Alcohol-preferring rats show decreased corticotropin-releasing hormone-2 receptor expression and differences in HPA activation compared to alcohol-nonpreferring rats.

BACKGROUND: Corticotropin-releasing hormone (CRH) and urocortins (UCNs) bind to corticotropin-releasing hormone type 2 receptor (CRF2 receptor ), a Gs protein-coupled receptor that plays an important role in modulation of anxiety and stress responses. The Crhr2 gene maps to a quantitative trait locus (QTL) for alcohol preference on chromosome 4 previously identified in inbred alcohol-preferring (iP) and-nonpreferring (iNP) F2 rats. METHODS: Real-time polymerase chain reaction was utilized to screen for differences in Crhr2 mRNA expression in the central nervous system (CNS) of male iP and iNP rats. DNA sequence analysis was then performed to screen for polymorphism in Crhr2 in order to identify genetic variation, and luciferase reporter assays were then applied to test their functional significance. Next, binding assays were used to determine whether this polymorphism affected CRF2 receptor binding affinity as well as CRF2 receptor density in the CNS. Finally, social interaction and corticosterone levels were measured in the P and NP rats before and after 30-minute restraint stress. RESULTS: Crhr2 mRNA expression studies found lower levels of Crhr2 mRNA in iP rats compared to iNP rats. In addition, DNA sequencing identified polymorphisms in the promoter region, coding region, and 3'-untranslated region between the iP and iNP rats. A 7 bp insertion in the Crhr2 promoter of iP rats altered expression in vitro as measured by reporter assays, and we found that CRF2 receptor density was lower in the amygdala of iP as compared to iNP rats. Male P rats displayed decreased social interaction and significantly higher corticosterone levels directly following 30-minute restraint when compared to male NP rats. CONCLUSIONS: This study identified Crhr2 as a candidate gene of interest underlying the chromosome 4 QTL for alcohol consumption that was previously identified in the P and NP model. Crhr2 promoter polymorphism is associated with reduced mRNA expression in certain brain regions, particularly the amygdala, and lowered the density of CRF2 receptor in the amygdala of iP compared to iNP rats. Together, these differences between the animals may contribute to the drinking disparity as well as the anxiety differences of the P and NP rats.

Quantitative trait locus for body weight identified on rat chromosome 4 in inbred alcohol-preferring and -nonpreferring rats: potential implications for neuropeptide Y and corticotrophin releasing hormone 2.

The alcohol-preferring (P) and -nonpreferring (NP) rat lines were developed using bidirectional selective breeding for alcohol consumption (g/kg/day) and alcohol preference (water:ethanol ratio). During a preliminary study, we detected a difference in body weight between inbred P (iP) and inbred NP (iNP) rats that appeared to be associated with the transfer of the Chromosome 4 quantitative trait locus (QTL) seen in the P.NP and NP.P congenic strains. After the initial confirmation that iP rats displayed lower body weight when compared to iNP rats (data not shown), body weight and growth rates of each chromosome 4 reciprocal congenic rat strain (P.NP and NP.P) were measured, and their body weight was consistent with their respective donor strain phenotype, confirming that a quantitative trait locus for body weight mapped to the chromosome 4 interval. Utilizing the newly developed interval-specific congenic strains (ISCS-A and ISCS-B), the QTL interval was further narrowed identifying the following candidate genes of interest: neuropeptide Y (Npy), juxtaposed with another zinc finger gene 1 (Jazf1), corticotrophin releasing factor receptor 2 (Crfr2) and LanC lantibiotic synthetase component C-like 2 (Lancl2). These findings indicate that a biologically active variant(s) regulates body weight on rat chromosome 4 in iP and iNP rats. This QTL for body weight was successfully captured in the P.NP and NP.P congenic strains, and interval-specific congenic strains (ISCSs) were subsequently employed to fine-map the QTL interval identifying the following candidate genes of interest: Npy, Jazf1, Crfr2 and Lancl2. Both Npy and Crfr2 have been previously identified as candidate genes of interest underlying the chromosome 4 QTL for alcohol consumption in iP and iNP rats.

