Genome-wide association studies of maximum number of drinks

Maximum number of drinks (MaxDrinks) defined as “Maximum number of alcoholic drinks consumed in a 24-h period” is an intermediate phenotype that is closely related to alcohol dependence (AD). Family, twin and adoption studies have shown that the heritability of MaxDrinks is approximately 0.5. We conducted the first genome-wide association (GWA) study and meta-analysis of MaxDrinks as a continuous phenotype. 1059 individuals were from the Collaborative Study on the Genetics of Alcoholism (COGA) sample and 1628 individuals were from the Study of Addiction – Genetics and Environment (SAGE) sample. Family sample with 3137 individuals was from the Australian twin-family study of alcohol use disorder (OZALC). Two population-based Caucasian samples (COGA and SAGE) with 1 million single-nucleotide polymorphisms (SNPs) were used for gene discovery and one family-based Caucasian sample was used for replication. Through meta-analysis we identified 162 SNPs associated with MaxDirnks (p < 10⁻⁴). The most significant association with MaxDrinks was observed with SNP rs11128951 (p = 4.27 × 10⁻⁸) near SGOL1 gene at 3p24.3. Furthermore, several SNPs (rs17144687 near DTWD2, rs12108602 near NDST4, and rs2128158 in KCNB2) showed significant associations with MaxDrinks (p < 5 × 10⁻⁷) in the meta-analysis. Especially, 8 SNPs in DDC gene showed significant associations with MaxDrinks (p < 5 × 10⁻⁷) in the SAGE sample. Several flanking SNPs in above genes/regions were confirmed in the OZALC family sample. In conclusions, we identified several genes/regions associated with MaxDrinks. These findings can improve the understanding about the pathogenesis of alcohol consumption phenotypes and alcohol-related disorders.     

Association study of the CNS patterning genes and autism in Han Chinese in Taiwan

Autism is a complex neurodevelopmental disorder with high heritability. Despite different approaches worldwide to identify susceptibility loci or genes for autism spectrum disorders (ASDs), no consistent result has been reported. CNS patterning genes have been recognized as candidate genes for autism based on neuroimage and neuropathology evidence. This study investigated four candidate genes (WNT2, EN2, SHANK3, and FOXP2) by a tag SNP approach in a family-based association study. The trio samples include 1164 subjects from 393 families, including 393 probands (aged 9.1 ± 4.0 years; male, 88.6%) diagnosed with autistic disorder (n = 373) or Asperger's disorder (n = 20) according to the DSM-IV diagnostic criteria and confirmed by the Chinese ADI-R interview. Three tag SNPs of EN2 (7q36), 6 SNPs of WNT2 (7q31-33), 5 SNPs of SHANK3 (22q13.3), 3 SNPs of FOXP2 (7q31) were genotyped. TDT analysis was done to test the association of each tag SNP and haplotype. There was no association with autism for 17 tag SNPs of WNT2, EN2, SHANK3, and FOXP2 based on SNP analyses. Haplotype analyses did not reveal significant association except for the 6 tag SNPs of WNT2 gene showing a significant association on one haplotype composed of rs2896218 and rs6950765 (G-G) (p = 0.0095). Other haplotypes composed of rs2896218 and rs6950765 (G-G) were also significantly associated with autism. The present study indicates that SHANK3 may not be a critical gene for the etiology of ASDs in Han Chinese population. Inconsistent findings in EN2 and FOXP2 in the Han Chinese population need further clarification. A haplotype of WNT2 (rs2896218-rs6950765: G-G) is significantly associated with ASDs in our trios samples, this finding warrants further validation by different sample and confirmation by functional study.     

