Investigating the role of dopaminergic and serotonergic candidate genes in obsessive-compulsive disorder

Microbial Reprogramming in Obsessive-Compulsive Disorders: A Review of Gut-Brain Communication and Emerging Evidence

Obsessive-compulsive disorder (OCD) is a debilitating mental health disorder characterized by intrusive thoughts (obsessions) and repetitive behaviors (compulsions). Dysbiosis, an imbalance in the gut microbial composition, has been associated with various health conditions, including mental health disorders, autism, and inflammatory diseases. While the exact mechanisms underlying OCD remain unclear, this review presents a growing body of evidence suggesting a potential link between dysbiosis and the multifaceted etiology of OCD, interacting with genetic, neurobiological, immunological, and environmental factors. This review highlights the emerging evidence implicating the gut microbiota in the pathophysiology of OCD and its potential as a target for novel therapeutic approaches. We propose a model that positions dysbiosis as the central unifying element in the neurochemical, immunological, genetic, and environmental factors leading to OCD. The potential and challenges of microbial reprogramming strategies, such as probiotics and fecal transplants in OCD therapeutics, are discussed. This review raises awareness of the importance of adopting a holistic approach that considers the interplay between the gut and the brain to develop interventions that account for the multifaceted nature of OCD and contribute to the advancement of more personalized approaches.

Epigenetic modifications and obsessive-compulsive disorder: what do we know?

Obsessive-Compulsive Disorder (OCD) is a chronic, severe disabling neuropsychiatric disorder whose pathophysiology is not yet well defined. Generally, the symptom onset occurs during pre-adult life and affects subjects in different life aspects, including professional and social relationships. Although robust evidence indicates the presence of genetic factors in the etiopathology of OCD, the entirely mechanisms are not totally clarified. Thus, the possible interactions between genes and environmental risk factors mediated by epigenetic mechanisms should be sought. Therefore, we provide a review of genetic and epigenetic mechanisms related to OCD with a deep focus on the regulation of critical genes of the central nervous system seeking possible potential biomarkers.

Genetic and epigenetic architecture of Obsessive-Compulsive Disorder: In search of possible diagnostic and prognostic biomarkers

Obsessive-Compulsive Disorder (OCD) is a prevalent and severe clinical condition whose hallmarks are excessive, unwanted thoughts (obsessions) and repetitive behaviors (compulsions). The onset of symptoms generally occurs during pre-adult life and typically affects subjects in different aspects of their life's, compromising social and professional relationships. Although robust evidence suggests a genetic component in the etiopathogenesis of OCD, the causes of the disorder are still not completely understood. It is thus of relevance to take into account how genes interact with environmental risk factors, thought to be mediated by epigenetic mechanisms. We here provide an overview of genetic and epigenetic mechanisms of OCD, focusing on the modulation of key central nervous system genes, in the attempt to suggest possible disease biomarkers.

Genome-wide mRNA expression analysis of peripheral blood from patients with obsessive-compulsive disorder

The onset of obsessive-compulsive disorder (OCD) involves the interaction of heritability and environment. The aim of this study is to identify the global messenger RNA (mRNA) expressed in peripheral blood from 30 patients with OCD and 30 paired healthy controls. We generated whole-genome gene expression profiles of peripheral blood mononuclear cells (PBMCs) from all the subjects using microarrays. The expression of the top 10 mRNAs was verified by real-time quantitative PCR (qRT-PCR) analysis. We also performed an enrichment analysis of the gene ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) annotations of the differentially expressed mRNAs. We identified 51 mRNAs that were significantly differentially expressed between the subjects with OCD and the controls (fold change ≥1.5; false discovery rate <0.05); 45 mRNAs were down-regulated and 6 mRNAs were up-regulated. The qRT-PCR analysis of 10 selected genes showed that they were all up-regulated, which was opposite to the results obtained from the microarrays. The GO and KEGG enrichment analysis showed that ribosomal pathway was the most enriched pathway among the differentially expressed mRNAs. Our findings support the idea that altered genome expression profiles may underlie the development of OCD.

Neonatal whisker trimming in WAG/Rij rat pups causes developmental delay, encourages maternal care and affects exploratory activity in adulthood

WAG/Rij rats are genetically predisposed to absence epilepsy. Maternal behavior in WAG/Rij female rats is known to differ from that in non-epileptic females. We hypothesize that (1) mother's behavior may be changed as response to changes in pup's conditions; (2) sensory deprivation at the neonatal age affect learning and behavior in adulthood. All whiskers in WAG/Rij rat pups were trimmed daily during PN1-PN8. Maternal behavior was examined during the same period. It was found that in the control group, WAG/Rij females often demonstrated abnormally long (>1 min) repetitive purposeless stereotypical actions that were roughly classified as compulsive-like behavior. Mothers of the trimmed pups showed less compulsive-like behavior and more intensively interacted with pups and built better nests. Rat pups in the trimmed group had lower body weight on PN7-PN19 as compared to the control. In the trimmed group, maturation of motor skills and early behavioral patterns (i.e. walking, grooming, vertical activity, motor functions of forelimbs) showed 1-2 days delay in comparison to the control. At the age of 2-2.5 months, the locomotor activity in the trimmed rats differed from the control, but the level of anxiety was the same (the open field and the elevated plus maze). At the age of 6 months, the trimmed and control rats showed no differences in conditioned avoidance learning test, therefore, neonatal whisker trimming did not influence fear-based learning abilities in adulthood. It is hypothesized that an enhanced maternal care is capable to modulate development of brain functions in sensory deprived progeny.

Association analysis of SLC6A4 and HTR2A genes with obsessive-compulsive disorder: Influence of the STin2 polymorphism

BACKGROUND

Obsessive-Compulsive Disorder (OCD) is a complex and chronic disorder characterized by recurrent thoughts and/or repetitive behaviors. Given the potent anti-obsessional effects of the so-called serotonin reuptake inhibitors, genes related to serotonergic system may be well implicated in the etiopathogenesis of OCD. The gene encoding the serotonin transporter (SLC6A4), which shows a variable number of tandem repeat (VNTR) polymorphism in intron 2 (STin2), have been previously associated with OCD. Additionally, the serotonin 2A receptor gene (HTR2A) has two polymorphisms (A-1438G - rs6311, and T102C - rs6313), which have also been overrepresented among OCD patients. Therefore, the aim of this study is to evaluate the association of these three polymorphisms with OCD, through the examination of potential sources of heterogeneity in previous studies including age of onset, sex and symptom dimensions.

METHODS

Polymorphisms were genotyped by Polymerase Chain Reaction (PCR) in a sample of 203 OCD patients and 205 healthy controls from Brazil.

RESULTS

Although we did not observe any statistically significant association between the HTR2A gene polymorphisms and OCD or its clinical features, SLC6A4 STin2 polymorphism was significantly more common among OCD patients as compared to health controls. Further, a significant association between the STin2.12 allele and OCD, as well as a dominant effect of the STin2.12 allele in OCD was seen. Of note, late-onset (>18years) OCD was significantly more often seen in association with homozygosis for STin2.12 allele. No significant associations were observed with different OCD symptom dimensions.

CONCLUSION

Our results indicate an important influence of the STin2 polymorphism in OCD, but more studies are warranted to confirm these results.