Fine mapping and expression of candidate genes within the chromosome 10 QTL region of the high and low alcohol-drinking rats.

The high and low alcohol-drinking (HAD and LAD) rats were selectively bred for differences in alcohol intake. The HAD/LAD rats originated from the N/Nih heterogeneous stock developed from intercrossing eight inbred rat strains. The HAD×LAD F2 were genotyped, and a powerful analytical approach, using ancestral recombination and F2 recombination, was used to narrow a quantitative trait loci (QTL) for alcohol drinking to a 2-cM region on distal chromosome 10 that was in common in the HAD1/LAD1 and HAD2/LAD2 analyses. Quantitative real-time PCR was used to examine mRNA expression of six candidate genes (Crebbp, Trap1, Gnptg, Clcn7, Fahd1, and Mapk8ip3) located within the narrowed QTL region in the HAD1/LAD1 rats. Expression was examined in five brain regions, including the nucleus accumbens, amygdala, caudate putamen, hippocampus, and prefrontal cortex. All six genes showed differential expression in at least one brain region. Of the genes tested in this study, Crebbp and Mapk8ip3 may be the most promising candidates with regard to alcohol drinking.

Identification of genes influencing skeletal phenotypes in congenic P/NP rats.

We previously showed that alcohol-preferring (P) rats have higher bone density than alcohol-nonpreferring (NP) rats. Genetic mapping in P and NP rats identified a major quantitative trait locus (QTL) between 4q22 and 4q34 for alcohol preference. At the same location, several QTLs linked to bone density and structure were detected in Fischer 344 (F344) and Lewis (LEW) rats, suggesting that bone mass and strength genes might cosegregate with genes that regulate alcohol preference. The aim of this study was to identify the genes segregating for skeletal phenotypes in congenic P and NP rats. Transfer of the NP chromosome 4 QTL into the P background (P.NP) significantly decreased areal bone mineral density (aBMD) and volumetric bone mineral density (vBMD) at several skeletal sites, whereas transfer of the P chromosome 4 QTL into the NP background (NP.P) significantly increased bone mineral content (BMC) and aBMD in the same skeletal sites. Microarray analysis from the femurs using Affymetrix Rat Genome arrays revealed 53 genes that were differentially expressed among the rat strains with a false discovery rate (FDR) of less than 10%. Nine candidate genes were found to be strongly correlated (r(2) > 0.50) with bone mass at multiple skeletal sites. The top three candidate genes, neuropeptide Y (Npy), alpha synuclein (Snca), and sepiapterin reductase (Spr), were confirmed using real-time quantitative PCR (qPCR). Ingenuity pathway analysis revealed relationships among the candidate genes related to bone metabolism involving beta-estradiol, interferon-gamma, and a voltage-gated calcium channel. We identified several candidate genes, including some novel genes on chromosome 4 segregating for skeletal phenotypes in reciprocal congenic P and NP rats.

Candidate genes for alcohol preference identified by expression profiling in alcohol-preferring and -nonpreferring reciprocal congenic rats.

BACKGROUND: Selectively bred alcohol-preferring (P) and alcohol-nonpreferring (NP) rats differ greatly in alcohol preference, in part due to a highly significant quantitative trait locus (QTL) on chromosome 4. Alcohol consumption scores of reciprocal chromosome 4 congenic strains NP.P and P.NP correlated with the introgressed interval. The goal of this study was to identify candidate genes that may influence alcohol consumption by comparing gene expression in five brain regions of alcohol-naïve inbred alcohol-preferring and P.NP congenic rats: amygdala, nucleus accumbens, hippocampus, caudate putamen, and frontal cortex. RESULTS: Within the QTL region, 104 cis-regulated probe sets were differentially expressed in more than one region, and an additional 53 were differentially expressed in a single region. Fewer trans-regulated probe sets were detected, and most differed in only one region. Analysis of the average expression values across the 5 brain regions yielded 141 differentially expressed cis-regulated probe sets and 206 trans-regulated probe sets. Comparing the present results from inbred alcohol-preferring vs. congenic P.NP rats to earlier results from the reciprocal congenic NP.P vs. inbred alcohol-nonpreferring rats demonstrated that 74 cis-regulated probe sets were differentially expressed in the same direction and with a consistent magnitude of difference in at least one brain region. CONCLUSIONS: Cis-regulated candidate genes for alcohol consumption that lie within the chromosome 4 QTL were identified and confirmed by consistent results in two independent experiments with reciprocal congenic rats. These genes are strong candidates for affecting alcohol preference in the inbred alcohol-preferring and inbred alcohol-nonpreferring rats.

