Association between DBH 19 bp insertion/deletion polymorphism and cognition in first-episode schizophrenic patients

Association between the HHEX polymorphism and delayed memory in first-episode schizophrenic patients

The hematopoietically-expressed homeobox gene (HHEX) played a critical role in regulating the immune system that the abnormality of which was involved in the psychopathology and cognitive deficits of psychiatric disorders. The aim of this study was to investigate the effect of HHEX rs1111875 polymorphism on the susceptibility and cognitive deficits of first-episode schizophrenic patients (FSP). We assessed cognitive function in 239 first-episode patients meeting DSM-IV for schizophrenia, and 368 healthy controls using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The HHEX rs1111875 polymorphism was genotyped. Our results showed that the allelic and genotypic frequencies of HHEX rs1111875 polymorphism didn't differ between FSP and healthy controls (both p > 0.05) after adjusting for sex and age. Cognitive test scores in FSP were significantly lower than those in healthy controls on all scales (all p < 0.001) except for the visuospatial/constructional score (p > 0.05) after adjusting for covariates. There was a significant genotype (p < 0.05) rather than genotype × diagnosis (p > 0.05) effect on the delayed memory score after adjusting for covariates. The HHEX rs1111875 polymorphism was significantly associated with the delayed memory score in FSP (p < 0.05), but not in healthy controls (p > 0.05) after adjusting for covariates. Our findings supported that the HHEX rs1111875 polymorphism did not contribute to the susceptibility to FSP. However, this polymorphism might influence the delayed memory in FSP. Moreover, FSP had poorer cognitive function than healthy controls except for the visuospatial/constructional domain.

Association between dopamine beta-hydroxylase polymorphism and attention function in suicide attempters with chronic schizophrenia

BACKGROUND

Patients with schizophrenia are at a higher risk for suicide compared with the general population. Dopamine beta-hydroxylase (DβH) plays a key role in the conversion of dopamine to norepinephrine, which is related to suicidal behavior and cognitive regulation.

OBJECTIVE

To examine whether there is the effect of DβH 5'-insertion/deletion (Ins/Del) polymorphism on cognitive performance in suicide attempters with chronic schizophrenia.

METHODS

This polymorphism was detected in 114 suicide attempters and 617 non-suicide attempters with chronic schizophrenia. Cognitive performance was assessed by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

RESULTS

The allelic and genotypic frequencies of this polymorphism between two groups did not differ after controlling for covariates (both, p > .05). There were no differences in RBANS scores between two groups after adjusting for covariates (all, p > .05). However, based on the genotype grouping in suicide attempters and non-attempters, the attention score significantly differed after adjusting for covariates (both, p < .05). Further analysis indicated that this polymorphism was associated with attention score in suicide attempters (p < .05), but not in non-suicide attempters (p > .05).

CONCLUSIONS

DβH 5'-Ins/Del polymorphism was not a risk locus of suicide attempters, but it was implicated in attention regulation in suicide attempters with chronic schizophrenia.

[A new look at the genetics of neurocognitive deficits in schizophrenia]

The article presents current literature data on genetic studies of neurocognitive deficit in schizophrenia, including the genes of neurotransmitter systems (dopaminergic, glutamatergic, and serotonergic); genes analyzed in genome-wide association studies (GWAS), as well as other genetic factors related to the pathophysiological mechanisms underlying schizophrenia and neurocognitive disorders.

Association of regulatory variants of dopamine β-hydroxylase with cognition and tardive dyskinesia in schizophrenia subjects

BACKGROUND

Dopamine-β-hydroxylase (DBH, EC 1.14.17.1), which converts dopamine to norepinephrine, is a candidate gene in neuropsychiatric diseases.

AIM

To assess the effect of regulatory variants in DBH on schizophrenia and its endophenotypes -cognition and tardive dyskinesia.

METHODS

We tested association of functional variants 19bp Ins/Del, rs1989787 and rs1611115 in DBH with i) schizophrenia (1236 cases, 1136 controls), ii) tardive dyskinesia (83 positive, 162 negative) and iii) performance functions of cognition (357 cases, 306 controls) estimated by the Penn Computerized Neurocognitive Battery.