A review of the role of serotonin system genes in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric disorder that causes the patient to experience intrusive thoughts and/or to carry out repetitive, ritualized behaviors that are time consuming and impairing. OCD is familial and heritable. The genetic factors responsible for pathogenesis, however, remain largely unknown despite the numerous candidate gene studies conducted. Based on efficacy of serotonin reuptake inhibitors (SRIs) in treating OCD, serotonin system genes have been a dominant focus in OCD candidate gene studies. We review the most commonly studied candidate serotonin system gene variants (specifically in SLC6A4, HTR2A, HTR1B, and HTR2C) and their association with OCD. Although findings to date are mixed, serotonin transporter polymorphism 5-HTTLPR and HTR2A polymorphism rs6311 (or rs6313) are most consistently associated with OCD. Mixed findings may be the result of genetic complexity and phenotypic heterogeneity that future studies should account for. Homogenous patient subgroups reflecting OCD symptom dimensions, OCD subtypes, and sex should be used for gene discovery.

Modification of the association between early adversity and obsessive-compulsive disorder by polymorphisms in the MAOA, MAOB and COMT genes

The monoamine oxidases (MAOA/B) and catechol-O-methyltransferase (COMT) enzymes break down regulatory components within serotonin and dopamine pathways, and polymorphisms within these genes are candidates for OCD susceptibility. Childhood trauma has been linked OCD psychopathology, but little attention has been paid to the interactions between genes and environment in OCD aetiology. This pilot study investigated gene-by-environment interactions between childhood trauma and polymorphisms in the MAOA, MAOB and COMT genes in OCD. Ten polymorphisms (MAOA: 3 variants, MAOB: 4 variants, COMT: 3 variants) were genotyped in a cohort of OCD patients and controls. Early-life trauma was assessed using the Childhood Trauma Questionnaire (CTQ). Gene-by-gene (GxG) and gene-by-environment interactions (GxE) of the variants and childhood trauma were assessed using logistic regression models. Significant GxG interactions were found between rs362204 (COMT) and two independent polymorphisms in the MAOB gene (rs1799836 and rs6651806). Haplotype associations for OCD susceptibility were found for MAOB. Investigation of GxE interactions indicated that the sexual abuse sub-category was significantly associated with all three genes in haplotype x environment interaction analyses. Preliminary findings indicate that polymorphisms within the MAOB and COMT genes interact resulting in risk for OCD. Childhood trauma interacts with haplotypes in COMT, MAOA and MAOB, increasing risk for OCD.

Strain and sex based characterization of behavioral expressions in non-induced compulsive-like mice

There is currently a lack of understanding how genetic background and sex differences attribute to the heterogeneity of obsessive-compulsive disorder (OCD). An animal model of compulsive-like behaviors has been developed through bidirectional selection of house mice (Mus musculus) for high (big cotton nests; BIG mice) and low levels (small nests; SMALL mice) of nest-building behavior. The BIG male strains have predictive and face validity as a spontaneous animal model of OCD. Here, we evaluated compulsive-, anxiety-, cognitive-, and depression-like behaviors among male and proestrus female replicate strains each of BIG (BIG1, BIG2) and SMALL (SML1, SML2) nest-builders, and randomly-bred Controls (C1, C2). BIG1 and BIG2 males and females had higher nesting scores when compared to SMALL and Control strains. Male BIG1 and BIG2 strains showed more compulsive-like nesting than BIG1 and BIG2 proestrus females, which was not observed among the other strains. Nesting scores were also different between BIG replicate male strains. A similar pattern was observed in the compulsive-like marble burying behavior with BIG strains burying more marbles than SMALL and Control strains. Significant replicate and sex differences were also observed in marble burying among the BIG strains. The open field test revealed replicate effects while the BIG strains showed less anxiety-like behavior in the elevated plus maze test compared to the SMALL strains. For novel object recognition only the Control strains showed replicate and sex differences. In the depression-like forced swim test proestrus females demonstrated less depression-like behavior than males. BIG and SMALL nest-building strains had a higher corticosterone stress response than the Control strains. Together these results indicate a strong interplay of genetic background and sex in influencing expression of behaviors in our compulsive-like mouse model. These results are in congruence with the clinical heterogeneity of OCD.

The need for inclusion of sex and age of onset variables in genetic association studies of obsessive-compulsive disorder: Overview

Obsessive-compulsive disorder (OCD) is a heterogeneous mental disorder that significantly impairs an individual's functioning. The candidate gene approach has proven to be a useful tool in investigating potential risk genes for OCD, but genetic studies have been largely inconclusive. Etiologically distinct forms of obsessive-compulsive disorder based on sex and age of onset have been identified, yet many genetic studies fail to examine the association by these subtypes. Due to the sexually dimorphic nature of the disorder, positive associations have been found with OCD in males only, suggesting the potential for identifying risk genes that contribute to OCD in women, such as perinatal OCD. This review includes a brief overview of the disorder and its subtypes, with a current update on candidate genes that may contribute to OCD using single nucleotide polymorphisms (SNPs) and genome wide association studies (GWAS).

Symmetry symptoms in obsessive-compulsive disorder: clinical and genetic correlates

Objective:

In obsessive-compulsive disorder (OCD), symmetry-related symptoms may be important. Although clinical correlates of symmetry-related symptoms have been identified in OCD, few data exist on genetic associations. Animal studies indicate involvement of dopamine in symmetry-related behavior, suggesting this may be relevant to analogous symptoms in OCD. Alterations in dopamine may also reflect environmental influences. However, the association of symmetry-related symptomatology, early adversity, and polymorphisms in dopaminergic genes has not been investigated in OCD.

Methods:

Clinical information and polymorphisms in key dopaminergic genes were compared between OCD patients with primary symmetry symptoms and those without.

Results:

OCD patients with primary symmetry symptoms comprised 46.6% (n=210) of the sample (n=451), and were older (p < 0.01), had longer illness duration (p < 0.01), higher OCD severity scores (p = 0.01), and greater comorbidity (p < 0.01) than those without. In Caucasians (n=343), genotype frequency differed significantly between groups for ANKK1 rs1800497, with more OCD patients with symmetry symptoms being homozygous for the A2 (CC) genotype (χ² = 7.296; p = 0.026).

Conclusion:

Symmetry symptoms have some distinct clinical features and may represent a marker of severity in OCD. However, clinical associations, in combination with the association found with the ANKK1 rs1800497 A2 variant, suggest that primary symmetry symptoms may represent a distinctive clinical and psychobiological profile.

Genetics of obsessive–compulsive disorder: a research update

The genetic study of obsessive-compulsive disorder (OCD) has made significant gains in the past decade. However, etiological gene findings are still elusive. Epidemiological studies, including family and twin studies, strongly support a genetic component for OCD. In addition, complex segregation analyses suggest the presence of at least one major gene. The neurobiology of OCD also lends support to the notion that programmed CNS-based biological processes underlie OCD symptom expression, with mapping of brain circuits to fronto-subcortical circuits in a consistent manner. Genetic linkage studies of OCD, using families with multiple affected relatives, have generated several suggestive linkage peaks, regions that may harbor a gene or genes for OCD. However, the presence of multiple linkage peaks has added to the complexity of OCD genetics, suggesting that the exploration of gene-gene interactions and gene-environment interactions, in addition to the exploration of alternate phenotypes based on symptom expression, age at onset or comorbid conditions, may be key in locating etiologic genes. Finally, candidate gene studies, while promising, are not yet associated with linkage regions, except in the case of the glutamate transporter gene SLC1A1 in 9p24. While OCD appears to have a genetic component, additional innovative research is needed to unravel the genetic influences in the disorder.

DRD4 gene and obsessive compulsive disorder: do symptom dimensions have specific genetic correlates?