Associations between the oxytocin receptor gene (OXTR) and affect,loneliness and intelligence in normal subjects

Associations of oxytocin receptor gene (OXTR) variants and autism spectrum disorders (ASD) have been reported in earlier studies; in one of the studies associations with IQ and daily living skills were found additionally. Variations of the oxytocin receptor gene might also regulate affect, attachment and separation beyond the diagnostic borders of autism. We tested hypotheses of associations between positive and negative affects and social and emotional loneliness (285 adults), IQ (117 adolescents) and polymorphisms of the oxytocin receptor gene (OXTR rs53576, rs2254298 and rs2228485) in normal subjects. Individuals with the oxytocin OXTR rs53576 A/A genotype showed lower positive affect scores (F = 5.532, df = 1; p = 0.019). This effect was restricted to males (F = 13.098, df = 1; p = 0.00047). Haplotypes constructed with the three markers were associated with positive affect (p = 0.0012), negative affect (p < 0.0001) and emotional loneliness (p < 0.0001). Non-verbal intelligence was significantly reduced in rs53576 A/A adolescents (T = 2.247, p = 0.027). Our findings support a role for the oxytocin receptor haplotypes in the generation of affectivity, emotional loneliness and IQ.     

Gene variants associated with schizophrenia in a Norwegian genome-wide study are replicated in a large European cohort

We have performed a genome-wide association study (GWAS) of schizophrenia in a Norwegian discovery sample of 201 cases and 305 controls (TOP study) with a focused replication analysis in a larger European sample of 2663 cases and 13,780 control subjects (SGENE-plus study). Firstly, the discovery sample was genotyped with Affymetrix Genome-Wide Human SNP Array 6.0 and 572,888 markers were tested for schizophrenia association. No SNPs in the discovery sample attained genome-wide significance (P < 8.7 × 10⁻⁸). Secondly, based on the GWAS data, we selected 1000 markers with the lowest P values in the discovery TOP sample, and tested these (or HapMap-based surrogates) for association in the replication sample. Sixteen loci were associated with schizophrenia (nominal P value < 0.05 and concurring OR) in the replication sample. As a next step, we performed a combined analysis of the findings from these two studies, and the strongest evidence for association with schizophrenia was provided for markers rs7045881 on 9p21, rs433598 on 16p12 and rs10761482 on 10q21. The markers are located in PLAA, ACSM1 and ANK3, respectively. PLAA has not previously been described as a susceptibility gene, but 9p21 is implied as a schizophrenia linkage region. ACSM1 has been identified as a susceptibility gene in a previous schizophrenia GWAS study. The association of ANK3 with schizophrenia is intriguing in light of recent associations of ANK3 with bipolar disorder, thereby supporting the hypothesis of an overlap in genetic susceptibility between these psychopathological entities.     

Common Variants in HLA-DRA Gene are Associated with Alcohol Dependence in Two Caucasian Samples

HLA-DRA gene polymorphisms might play an important role in alcohol dependence (AD). We examined genetic associations of 29 single-nucleotide polymorphisms (SNPs) within the HLA-DRA gene with AD using two Caucasian samples—the Collaborative Study on the Genetics of Alcoholism (COGA) sample (660 AD cases and 400 controls) and the Study of Addiction: Genetics and Environment (SAGE) sample (623 cases and 1,016 controls). Logistic regression analysis using PLINK showed that 16 SNPs were associated with AD in the COGA sample and 13 SNPs were associated with AD in the SAGE sample (p?<?0.05). The best novel signal was SNP rs2239803 associated with AD in both samples (p?=?0.000817 for the COGA sample and p?=?0.0026 for the SAGE sample, respectively) while one flanking SNP rs4935356 also showed strong association in both samples (p?=?0.00219 and 0.0026 for the COGA and SAGE samples, respectively). Furthermore, these two SNPs revealed stronger associations in meta-analysis of these two samples (p?=?8.97?×?10^?6 and 2.02?×?10^?5 for rs2239803 and rs4935356, respectively). In addition, the G-A haplotype from these two SNPs revealed a significant association with AD in both the COGA and SAGE samples (p?=?0.0007 and 0.0019, respectively). These findings highlight the novel associations with HLA-DRA that may play an important role in the etiology of AD.     