Identification of a novel cytosolic aldehyde dehydrogenase allele, ALDH1A1*4.

This paper reports the identification of a novel cytosolic aldehyde dehydrogenase 1 ( ALDH1A1 ) allele. One hundred and sixty-two Indo-Trinidadian and 85 Afro-Trinidadian individuals were genotyped. A novel ALDH1A1 allele, ALDH1A1*4 , was identified in an Indo-Trinidadian alcoholic with an A inserted at position -554 relative to the translational start site, +1. It was concluded that a wider cross-section of individuals needs to be evaluated in order to determine the representative frequency of the allele, and to see if it is associated with risk of alcoholism.

Gene expression changes in the nucleus accumbens of alcohol-preferring rats following chronic ethanol consumption.

The objective of this study was to determine the effects of binge-like alcohol drinking on gene expression changes in the nucleus accumbens (ACB) of alcohol-preferring (P) rats. Adult male P rats were given ethanol under multiple scheduled access (MSA; three 1-h dark cycle sessions/day) conditions for 8 weeks. For comparison purposes, a second ethanol drinking group was given continuous/daily alcohol access (CA; 24h/day). A third group was ethanol-naïve (W group). Average ethanol intakes for the CA and MSA groups were approximately 9.5 and 6.5 g/kg/day, respectively. Fifteen hours after the last drinking episode, rats were euthanized, the brains extracted, and the ACB dissected. RNA was extracted and purified for microarray analysis. The only significant differences were between the CA and W groups (p<0.01; Storey false discovery rate=0.15); there were 374 differences in named genes between these 2 groups. There were 20 significant Gene Ontology (GO) categories, which included negative regulation of protein kinase activity, anti-apoptosis, and regulation of G-protein coupled receptor signaling. Ingenuity analysis indicated a network of transcription factors, involving oncogenes (Fos, Jun, Junb had higher expression in the ACB of the CA group), suggesting increased neuronal activity. There were 43 genes located within rat QTLs for alcohol consumption and preference; 4 of these genes (Tgfa, Hspa5, Mtus1 and Creb3l2) are involved in anti-apoptosis and increased transcription, suggesting that they may be contributing to cellular protection and maintaining high alcohol intakes. Overall, these findings suggest that chronic CA drinking results in genomic changes that can be observed during the early acute phase of ethanol withdrawal. Conversely, chronic MSA drinking, with its associated protracted withdrawal periods, results in genomic changes that may be masked by tight regulation of these genes following repeated experiences of ethanol withdrawal.

From QTL to candidate gene: a genetic approach to alcoholism research.

A major focus of research in alcohol-related disorders is to identify the genes and pathways that modulate alcohol-seeking behavior. In light of this, animal models have been established to study various aspects of alcohol dependence. The selectively bred alcohol-preferring (P) and -nonpreferring (NP) lines were developed from Wistar rats to model high and low voluntary alcohol consumption, respectively. Using inbred P and NP strains, a strong QTL (LOD-9.2) for alcohol consumption was identified on rat chromosome 4. To search for candidate genes that underlie this chromosomal region, complementary molecular-based strategies were implemented to identify genetic targets that likely contribute to the linkage signal. In an attempt to validate these genetic targets, corroborative studies have been utilized including pharmacological studies, knock-out/transgenic models as well as human association studies. Thus far, three candidate genes, neuropeptide Y (Npy), alpha-synuclein (Snca), and corticotrophin-releasing factor receptor 2 (Crhr2), have been identified that may account for the linkage signal. With the recent advancements in bioinformatics and molecular biology, QTL analysis combined with molecular-based strategies provides a systematic approach to identify candidate genes that contribute to various aspects of addictive behavior.

