Pawel Kapelski

The DTNBP1 (Dysbindin) Gene Contributes to Schizophrenia, Depending on Family History of the Disease

We have investigated the gene for dystrobrevin-binding protein 1 (DTNBP1), or dysbindin, which has been strongly suggested as a positional candidate gene for schizophrenia, in three samples of subjects with schizophrenia and unaffected control subjects of German (418 cases, 285 controls), Polish (294 cases, 113 controls), and Swedish (142 cases, 272 controls) descent. We analyzed five single-nucleotide polymorphisms (P1635, P1325, P1320, P1757, and P1578) and identified significant evidence of association in the Swedish sample but not in those from Germany or Poland. The results in the Swedish sample became even more significant after a separate analysis of those cases with a positive family history of schizophrenia, in whom the five-marker haplotype A-C-A-T-T showed a P value of.00009 (3.1% in controls, 17.8% in cases; OR 6.75; P=.00153 after Bonferroni correction). Our results suggest that genetic variation in the dysbindin gene is particularly involved in the development of schizophrenia in cases with a familial loading of the disease. This would also explain the difficulty of replicating this association in consecutively ascertained case-control samples, which usually comprise only a small proportion of subjects with a family history of disease.

Prefrontal cognition in schizophrenia and bipolar illness in relation to Val66Met polymorphism of the brain-derived neurotrophic factor gene

Abstract  The measures of prefrontal cognition have been used as endophenotype in molecular‐genetic studies. Brain‐derived neurotrophic factor (BDNF) has been implicated in cognitive functions and in the pathogenesis of major psychoses. This study investigates the relationship between Val66Met polymorphisms of the BDNF gene and prefrontal cognitive function in 129 patients with schizophrenia and 111 patients with bipolar mood disorder. Cognitive tests included the Wisconsin Card Sorting Test (WCST), with such domains as number of perseverative errors, non‐perseverative errors, completed corrected categories, conceptual level responses, and set to the first category, and the N‐back test, where mean reaction time and percent of correct reactions were measured. Genotyping for Val66Met BDNF polymorphism was done by polymerase chain reaction method. In schizophrenia, no relationship between Val66Met polymorphism of the BDNF gene and the results of the WCST was observed. Patients with Val/Val genotype had a higher percentage of correct reactions in the N‐back test than those with the remaining genotypes. Bipolar patients with Val/Val genotype obtained significantly better results on three of five domains of the WCST. No relationship between BDNF polymorphism and the results of the N‐back test was found in this group. A limitation to the results could be variable psychopathological state and medication during cognitive testing and lack of Hardy–Weinberg equilibrium in schizophrenia group. Val66Met polymorphism of the BDNF gene may be associated with cognitive performance on the WCST in bipolar mood disorder but not in schizophrenia. An association of this polymorphism with performance on the N‐back test in schizophrenia and not in bipolar illness may suggest that in schizophrenia, the BDNF system may be connected with early phases of information processing.

Association analysis of brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism in schizophrenia and bipolar affective disorder

Summary Brain-derived neurotrophic factor (BDNF) has been implicated in the pathogenesis of schizophrenia and bipolar disorder. A functional polymorphism Val66Met of BDNF gene was studied in patients with schizophrenia (n=336), bipolar affective disorder (n=352) and healthy controls (n=375). Consensus diagnosis by at least two psychiatrists, according to DSM-IV and ICD-10 criteria, was made for each patient using a structured clinical interview for DSM-IV Axis I disorders (SCID). No association was found between the studied polymorphism and schizophrenia or bipolar affective disorder either for genotype or allele distribution (for genotype: p=0.210 in schizophrenia, p=0.400 in bipolar disorder; for alleles: p=0.260 in schizophrenia, p=0.406 in bipolar disorder). Results were also not significant when analysed by gender. For males genotype distribution and allele frequency were (respectively): p=0.480 and p=0.312 in schizophrenia, p=0.819 and p=0.673 in bipolar affective disorder. Genotype distribution and allele frequency observed in the female group were: p=0.258 for genotypes, p=0.482 for alleles in schizophrenia; p=0.432 for genotypes, p=0.464 for alleles in bipolar affective disorder. A subgroup of schizophrenic (n=62) and bipolar affective patients (n=28) with early age at onset (18 years or younger) was analysed (p=0.328 for genotypes, p=0.253 for alleles in schizophrenia; p=0.032 for genotypes, p=0.858 for alleles in bipolar affective disorder).