A meta-analysis of two genome-wide association studies identifies 3 new loci for alcohol dependence

Family, twin and adoption studies have clearly demonstrated that genetic factors are important in modulating the vulnerability to alcohol dependence. Several genome-wide association (GWA) studies of alcohol dependence have been conducted; however, few loci have been replicated. A meta-analysis was performed on two GWA studies of 1283 cases of alcohol dependence and 1416 controls in Caucasian populations. Through meta-analysis we identified 131 SNPs associated with alcohol dependence with p < 10⁻⁴. The best novel signal was rs6701037 (p = 1.86 × 10⁻⁷) at 1q24-q25 within KIAA0040 gene while the second best novel hit was rs1869324 (p = 4.71 × 10⁻⁷) at 2q22.1 within THSD7B. The third novel locus was NRD1 at 1p32.2 (the top SNP was rs2842576 with p = 7.90 × 10⁻⁶). We confirmed the association of PKNOX2 at 11q24.4 with alcohol dependence. The top hit of PKNOX2 (rs750338 with p = 1.47 × 10⁻⁶) in the meta-analysis was replicated with the Australian Twin-Family Study of 778 families (p = 1.39 × 10⁻²) Furthermore, several flanking SNPs of the top hits in the meta-analysis demonstrated borderline associations with alcohol dependence in the family sample (top SNPs were rs2269655, rs856613, and rs10496768 with p = 4.58 × 10⁻³, 2.1 × 10⁻⁴, and 2.86 × 10⁻³ for KIAA0040, NRD1 and THSD7B, respectively). In addition, ALK, CASC4, and SEMA5A were strongly associated with alcohol dependence (p < 2 × 10⁻⁵) in the meta-analysis. In conclusion, we identified three new loci (KIAA0040, THSD7B and NRD1) and confirmed the previous association of PKNOX2 with alcohol dependence. These findings offer the potential for new insights into the pathogenesis of alcohol dependence.     

Neurotrophin-3 gene,intelligence, and selective attention deficit in a Korean sample with attention-deficit/hyperactivity disorder

Objective

Attention-deficit/hyperactivity disorder (ADHD) is a complex neurodevelopmental disorder with a strong genetic component. Neurotrophin-3 (NTF3), which participates in the differentiation and survival of dopaminergic and noradrenergic neurons, has been identified as a factor in the development of ADHD. We investigated the relationships between ADHD and NTF3 gene polymorphism.

Methods

We conducted a case–control analysis of 202 ADHD subjects and 159 controls, performed a transmission disequilibrium test (TDT) on 151 trios, and compared the intelligence quotient (IQ) and a continuous performance test (CPT) according to the genotype of two single-nucleotide polymorphisms (SNPs) (rs6332 and rs6489630) in the NTF3 gene.

Results

In the case–control and family-based analyses, NTF3 was not significantly associated with ADHD. However, in the ADHD probands, the subjects with AA genotype in the rs6332 SNP had significantly higher mean T-scores for commission errors on the CPT than did those with the AG genotypes (p = 0.045). The mean IQ of the ADHD probands who had the CC genotype of the rs6489630 SNP were higher compared with those who had the CT or TT genotype (p = 0.035). The mean T-score for response time on the CPT was higher in the subjects with TT genotype in the rs6489630 SNP compared to those with the CC or CT genotype, even after adjusting for the effect of IQ (p = 0.021).

Conclusions

These results provide preliminary evidence of an association between NTF3 and the intelligence and selective attention deficit in the Korean population.     

