Jens R. Wendland

Simultaneous genotyping of four functional loci of human SLC6A4, with a reappraisal of 5-HTTLPR and rs25531.

Simultaneous genotyping of four functional loci of human SLC6A4 , with a reappraisal of 5-HTTLPR and rs25531

Monoamine oxidase A gene promoter variation and rearing experience influences aggressive behavior in rhesus monkeys

BACKGROUND Allelic variation of the monoamine oxidase A (MAOA) gene has been implicated in conduct disorder and antisocial, aggressive behavior in humans when associated with early adverse experiences. We tested the hypothesis that a repeat polymorphism in the rhesus macaque MAOA gene promoter region influences aggressive behavior in male subjects. METHODS Forty-five unrelated male monkeys raised with or without their mothers were tested for competitive and social group aggression. Functional activity of the MAOA gene promoter polymorphism was determined and genotypes scored for assessing genetic and environmental influences on aggression. RESULTS Transcription of the MAOA gene in rhesus monkeys is modulated by an orthologous polymorphism (rhMAOA-LPR) in its upstream regulatory region. High- and low-activity alleles of the rhMAOA-LPR show a genotype x environment interaction effect on aggressive behavior, such that mother-reared male monkeys with the low-activity-associated allele had higher aggression scores. CONCLUSIONS These results suggest that the behavioral expression of allelic variation in MAOA activity is sensitive to social experiences early in development and that its functional outcome might depend on social context.

Identification of 15 genetic loci associated with risk of major depression in individuals of European descent

Despite strong evidence supporting the heritability of major depressive disorder (MDD), previous genome-wide studies were unable to identify risk loci among individuals of European descent. We used self-report data from 75,607 individuals reporting clinical diagnosis of depression and 231,747 individuals reporting no history of depression through 23andMe and carried out meta-analysis of these results with published MDD genome-wide association study results. We identified five independent variants from four regions associated with self-report of clinical diagnosis or treatment for depression. Loci with a P value <1.0 × 10−5 in the meta-analysis were further analyzed in a replication data set (45,773 cases and 106,354 controls) from 23andMe. A total of 17 independent SNPs from 15 regions reached genome-wide significance after joint analysis over all three data sets. Some of these loci were also implicated in genome-wide association studies of related psychiatric traits. These studies provide evidence for large-scale consumer genomic data as a powerful and efficient complement to data collected from traditional means of ascertainment for neuropsychiatric disease genomics.

How the Serotonin Story is Being Rewritten By New Gene-Based Discoveries Principally Related to SLC6A4, the Serotonin Transporter Gene, Which Functions To Influence All Cellular Serotonin Systems

Discovered and crystallized over sixty years ago, serotonins important functions in the brain and body were identified over the ensuing years by neurochemical, physiological and pharmacological investigations. This 2008 M. Rapport Memorial Serotonin Review focuses on some of the most recent discoveries involving serotonin that are based on genetic methodologies. These include examples of the consequences that result from direct serotonergic gene manipulation (gene deletion or overexpression) in mice and other species; an evaluation of some phenotypes related to functional human serotonergic gene variants, particularly in SLC6A4, the serotonin transporter gene; and finally, a consideration of the pharmacogenomics of serotonergic drugs with respect to both their therapeutic actions and side effects. The serotonin transporter (SERT) has been the most comprehensively studied of the serotonin system molecular components, and will be the primary focus of this review. We provide in-depth examples of gene-based discoveries primarily related to SLC6A4 that have clarified serotonins many important homeostatic functions in humans, non-human primates, mice and other species.

Genetics of early-onset obsessive-compulsive disorder

Obsessive–compulsive disorder (OCD) is characterized by recurrent, intrusive and disturbing thoughts as well as by repetitive stereotypic behaviors. Epidemiological data are similar in children and adults, i.e., between 1 and 3% of the general population suffer from OCD. Children with OCD are often seriously impaired in their development. OCD, especially of early onset, has been shown to be familial. Several candidate genes of predominantly neurotransmitter systems have been analyzed and a total of three genome-wide linkage scans have been performed until now. Analyses of candidate genes in linkage regions have not provided evidence for their involvement in OCD, with the exception of the glutamate transporter gene SLC1A1 on 9p24. Genome-wide association analyses are in progress and the results will promote further independent replication studies. The consideration of subtypes regarding age of onset, symptom dimensions and/or comorbid disorders is needed.

Meta-analysis of genome-wide association data identifies a risk locus for major mood disorders on 3p21.1.

The major mood disorders, which include bipolar disorder and major depressive disorder (MDD), are considered heritable traits, although previous genetic association studies have had limited success in robustly identifying risk loci. We performed a meta-analysis of five case-control cohorts for major mood disorder, including over 13,600 individuals genotyped on high-density SNP arrays. We identified SNPs at 3p21.1 associated with major mood disorders (rs2251219, P = 3.63 × 10−8; odds ratio = 0.87; 95% confidence interval, 0.83–0.92), with supportive evidence for association observed in two out of three independent replication cohorts. These results provide an example of a shared genetic susceptibility locus for bipolar disorder and MDD.