Differential gene expression in the nucleus accumbens with ethanol self-administration in inbred alcohol-preferring rats.

The current study examined the effects of operant ethanol (EtOH) self-administration on gene expression kin the nucleus accumbens (ACB) and amygdala (AMYG) of inbred alcohol-preferring (iP) rats. Rats self-trained on a standard two-lever operant paradigm to administer either water-water, EtOH (15% v/v)-water, or saccharin (SAC; 0.0125% g/v)-water. Animals were killed 24 h after the last operant session, and the ACB and AMYG dissected; RNA was extracted and purified for microarray analysis. For the ACB, there were 513 significant differences at the p<0.01 level in named genes: 55 between SAC and water; 215 between EtOH and water, and 243 between EtOH and SAC. In the case of the AMYG (p<0.01), there were 48 between SAC and water, 23 between EtOH and water, and 63 between EtOH and SAC group. Gene Ontology (GO) analysis indicated that differences in the ACB between the EtOH and SAC groups could be grouped into 15 significant (p<0.05) categories, which included major categories such as synaptic transmission, cell and ion homeostasis, and neurogenesis, whereas differences between the EtOH and water groups had only 4 categories, which also included homeostasis and synaptic transmission. Several genes were in common between the EtOH and both the SAC and water groups in the synaptic transmission (e.g., Cav2, Nrxn3, Gabrb2, Gad1, Homer1) and homeostasis (S100b, Prkca, Ftl1) categories. Overall, the results suggest that changes in gene expression in the ACB of iP rats are associated with the reinforcing effects of EtOH.

Ethnic differences in level of response to alcohol between Chinese Americans and Korean Americans.

OBJECTIVE: Koreans have higher rates of alcohol-use disorders and family history of alcoholism, compared with Chinese. These differences likely reflect both environmental and genetic influences. One genetically influenced characteristic that may contribute to these ethnic differences is level of response to alcohol. Variant alleles of aldehyde dehydrogenase (ALDH2) and alcohol dehydrogenase (ADH1B) genes are prevalent in individuals of Asian heritage and have been associated with an increased level of response to alcohol and a decreased risk for alcohol dependence. Additionally, a low level of response to alcohol is more common in individuals with a first-degree family history of alcoholism and is predictive of increased risk for this disorder. It also is possible that sociocultural factors have an impact on an individual's response to alcohol. The current study examined self-report level of response to alcohol, ALDH2 and ADH1B, country of origin, and family history of alcoholism in 154 Chinese- and 181 Korean-American college students. METHOD: Participants were evaluated via in-person interviews and genotyped at the ALDH2 and ADH1B loci. RESULTS: Ethnicity was significantly related to level of response to alcohol, with Koreans having a lower self-reported level of response than Chinese. This relationship remained significant after considering the effects of gender, height, weight, quantity and frequency of alcohol consumption (over the previous 90 days), ALDH2 genotype, ADH1B genotype, country of origin, and first-degree family history of alcohol dependence. CONCLUSIONS: The results suggest that a low level of response to alcohol may contribute to the increased risk for alcohol abuse and dependence found in Koreans, relative to Chinese. More research is needed to determine additional factors that may be contributing to the low alcohol response and high rates of alcoholism in Koreans.

Sex-specific genetic loci for femoral neck bone mass and strength identified in inbred COP and DA rats.