Effects of crack cocaine addiction and stress-related genes on peripheral BDNF levels

This study examined the effects of glucocorticoid receptor (NR3C1), corticotropin-releasing hormone receptor 1 (CRHR1), and brain-derived neurotrophic factor (BDNF) genes on susceptibility to crack cocaine addiction and BDNF levels. Crack addicted patients who sought treatment (n = 280) and non-addicted individuals (n = 241) were assessed. Three SNPs in NR3C1 (rs6198, rs41423247, and rs10052957), three in CRHR1 (rs12944712, rs110402, and rs878886), and one in BDNF (rs6265) were genotyped. No significant effect was seen in the case-control analyses. Crack cocaine addicted patients showed significantly lower serum BDNF levels. Significant effects were observed for NR3C1 rs41423247 and rs10052957. These effects were restricted to non-addicted individuals and they were supported by significant gene-by-disease status interactions. For CRHR1, all SNPs were associated with BDNF levels. Although there were significant effects only in the analysis restricted to non-addicted individuals, the lack of significant results in the gene-by-disease status interaction analyses suggest a general effect on BDNF levels. The haplotype analyses presented the same effect seen in the single marker analyses. This study suggests that SNPs in the NR3C1 and CRHR1 genes may influence BDNF levels, but this effect is blunted in the context of crack cocaine addiction. Therefore, our data may be interpreted in light of several studies showing pronounced effects of crack cocaine on BDNF levels. Since peripheral BDNF is a biomarker for several psychiatric phenotypes, our results may be useful in interpreting previous associations between stress-related SNPs, drug addiction, and depression.     

Genetic Variants in the Fat Mass- and Obesity-Associated (FTO) Gene are Associated with Alcohol Dependence

Variants (such as rs9939609) in the fat mass- and obesity-associated (FTO) gene have been associated with obesity, type 2 diabetes, some cancers, and alcohol consumption. This study tested the associations of 167 single-nucleotide polymorphisms (SNPs) within FTO gene with alcohol dependence (AD) using two Caucasian samples: the Collaborative Study on the Genetics of Alcoholism (COGA) sample (660 AD cases and 400 controls) and the Study of Addiction: Genetics and Environment (SAGE) sample (623 cases and 1,016 controls). Logistic regression analysis of AD as a binary trait was performed using the PLINK software. For the SAGE sample, the top three SNPs showing associations with AD were rs8062891, rs1108086, and rs1420318 (p?=?0.00088, 0.00086 and 0.00086, respectively). Two SNPs (rs12597786 and rs7204609) associated with AD in the SAGE sample (p?=?0.017 and 0.034, respectively) were replicated in the COGA sample (p?=?0.017 and 0.014, respectively). Through meta-analysis of two samples using PLINK, the top three SNPs associated with AD were rs8062891, rs12597786, and rs7204609 (p?=?0.00064, 0.00076 and 0.0011, respectively). Haplotype analysis in the SAGE sample further supported the associations with AD in single-marker analysis. In addition, we found association of rs17817449 (which has a strong linkage disequilibrium with rs9939609) with AD in the SAGE sample (p?=?0.00339). The findings provide evidence of joint intervention and prevention of AD and obesity.     

Association study of RELN polymorphisms with schizophrenia in Han Chinese population

Schizophrenia (SZ) is a common and complex psychiatric disorder with a strong genetic component. Previous research suggests that mutations altering genes in neurodevelopmental pathways contribute to SZ. Reelin gene (RELN) maps to chromosome 7q22.1, the encoded protein plays a pivotal role in guiding neuronal migration, lamination and connection during embryonic brain development. Several reports had indicated that reduced RELN expression is associated with human mental illnesses such as SZ, mood disorders and autism. In this study, case-control association analyses were performed in the Han Chinese population to determine if the RELN gene is a susceptibility gene for SZ. Thirty-seven single nucleotide polymorphisms (SNPs) were genotyped in 528 paranoid SZ patients and 528 control subjects. A significant association was found between rs12705169 and SZ (p = 0.001). Moreover, the haplotypes constructed from five SNPs showed significant differences between cases and controls (p = 0.041). When subjects were divided by gender, rs12705169 remained significant difference only in females (OR = 0.24, 95%CI = 0.14-0.40 for CC and OR = 0.40, 95%CI = 0.27-0.58 for AC), both in the allele and genotype (p = 0.0001 for both). This study describes a positive association between RELN and SZ in the Han Chinese population, and provides genetic evidence to support the gender difference of SZ.     