INTRODUCTION

The dopamine D4 receptor (DRD4) is a promising candidate gene in obsessive compulsive disorder (OCD). A 48-bp variable number of tandem repeats (VNTR) sequence in exon 3 has been studied previously, and alleles containing 2-11 repeats (2R-11R) have been identified. We investigated the association of DRD4 VNTR polymorphism with OCD and its relationship with various clinical parameters (age of onset, gender, family history, co-morbidity, factor-analyzed symptom dimensions and insight).

METHODOLOGY

One hundred and seventy three South Indian OCD patients (DSM-IV) recruited from a specialty OCD clinic were evaluated using the Yale-Brown obsessive compulsive scale (YBOCS), YBOCS item-11 for insight, Mini International Neuropsychiatric Interview (MINI) plus, tic disorder subsection of the MINI-KID and Clinical Global Impression scale. 201 healthy controls were evaluated using MINI plus. All subjects were genotyped for the DRD4 VNTR polymorphism.

RESULTS

Genotype frequencies did not deviate significantly from the Hardy-Weinberg equilibrium. Case-control association analysis revealed that the 7R allele frequency was significantly greater in OCD patients than controls. This difference was restricted to the women subsample when performing the gender sub-analysis. Among other clinical variables examined, factor 3 (symmetry) was associated with presence of 2R allele. Linear regression analysis confirmed the association of symmetry dimension with the 2R allele (Beta=0.23, t=2.96, p=0.004, CI=0.19-0.95).

CONCLUSIONS

Our data provides further evidence that DRD4 VNTR polymorphism is associated with OCD. Furthermore, the presence of the 2R allele was significantly associated with the symmetry dimension. This dimension may represent a more homogeneous subtype of OCD with a genetic etiology.

Anxiety and affective disorder comorbidity related to serotonin and other neurotransmitter systems: obsessive-compulsive disorder as an example of overlapping clinical and genetic heterogeneity

Individuals with obsessive-compulsive disorder (OCD) have also been shown to have comorbid lifetime diagnoses of major depressive disorder (MDD; rates greater than 70%), bipolar disorder (rates greater than 10%) and other anxiety disorders (e.g. panic disorder, post-traumatic stress disorder (PTSD)). In addition, overlap exists in some common genetic variants (e.g. the serotonin transporter gene (SLC6A4), the brain-derived neurotrophic factor (BDNF) gene), and rare variants in genes/chromosomal abnormalities (e.g. the 22q11 microdeletion syndrome) found across the affective/anxiety disorder spectrums. OCD has been proposed as a possible independent entity for DSM-5, but by others thought best retained as an anxiety disorder subtype (its current designation in DSM-IV), and yet by others considered best in the affective disorder spectrum. This review focuses on OCD, a well-studied but still puzzling heterogeneous disorder, regarding alterations in serotonergic, dopaminergic and glutamatergic neurotransmission in addition to other systems involved, and how related genes may be involved in the comorbidity of anxiety and affective disorders. OCD resembles disorders such as depression, in which gene × gene interactions, gene × environment interactions and stress elements coalesce to yield OC symptoms and, in some individuals, full-blown OCD with multiple comorbid disorders.

Dopamine-system genes, childhood abuse, and clinical manifestations in women with Bulimia-Spectrum Disorders

OBJECTIVE

We explored interaction effects involving polymorphisms of targeted dopamine system genes and selected forms of childhood abuse (sexual, physical and emotional) acting upon severity of binge-eating and psychopathological symptoms in women with Bulimia-Spectrum Disorders (BSDs).

METHODS

Women diagnosed with a BSD (n = 216) were assessed for childhood traumata, eating-disorder (ED) symptoms, and selected psychopathological features (sensation seeking, impulsivity, compulsivity and affective instability), and then provided blood samples for genotyping of main polymorphisms of dopamine-2 receptor (DRD2), dopamine transporter (DAT1) and catechol o-methyltransferase (COMT) genes.

RESULTS

Sensation Seeking was elevated in carriers of the low-function allele of the DRD2 Taq1A polymorphism who also reported childhood sexual abuse, relative to that in individuals showing other combinations of alleles and abuse exposures. In addition, carriers of a low-function allele of COMT scored higher on compulsivity, lower on impulsivity, and marginally lower on frequency of binge-eating than did individuals in whom the allele was absent.

DISCUSSION

Our results suggest that genes acting within the dopamine system may contribute, either directly or indirectly (i.e., in interaction with traumatic childhood experiences), to variations in the presentation of comorbid traits and, possibly, of bulimic symptoms.

Pilot study on HTR2A promoter polymorphism, -1438G/A (rs6311) and a nearby copy number variation showed association with onset and severity in early onset obsessive-compulsive disorder

A previous study showed that a single nucleotide polymorphism (SNP), -1438G/A (rs6311), found in the transcriptional control region of the gene that encodes the serotonin-receptor 2A (HTR2A) was associated with obsessive-compulsive disorder (OCD) in a sample of children and adolescents. In this study, we reanalyzed the association of this SNP with OCD in an enlarged population of 136 cases (55 previous + 81 new cases) and compared them to 106 newly recruited, healthy, age-matched controls. We also investigated whether this SNP or its copy number variations (CNV) was associated with OCD severity and age of onset. The CNV was analyzed in a DNA region located near rs6311. The results confirmed the association between the A-allele and early onset OCD in children and adolescents, with an odds ratio (OR) of 1.69 [95% CI (1.17, 2.46); p = 0.005]. Strikingly, we found that carriers of one copy (deletion) of the CNV were associated with a very early onset OCD (2.5 years earlier than the typical onset), and they had increased CY-BOCS scores (8.7 points higher compared to "normal" CNV and duplications); which is related to increased severity of OCD symptoms (p = 0.031; p = 0.004, respectively). Compared to the normal CNV and duplications, the association between the deletion and OCD showed an OR of 7.56 [95% CI (1.32, 142.84); p = 0.020]. These results pointed to the functional importance of this promoter region of HTR2A; it influenced the occurrence, the onset, and the severity of OCD.

Association of catechol-O-methyl transferase (COMT) gene -287A/G polymorphism with susceptibility to obsessive-compulsive disorder in Chinese Han population

Several studies suggested a genetic component in the etiology of obsessive-compulsive disorder (OCD). COMT involves in the degradation of dopamine and norepinephrin. As another functional SNP locus, COMT -287A/G polymorphism showed an effect on enzyme activity, suggesting that it may influence brain dopamine levels. To identify association of COMT -287A/G polymorphism with susceptibility to OCD in Chinese Han population. We evaluate the genetic contribution of the COMT -287A/G polymorphism in 200 OCD patients and 403 OCD-free control of Chinese Han population by PCR-RFLP. In addition, we investigate whether COMT -287A/G polymorphism is associated with one or more of these symptom dimensions or other characteristics such as sex, age of onset, and tic-relatedness and evaluate the association of the factorial structure of OCD symptoms from the Y-BOCS checklist with the COMT -287A/G polymorphism. A statistical difference was found in the genotypic frequencies of COMT -287A/G between the OCD and control groups (χ(2)  = 13.99, DF = 2, P = 0.00091) and in the genotypic frequencies of GG genotype versus AA and AG genotypes of COMT -287 (χ(2)  = 13.49, DF = 1, P = 0.00024, OR = 3.43, 95% CI = 1.78-6.62). There was a trend for an association in the genotypic distributions of COMT -287A/G polymorphism of males (χ(2)  = 27.81; DF = 2; P < 0.001) and females (χ(2)  = 7.31; DF = 2; P = 0.026) between the OCD patients and the controls. Using principal component analysis, we derived 5 factors from 12 main contents of OCD symptoms from the Y-BOCS checklist and found no association with COMT -287A/G polymorphism. Our study supports the involvement of the COMT -287A/G polymorphism in the genetic susceptibility to OCD in Chinese Han population.