Tryptophan hydroxylase-2 gene variation influences personality traits and disorders related to emotional dysregulation

Variation in the tryptophan hydroxylase-2 gene (TPH2) coding for the rate-limiting enzyme of serotonin (5-HT) synthesis in the brain modulates responses of limbic circuits to emotional stimuli and has been linked to a spectrum of clinical populations characterized by emotional dysregulation. Here, we tested a set of common single nucleotide polymorphisms (SNPs) in and downstream of the transcriptional control region of TPH2 for association with personality traits and with risk for personality disorders in two cohorts comprising of 336 healthy individuals and 420 patients with personality disorders. Personality dimensions were assessed by the Tridimensional Personality Questionnaire (TPQ) and the revised NEO Personality Inventory (NEO-PI-R). Personality disorders were diagnosed with the Structured Clinical Interview of DSM-IV and were allocated to clusters A, B, and C. Individual SNP and haplotype analyses revealed significant differences in genotype frequencies between controls and cluster B as well as cluster C patients, respectively. In both patient groups, we observed overrepresentation of T allele carriers of a functional polymorphism in the upstream regulatory region of TPH2 (SNP G-703T, rs4570625) which was previously shown to bias responsiveness of the amygdala, a structure critically involved in emotionality. Furthermore, significant effects of TPH2 variants on anxiety-related traits defined primarily by the TPQ Harm Avoidance were found in healthy individuals. The results link potentially functional TPH2 variants to personality traits related to emotional instability as well as to cluster B and cluster C personality disorders. These findings implicate alterations of 5-HT synthesis in emotion regulation and confirm TPH2 as a susceptibility and/or modifier gene of affective spectrum disorders.

Genome-wide association study meta-analysis of European and Asian-ancestry samples identifies three novel loci associated with bipolar disorder

Meta-analyses of bipolar disorder (BD) genome-wide association studies (GWAS) have identified several genome-wide significant signals in European-ancestry samples, but so far account for little of the inherited risk. We performed a meta-analysis of ∼750 000 high-quality genetic markers on a combined sample of ∼14 000 subjects of European and Asian-ancestry (phase I). The most significant findings were further tested in an extended sample of ∼17 700 cases and controls (phase II). The results suggest novel association findings near the genes TRANK1 (LBA1), LMAN2L and PTGFR. In phase I, the most significant single nucleotide polymorphism (SNP), rs9834970 near TRANK1, was significant at the P=2.4 × 10−11 level, with no heterogeneity. Supportive evidence for prior association findings near ANK3 and a locus on chromosome 3p21.1 was also observed. The phase II results were similar, although the heterogeneity test became significant for several SNPs. On the basis of these results and other established risk loci, we used the method developed by Park et al. to estimate the number, and the effect size distribution, of BD risk loci that could still be found by GWAS methods. We estimate that >63 000 case–control samples would be needed to identify the ∼105 BD risk loci discoverable by GWAS, and that these will together explain <6% of the inherited risk. These results support previous GWAS findings and identify three new candidate genes for BD. Further studies are needed to replicate these findings and may potentially lead to identification of functional variants. Sample size will remain a limiting factor in the discovery of common alleles associated with BD.

Valproic acid induces functional heat-shock protein 70 via Class I histone deacetylase inhibition in cortical neurons: a potential role of Sp1 acetylation.

Neuroprotective properties of the mood stabilizer valproic acid (VPA) are implicated in its therapeutic efficacy. Heat‐shock protein 70 (HSP70) is a molecular chaperone, neuroprotective and anti‐inflammatory agent. This study aimed to investigate underlying mechanisms and functional significance of HSP70 induction by VPA in rat cortical neurons. VPA treatment markedly up‐regulated HSP70 protein levels, and this was accompanied by increased HSP70 mRNA levels and promoter hyperacetylation and activity. Other HDAC inhibitors – sodium butyrate, trichostatin A, and Class I HDAC‐specific inhibitors MS‐275 and apicidin, – all mimicked the ability of VPA to induce HSP70. Pre‐treatment with phosphatidylinositol 3‐kinase inhibitors or an Akt inhibitor attenuated HSP70 induction by VPA and other HDAC inhibitors. VPA treatment increased Sp1 acetylation, and a Sp1 inhibitor, mithramycin, abolished the induction of HSP70 by HDAC inhibitors. Moreover, VPA promoted the association of Sp1 with the histone acetyltransferases p300 and recruitment of p300 to the HSP70 promoter. Further, VPA‐induced neuroprotection against glutamate excitotoxicity was prevented by blocking HSP70 induction. Taken together, the data suggest that the phosphatidylinositol 3‐kinase/Akt pathway and Sp1 are likely involved in HSP70 induction by HDAC inhibitors, and induction of HSP70 by VPA in cortical neurons may contribute to its neuroprotective and therapeutic effects.