Association of FKBP5 gene haplotypes with completed suicide in the Japanese population

Background

The hypothalamus-pituitary-adrenal (HPA) axis is known to have a role in suicidal behaviors in patients with affective disorders. However, the incomplete overlapping of the genetic factors of suicidal behaviors and the genetic factors of affective disorders suggest that the genes associated with predisposition to suicidal behaviors and affective disorders are different. There is increasing evidence that genes regulating the HPA axis have effects on suicidal behaviors. To test this idea, we examined the association of three HPA axis-related genes (glucocorticoid receptor (NR3C1), mineralocorticoid receptors (NR3C2), and FK506 binding protein 5 (FKBP5)) with suicide.

Methods

We selected 3 SNPs of the FKBP5 (rs3800373, rs1360780, and rs2395635), 2 SNPs of the NR3C1 (rs6196 and rs10052957), and 3 SNPs of the NR3C2 genes (rs5525, rs5522, and rs2070951) based on their frequency in the Japanese population. Using TaqMan probe assays, we determined these SNPs in 219 completed suicide victims and 228 age- and gender-matched healthy control subjects.

Results

No significant differences in genotypic distribution or allelic frequency of any single SNPs between the completed suicide and control groups were observed. The distributions of TT, TC, and GT haplotypes of the FKBP5 gene (comprised of rs3800373 and rs1360780) between the completed suicide and control groups were significantly different (p < 0.05 for each haplotype). The TC haplotype withstood correction for multiple comparisons (corrected p = 0.034).

Conclusion

Our results suggest that haplotypes in FKBP5 gene are associated with completed suicide. This finding needs to be confirmed using rigorous SNPs selection in a larger sample.     

A genetic association study of D-dimer levels with 50 K SNPs from a candidate gene chip in four ethnic groups

Introduction

D-dimer, a fibrin degradation product, is related to risk of cardiovascular disease and venous thromboembolism. Genetic determinants of D-dimer are not well characterized; notably, few data have been reported for African American (AA), Asian, and Hispanic populations.

Materials and Methods

We conducted a large-scale candidate gene association study to identify variants in genes associated with D-dimer levels in multi-ethnic populations. Four cohorts, comprising 6,848 European Americans (EAs), 2,192 AAs, 670 Asians, and 1,286 Hispanics in the National Heart, Lung, and Blood Institute Candidate Gene Association Resource consortium, were assembled. Approximately 50,000 genotyped single nucleotide polymorphisms (SNPs) in 2,000 cardiovascular disease gene loci were analyzed by linear regression, adjusting for age, sex, study site, and principal components in each cohort and ethnic group. Results across studies were combined within each ethnic group by meta-analysis.

Results

Twelve SNPs in coagulation factor V (F5) and 3 SNPs in the fibrinogen alpha chain (FGA) were significantly associated with D-dimer level in EAs with p < 2.0 × 10^− 6. The signal for the most associated SNP in F5 (rs6025, factor V Leiden) was replicated in Hispanics (p = 0.023), while that for the top functional SNP in FGA (rs6050) was replicated in AAs (p = 0.006). No additional SNPs were significantly associated with D-dimer.

Conclusions

Our study replicated previously reported associations of D-dimer with SNPs in F5 and FGA in EAs; we demonstrated replication of the association of D-dimer with FGA rs6050 in AAs and the factor V Leiden variant in Hispanics.     

