768046) or CSF p-tau (rs913275) relative to t-tau levels in AD compared to controls. These results suggest that rs7768046 and rs913275 both influence CSF tau levels in an AD-associated manner.

Synchrotron ultraviolet microspectroscopy on rat cortical bone: involvement of tyrosine and tryptophan in the osteocyte and its environment

Alcohol induced osteoporosis is characterized by a bone mass decrease and microarchitecture alterations. Having observed an excess in osteocyte apoptosis, we aimed to assess the bone tissue biochemistry, particularly in the osteocyte and its environment. For this purpose, we used a model of alcohol induced osteoporosis in rats. Bone sections of cortical bone were investigated using synchrotron UV-microspectrofluorescence at subcellular resolution. We show that bone present three fluorescence peaks at 305, 333 and 385 nm, respectively corresponding to tyrosine, tryptophan and collagen. We have determined that tyrosine/collagen and tryptophan/collagen ratios were higher in the strong alcohol consumption group. Tryptophan is related to the serotonin metabolism involved in bone formation, while tyrosine is involved in the activity of tyrosine kinases and phosphatases in osteocytes. Our experiment represents the first combined synchrotron UV microspectroscopy analysis of bone tissue with a quantitative biochemical characterization in the osteocyte and surrounding matrix performed separately.

Src family kinases: modulators of neurotransmitter receptor function and behavior

Src family kinases (SFKs) are non-receptor-type protein tyrosine kinases that were originally identified as the products of proto-oncogenes and were subsequently implicated in the regulation of cell proliferation and differentiation in the developing mammalian brain. Recent studies using transgenic mouse models have demonstrated that SFKs that are highly expressed in the adult brain regulate neuronal plasticity and behavior through tyrosine phosphorylation of key substrates such as neurotransmitter receptors. Here, we provide an overview of these recent studies, as well as discussing how modulation of the endocytosis of neurotransmitter receptors by SFKs contributes, in part, to this regulation. Deregulation of SFK-dependent tyrosine phosphorylation of such substrates might underlie certain brain disorders.

Network analysis of EtOH-related candidate genes

Recently, we collected many large-scale datasets for alcohol dependence and EtOH response in five organisms and deposited them in our EtOH-related gene resource database (ERGR, http://bioinfo.mc.vanderbilt.edu/ERGR/). Based on multidimensional evidence among these datasets, we prioritized 57 EtOH-related candidate genes. To explore their biological roles, and the molecular mechanisms of EtOH response and alcohol dependence, we examined the features of these genes by the Gene Ontology (GO) term-enrichment test and network/pathway analysis. Our analysis revealed that these candidate genes were highly enriched in alcohol dependence/alcoholism and highly expressed in brain or liver tissues. All the significantly enriched GO terms were related to neurotransmitter systems or EtOH metabolic processes. Using the Ingenuity Pathway Analysis system, we found that these genes were involved in networks of neurological disease, cardiovascular disease, inflammatory response, and small molecular metabolism. Many key genes in signaling pathways were in the central position of these networks. Furthermore, our protein-protein interaction (PPI) network analysis suggested some novel candidate genes which also had evidence in the ERGR database. This study demonstrated that our candidate gene selection is effective and our network/pathway analysis is useful for uncovering the molecular mechanisms of EtOH response and alcohol dependence. This approach can be applied to study the features of candidate genes of other complex traits/phenotypes.

The clock gene PER2 and sleep problems: association with alcohol consumption among Swedish adolescents

BACKGROUND

Alcohol abuse is associated with sleep problems, which are often linked to circadian rhythm disturbances. Previous studies have separately examined the effects of mutations in the clock gene PER2 on alcohol consumption and sleep problems. Here we hypothesized that an allelic variation in the PER2 gene is associated with alcohol consumption in interaction with sleep problems among adolescents.