Genetic Predictors of Increase in Suicidal Ideation During Antidepressant Treatment in the GENDEP Project

The aim of this study was to investigate genetic predictors of an increase in suicidal ideation during treatment with a selective serotonin reuptake inhibitor or a tricyclic antidepressant. A total of 796 adult patients with major depressive disorder who were treated with a flexible dosage of escitalopram or nortriptyline in Genome-based Therapeutic Drugs for Depression (GENDEP) were included in the sample and provided data on suicidal ideation. Nine candidate genes involved in neurotrophic, serotonergic, and noradrenergic pathways were selected based on previous association studies with suicidal ideation or behavior. Using a logistic regression model, 123 polymorphisms in these genes were compared between subjects with an increase in suicidal ideation and those without any increase in suicidal ideation. Polymorphisms in BDNF, the gene encoding the brain-derived neurotrophic factor, were significantly associated with an increase in suicidal ideation. The strongest association was observed for rs962369 in BDNF (p=0.0015). Moreover, a significant interaction was found between variants in BDNF and NTRK2, the gene encoding the BNDF receptor (p=0.0003). Among men taking nortriptyline, suicidality was also associated with rs11195419 SNP in the alpha2A-adrenergic receptor gene (ADRA2A) (p=0.007). The associations observed with polymorphisms in BDNF suggest the involvement of the neurotrophic system in vulnerability to suicidality. Epistasis between BDNF and NTRK2 suggests that genetic variations in the two genes are involved in the same causal mechanisms leading to suicidality during antidepressant treatment. Among men, genetic variation in noradrenergic signaling may interact with norepinephrine reuptake-inhibiting antidepressants, thereby contributing to suicidality.

Association Analysis of the GSK-3β T–50C Gene Polymorphism with Schizophrenia and Bipolar Disorder

Glycogen synthase kinase-3β (GSK-3β) has been implicated in the pathogenesis of major psychoses. In this paper, the T–50C polymorphism of the GSK-3β gene has been studied in patients with schizophrenia (n = 432), patients with bipolar disorder (n = 416) and in a healthy control group (n = 408). Consensus diagnosis by at least two psychiatrists was made for each patient, according to DSM-IV and ICD-10 criteria, using the Structured Clinical Interview for DSM-IV Axis I Disorders. Genotypes were established by the polymerase chain reaction-restriction fragment length polymorphism method. We have found a trend towards an association for the C allele in the whole group of schizophrenic patients (p = 0.088) and for the heterozygous T/C genotype of bipolar patients (0.095). Significant differences of genotype distribution and allele frequencies of the T–50C polymorphism were found in the female group of bipolar II patients (p = 0.015 for genotypes and p = 0.009 for alleles). In conclusion, this polymorphism may be associated with female gender in bipolar II disorder.

Dopamine receptor D1 gene -48A/G polymorphism is associated with bipolar illness but not with schizophrenia in a Polish population.

Dysregulation of dopaminergic neurotransmission has been implicated in the etiology of major psychoses. The dopamine D1 receptor (DRD1) plays a role in some brain functions and mechanisms of psychotropic drugs. Therefore, the DRD1 gene makes a good candidate gene for molecular genetic studies in schizophrenia and bipolar affective disorder. In the present study, the –48A/G polymorphism of the DRD1 gene was estimated in patients with schizophrenia (n = 407) or bipolar affective disorder (n = 380), and in healthy controls (n = 399). No association was found between the polymorphism studied and schizophrenia, either in the whole group of patients or in subgroups divided by gender, age at onset or predominance of positive or negative symptoms. A statistical trend was obtained for an association between this polymorphism and bipolar affective disorder (p = 0.059 for genotypes, p = 0.073 for alleles). The G/G genotype and G allele were significantly more frequent in patients with bipolar disorder, type II (p = 0.016 for genotypes, p = 0.008 for alleles), especially in the women subgroup (p = 0.054 for genotypes, p = 0.024 for alleles). An association between the G/G genotype and bipolar affective disorder with disease onset after 18 years of age was also found (p = 0.022). These data suggest that the –48A/G polymorphism of the DRD1 gene may be involved in the etiology of bipolar disorder in a Polish population.