Association between DPYSL2 gene polymorphisms and alcohol dependence in Caucasian samples

The DPYSL2 gene at 8p22-p21 is expressed widely in neuronal tissues and has been implicated in multiple psychiatric disorders such as Alzheimer’s disease and schizophrenia. We therefore hypothesized that DPYSL2 gene polymorphisms may play a role in alcohol dependence (AD). We investigated the genetic associations of 57 single-nucleotide polymorphisms (SNPs) within the DPYSL2 gene with AD using two Caucasian samples—the Collaborative Study on the Genetics of Alcoholism (COGA) sample (660 AD cases and 400 controls), and the Study of Addiction: Genetics and Environment (SAGE) sample (623 cases and 1,016 controls). The SNP rs11995227 was most significantly associated with AD (p = 0.000122) in the COGA sample while one flanking SNP rs7832576 revealed the second most significant association with AD (p = 0.00163) in the COGA sample and association with AD (p = 0.0195) in the SAGE sample. Meta-analysis of two samples showed both rs119952227 and rs7832576 were associated with AD (p = 0.000363 and 0.000184, respectively). Furthermore, the C-A haplotype from rs11995227 and rs7832576 revealed significant association with AD (p = 0.0000899) in the COGA sample while the T-G haplotype revealed association with AD both in the COGA and SAGE samples (p = 0.00098 and 0.021, respectively). These findings suggest that genetic variants in DPYSL2 may play a role in susceptibility to AD.     

The association of the JAK2 46/1 haplotype with non-splanchnic venous thrombosis

Background

The inherited JAK2 46/1 haplotype is strongly associated with the development of myeloproliferative neoplasms (MPNs), and its increased frequency has also been reported in splanchnic venous thrombosis (SVT). In the present study, the role of the JAK2 46/1 haplotype in non-splanchnic venous thrombosis (non-SVT) was investigated.

Methods and Results

We genotyped 438 patients with non-SVT, 226 patients with MPNs and 459 healthy controls for three single nucleotide polymorphisms (SNPs) which tag the JAK2 46/1 haplotype (rs12342421 G > C, rs12343867 T > C and rs10974944 C > G). We found statistically significant association of the rs12342421 GC + CC genotypes (OR = 1.40; p = 0.023) and the rs12343867 TC + CC genotypes (OR = 1.83; p = 7.02x10^- 5) with non-SVT. We also found that the CC haplotype of these two SNPs was associated with an increased risk of the disease (OR = 1.68; p = 0.009). Stratification analysis indicated that the observed association of the JAK2 46/1 haplotype with non-SVT was probably largely free of confounding effect of thrombophilic risk factors. In addition, we established a strong association of SNPs rs12342421 and rs10974944 and their CG haplotype with MPNs and with JAK2 V617F-positive MPNs.

Conclusions

This study provides statistical evidence that SNPs rs12342421 and rs12343867 are associated with an increased risk of non-SVT. Consistently, haplotypes of the SNPs were also associated with non-SVT risk, suggesting that inherited genetic variation in the JAK2 gene may play a role in the pathogenesis of non-SVT. Furthermore, the reported associations of the JAK2 46/1 haplotype with MPNs as well as with the occurrence of the JAK2 V617F mutation in MPNs were confirmed.     

A genetic schizophrenia-susceptibility region located between the ANKK1 and DRD2 genes

Background

The gene coding for the D2 dopamine receptor (DRD2) is considered to be one of the most pertinent candidate genes in schizophrenia. However, genetic studies have yielded conflicting results whereas the promising TaqIA variant/rs1800497 has been mapped in a novel gene, ANKK1.

Methods

We investigated eleven single nucleotide polymorphisms (SNPs) spanning the DRD2 and ANKK1 genes, using both a case–control association study comparing 144 independent patients to 142 matched healthy subjects, and a transmission disequilibrium test in 108 trios. This classical genetic study was coupled with a cladistic phylogeny-based association test of human variants, and with an interspecies evolution study of ANKK1.

Results

Case–control study, followed by a 108 trios family-based association analysis for replication, revealed an association between schizophrenia and the ANKK1 rs1800497 (p = 0.01, Odds Ratio = 1.5, 95% Confidence Interval = 1.1–2.2), and the intergenic rs2242592 (p = 2 · 10^− 4, OR = 1.8, 95%CI = 1.3–2.5). A significant SNP–SNP interaction was also found (p < 10^− 5, OR = 2.0, 95%CI = 1.6–2.5). The phylogeny-based association test also identified an association between both these polymorphisms and schizophrenia. Finally, interspecies comparison of the sequences from chimpanzee, orangutan, rhesus macaque and human species suggested specific involvement of ANKK1 in the human lineage.