METHODS

The Survey of Adolescent Life and Health in Västmanland 2006, a Swedish county, including 1254 students 17-18 years old, was used as a population-representative sample of adolescents. We investigated the PER2 Single Nucleotide polymorphism (SNP) 10870 (A/G) in the cohort together with an assessment of alcohol consumption according to the AUDIT-C questionnaire, and sleep problems using a survey consisting of 18 items. Furthermore, we carried out an exploratory analysis on the PER2 Single Nucleotide Polymorphism 10870 polymorphism in a group of severely alcoholic females.

RESULTS

We found a significant association of the SNP 10870 in adolescent boys, where the genotype AA, in the presence of several and frequent sleep problems, was associated with increased alcohol consumption. Among adolescent girls, only sleep problems were related to alcohol consumption. A non-significant trend was observed among the severely alcoholic females, with the G allele being over-represented in the severely alcoholic females group in comparision to the control females.

CONCLUSION

These results indicate that PER2 gene variation is associated with alcohol consumption in interaction with sleep problems among Swedish adolescent boys.

Review. Genetics of addictions: strategies for addressing heterogeneity and polygenicity of substance use disorders

Addictions are common psychiatric disorders that exert high cost to the individual and to society. Addictions are a result of the interplay of multiple genetic and environmental factors. They are characterized by phenotypic and genetic heterogeneity as well as polygenicity, implying a contribution of different neurobiological mechanisms to the clinical diagnosis. Therefore, treatments for most substance use disorders are often only partially effective, with a substantial proportion of patients failing to respond. To address heterogeneity and polygenicity, strategies have been developed to identify more homogeneous subgroups of patients and to characterize genes contributing to their phenotype. These include genetic linkage and association studies as well as functional genetic analysis using endophenotypes and animal behavioural experimentation. Applying these strategies in a translational context aims at improving therapeutic response by the identification of subgroups of addiction patients for individualized, targeted treatment strategies. This article aims to discuss strategies addressing heterogeneity and polygenicity of substance use disorders by presenting results of recent research on genetic and environmental components of addiction. It will also introduce the European IMAGEN study that aims to integrate methodical approaches discussed in order to identify the genetic and neurobiological basis of behavioural traits relevant to the development of addictions.

Protein kinases and addiction

Although drugs of abuse have different chemical structures and interact with different protein targets, all appear to usurp common neuronal systems that regulate reward and motivation. Addiction is a complex disease that is thought to involve drug-induced changes in synaptic plasticity due to alterations in cell signaling, gene transcription, and protein synthesis. Recent evidence suggests that drugs of abuse interact with and change a common network of signaling pathways that include a subset of specific protein kinases. The best studied of these kinases are reviewed here and include extracellular signal-regulated kinase, cAMP-dependent protein kinase, cyclin-dependent protein kinase 5, protein kinase C, calcium/calmodulin-dependent protein kinase II, and Fyn tyrosine kinase. These kinases have been implicated in various aspects of drug addiction including acute drug effects, drug self-administration, withdrawal, reinforcement, sensitization, and tolerance. Identifying protein kinase substrates and signaling pathways that contribute to the addicted state may provide novel approaches for new pharmacotherapies to treat drug addiction.

Approach to the genetics of alcoholism: A review based on pathophysiology

Alcohol dependence is a common disorder with a heterogenous etiology. The results of family, twin and adoption studies on alcoholism are reviewed. These studies have revealed a heritability of alcoholism of over 50%. After evaluating the results, it was epidemiologically stated that alcoholism is heterogenous complex disorder with a multiple genetic background. Modern molecular genetic techniques allow examining specific genes involved in the pathophysiology of complex diseases such as alcoholism. Strategies for gene identification are introduced to the reader, including family-based and association studies. The susceptibility genes that are in the focus of this article have been chosen because they are known to encode for underlying mechanisms that are linked to the pathophysiology of alcoholism or that are important for the pharmacotherapeutic approaches in the treatment of alcohol dependence. Postulated candidate genes of the metabolism of alcohol and of the involved neurotransmitter systems are introduced. Genetic studies on alcoholism examining the metabolism of alcohol and the dopaminergic, GABAergic, glutamatergic, opioid, cholinergic and serotonergic neurotransmitter systems as well as the neuropeptide Y are presented. The results are critically discussed followed by a discussion of possible consequences.