RESULTS

A modest haplotypic (Ins-C; 19bp Ins/Del - rs1989787 C>T; p=0.04) association was observed with schizophrenia. We observed ~39% reduction in activity of 19bp Del allele on luciferase assay. Analysis of covariance revealed interactions of tardive dyskinesia status and: i) 19bp Ins/Del (genotypic, p=0.04) and ii) rs1989787 and rs1611115 (combined genotypic, p=0.004) on Abnormal Involuntary Movement Scale total score. Association of rs1611115 with positive and negative syndrome scale (PANSS) total score (p=0.05) and allelic/genotypic association with lower positive (p=0.03/0.04), general psychopathology (p=0.01/0.01) PANSS scales in tardive dyskinesia-positive; and allelic/genotypic (p=0.02/0.05) with higher score of depressive factors in tardive dyskinesia-negative subgroups were observed. Analysis of covariance with continuous variable of cognition showed interaction of health status with: i) rs1989787 on accuracy and efficiency (p=0.03) of abstraction and mental flexibility; ii) rs1611115 on accuracy of working memory and emotion (p=0.05); iii) 19bp Ins/Del on processing speed of emotion (p=0.03). Allelic/genotypic association of rs1989787 with spatial ability (p=0.02-0.05) among healthy controls; association of rs1611115 with Global Assessment Scale scores in the past month (p=0.05) among schizophrenia subjects of cognition cohort was also observed.

CONCLUSIONS

With modest genotype-phenotype correlations available for DBH variants, personalized treatment regimens based on DBH activity for ameliorating tardive dyskinesia and cognitive symptoms may be plausible.

Dopaminergic gene methylation is associated with cognitive performance in a childhood monozygotic twin study

Individual differences in cognitive function are due to a combination of heritable and non-heritable factors. A large body of evidence from clinical, cognitive, and pharmacological neuroscience implicates dopaminergic gene variants as modulators of cognitive functions. Neuroepigenetic studies demonstrate environmental factors also influence complex phenotypes by affecting gene expression regulation. To evaluate the mechanism of environmental influence on cognitive abilities, we examined if epigenetic regulation of dopaminergic genes plays a role in cognition. Using a DNA methylation profiling microarray, we used a monozygotic (MZ) twin difference design to evaluate if co-twin differences in methylation of CpG sites near six dopaminergic genes predicted differences in response inhibition and memory performance. Studying MZ twins allows us to assess if environmentally driven differences in methylation affect differences in phenotype while controlling for the influence of genotype and shared family environment. Response inhibition was assessed with the flanker task and short-term and working memory were assessed with digit span recall. We found MZ co-twin differences in DRD4 gene methylation predicted differences in short-term memory. MZ differences in COMT, DBH, DAT1, DRD1, and DRD2 gene methylation predicted differences in response inhibition. Taken together, findings suggest methylation status of dopaminergic genes may influence cognitive functions in a dissociable manner. Our results highlight the importance of the epigenome and environment, over and above the influence of genotype, in supporting complex cognitive functions.

Coping styles and symptomatic manifestation of first-episode psychosis: Focus on cognitive performance

Cognitive deficits are widely observed in patients with psychosis and represent one of most important determinants of functional outcomes. It has been shown that patients with psychosis prefer maladaptive coping strategies over active coping styles. However, it remains unknown whether cognitive impairments are related to coping styles in psychotic disorders. Therefore, the aim of this study was to assess whether cognitive deficits observed in patients with first-episode psychosis (FEP) might impact the use of specific coping strategies. We recruited 40 FEP patients and 35 healthy controls. In our study, FEP patients were more likely to use maladaptive coping styles after adjustment for education level and medication effects. The use of maladaptive coping strategies was associated with greater impairments of visuospatial/constructional abilities and language skills in FEP patients. In addition, lower odds of using adaptive coping were related to higher levels of depressive symptoms in the group of patients. Adaptive coping was associated with better global cognitive performance in healthy controls. Our results indicate that cognitive impairments, especially worse performance of visuospatial/constructional abilities and language skills, might be related to the preference of maladaptive coping strategies. Lower odds of using adaptive coping styles might be associated with more severe depressive symptomatology.

Associations between the DBH gene, plasma dopamine β-hydroxylase activity and cognitive measures in Han Chinese patients with schizophrenia