Conclusions

Intergenic rs2242592 appears to be involved in the genetic vulnerability to schizophrenia, whereas the ANKK1 rs1800497 appears to have a modifying rather than causative effect. Finally, ANKK1 may be a specific human lineage-trait involved in a specific human disease, schizophrenia.     

The role of dopamine transporter (SLC6A3) and dopamine D2 receptor/ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1) gene polymorphisms in personality traits

Variations in personality traits are caused by interactions between multiple genes of small effect and environmental factors. To date, gender- and ethnicity-specific variations in personality have been established. In the present study, we aimed to test: 1) the effects of four polymorphisms of dopamine system genes: ANKK1/DRD2 Taq1A, DRD2 rs6275, SLC6A3 40-bp VNTR and rs27072, on personality traits; 2) whether these effects differ between men and women and between Russians and Tatars. A sample of 652 healthy individuals (222 men and 430 women) of Caucasian origin (233 Russians and 419 Tatars) from Russia was subjected to personality traits assessment with Eysenck Personality Inventory (EPI) and Temperament and Character Inventory-125 (TCI-125). The associations between each personality trait and polymorphisms were assessed with regression models adjusted for gender and ethnicity. There were significant effects of ANKK1/DRD2 Taq1A on Neuroticism (p = 0.016) and of SLC6A3 rs27072 on Persistence (p = 0.021) in both genders. The association between ANKK1/DRD2 Taq1A A2/A2-genotype and higher Novelty Seeking and lower Reward Dependence was shown in men only (p for gender interaction = 0.018). In women only, there was a significant association between SLC6A3 10R*G-haplotype and higher Persistence (p = 0.002). Our findings provide evidence for a modifying effect of gender on the associations between dopamine system genes and approach-related traits (in men) and Persistence (in women).     

Interleukin 10 family gene polymorphisms are not associated with major depressive disorder and panic disorder phenotypes

Genetic regulation of immune system and inflammatory response may be related to the pathogenesis and manifestations of mood and anxiety disorders. In the present study we examined a range of single-nucleotide polymorphisms (SNP) in chromosomal region 1q32, the locus of interleukin 10 (IL10) gene, in patients with major depressive disorder (n = 312) and panic disorder (n = 210), and matched healthy controls (n = 356). We found no significant associations of the SNPs in IL10 family genes with either diagnostic group. Haplotype analysis revealed seven haplotype blocks, but their frequencies did not differ between patients and controls. Significant associations were detected for SNP rs1539243 in IKBKE (inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase epsilon) gene showing different allelic and genotypic distributions in the total as well as in separate diagnostic groups as compared to controls. IKBKE emerged as a candidate for further studies of genetic factors associated with panic disorder and major depressive disorder.     

Exploring the genetic link between RLS and ADHD

Attention deficit/hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder of childhood onset. Clinical and biological evidence points to shared common central nervous system (CNS) pathology of ADHD and restless legs syndrome (RLS). It was hypothesized that variants previously found to be associated with RLS in two large genome-wide association studies (GWA), will also be associated with ADHD.SNPs located in MEIS1 (rs2300478), BTBD9 (rs9296249, rs3923809, rs6923737), and MAP2K5 (rs12593813, rs4489954) as well as three SNPs tagging the identified haplotype in MEIS1 (rs6710341, rs12469063, rs4544423) were genotyped in a well characterized German sample of 224 families comprising one or more affected sibs (386 children) and both parents.We found no evidence for preferential transmission of the hypothesized variants to ADHD. Subsequent analyses elicited nominal significant association with haplotypes consisting of the three SNPs in BTBD9 (χ² = 14.8, df = 7, nominal p = 0.039). According to exploratory post hoc analyses, the major contribution to this finding came from the A-A-A-haplotype with a haplotype-wise nominal p-value of 0.009. However, this result did not withstand correction for multiple testing.In view of our results, RLS risk alleles may have a lower effect on ADHD than on RLS or may not be involved in ADHD. The negative findings may additionally result from genetic heterogeneity of ADHD, i.e. risk alleles for RLS may only be relevant for certain subtypes of ADHD. Genes relevant to RLS remain interesting candidates for ADHD; particularly BTBD9 needs further study, as it has been related to iron storage, a potential pathophysiological link between RLS and certain subtypes of ADHD.     