Candidate genes, pathways and mechanisms for alcoholism: an expanded convergent functional genomics approach

We describe a comprehensive translational approach for identifying candidate genes for alcoholism. The approach relies on the cross-matching of animal model brain gene expression data with human genetic linkage data, as well as human tissue data and biological roles data, an approach termed convergent functional genomics. An analysis of three animal model paradigms, based on inbred alcohol-preferring (iP) and alcohol-non-preferring (iNP) rats, and their response to treatments with alcohol, was used. A comprehensive analysis of microarray gene expression data from five key brain regions (frontal cortex, amygdala, caudate-putamen, nucleus accumbens and hippocampus) was carried out. The Bayesian-like integration of multiple independent lines of evidence, each by itself lacking sufficient discriminatory power, led to the identification of high probability candidate genes, pathways and mechanisms for alcoholism. These data reveal that alcohol has pleiotropic effects on multiple systems, which may explain the diverse neuropsychiatric and medical pathology in alcoholism. Some of the pathways identified suggest avenues for pharmacotherapy of alcoholism with existing agents, such as angiotensin-converting enzyme (ACE) inhibitors. Experiments we carried out in alcohol-preferring rats with an ACE inhibitor show a marked modulation of alcohol intake. Other pathways are new potential targets for drug development. The emergent overall picture is that physical and physiological robustness may permit alcohol-preferring individuals to withstand the aversive effects of alcohol. In conjunction with a higher reactivity to its rewarding effects, they may able to ingest enough of this nonspecific drug for a strong hedonic and addictive effect to occur.

Identifikation von Risikogenen für Alkoholabhängigkeit

Alcohol dependence is one of the most common addictive diseases and known to be in part genetically transmitted, based on an oligogenic background in which each gene involved contributes only little to the resulting phenotype. Besides influencing other signal transduction mechanisms, alcohol specifically inhibits the NMDA signaling cascade, which mediates the excitatory effects of glutamate in the brain. Target molecules, sensitive to ethanol, include the NMDA receptors as well as downstream molecules of the glutamatergic system, glutamate transporters, and associated regulatory proteins. Adaptive processes of the glutamatergic system during chronic alcohol consumption may play a major role for later development of reward symptoms. Candidate gene studies, including association studies and animal models, are powerful and sensitive for detecting oligogenic effects and thus important to alcoholism research.

Ethanol induces cell-cycle activity and reduces stem cell diversity to alter both regenerative capacity and differentiation potential of cerebral cortical neuroepithelial precursors

Background

The fetal cortical neuroepithelium is a mosaic of distinct progenitor populations that elaborate diverse cellular fates. Ethanol induces apoptosis and interferes with the survival of differentiating neurons. However, we know little about ethanol's effects on neuronal progenitors. We therefore exposed neurosphere cultures from fetal rat cerebral cortex, to varying ethanol concentrations, to examine the impact of ethanol on stem cell fate.

Results

Ethanol promoted cell cycle progression, increased neurosphere number and increased diversity in neurosphere size, without inducing apoptosis. Unlike controls, dissociated cortical progenitors exposed to ethanol exhibited morphological evidence for asymmetric cell division, and cells derived from ethanol pre-treated neurospheres exhibited decreased proliferation capacity. Ethanol significantly reduced the numbers of cells expressing the stem cell markers CD117, CD133, Sca-1 and ABCG2, without decreasing nestin expression. Furthermore, ethanol-induced neurosphere proliferation was not accompanied by a commensurate increase in telomerase activity. Finally, cells derived from ethanol-pretreated neurospheres exhibited decreased differentiation in response to retinoic acid.