Allele and genotype frequencies of serotonin and dopamine transporter and receptor polymorphisms in a Norwegian population

Polymorphisms in genes coding for dopaminergic and serotonergic receptors and transporters have been associated with the clinical effects and adverse drug reactions of antipsychotic and antidepressant drugs. The objective of this study was to investigate the frequency and combinations of common polymorphisms in the dopamine transporter (DAT1), dopamine D(2) receptor (DRD2), dopamine D(3) receptor (DRD3), serotonin transporter (5HTT), and serotonin 2A receptor (5HTR2A) genes in a Norwegian population. To determine the background frequency in the population, 250 blood samples were consecutively collected from healthy Norwegian blood donors (125 men and 125 women; mean age: 48±11 years). Samples were tested for DAT1 VNTR, DRD2 Taq1A, DRD3 Ser9Gly, 5HTTLPR, and four polymorphisms (102 T>C, His452Tyr, 516 C>T, and Thr25Asn) in the 5HTR2A, using polymerase chain reaction and real-time polymerase chain reaction. We observed the frequency of the nine-repeat allele of DAT1 VNTR polymorphism as 20% (95% confidence interval [CI]: 0.18-0.23), the A1 allele of DRD2 Taq1A polymorphism as 21% (95% CI: 0.19-0.23), the A1 allele of DRD3 Ser9Gly polymorphism as 68% (95% CI: 0.66-0.70), the short allele of 5HTTLPR as 38% (95% CI: 0.36-0.40), and the T allele of 5HTR2A 102 T>C polymorphism as 41% (95% CI: 0.39-0.41), and the frequencies of 5HTR2A His452Tyr and 5HTR2A Thr25Asn were 93% and 95%, respectively. The tested polymorphisms showed differences compared with other European populations. Further studies are necessary to better understand the effect of these alleles and their combinations on personality, mental disorders, drug response, and adverse reactions of psychotropic drugs.

The genetics of obsessive-compulsive disorder: a review

Obsessive-compulsive disorder (OCD) is a serious psychiatric disorder that affects approximately 2% of the populations of children and adults. Family aggregation studies have demonstrated that OCD is familial, and results from twin studies demonstrate that the familiality is due in part to genetic factors. Only three genome-wide linkage studies have been completed to date, with suggestive but not definitive results. In addition, over 80 candidate gene studies have been published. Most of these studies have focused on genes in the serotonergic and dopaminergic pathways. Unfortunately, none have achieved genome-wide significance, and, with the exception of the glutamate transporter gene, none have been replicated. Future research will require the collaboration of multidisciplinary teams of investigators to (i) achieve sufficiently large samples of individuals with OCD; (ii) apply the state-of-the-art laboratory techniques; and (iii) perform the bioinformatic analyses essential to the identification of risk loci.

The genetics of obsessive-compulsive disorder and Tourette syndrome: an epidemiological and pathway-based approach for gene discovery

OBJECTIVE

To provide a contemporary perspective on genetic discovery methods applied to obsessive-compulsive disorder (OCD) and Tourette syndrome (TS).

METHOD

A review of research trends in genetics research in OCD and TS is conducted, with emphasis on novel approaches.

RESULTS

Genome-wide association studies (GWAS) are now in progress in OCD and TS and will provide a platform for future discovery of common gene variants. Optimally, newer next-generation genome sequencing methods can also be used to detect larger effect genes (rare gene variants), taking advantage of pedigrees. Studies of gene networks or sets rather than individual genes will be required to elucidate biological etiology, as neural systems appear to act redundantly. Newer phenotyping strategies, such as symptom-based subtypes, cross-disorder latent class types, and intermediate phenotypes (endophenotypes) will need to be developed and tested to better align clinical and physiological measures with genetic architecture.

CONCLUSION

Although genetics research has made significant advances based on computational strength and bioinformatics advances, newer approaches to phenotyping and judicious study of gene etiological networks will be needed to uncover the genetic etiology of OCD and TS.

The Genetics of Obsessive-Compulsive Disorder

OCD is a psychiatric disorder with a lifetime prevalence of 1-3% and is a significant cause of disability worldwide. Family studies indicate that OCD has a significant hereditable component, with relatives of OCD cases being 4 times more likely to develop the disorder than the general population. Linkage studies in OCD have generally been underpowered and have failed to reach the statistical threshold for genome-wide significance, but they have nevertheless been useful for revealing potential regions of interest for future candidate gene studies. Candidate gene studies in OCD have thus far focused on genes involved in the serotonergic, dopaminergic, and glutamatergic pathways. These studies have been for the most part inconclusive, and failures to replicate have been the norm until very recently. The only genetic association replicated by multiple groups was with a glutamate transporter gene (SLC1A1). Genome-wide association studies in OCD are in progress, but final results have not yet been reported. As with the study of many other psychiatric disorders, an improved understanding of OCD will only be achieved (1) with larger collaborative efforts involving more probands, (2) the use of probands and controls drawn from epidemiologically-based populations rather than clinical samples, (3) developing a more precise phenotypic description of OCD and (4) measuring important environmental influences that affect OCD pathogenesis and severity.

Genetics of obsessive-compulsive disorder

Obsessive-compulsive disorder is a common debilitating condition affecting individuals from childhood through adult life. There is good evidence of genetic contribution to its etiology, but environmental risk factors also are likely to be involved. The condition probably has a complex pattern of inheritance. Molecular studies have identified several potentially relevant genes, but much additional research is needed to establish definitive causes of the condition.

Overview of genetics and obsessive-compulsive disorder

This paper reviews the current state of research into the genetics of obsessive-compulsive disorder (OCD). Heredity has a major role in OCD etiology. This evidence comes from several methodological approaches such as family, twin, and segregation analysis studies. A major single gene effect as well as a polygenic hypothesis has been suggested based on segregation studies. In addition, candidate gene association and linkage analyses have shown not only one gene, but a few interesting genes and areas of the genome that may be relevant in OCD. In this search for genes, new definitions of the OCD phenotype have emerged, and some of them may be considered intermediate phenotypes between the gene effect and OCD-DSM-IV diagnosis. The phenotypic and genetic heterogeneity of OCD magnifies the challenge of locating susceptibility genes; at the same time, the identification of vulnerability genes will elucidate the identification of subtypes or dimensions of the disorder. Therefore research strategies that take advantage of clinical subtyping and that redefine the OCD phenotype in the context of genetic studies may potentially contribute to the nosology of OCD and ultimately pathophysiology. There is a lack of understanding about how genes and environment interact in OCD. However, there are some reports that will be discussed, which have attempted to evaluate how the environment contributes to OCD.

Gender differences in genetic linkage and association on 11p15 in obsessive-compulsive disorder families

Several clinical and genetic studies have reported gender differences in obsessive-compulsive disorder (OCD). Previously, we conducted a linkage genome scan using multipoint allele-sharing methods to test for linkage in 219 families participating in the OCD Collaborative Genetics Study. When these families were stratified by proband's gender, suggestive linkage to chromosome 11p15 at marker D11S2362 (KAC(all) = 2.92, P = 0.00012) was detected in families with male probands, but not in the ones with female probands. We have since conducted fine mapping with a denser microsatellite marker panel in the region of 11p15, and detected a significant linkage signal at D11S4146 (KAC(all) = 5.08, P < 0.00001) in the families of male probands. Subsequently, 632 SNPs were genotyped spanning a 4.0 Mb region of the 1 LOD unit interval surrounding the linkage peak in the original families and an additional 165 families. Six SNPs were associated with OCD (P < 0.001): two SNPs were identified when all the families were included, and four SNPs only in male proband families. No SNP showed significant association with the OCD phenotype only in the families with a female proband. The results suggest a possible gender effect in the etiology of OCD.