The dopamine (DA) and norepinephrine (NE) systems modulate cognitive function. Dopamine β-hydroxylase (DβH) converts DA to NE, and its activity is under strong genetic control. This study examines the association of plasma DβH (pDβH) activity, DBH gene polymorphisms (-1021C>T, rs1611115 and 444G>A, rs1108580) and cognitive deficits in Han Chinese patients with schizophrenia. We assessed pDβH activity and cognitive function using the Verbal Fluency Test (VFT), Trail Making Test (TMT) A-B, Stroop color-word test and Wisconsin Card Sorting Test (WCST) in 200 patients with schizophrenia before and after 8weeks of antipsychotic treatment (96 patients completed assessments at baseline and post-treatment). We found that rs1611115 was significantly associated with pDβH activity, and there was strong LD between rs1611115 and rs1108580 polymorphisms. Correlation analysis indicated that pDβH activity correlated nominally with improvement in VFT score after 8weeks antipsychotic treatment. Moreover, there was a significant genotype effect of the rs1108580 on VFT: the VFT score of patients with AA genotype was higher than that of patients with AG/GG genotype either at baseline or the end of 8 weeks after treatment. However, this difference was not observed for rs1611115. Our findings confirm a strong association between genotype at rs1611115 and pDβH activity in Chinese patients with schizophrenia. Our data also suggest the rs1108580 polymorphism may influence some aspects of cognitive function in schizophrenia.

Association between DBH 19bp insertion/deletion polymorphism and cognition in schizophrenia with and without tardive dyskinesia

Long-term antipsychotic treatment for schizophrenia is associated with the development of tardive dyskinesia (TD), which is involved in increased cognitive impairment. Dopamine beta-hydroxylase (DBH) gene associated with dopamine and norepinephrine systems influences cognition. Schizophrenia with TD have higher DBH activity than those without TD. This study examined whether DBH5'-insertion/deletion (-Ins/Del) polymorphism could influence cognitive function in schizophrenia with and without TD. The presence of DBH5'-Ins/Del polymorphism was determined in 345 schizophrenia with TD and 397 schizophrenia without TD. The Abnormal Involuntary Movement Scale and Repeatable Battery for Assessment of Neuropsychological Status (RBANS) were used to assess TD severity and cognition. The allele and genotype frequencies of DBH5'-Ins/Del polymorphism did not differ between patients with and without TD (both p>0.05). RBANS total score and subscales did not differ by DBH5'-Ins/Del genotype groups in patients with TD (all p>0.05). However, attention score significantly differed by DBH5'-Ins/Del genotype groups in those without TD (p<0.05). Patients without TD who were Del homozygous had significantly lower attention score than those without TD who were Ins alleles (p<0.05). Immediate memory and attention scores were lower in patients with TD than without TD (both p<0.05). This study indicated that DBH5'-Ins/Del polymorphism may not play a role in the susceptibility to TD and cognitive deficits in schizophrenia with TD, but it may influence cognitive function in schizophrenia with non-TD. Moreover, schizophrenia with TD experienced greater cognitive deficits than those with non-TD, especially in immediate memory and attention.

TCF4 gene polymorphism is associated with cognition in patients with schizophrenia and healthy controls

BACKGROUND

Cognitive deficits have been identified as an important core feature of schizophrenia. Single nucleotide polymorphisms in the transcription factor 4 (TCF4) gene have been reported to be involved in the susceptibility to schizophrenia and be significantly related to cognitive deficits of schizophrenia and controls. This study examines whether the TCF4 rs2958182 polymorphism influences cognitive functions in chronic schizophrenia and controls.

METHODS

The presence of the TCF4 rs2958182 was determined in 976 patients and 420 controls using a case-control design. We assessed all the patients' psychopathology using the Positive and Negative Syndrome Scale (PANSS). Cognition was assessed in 777 patients and 399 controls by using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

RESULTS

There were marginally significant differences in the TCF4 rs2958182 allelic and genotypic distributions between patients and controls (χ2 = 3.48, p = 0.062 and χ2 = 0.036, p = 0.036, respectively). Cognitive test scores were significantly lower in patients than in controls on all scales (all p < 0.001) except for the visuospatial/constructional index (p > 0.05). There were significant genotype effects on delayed memory score (p = 0.013), the RBANS total score (p = 0.028) and language score (p = 0.034). Further analysis showed that the language score significantly differed according to the genotypic groups (A/A+T/A group versus T/T group) (p = 0.007) in patients but not in controls (p > 0.05), and the delayed memory score also significantly differed according to the genotypic groups (A/A+T/A group versus T/T group) (p = 0.021) in controls but not in patients (p > 0.05).

CONCLUSIONS

This study found that the A allele of the TCF4 rs2958182 polymorphism was the risk allele of schizophrenia, and was associated with lower cognitive performance in language in schizophrenia and delayed memory in controls. In contrast, the T allele of this polymorphism was found to be the schizophrenia risk allele in another study in Han Chinese people.