INTRODUCTION: Hip fracture is the most devastating osteoporotic fracture type with significant morbidity and mortality. Several studies in humans identified chromosomal regions linked to hip size and bone mass. Animal models, particularly the inbred rat, serve as complementary approaches for studying the genetic influence on hip fragility. The purpose of this study is to identify sex-independent and sex-specific quantitative trait loci (QTLs) for femoral neck density, structure, and strength in inbred Copenhagen 2331 (COP) and Dark Agouti (DA) rats. MATERIALS AND METHODS: A total of 828 (405 males and 423 females) F(2) progeny derived from the inbred COP and DA strains of rats were phenotyped for femoral neck volumetric BMD (vBMD), cross-sectional area, polar moment of inertia (Ip), neck width, ultimate force, and energy to break. A whole genome screen was performed using 93 microsatellite markers with an average intermarker distance of 20 cM. Recombination-based marker maps were generated using MAPMAKER/EXP from the COP x DA F(2) data and compared with published Rat Genome Database (RGD) maps. These maps were used for genome-wide linkage analyses to detect sex-independent and sex-specific QTLs. RESULTS: Significant evidence of linkage (p < 0.01) for sex-independent QTLs were detected for (1) femoral neck vBMD on chromosomes (Chrs) 1, 6, 10, and 12, (2) femoral neck structure on Chrs 5, 7, 10, and 18, and (3) biomechanical properties on Chrs 1 and 4. Male-specific QTLs were discovered on Chrs 2, 9, and 18 for total vBMD, on Chr 17 for trabecular vBMD, on Chr 9 for total bone area, and on Chr 15 for ultimate force. A female-specific QTL was discovered on Chr 2 for ultimate force. The effect size of the individual QTL varied between 1% and 4%. CONCLUSIONS: We detected evidence that sex-independent and sex-specific QTLs contribute to hip fragility in the inbred rat. Several QTLs regions identified in this study are homologous to human chromosomal regions previously linked to QTLs contributing to femoral neck and related phenotypes.

Drd2 expression in the high alcohol-preferring and low alcohol-preferring mice.

The high alcohol-preferring (HAP) and low alcohol-preferring (LAP) mice were selectively bred for differences in alcohol preference and consumption. Recently, a large-effect QTL was identified on chromosome 9. The peak for this QTL is near the Drd2 (dopamine receptor 2) locus. The present study examined Drd2 mRNA expression differences between the HAP1 and LAP1 mice in brain regions important in the dopaminergic-reward pathway, including the nucleus accumbens, hippocampus, amygdala, and septum. Results show that alcohol-naïve HAP1 mice exhibited lower levels of Drd2 mRNA expression in the nucleus accumbens and the hippocampus compared to LAP1 mice. No differences were found in the amygdala or septum. To determine if a sequence difference might underlie the expression difference, the Drd2 cDNA was sequenced in each line and one single nucleotide polymorphism (SNP) was identified in the 3' UTR. Both HAP and LAP 3' UTR were cloned in the luc-pGL3-promoter-luc vector. The polymorphism in the Drd2 3' UTR was assessed to determine its functional significance in modulating expression. In vitro expression analysis using neuroblastoma SK-N-SH cells resulted in a significant decrease in expression of the HAP 3' UTR luc construct compared with the LAP 3' UTR construct. This decreased expression is consistent with lower levels of Drd2 expression in the nucleus accumbens and the hippocampus as evidenced by qRT-PCR. These results suggest that the SNP may play a role in the differential expression of Drd2 between the HAP and LAP mice and that the polymorphism in Drd2 may contribute to alcohol preference.

Genetic loci affecting bone structure and strength in inbred COP and DA rats.

Previous studies have shown that the Copenhagen 2331 (COP) and Dark Agouti (DA) rats have significant differences in bone structure and strength despite their similar body mass. Thus, these inbred rat strains may provide a unique resource to identify the genetics underlying the phenotypic variation in bone fragility. A sample of 828 (405 males and 423 females) COPxDA F2 progeny had extensive phenotyping for bone structure measures including cortical bone area and polar moment of inertia at the femur midshaft and total, cortical and trabecular bone areas, for the lumbar vertebra 5 (L5). Bone strength phenotypes included ultimate force, stiffness and work to failure of femur and L5. These skeletal phenotypes were measured using peripheral quantitative computed tomography (pQCT) and mechanical testing. A whole-genome screen was conducted in the F2 rats, using microsatellite markers spaced at approximately 20 cM intervals. Genetic marker maps were generated from the F2 data and used for genome-wide linkage analyses to detect linkage to the bone structure and strength phenotypes. Permutation testing was employed to obtain the thresholds for genome-wide significance (p<0.01). Significant QTL for femur structure and strength were identified on chromosome (Chr) 1 with a maximum LOD score of 33.5; evidence of linkage was found in both the male and female rats. In addition, Chrs 6, 7, 10, 13, 15 and 18 were linked to femur midshaft structure. QTL linked to femur strength were identified on Chrs 5 and 10. For L5 vertebrae, Chrs 2, 16, and 18 harbored QTL for cortical structure and trabecular structure for L5 was linked to Chrs 1, 7, 12, and 18. One female-specific QTL for femur ultimate force was identified on Chr 5, and two male-specific QTL for L5 cortical area were found on Chrs 2 and 18. Our study demonstrates strong evidence of linkage for bone structure and strength to multiple rat chromosomes.