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, serotonin's 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 serotonin's many important homeostatic functions in humans, non-human primates, mice and other species.

Association of dopamine transporter and monoamine oxidase molecular polymorphisms with sudden infant death syndrome and stillbirth: new insights into the serotonin hypothesis

Recent findings demonstrated the role of neurotransmitters in the aetiopathogenesis of sudden unexpected deaths in infancy. Although genes involved in serotonin metabolism have been proposed as risk factors for sudden infant death syndrome (SIDS), the contribution of additional neurotransmitters and genes different from the serotonin transporter (SLC6A4, 5-HTT) has not been investigated. Considering the common metabolic pathway and synergism between dopamine and serotonin, the role of dopamine transporter (SLC6A3, DAT) and monoamine oxidase A (MAOA) genes in SIDS and stillbirth (sudden intrauterine unexplained death, SIUD) was investigated. Genotypes and allelic frequencies of DAT and MAOA were determined in 20 SIDS and five stillbirth cases and compared with 150 controls. No association was found between DAT polymorphisms and SIDS either at genotype (P = 0.64) or allelic (P = 0.86) level; however, a highly significant association was found between MAOA genotypes (P = 0.047) and alleles (P = 0.002) regulating different expression patterns (3R/3R vs 3.5R/3.5R + 4R/4R) in SIDS + SIUD and controls. Analysis of combined 5-HTTLPR (serotonin transporter linked polymorphic region)/MAOA genotypes revealed that frequency of L/L-4R/4R genotype combination was eightfold higher in SIDS + SIUD than in controls (P < 0.001). Findings are discussed considering the metabolic association among DAT, 5-HTT and MAOA with special emphasis on the linked action of 5-HTT/MAOA in regulating serotonin metabolism of SIDS and SIUD infants.

SERT Ileu425Val in autism, Asperger syndrome and obsessive-compulsive disorder

BACKGROUND

SERT I425V, an uncommon missense single nucleotide polymorphism producing a gain-of-function of the serotonin transporter (SERT), was originally found to segregate with a primarily obsessive-compulsive disorder (OCD) but complexly comorbid phenotype in two unrelated families.

OBJECTIVE

As two individuals with SERT I425V and OCD also had Asperger syndrome (AS), an autism spectrum disorder, and as other rare SERT variants have recently shown significant associations with autism, we set out to extend our original OCD study by genotyping additional autism/AS and OCD samples.

METHODS

Case-control association study of SERT I425V in 210 AS/autism probands and 215 controls, plus 335 OCD probands and their family members.

RESULTS

SERT I425V was not found in any of the individuals with AS/autism, OCD alone or OCD comorbid with AS and other disorders, or in controls. This results in new estimates of SERT I425V having a 1.5% prevalence in 530 individuals with OCD from five unrelated families genotyped by us and by one other group and a 0.23% frequency in four control populations totaling 1300 individuals, yielding a continuing significant OCD-control difference (Fisher's exact test corrected for family coefficient of identity P=0.004, odds ratio=6.54).

CONCLUSION

As several other uncommon, less well quantitated genetic variations occur with an OCD phenotype, including chromosomal anomalies and some other rare gene variants (SGCE, GCH1 and SLITRK1), a tentative conclusion is that OCD resembles other complex disorders in being etiologically heterogeneous and in having both highly penetrant familial subtypes associated with rare alleles or chromosomal anomalies, as well as having a more common, polygenetic form that may involve polymorphisms in such genes as BDNF, COMT, GRIN2beta, TPH2, HTR2A and SLC1A1.

Transmission disequilibrium studies in early onset of obsessive-compulsive disorder for polymorphisms in genes of the dopaminergic system

The dopaminergic system has been shown to be involved in the aetiology of obsessive-compulsive disorder (OCD). Family studies suggest a higher genetic loading in patients with early onset OCD. Our investigation is the first family-based association study concerning polymorphisms in genes of the dopaminergic system in early onset OCD. We studied polymorphisms within the dopamine-4 receptor gene (DRD4), the dopamine transporter gene (DAT1) and the catecholamine-O-methyltransferase gene (COMT). Associations of alleles of DRD4 and COMT with OCD have previously been reported in adults, while a trend towards an association was found for DAT1 alleles. In our study we observed transmission disequilibrium for the 48-bp repeat polymorphism of the DRD4 gene using the ETDT (P=0.047) in 69 trios comprising patients with early onset OCD and both of their parents. Post hoc TDT analysis of the DRD4 showed reduced transmission of the 4-repeat allele and a slightly increased transmission rate for the 7- and the 2-repeat allele. No evidence of transmission disequilibrium was detected for alleles of the DAT1 and COMT polymorphisms. These polymorphisms do not appear to play a major role in the genetic predisposition to early onset OCD in our study group.

Association study between obsessive-compulsive disorder and serotonergic candidate genes

BACKGROUND

To date, research examining the relationship between serotonergic genes and obsessive-compulsive disorder (OCD) has yielded conflicting results. The purpose of this study is to investigate the association between four serotonergic polymorphisms (STin2 VNTR and 5-HTTLPR of the SLC6A4 gene, and A-1438G (rs6311) and T102C (rs6313) of the HTR2A gene) and OCD.

METHODS

99 OCD patients, 456 non-OCD psychiatric patients, and 420 healthy controls from a homogeneous Spanish Caucasian population were genotyped using standard methods.

RESULTS

All groups showed Hardy-Weinberg equilibrium for the analyzed genetic variability. A-1438G and T102C polymorphisms were in complete linkage disequilibrium. OCD patients showed an excess of STin2.12 carriers (12/12, 12/10, and 12/9 genotypes) compared with healthy controls (chi(2) (1)=7.21, corrected p=0.021; OR=3.38, 95% CI=1.32-8.62) and non-OCD psychiatric patients (chi(2) (1)=6.70, corrected p=0.030; OR=3.24, 95% CI=1.27-8.26). However, no differences were found between non-OCD patients and healthy controls (chi(2) (1)=0.05, corrected p>1; OR=1.04, 95% CI=0.72-1.51). No significant differences were found with respect to A-1438G and 5-HTTLPR polymorphisms.

CONCLUSIONS

Our data provide supporting evidence of an association between the STin2 VNTR polymorphism of the SLC6A4 gene and OCD.

Investigating the possible effects of trauma experiences and 5-HTT on the dissociative experiences of patients with OCD using path analysis and multiple regression

Dissociation is defined as the disruption of the usually integrated functions of consciousness, such as memory, identity, and perceptions of the environment. Causes include various psychological, neurological and neurobiological mechanisms, none of which have been consistently supported. To our knowledge, the role of gene-environment interactions in dissociative experiences in obsessive-compulsive disorder (OCD) has not previously been investigated. Eighty-three Caucasian patients (29 male, 54 female) with a principal diagnosis of OCD were included. The Dissociative Experiences Scale was used to assess dissociation. The role of childhood trauma (assessed with the Childhood Trauma Questionnaire), and a functional 44-bp insertion/deletion polymorphism in the promoter region of the serotonin transporter, or 5-HTT, in mediating dissociation, was investigated using multiple regression analysis and path analysis using the partial least squares model. Both analyses indicated that an interaction between physical neglect and the S/S genotype of the 5-HTT gene significantly predicted dissociation in patients with OCD. Dissociation may be a predictor of poorer treatment outcome in patients with OCD; therefore, a better understanding of the mechanisms that underlie this phenomenon may be useful. Here, two different but related statistical techniques (multiple regression and partial least squares), confirmed that physical neglect and the 5-HTT genotype jointly play a role in predicting dissociation in OCD.