An association study of dopamine receptors polymorphisms and the Wisconsin Card Sorting Test in schizophrenia

Summary.Dopamine (DA), an important neurotransmitter in prefrontal cortex (PFC), is involved in the pathogenesis of schizophrenia. The aim of the study was to test an association between common polymorphism of genes for DA receptors DRD1, DRD2, DRD3, DRD4, and performance on the Wisconsin Card Sorting Test (WCST), measuring various functions of PFC, in 138 schizophrenic patients. Patients with G/G genotype of DRD1 tended to obtain worse results in all domains of WCST compared to patients with remaining genotypes, particularly for number of completed corrected categories, and trials to set the first category. A relationship was also found in female patients between DRD2 polymorphism and number of perseverative errors, while no association between WCST results and DRD3 or DRD4 polymorphism was observed in patients studied. The results may suggest an association between DRD1 gene polymorphism and performance on PFC test in schizophrenia. Also, the gender-dependent role of DRD2 in this process may be presumed.

Lack of support for a genetic association of the XBP1 promoter polymorphism with bipolar disorder in probands of European origin

Lack of support for a genetic association of the XBP1 promoter polymorphism with bipolar disorder in probands of European origin

Association of Tumor Necrosis Factor –308G/A Promoter Polymorphism with Schizophrenia and Bipolar Affective Disorder in a Polish Population

Background/Aims: Schizophrenia (SCH) and bipolar affective disorder (BPAD) are complex disorders with significant participation of genetic risk factors. Several lines of evidence point to the role of shared neurobiological mechanisms and common genetic background in SCH and BPAD. Immune disturbances have been suggested as contributing factor in the pathogenesis of both SCH and BPAD. The gene coding cytokine tumor necrosis factor (TNF) has been the object of a number of association studies in SCH, with ambiguous results. Only 3 such studies were performed in BPAD. The aim of our study was to perform a case-control association analysis of the TNF –308G/A polymorphism in a Polish sample of patients with SCH, BPAD and healthy controls. Methods: We genotyped the TNF –308G/A polymorphism (rs1800629) by PCR-RFLP in 348 patients with SCH, 361 patients with BPAD and in 351 controls. Results: We observed an association of the –308G allele with both SCH (p = 0.008) and BPAD (p = 0.039), and also with a positive family history in patients with SCH (p = 0.048) and BPAD (p = 0.027). For TNF genotypes, the association was only seen in SCH (p = 0.018). Conclusions: Our results may point to an association of the TNF –308G allele and –308G/G genotype with both SCH and BPAD, and to a relationship of the –308G allele with the risk of SCH and BPAD in patients with a positive family history. TNF could be potentially a susceptibility gene, shared between SCH and BPAD. Complex TNF gene studies – based on multiple single-nucleotide polymorphisms and involving haplotype analysis – are necessary for the clarification of currently contradictory findings.

Functional polymorphism of the matrix metalloproteinase-9 (MMP-9) gene in schizophrenia

Matrix metalloproteinase-9 (MMP-9) plays a role in many pathological conditions (e.g. cancer and heart disease). Recently, MMP-9 has been implicated in the activity of the prefrontal cortex and we therefore hypothesized that the MMP-9 gene may be associated with schizophrenia. We genotyped the functional -1562C/T polymorphism in a group of 442 schizophrenia patients and in 558 healthy control subjects. A significant preponderance of C/C genotype and C allele was found in the schizophrenia subjects compared to healthy controls. The results may provide the first evidence for involvement of the MMP-9 gene in the pathogenesis of schizophrenia and could also contribute to explaining a genetic connection between schizophrenia and some somatic illnesses.