Genome-wide association study identifies 5q21 and 9p24.1 (<Emphasis Type="Italic">KDM4C</Emphasis>) loci associated with alcohol withdrawal symptoms

Several genome-wide association (GWA) studies of alcohol dependence (AD) and alcohol-related phenotypes have been conducted; however, little is known about genetic variants influencing alcohol withdrawal symptoms (AWS). We conducted the first GWA study of AWS using 461 cases of AD with AWS and 408 controls in Caucasian population in the Collaborative Study on the Genetics of Alcoholism (COGA) sample. Logistic regression analysis of AWS as a binary trait, adjusted for age and sex, was performed using PLINK. We identified 51 SNPs associated with AWS with p < 10⁻⁴. The first best signal was rs770182 (p = 3.65 × 10⁻⁶) at 5q21 near EFNA5 gene which was replicated in the Australian twin-family study of 273 families (p = 0.0172). Furthermore, three SNPs (rs10975990, rs10758821 and rs1407862) within KDM4C gene at 9p24.1 showed p < 10⁻⁴ (p = 7.15 × 10⁻⁶, 2.79 × 10⁻⁵ and 4.93 × 10⁻⁵, respectively) in the COGA sample while one SNP rs12001158 within KDM4C with p = 1.97 × 10⁻⁴ in the COGA sample was replicated in the family sample (p = 0.01). Haplotype analysis further supported the associations of single-marker analyses of KDM4C in the COGA sample. Moreover, two SNPs (rs2046593 and rs10497668) near FSIP2 at 2q32.1 with moderate associations with AWS in the COGA sample (p = 2.66 × 10⁻⁴ and 9.48 × 10⁻⁵, respectively) were replicated in the family sample (p = 0.0013 and 0.0162, respectively). In addition, several SNPs in GABRA1, GABRG1, and GABRG3 were associated with AWS (p < 10⁻²) in the COGA sample. In conclusion, we identified several loci associated with AWS. These findings offer the potential for new insights into the pathogenesis of AD and AWS.     

An exploratory model for G × E interaction on hippocampal volume in schizophrenia; obstetric complications and hypoxia-related genes

Background

Smaller hippocampal volume has repeatedly been reported in schizophrenia patients. Obstetric complications (OCs) and single nucleotide polymorphism (SNP) variation in schizophrenia susceptibility genes have independently been related to hippocampal volume. We investigated putative independent and interaction effects of severe hypoxia-related OCs and variation in four hypoxia-regulated schizophrenia susceptibility genes (BDNF, DTNBP1, GRM3 and NRG1) on hippocampal volume in schizophrenia patients and healthy controls.

Methods

Clinical assessment, structural MRI scans, and blood samples for genotyping of 32 SNPs were obtained from 54 schizophrenia patients and 53 control subjects. Information on obstetric complications was collected from original birth records.

Results

Severe OCs were related to hippocampal volume in both patients with schizophrenia and healthy control subjects. Of the 32 SNPs studied, effects of severe OCs on hippocampal volume were associated with allele variation in GRM3 rs13242038, but the interaction effect was not specific for schizophrenia. SNP variation in any of the four investigated genes alone did not significantly affect hippocampal volume.

Conclusions

The findings suggest a gene–environment (G × E) interaction between GRM3 gene variants and severe obstetric complications on hippocampus volume, independent of a diagnosis of schizophrenia. Due to the modest sample size, the results must be considered preliminary and require replication in independent samples.