Renner T, Wewetzer C, Warnke A. Genetische Befunde bei Zwangsstörungen im Kindes- und Jugendalter und bei Erwachsenen

Zusammenfassung: Im Kindes- und Jugendalter sind Zwangsstörungen bei einer Inzidenz von ein bis zwei Prozent keine Seltenheit und können die Betroffenen in ihrer Entwicklung deutlich beeinträchtigen. Die Erkrankung ist durch wiederkehrende und anhaltende Verhaltensweisen, Gedanken und Impulse gekennzeichnet, die als quälend erlebt werden und sich je nach Entwicklungstand gegen inneren Widerstand aufdrängen und vom Patienten als unsinnig und übertrieben wahrgenommen werden. Die Entstehung von Zwangsstörungen hängt sowohl von Umweltfaktoren, nicht genetischen hirnpathologischen als auch von genetischen Einflussfaktoren ab. Die Mehrheit der bisherigen Ergebnisse bezieht sich dabei auf Untersuchungen im Erwachsenenalter. Es wird eine aktuelle Übersicht über genetische Befunde bei Zwangsstörungen unter besonderer Berücksichtigung des Kindes- und Jugendalters gegeben. Bei jung erkrankten Patienten findet sich eine deutlichere familiäre Belastung. Befunde aus Kopplungs- und Assoziationsstudien sowie Tiermodellen werden vorgestellt und diskutiert. Die phänotypische und genetische Heterogenität von Zwangsstörungen trägt zu den unterschiedlichen Studienergebnissen bei und erfordert für künftige Untersuchungen die Differenzierung von Subtypen, z.B. die Einbeziehung des Alters bei Erkrankungsbeginn, von Symptomdimensionen, geschlechtlichen Besonderheiten und komorbider Störungen.

Association analysis between a VNTR intron 8 polymorphism of the dopamine transporter gene (SLC6A3) and obsessive- compulsive disorder in a Brazilian sample

Family, twin and segregation analysis have provided evidences that genetic factors are implicated in the susceptibility for obsessive-compulsive disorder (OCD). Several lines of research suggest that the dopaminergic system may be involved in the pathophysiology of OCD. Thus, the aim of the present study was to investigate a possible association between a polymorphism located in intron 8 of the dopamine transporter gene (SLC6A3) and OCD in a Brazilian sample composed by 208 patients and 865 healthy controls. No statistically differences were observed in allelic and genotype distributions between cases and controls. No association was also observed when the sample was divided according to specific phenotypic features such as gender, presence of tic disorders co-morbidity and age at onset of obsessive-compulsive symptoms (OCS). Our results suggest that the intron 8 VNTR of the SLC6A3 investigated in this study is not related to the susceptibility for OCD in our Brazilian sample.

Hyperkalemia and hyperdopaminemia induced by an obsessive eating of banana in an anorexia nervosa adolescent

Banana is known as a dopamine-rich and potassium-rich food, however no previous data regarding biochemical or psychological alteration induced by excess intake of banana has been reported. We have experienced an adolescent female case of Anorexia nervosa (AN) who denied eating anything but maximum 20 bananas and less than 500 ml mineral water per day for more than two years. During the period of massive banana eating habit, she showed increase of serum potassium (from 4.7 mEq/l to 6.1 mEq/l) and whole blood dopamine (from 11 ng/ml to 210 ng/ml; normal range 0.5-6.2 ng/ml), and obvious dysthymia that is inexplicable only by the pathology of AN. When the patient resumed other food ingestion after 26 months of obsessive and restricted eating of banana, the abnormalities in her blood data and her psychological state were all corrected toward normal. We conclude that in this case, the obsessive and restricted habit of banana ingestion resulted in hyperkalemia, hyperdopaminemia, and psychological change.

Association studies of serotonin system candidate genes in early-onset obsessive-compulsive disorder

BACKGROUND

Family-based evidence for association at serotonin system genes SLC6A4, HTR1B, HTR2A, and brain-derived neurotrophic factor (BDNF) has been previously reported in obsessive-compulsive disorder (OCD). Early-onset OCD is a more familial form of the disorder.

METHODS

We used the transmission-disequilibrium test of association at common polymorphisms in each of these genes in 54 parent-child trios ascertained through probands with early-onset OCD.

RESULTS

No evidence for association was detected at any of the polymorphisms in the entire set of subjects. Nominally significant association was found at the HTR2A rs6311 polymorphism in subjects with tic disorder and OCD (p = .05), replicating a previous finding in Tourette syndrome and OCD. Nominally significant association was also found for the SLC6A4 HT transporter gene-linked polymorphic region (5-HTTLPR) polymorphism for female subjects (p = .03). Neither association would remain significant after statistical correction for multiple testing. Despite no individual study reporting replication, a pooled analysis of five replication studies of the SLC6A4 5-HTTLPR polymorphism supports association (p = .02).

CONCLUSIONS

Low power across individual association studies in OCD may lead to a false acceptance of the null hypothesis. Accumulation of evidence from multiple studies will be necessary to evaluate the potential role for these genes in contributing to susceptibility to OCD.

The genetic studies of obsessive-compulsive disorder and its future directions

Obsessive-compulsive disorder (OCD) is characterized by recurrent and persistent thoughts (obsessions), and repetitive behaviors or mental acts (compulsions). In Korea, an epidemiological study reported that the lifetime prevalence of OCD in the population was greater than two percent. The exact cause of OCD is still unknown. Evidence from familial, twin and segregation studies supports the role of a genetic component in the etiology of OCD. In addition, there is growing evidence that OCD has a specific neurochemical and neuroanatomical basis. According to this evidence, researchers have selected various candidate genes which have been implicated in the neurophysiology of OCD, and differences of allelic variants in OCD patients and controls have been analyzed. In this review we will introduce the results of previous genetic studies of OCD which have been performed in other populations, including twin studies, family studies, segregation analyses, linkage analyses, and association studies. In addition to these studies, we will present the results of our genetic studies of OCD performed in Korea.