Stability of heavy episodic drinking in Chinese- and Korean-American college students: effects of ALDH2 gene status and behavioral undercontrol.

OBJECTIVE: A previous cross-sectional study showed that, among individuals of Chinese and Korean descent, possession of ALDH2*2 alleles was associated with protection against alcohol dependence, whereas conduct disorder was associated with increased vulnerability to dependence. The purpose of this longitudinal study was to examine the roles of ALDH2 and behavioral undercontrol (a temperamental trait that is associated with conduct disorder) in stability of heavy episodic drinking. METHOD: Chinese- and Korean-American college students (N = 336; 51% female), who had initiated alcohol use before study enrollment, provided information on drinking habits during their freshman and sophomore years. Participants were classified as (1) stable nonheavy drinkers, (2) regressors, (3) progressors, or (4) stable heavy drinkers. RESULTS: Participants with ALDH2*2 alleles were more likely to be classified as stable nonheavy drinkers than as progressors (z = -2.49, p = .013). Higher levels of behavioral undercontrol were associated with a greater probability of being classified as a stable heavy drinker relative to a stable nonheavy drinker (z = 2.26, p = .024). Stable heavy drinkers reported the most alcohol-related problems, whereas progressors reported more problems than either regressors or stable nonheavy drinkers, particularly at Year 2. CONCLUSIONS: Elevated behavioral undercontrol appears to predispose Asian-American college students to increased frequency of heavy drinking, whereas ALDH2*2 may act as a protective factor. The degree of alcohol consumption observed among participants with ALDH2*2 alleles is consistent with previous findings showing that, although their presence may be protective, it does not preclude heavy drinking episodes.

Association of the aldehyde dehydrogenase 2 promoter polymorphism with alcohol consumption and reactions in an American Jewish population.

BACKGROUND: Reduction in activity of the mitochondrial aldehyde dehydrogenase 2 (ALDH2) enzyme due to genetic deficiency causes reactions related to alcohol consumption and lowers the risk of alcoholism. ALDH2*2 is the only functionally significant polymorphism of the ALDH2 gene. An additional polymorphic locus in the promoter (G to A substitution approximately 360 bp from the translation start site) may influence ALDH2 activity through effects on transcriptional activity. The A allele is predicted to be less active transcriptionally than the G allele. Therefore, we hypothesized that individuals with 1 or 2 A alleles would have exaggerated reactions to alcohol. METHODS: Fifty-three Jewish college students from a Midwestern University and 76 Jewish individuals living in a large Midwestern city (all of Ashkenazi descent) were tested for associations between ALDH2*G and ALDH2*A alleles and self-reported alcohol consumption and responses to alcohol. Genotype determination was performed using PCR and slot-blot hybridization. As alcohol drinking behavior differed substantially between the college students and the general population, as well as between males and females, the analyses were performed separately in each group. RESULTS: The frequency of the ALDH2*A allele was 0.87 in the 129 Jewish individuals tested. Among the general Jewish population, those who were homozygous for ALDH2*A drank fewer drinks per occasion than individuals who were not homozygous for the ALDH2*A allele, but did not drink significantly less frequently. When the other covariates (ADH1B genotype, gender, and population) were controlled for, there was a marginal association between ALDH2A genotype and quantity of alcohol consumed and the number of drinks consumed before feeling drowsy. CONCLUSION: This study suggests that the ALDH2*A allele status may correlate with variations in alcohol consumption patterns among Jews, independent of the effect of ADH1B genotype.

Variations in alcohol-metabolizing enzymes in people of East Indian and African descent from Trinidad and Tobago.