Multiple rare SAPAP3 missense variants in trichotillomania and OCD

Obsessive–compulsive disorder (OCD) and the spectrum of associated conditions, such as trichotillomania (TTM), Tourette syndrome and body dysmorphic disorder, affect about 2–4% of the world population. 1,2 Clinically OCD spectrum disorders are characterized by persistent intrusive thoughts (obsessions), repetitive actions (compulsions) and excessive anxiety. Although heritability studies in OCD have shown a 3–12 times increased risk for first-degree relatives and twin studies revealed higher concordance amongst monozygotic twins (80–90%) compared to dizygotic twins (47–50%), the identification of the underlying risk-conferring genetic variation by means of classic genetic association studies has proven to be difficult.3 Recently, it has been shown that mice deficient of the postsynaptic synapse-associated protein 90 (SAP90)/postsynaptic density-95 (PSD95)-associated protein 3 (SAPAP3, also known as Dlgap3) develop an OCD-like phenotype, which includes compulsive grooming and increased anxiety. Interestingly, the phenotype of Sapap3 knock-out mice can be rescued by administering selective serotonin reuptake inhibitors.4 We hypothesized that rare variants in the human orthologue SAPAP3 could contribute to disorders in the OCD spectrum. To test this, we resequenced SAPAP3 in three case populations, including 77 unrelated TTM probands collected at Duke University, 44 OCD with TTM probands from National Institute of Mental Health (NIMH), and 44 OCD cases without TTM from NIMH.5,6 Controls were 48 OCD spectrum-negative subjects from NIMH6 and a psychiatric comparison sample of 138 subjects screened for depression but not specifically for OCD from Duke University.7 A board-certified psychiatrist saw all patients and controls and diagnoses met Diagnostic and Statistical Manual of Mental Disorders, 4th edn. criteria. Samples were collected under approved institutional review board protocols. In 165 cases and 178 controls the complete coding region and flanking intronic sequence of SAPAP3 was resequenced using standard capillary sequencing methods (Applied Biosystems, Foster City, CA, USA). We detected seven novel nonsynonymous heterozygous variants, with all but A189V occurring only once (Table 1; Figure 1). Thus, in total, heterozygous SAPAP3 variants were present in 4.2% of diagnosed TTM/OCD patients, but only in 1.1% of controls (two changes in Duke control samples, with one developing depression subsequent to entry into the study). The majority of changes presented missense mutations; one variant was an in-frame insertion of five amino acids, A148insGPAGA. In silico analysis of the missense variants applying PMut and PolyPhen predicted two, or three, respectively, variants as of functional relevance (Table 1). The remaining polymorphisms were considered benign, including the two changes detected in controls. Further, we genotyped 6 of the identified variants in the TTM/OCD subjects in an additional sample of 281 OCD cases and in 751 general population controls.6 R13C and P606T were found in one control each, whereas A189V was present in three controls. This suggests that these specific variants are not by themselves disease-causing abnormalities, but still leaves open the possibility that an aggregate of susceptibility variants may prove contributory to disease, as suggested for some other disorders including autism as well as OCD. The combined analyses of 2766 alleles showed that all changes are very rare, with minor allele frequencies between 0.00036 (T523K, K910R) and 0.002 (A189V). Figure 1 Identified rare nonsynonymous polymorphisms in synapse-associated protein 90/postsynaptic density-95-associated protein 3 (SAPAP3). (a) Schematic of SAPAP3, which consists of 10 coding exons (blue boxes). Seven rare changes were identified in trichotillomania ... Table 1 Identified rare variants in SAPAP3 and predicted functional relevance Available pedigrees from TTM/OCD mutation carriers were enriched for a diverse set of psychiatric conditions, including panic disorder, attention deficit hyperactivity disorder (ADHD), depression, bipolar disorder and substance abuse as well as OCD spectrum disorders (details are given in Supplementary Figure 1 and Supplementary Table 1). This situation is quite typical for psychiatric genetic studies and complicates allele segregation studies. Cosegregation of genotype and phenotype is also confounded by phenotypic penetrance rates, limited psychometric instruments and assortative mating. Thus, we consider it more significant to study the combined mutation load of SAPAP3 comparing cases to controls. Similar approaches were recently adopted by other studies.8 We observed a significant case–control association in our moderately sized sample (Fisher’s one-sided exact test P = 0.045). With generally still limited abilities to determine functional consequences of genetic variants, we speculate that the predicted moderate functional consequences (Table 1) are not detrimental for protein function but rather increase susceptibility for OCD spectrum behavior, possibly through permissive or epistatic interactions with additional genetic and environmental factors. A recent study estimated that up to 70% of low-frequency missense alleles in humans have mildly deleterious effects.9 The excess of rare mildly deleterious variants in any OCD risk gene could be promoted by an inefficient evolutionary selection against OCD risk alleles, which is supported by the high OCD spectrum frequency of 2–4% in the population, early disease onset and normal reproductive fitness. In summary, on the background of an intriguing Sapap3-OCD mouse model we suggest that the present data support a role for SAPAP3 in TTM and OCD. Expansion of our approach and modeling of rare genetic variants in SAPAP3 will be essential to further test this hypothesis.