Conclusion

The reduction in stem cell number along with a transient ethanol-driven increase in cell proliferation, suggests that ethanol promotes stem to blast cell maturation, ultimately depleting the reserve proliferation capacity of neuroepithelial cells. However, the lack of a concomitant change in telomerase activity suggests that neuroepithelial maturation is accompanied by an increased potential for genomic instability. Finally, the cellular phenotype that emerges from ethanol pre-treated, stem cell depleted neurospheres is refractory to additional differentiation stimuli, suggesting that ethanol exposure ablates or delays subsequent neuronal differentiation.

GRIN1 locus may modify the susceptibility to seizures during alcohol withdrawal

N-Methyl-D-aspartate (NMDA) receptors, members of the glutamate receptor channel superfamily, are generally inhibited by alcohol. The expression and alternative splicing of the obligatory NR1 subunit is altered by alcohol exposure, emphasizing the involvement of the NR1 subunit, which is coded by the GRIN1 gene, in alcohol-mediated effects. We performed an association study in patients with alcohol dependence with the GRIN1 locus. Two independent case control samples consisting of a total of 442 alcohol-dependent patients and 442 unrelated controls were included. There was no overall difference in allele or genotype frequency between patients and controls. However, the 2108A allele and A-containing genotypes were over-represented in the patients with a history of withdrawal-induced seizures when compared to healthy volunteers (allele: chi(2) = 5.412, df = 1, P = 0.020) or an independent sample of patients without a history of seizures (allele: chi(2) = 4.185, df = 1, P = 0.041). Age at onset, years of alcohol dependence, and a history of delirium tremens did not differ between genotype or allele groups. These findings support the hypothesis that the GRIN1 locus may modify the susceptibility to seizures during alcohol withdrawal. This novel finding warrants replication.

The clock gene Per2 influences the glutamatergic system and modulates alcohol consumption

Period (Per) genes are involved in regulation of the circadian clock and are thought to modulate several brain functions. We demonstrate that Per2(Brdm1) mutant mice, which have a deletion in the PAS domain of the Per2 protein, show alterations in the glutamatergic system. Lowered expression of the glutamate transporter Eaat1 is observed in these animals, leading to reduced uptake of glutamate by astrocytes. As a consequence, glutamate levels increase in the extracellular space of Per2(Brdm1) mutant mouse brains. This is accompanied by increased alcohol intake in these animals. In humans, variations of the PER2 gene are associated with regulation of alcohol consumption. Acamprosate, a drug used to prevent craving and relapse in alcoholic patients is thought to act by dampening a hyper-glutamatergic state. This drug reduced augmented glutamate levels and normalized increased alcohol consumption in Per2(Brdm1) mutant mice. Collectively, these data establish glutamate as a link between dysfunction of the circadian clock gene Per2 and enhanced alcohol intake.

No genetic association between Fyn kinase gene polymorphisms (−93A/G, IVS10+37T/C and Ex12+894T/G) and Japanese sporadic Alzheimer's disease

Several groups have reported that abnormal phosphorylation of tau by Fyn, a protein-tyrosine kinase, may play a role in the neuropathogenesis of Alzheimer's disease (AD). In the present study, three common Japanese polymorphisms of the Fyn gene (-93A/G in the 5'-flanking region, IVS10+37T/C in intron 10 and Ex12+894T/G in the 3'-untranslated region) were studied in 127 healthy controls and 182 sporadic AD cases using a polymerase chain reaction restriction fragment length polymorphism method. A comparison of the allelic and genotypic frequencies of these polymorphisms between controls and sporadic AD cases failed to show any significant difference. These results suggest that the Fyn polymorphisms (-93A/G, IVS10+37T/C and Ex12+894T/G) investigated here have no genetic association with sporadic AD.