The population of Trinidad and Tobago is composed mainly of people of East Indian (Indo-Trinidadians) and African (Afro-Trinidadians) ancestry. Differences in alcoholism rates exist between these two ethnic groups, and researchers have investigated whether these differences can be explained in part by variations in the genes encoding the alcohol-metabolizing enzymes alcohol dehydrogenase (ADH) 1B and 1C, and aldehyde dehydrogenase (ALDH) 1 and 2. Studies have demonstrated that a certain variant of the gene encoding ADH1B (ADH1B*3) is associated with a reduced risk of alcoholism in Afro-Trinidadians, as is a variant of the gene encoding ADH1C (i.e., ADH1C*1) in Indo-Trinidadians. An ALDH2 variant shown to have protective effects primarily in East Asians was not found in either Trinidadian ethnic group. However, a variant in the gene encoding cytosolic ALDH1A (i.e. ALDH1A1*1/*2) was found to be associated with an increase in alcohol dependence in Indo-Trinidadians.

Effect of ADH1B genotype on alcohol consumption in young Israeli Jews.

BACKGROUND: The alcohol dehydrogenase 1B (ADH1B) genotype affects the risk for alcoholism, with elevated prevalence of a protective allele in Jews. Alcohol consumption is increasing among younger Israeli Jews, reflecting environmental influences. We investigated whether the relationship of ADH1B genotype with alcohol consumption differed between younger and older adult Israelis. METHODS: Israeli community residents aged 22 to 65 participated in a structured interview that included questions on the maximum number of drinks on an occasion (Maxdrinks). The ADH1B genotype was determined for 68 participants and dichotomized into nonprotective (ADH1B(*)1/1) and protective (ADH1B(*)1/2 or ADH1B(*)2/2) genotypes. Using Maxdrinks as the dependent variable, Poisson's regression was used to test an age x genotype interaction. RESULTS: The ADH1B genotype interacted significantly with age (p=0.01) in a Poisson's model with Maxdrinks as the outcome. Among participants >or=33 years, Maxdrinks was low and unrelated to the ADH1B genotype. Among participants <33 years with ADH1B(*)1/2 or ADH1B(*)2/2, Maxdrinks was also low (mean, 2.6 drinks) but among those with ADH1B(*)1/1, Maxdrinks was substantially higher (mean, 6.2 drinks). CONCLUSION: Maximum lifetime drinking among younger adult Israelis without genetic protection exceeded thresholds for risky and unsafe drinking (>or=5 drinks). Environmental influences promoting greater drinking among younger Israelis may particularly affect those with the nonprotective, more common ADH1B genotype.

Functional gene expression differences between inbred alcohol-preferring and -non-preferring rats in five brain regions.

The objective of this study was to determine if there are innate differences in gene expression in selected CNS regions between inbred alcohol-preferring (iP) and -non-preferring (iNP) rats. Gene expression was determined in the nucleus accumbens (ACB), amygdala (AMYG), frontal cortex (FC), caudate-putamen (CPU), and hippocampus (HIPP) of alcohol-naïve adult male iP and iNP rats, using Affymetrix Rat Genome U34A microarrays (n = 6/strain). Using Linear Modeling for Microarray Analysis with a false discovery rate threshold of 0.1, there were 16 genes with differential expression in the ACB, 54 in the AMYG, 8 in the FC, 24 in the CPU, and 21 in the HIPP. When examining the main effect of strain across regions, 296 genes were differentially expressed. Although the relatively small number of genes found significant within individual regions precluded a powerful analysis for over-represented Gene Ontology categories, the much larger list resulting from the main effect of strain analysis produced 17 over-represented categories (P < .05), including axon guidance, gliogenesis, negative regulation of programmed cell death, regulation of programmed cell death, regulation of synapse structure function, and transmission of nerve impulse. Co-citation analysis and graphing of significant genes revealed a network involved in the neuropeptide Y (NPY) transmitter system. Correlation of all significant genes with those located within previously established rat alcohol QTLs revealed that of the total of 313 significant genes, 71 are located within such QTLs. The many regional and overall gene expression differences between the iP and iNP rat lines may contribute to the divergent alcohol drinking phenotypes of these rats.