The current status of association studies in obsessive-compulsive disorder

During the last 2 decades, a large number of association studies have been dedicated to disentangling the genetic components that may be involved in the etiology of OCD. The preliminary and frequently in consistent nature of the data represented in the majority of OCD psychiatric genetic-association studies may seem discouraging. Failure to replicate, and thus to confirm, previously identified susceptibility loci could result from a number of reasons, including the potential for population admixture, the clinical heterogeneity of OCD, small sample sizes (and subsequent lack of power),publication bias, epistasis, or failure to account for multiple testing. Various methods of accounting for these confounders do exist and should be implemented in any genetic-association study that is to be regarded as robust and replicable. Discrepancy between results, however, might be ascribed to the underlying genetic differences between the populations in the respective studies (ie, the investigated variant may be in linkage disequilibrium with the causal variant in one population but not in another). Such discrepancies are difficult to reconcile in single-locus association studies; haplotype analyses(in which a number of variants, usually single-nucleotide polymorphisms occurring on the same gene, are analyzed as a unit) may be able to resolve these uncertainties. Investigating epistatic interactions between variants in other genes that might be involved in the same physiologic pathways would be an alternative means of deciphering the reason for discrepant genetic association results.A valid means of increasing the power (by reducing background noise)would be to stratify the patient sample according to clinically defined sub-types, such as obsession and compulsion subtypes, age at onset of the disorder, and severity of the disorder. Although many of the OCD genetics studies have incorporated investigations of these subtypes [65,66,68,77,84-86,89,107,118,132,133,145,148,149], the number of subjects decreases after stratification, thereby limiting the power of the studies. It may therefore be useful to employ other quantitative approaches in the design of the investigation: the possibility should be considered that OCD symptoms can be broken down into multiple dimensions that are continuous with the normal population [150]. This division would represent an important route to disentangling the complex inheritance of OCD. The results obtained from genetic investigations should be incorporated with clinical and epidemiologic parameters to elucidate correctly the cause of OCD. Future studies should also be extended to incorporate the screening of more polymorphisms, because high-resolution mapping within specific chromosomes will improve knowledge regarding the impact of genetic diversity within the genes or linked chromosomal regions in OCD. The advantages ofa gene-based over a single-nucleotide polymorphism based approach are becoming ever more apparent [151]. Therefore, a more complete assessment of candidate genes, possibly using haplotype blocks that span larger regions,is proposed. In addition, increasing the amount of information on human genome sequences and polymorphisms will make it possible to characterize the amount of sequence variation expressed in the brain and to delineate the potential effects that these variations may have on the development of OCD. Knowledge of new functional variants will emerge as researchers gain an understanding of the potential for genetic variants in the coding and regulatory regions to impact gene expression.

Isolated eyebrow and eyelash trichotillomania mimicking alopecia areata

BACKGROUND

Isolated Trichotillomania (TM) of the eyebrows and eyelashes is occasionally seen and may be mistaken for alopecia areata (AA).

OBJECTIVE

The clinical study of the patients with isolated eyebrows and eyelashes alopecia suggesting of TM.

PATIENTS AND METHOD

Seven children and young adult patients who referred with recalcitrant eyebrows and eyelashes alopecia were diagnosed as TM based on the clinical criteria for TM. The hair specifications for TM were include: hairs are broken at different levels, they may be tufted, tortuous and some hair fibers may be abnormally longer than others. The hair follicles may be prominent. The patients and their parents studied for psychopathology using a semistructured interview based on the Diagnostic Statistical manual of Psychiatric disorders (DSM-1V) and maudsley inventory.

RESULTS

Our clinical study, interview with the patients and their parents and the clinical criteria used to differentiate TM from AA all support the clinical diagnosis of TM. The patients and their parents mainly suffered from obsessive-compulsive disorders (OCD) and obsessive-compulsive spectrum disorders (OCSDs).

CONCLUSION

TM as a hair pulling habit in patients with underlying psychopathology can be considered in cases with isolated eyebrows and eyelashes alopecia when the hair are broken at different levels. And they may be malaligned, nonuniform, tortuous, and tufted.

Risk factors for extrapyramidal symptoms during treatment with selective serotonin reuptake inhibitors, including cytochrome P-450 enzyme, and serotonin and dopamine transporter and receptor polymorphisms

INTRODUCTION

Extrapyramidal symptoms (EPS) are rare adverse drug reactions to selective serotonin reuptake inhibitors (SSRIs). This study aimed to investigate the potential risk factors for EPS associated with SSRIs including polymorphisms of cytochrome P-450 isoenzymes, and serotonin and dopamine transporters and receptors.

METHODS

All spontaneous adverse drug reaction reports received by the Swedish Medical Products Agency until December 1999 that were coded with EPS and judged to be at least possibly related to SSRI treatment were included in the study. Reporting physicians received a form for collection of relevant information including current and previous use of SSRIs and antipsychotics, alcohol or substance abuse, central nervous system damage, a history of epilepsy or EPS, and a family history of Parkinson disease. A blood sample was also requested for genotyping of selected cytochrome P-450, and serotonin and dopamine transporter and receptor mutations.

RESULTS

A total of 64 cases of EPS were reported. Twenty-eight forms (46%) were returned, and 20 blood samples were obtained. Identified potential risk factors included age of 65 years or older and the presence of the A1 allele of the D2 dopamine receptor gene (DRD2) Taq1A polymorphism (relative risk, 2.4; 95% confidence interval, 1.2-4.5 vs literature controls). No relationship was apparent for sex, drug dose, or other genetic polymorphisms. At least 1 additional potential risk factor for EPS, such as a history of central nervous system damage, alcohol or substance abuse, epilepsy, Parkinson disease, previous or current exposure to antipsychotic drugs, concomitant treatment with other antidopaminergic or serotonergic agents, or a history of EPS, was found in 93% of the cases.

CONCLUSION

The risk of EPS with SSRIs seems to increase with advanced age and with the presence of the A1 allele of DRD2 Taq1A polymorphism. Because of the small sample size of our study and the use of historical controls rather than patients who did not experience EPS during SSRIs treatment, the DRD2 finding is preliminary and needs to be replicated in other studies before firm conclusions can be drawn. At least 1 additional potential risk factor was found in almost all cases.

Estudos de associação entre transtorno obsessivo-compulsivo e genes candidatos: uma revisão

OBJETIVO: Nos últimos anos, o papel dos genes dos sistemas serotoninérgicos e dopaminérgicos tem sido sistematicamente investigado em pacientes com transtorno obsessivo-compulsivo (TOC), uma vez que esses neurotransmissores apresentam uma provável implicação na fisiopatologia do TOC. Este artigo objetiva revisar os principais resultados de estudos de associação entre genes candidatos e TOC. MÉTODOS: Revisão da literatura na base de dados Medline até agosto de 2006, utilizando as palavras-chave obsessive-compulsive disorder (OCD) e/ou gene(s), polymorphism(s), genetics. RESULTADOS: Inúmeros estudos têm apresentado resultados negativos ao compararem pacientes com TOC e controles, entretanto resultados positivos têm sido observados em pacientes com TOC com características clínicas particulares (sexo, idade de início, dimensão ou gravidade dos sintomas obsessivos ou compulsivos e presença de tiques). CONCLUSÃO: Para garantir a continuidade do avanço de estudos genéticos, é necessária a identificação de subgrupos homogêneos de pacientes com TOC. Diante desses grupos, será possível delinear endofenótipos confiáveis que permitam explorar de forma mais específica a contribuição dos diferentes genes na patogênese da doença.

The serotonin-1Dbeta receptor gene and severity of obsessive-compulsive disorder in women with bulimia nervosa

BACKGROUND

There is significant evidence that eating disorders have an important biological overlap with obsessive-compulsive disorder (OCD), though the specific mediators of this relationship remain unclear. Recent evidence suggests that the G861C polymorphism of the 5HT-1Dbeta receptor gene and the G allele in particular may play a role in OCD. We thus hypothesized that, among a heterogenous group of probands with bulimia nervosa (BN), this same G allele might predict the presence and/or severity of OCD pathology.

METHODS

165 consecutive female probands with BN were genotyped for the G861C polymorphism of the 5HT-1Dbeta receptor gene. Rates of full syndrome OCD, partial syndrome OCD and no OCD were compared across the three genotypic groups defined by this polymorphism.