Meta-analyses of 10 polymorphisms associated with the risk of schizophrenia

Schizophrenia (SCZ) is a severe complex psychiatric disorder that generates problems for the associated family and society and causes disability with regards to work for patients. The aim of the present study was to assess the contribution of 10 genetic polymorphisms to SCZ susceptibility. Meta-analyses were conducted using the data without a limitation for time or language. A total of 27 studies with 7 genes and 10 polymorphisms were selected for the meta-analyses. Two polymorphisms were found to be significantly associated with SCZ. SNAP25 rs3746544 was shown to increase the SCZ risk by 18% [P=0.01; odds ratio (OR), 1.18; 95% confidence interval (CI), 1.05-1.34] and GRIK3 rs6691840 was found to increase the risk by 30% (P=0.008; OR, 1.30; 95% CI, 1.07-1.58). Significant results were found under the dominant (P=0.001; OR, 1.36; 95% CI, 1.13-1.65) and additive (P=0.02; OR, 1.45; 95% CI, 1.06-1.98) model for the SNAP25 rs3746544 polymorphism and under the additive model for the GRIK3 rs6691840 polymorphism (P=0.03; OR, 1.73; 95% CI, 1.04-2.85). There were no significant results observed for the other eight polymorphisms, which were CCKAR rs1800857, CHRNA7 rs904952, CHRNA7 rs6494223, CHRNA7 rs2337506, DBH Ins>Del, FEZ1 rs559668, FEZ1 rs597570 and GCLM rs2301022. In conclusion, the present meta-analyses indicated that the SNAP25 rs3746544 and GRIK3 rs6691840 polymorphisms were risk factors of SCZ, which may provide valuable information for the clinical diagnosis of SCZ.

Genetic modulation of working memory deficits by ankyrin 3 gene in schizophrenia

Neuropsychological endophenotype approach is an emerging strategy in schizophrenia research to understand and identify the functional importance of genetically transmitted, brain-based deficits present in this disorder. Accumulating evidence indicated that working memory deficit is a core neuropsychological dysfunction in schizophrenia and a primary endophenotype indexing the liability to develop schizophrenia. Genetic variation in ankyrin 3 gene (ANK3) is likely to have widespread cognitive effects. Our previous study has identified a significant association of ANK3 SNPs and schizophrenia. In this study, we aimed to examine whether the schizophrenia-risk SNPs within ANK3 may affect working memory deficits in schizophrenia patients. Herein, we assess the working memory performance in 163 patients with first-episode, antipsychotic-naïve schizophrenia and 42 sex, age-matched healthy subjects using N-back task. Two SNPs rs10761482 and rs10994336 were genotyped among the patients and 209 controls. Our results showed that schizophrenia patients showed significantly poorer performance than healthy controls on N-back task (ps<0.01). After adjusting for the scores of intelligence quotient, memory quotient and the demographic factors, there was a significant genotype effect of the rs10994336 on the accuracy rate and reaction time of 2-back item (p=0.048 and 0.024, respectively). Post-hoc analyses showed that patients with rs10994336T/T genotype had significantly lower accuracy rate and more reaction time at 2-back task than those with T/C and C/C genotypes. The association of SNP rs10994336 with schizophrenia was replicated in our sample (genotypic p=0.024 and allelic p=0.006). However, we did not find any significant association of rs10761482 with schizophrenia and parameters in N-back task. Our results indicated that genetic variation within ANK3 may exert gene-specific modulating effects on working memory deficits in schizophrenia.

Is elevated norepinephrine an etiological factor in some cases of schizophrenia?

A number of hypotheses have been put forth regarding the etiology of schizophrenia, including the dopamine hypothesis, NMDA receptor hypofunction hypothesis, and others. A lesser known theory is that elevated noradrenergic signaling plays a causative role in the disease. This paper briefly re-examines the merits of this hypothesis, including as it relates to some recently published studies. Several lines of evidence are investigated, including: endogenous level studies of norepinephrine (NE); modulation of the disease by noradrenergic drugs; association of the disease with bipolar disorder and hypertension, since these latter two conditions may involve elevated NE transmission; and effects of psychological stress on the disease, since stress can produce elevated release of NE. For many of these lines of evidence, their relationship with prepulse inhibition of startle is examined. A number of these studies support the hypothesis, and several suggest that elevated NE signaling plays a particularly prominent role in the paranoid subtype of schizophrenia. If the hypothesis is correct for some persons, conventional pharmaceutical treatment options, such as use of atypical antipsychotics (which may themselves modulate noradrenergic signaling), may be improved if selective NE transmission modulating agents are added to or even substituted for these conventional drugs.