Identification of candidate genes for alcohol preference by expression profiling of congenic rat strains.

BACKGROUND: A highly significant quantitative trait locus (QTL) on chromosome 4 that influenced alcohol preference was identified by analyzing crosses between the iP and iNP rats. Congenic strains in which the iP chromosome 4 QTL interval was transferred to the iNP (NP.P) exhibited the expected increase in alcohol consumption compared with the iNP background strain. This study was undertaken to identify genes in the chromosome 4 QTL interval that might contribute to the differences in alcohol consumption between the alcohol-naïve congenic and background strains. METHODS: RNA from 5 brain regions from each of 6 NP.P and 6 iNP rats was labeled and analyzed separately on an Affymetrix Rat Genome 230 2.0 microarray to look for both cis-regulated and trans-regulated genes. Expression levels were normalized using robust multi-chip average (RMA). Differential gene expression was validated using quantitative real-time polymerase chain reaction. Five individual brain regions (nucleus accumbens, frontal cortex, amygdala, hippocampus, and striatum) were analyzed to detect differential expression of genes within the introgressed QTL interval, as well as genes outside that region. To increase the power to detect differentially expressed genes, combined analyses (averaging data from the 5 discrete brain regions of each animal) were also carried out. RESULTS: Analyses within individual brain regions that focused on genes within the QTL interval detected differential expression in all 5 brain regions; a total of 35 genes were detected in at least 1 region, ranging from 6 genes in the nucleus accumbens to 22 in the frontal cortex. Analysis of the whole genome detected very few differentially expressed genes outside the QTL. Combined analysis across brain regions was more powerful. Analysis focused on the genes within the QTL interval confirmed 19 of the genes detected in individual regions and detected 15 additional genes. Whole genome analysis detected 1 differentially expressed gene outside the interval. CONCLUSIONS: Cis-regulated candidate genes for alcohol consumption were identified using microarray profiling of gene expression differences in congenic animals carrying a QTL for alcohol preference.

Association of ALDH1 promoter polymorphisms with alcohol-related phenotypes in Trinidad and Tobago.

OBJECTIVE: Two polymorphisms in the promoter region of the gene encoding cytosolic aldehyde dehydrogenase (ALDH1A1), ALDH1A1*2 and ALDH1A1*3, have recently been identified. The present study sought to determine whether an association exists between ALDH1A1 genotypes, alcohol dependence, drinking history, and liver function tests in the two major ethnic groups of Trinidad and Tobago (TT). METHOD: The participants in this study were 137 alcohol dependents of either East Indian ancestry (Indo-TT) or African ancestry (Afro-TT) and 108 controls matched by age, gender, and ethnicity. A structured interview was used to gather information on demographics, psychiatric diagnoses, and personal drinking and drug use. A blood sample was obtained from each participant, and leukocyte DNA was extracted and used to genotype for the presence of the ALDH1A1 promoter polymorphisms. Serum levels of hepatic enzymes, as well as presence of HIV, hepatitis B surface antigen, and antihepatitis C virus antibody, were also determined. RESULTS: Twenty-four participants (10%) possessed the ALDH1A1*1/*2 genotype (frequency = .05), 4 were Afro-TT (2 alcohol dependents, 2 controls), and 20 were Indo-TT (18 alcohol dependents, 2 controls). Two participants (1 Indo-TT alcohol dependent, 1 Afro-TT alcohol dependent) had the ALDH1A1*2/*2 genotype. Four participants possessed ALDH1A1*3, all of whom were Afro-TT controls. Indo-TT participants with at least one ALDH1A1*2 allele were more likely to have a lifetime diagnosis of Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised, alcohol dependence (p < .002). Indo-TT participants with ALDH1A1*2 also reported significantly higher levels of current alcohol consumption (p < .05). The small number of Afro-TT participants with atypical polymorphisms limits any conclusions on the possible impact on alcohol dependence in that population. CONCLUSIONS: Results from this study suggest that ALDH1A1*2 may be associated with increased risk for the development of alcohol dependence in Indo-Trinidadians.