RESULTS

45 out of 165 BN probands (27.3%) had either full or partial syndrome OCD. In the full sample, there was a significant difference in the distribution of the three diagnostic groups by genotype (chi2=10.07, df=4, p=.039). The G861C polymorphism did not strongly predict which probands had any vs. no OCD pathology. However, among the 45 probands with OCD symptoms, the G861C polymorphism did strongly differentiate full syndrome vs. partial syndrome OCD (chi2=9.26, df=2, p=.01; odds ratio for full syndrome OCD with GG genotype=7.69, 95% CI=1.45-40.9).

DISCUSSION

In women with BN, the G861C polymorphism of the 5HT-1Dbeta gene does not appear to be associated with the generation of OCD symptoms; however, it might directly or indirectly be associated with a modulatory effect on syndrome severity in probands otherwise predisposed to OCD. While preliminary and in need of replication in other samples, this is the first association study to suggest how a particular gene might influence OCD pathology in an eating disorder population.

Serotonin and dopamine transporter imaging in patients with obsessive-compulsive disorder

In obsessive-compulsive disorder (OCD), the success of pharmacological treatment with serotonin re-uptake inhibitors and atypical antipsychotic drugs suggests that both the central serotonergic and dopaminergic systems are involved in the pathophysiology of the disorder. We applied [123I]-2beta-carbomethoxy-3beta-(4-idiophenyl)tropane (beta-CIT) and a brain-dedicated high-resolution single photon emission computed tomography (SPECT) system to quantify dopamine transporter (DAT) and serotonin transporter (SERT) availability. By comparing 15 drug-naïve patients with OCD and 10 controls, we found a significantly reduced availability (corrected for age) of striatal DAT and of thalamic/hypothalamic, midbrain and brainstem SERT in OCD patients. Severity of OCD symptoms showed a significant negative correlation with thalamic/hypothalamic SERT availability, corrected for age and duration of symptoms. Our data provide evidence for imbalanced monoaminergic neurotransmitter modulation in OCD. Further studies with more selective DAT and SERT radiotracers are needed.

Prefrontal serotonin depletion affects reversal learning but not attentional set shifting

Recently, we have shown that serotonin (5-HT) depletion from the prefrontal cortex (PFC) of the marmoset monkey impairs performance on a serial discrimination reversal (SDR) task, resulting in perseverative responding to the previously correct stimulus (Clarke et al., 2004). This pattern of impairment is just one example of inflexible responding seen after damage to the PFC, with performance on the SDR task being dependent on the integrity of the orbitofrontal cortex. However, the contribution of 5-HT to other forms of flexible responding, such as attentional set shifting, an ability dependent on lateral PFC (Dias et al., 1996a), is unknown. The present study addresses this issue by examining the effects of 5,7-dihydroxytryptamine-induced PFC 5-HT depletions on the ability to shift attention between two perceptual dimensions of a compound visual stimulus (extradimensional shift). Monkeys with selective PFC 5-HT lesions, despite being impaired in their ability to reverse a stimulus-reward association, were unimpaired in their ability to make an extradimensional shift when compared with sham-operated controls. These findings suggest that 5-HT is critical for flexible responding at the level of changing stimulus-reward contingencies but is not essential for the higher-order shifting of attentional set. Thus, psychological functions dependent on different loci within the PFC are differentially sensitive to serotonergic modulation, a finding of relevance to our understanding of cognitive inflexibility apparent in disorders such as obsessive-compulsive disorder and schizophrenia.

Psychostimulant-induced behavior as an animal model of obsessive-compulsive disorder: an ethological approach to the form of compulsive rituals

Rats treated chronically with the D2/D3 dopamine receptor agonist quinpirole show a pattern of behavior that meets a set of ethologically derived criteria of compulsive behavior in obsessive-compulsive disorder (OCD). Moreover, in both quinpirole-treated rats and OCD patients, the structure of compulsive rituals appear similar in being composed of relatively few motor acts that are organized in a flexible yet recurrent manner. In addition, the development of compulsive behavior in quinpirole-treated rats is attenuated by the OCD pharmacotherapeutic drug clomipramine. These similarities support the validity of quinpirole-treated rats as a psychostimulant-induced animal model of OCD. Considering that the induction of compulsive behavior in the rat model involves chronic hyperstimulation of dopamine receptors, this raises the possibility that dopaminergic mechanisms may play a role in OCD, at least in some subtypes of this disorder.

Cluster analysis of obsessive-compulsive spectrum disorders in patients with obsessive-compulsive disorder: clinical and genetic correlates

BACKGROUND

Comorbidity of certain obsessive-compulsive spectrum disorders (OCSDs; such as Tourette's disorder) in obsessive-compulsive disorder (OCD) may serve to define important OCD subtypes characterized by differing phenomenology and neurobiological mechanisms. Comorbidity of the putative OCSDs in OCD has, however, not often been systematically investigated.

METHODS

The Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition , Axis I Disorders-Patient Version as well as a Structured Clinical Interview for Putative OCSDs (SCID-OCSD) were administered to 210 adult patients with OCD (N = 210, 102 men and 108 women; mean age, 35.7 +/- 13.3). A subset of Caucasian subjects (with OCD, n = 171; control subjects, n = 168), including subjects from the genetically homogeneous Afrikaner population (with OCD, n = 77; control subjects, n = 144), was genotyped for polymorphisms in genes involved in monoamine function. Because the items of the SCID-OCSD are binary (present/absent), a cluster analysis (Ward's method) using the items of SCID-OCSD was conducted. The association of identified clusters with demographic variables (age, gender), clinical variables (age of onset, obsessive-compulsive symptom severity and dimensions, level of insight, temperament/character, treatment response), and monoaminergic genotypes was examined.

RESULTS

Cluster analysis of the OCSDs in our sample of patients with OCD identified 3 separate clusters at a 1.1 linkage distance level. The 3 clusters were named as follows: (1) "reward deficiency" (including trichotillomania, Tourette's disorder, pathological gambling, and hypersexual disorder), (2) "impulsivity" (including compulsive shopping, kleptomania, eating disorders, self-injury, and intermittent explosive disorder), and (3) "somatic" (including body dysmorphic disorder and hypochondriasis). Several significant associations were found between cluster scores and other variables; for example, cluster I scores were associated with earlier age of onset of OCD and the presence of tics, cluster II scores were associated with female gender and childhood emotional abuse, and cluster III scores were associated with less insight and with somatic obsessions and compulsions. However, none of these clusters were associated with any particular genetic variant.

CONCLUSION

Analysis of comorbid OCSDs in OCD suggested that these lie on a number of different dimensions. These dimensions are partially consistent with previous theoretical approaches taken toward classifying OCD spectrum disorders. The lack of genetic validation of these clusters in the present study may indicate the involvement of other, as yet untested, genes. Further genetic and cluster analyses of comorbid OCSDs in OCD may ultimately contribute to a better delineation of OCD endophenotypes.

Genetic epidemiology of anxiety disorders

This chapter reviews the genetic epidemiology of the major subtypes of anxiety disorders including panic disorder, phobic disorders, generalized anxiety disorder, and obsessive-compulsive disorder. Controlled family studies reveal that all of these anxiety subtypes are familial, and twin studies suggest that the familial aggregation is attributable in part to genetic factors. Panic disorder and, its spectrum have the strongest magnitude of familial clustering and genetic underpinnings. Studies of offspring of parents with anxiety disorders an increased risk of mood and anxiety disorders, but there is far less specificity of the manifestations of anxiety in children and young adolescents. Although there has been a plethora of studies designed to identify genes underlying these conditions, to date, no specific genetic loci have been identified and replicated in independent samples.