Effect of DISC1 Polymorphisms on the Long-term Course of Neurocognitive Deficits in Non-affective Psychosis

Combining fMRI and DISC1 gene haplotypes to understand working memory-related brain activity in schizophrenia

The DISC1 gene is one of the most relevant susceptibility genes for psychosis. However, the complex genetic landscape of this locus, which includes protective and risk variants in interaction, may have hindered consistent conclusions on how DISC1 contributes to schizophrenia (SZ) liability. Analysis from haplotype approaches and brain-based phenotypes can contribute to understanding DISC1 role in the neurobiology of this disorder. We assessed the brain correlates of DISC1 haplotypes associated with SZ through a functional neuroimaging genetics approach. First, we tested the association of two DISC1 haplotypes, the HEP1 (rs6675281-1000731-rs999710) and the HEP3 (rs151229-rs3738401), with the risk for SZ in a sample of 138 healthy subjects (HS) and 238 patients. This approach allowed the identification of three haplotypes associated with SZ (HEP1-CTG, HEP3-GA and HEP3-AA). Second, we explored whether these haplotypes exerted differential effects on n-back associated brain activity in a subsample of 70 HS compared to 70 patients (diagnosis × haplotype interaction effect). These analyses evidenced that HEP3-GA and HEP3-AA modulated working memory functional response conditional to the health/disease status in the cuneus, precuneus, middle cingulate cortex and the ventrolateral and dorsolateral prefrontal cortices. Our results are the first to show a diagnosis-based effect of DISC1 haplotypes on working memory-related brain activity, emphasising its role in SZ.

Distinctively lower DISC1 mRNA levels in patients with schizophrenia, especially in those with higher positive, negative, and depressive symptoms

BACKGROUND

The issue of genetic influence on schizophrenia has received considerable attention. The DISC1 gene has been shown in several studies to play a role in the pathophysiology of schizophrenia. However, the relationship between DISC1 mRNA expression vs. schizophrenia and its clinical symptoms is uncertain.

METHODS

Fifty-six subjects (32 patients with schizophrenia and 24 healthy controls) were enrolled. Peripheral blood was obtained from all subjects to exam the DISC1 mRNA expression. Schizophrenia patients were evaluated with Hamilton Rating Scale for Depression (HAMD), Positive and Negative Syndrome Scale (PANSS), Brief Psychiatric Rating Scale (BPRS) and Scale for the Assessment of Negative Symptoms (SANS) scales. Healthy subjects were assessed with HAMD scale.

RESULTS

Patients with schizophrenia had significantly lower levels of the DISC1 mRNA expression than the healthy control (P = 0.002). We also found that lower DISC1 mRNA levels in schizophrenia patients were associated with higher degree of depression in HAMD (P = 0.037), severer positive symptoms in PANSS (P = 0.032) and more negative symptoms in SANS (P = 0.038).

CONCLUSION

The results showed that schizophrenia patients had lower levels of DISC1 mRNA than healthy individuals, and that the schizophrenia patients with lower DISC1 mRNA levels were more likely to manifest more marked symptoms, including positive, negative, and depressive symptoms. The findings suggest that lower DISC1 expression may be related with the pathogenesis and phenotypes of schizophrenia. Future studies are needed to replicate the results and to further establish its potential role in clinical application of early diagnosis and outcome follow-up.

Gene polymorphisms of DISC1 is associated with schizophrenia: Evidence from a meta-analysis

BACKGROUND

Previous studies suggest an association between Disrupted in schizophrenia 1 (DISC1) polymorphisms and schizophrenia (SCZ). However, the available data are often inconsistent, regarding the difference in sample size, ethnicity, genotyping method, etc. Thus, we carried out a meta-analysis to determine whether DISC1 polymorphisms contributed susceptibility to SCZ.

METHODS

A methodical literature review was operated using the English and Chinese core electronic databases. Odds ratios (ORs) with 95% confidence intervals (CIs) were applied to determine the correlation between DISC1 gene polymorphisms and SCZ susceptibility. Subgroup analyses were carried out by stratification of ethnicity. P values were Bonferroni adjusted to account for multiple testing. Publication bias was evaluated by funnel plots, Egger's test and the trim and fill method.

RESULTS

Meta-analyses results suggested that DISC1 polymorphisms (rs821616 and rs821597) increased SCZ risk in overall populations. In subgroups of ethnicity, DISC1 polymorphisms (rs821616 and rs821597) was associated with susceptibility to SCZ among the Chinese population (for rs821616: TT+AT vs. AA: OR=1.338, 95% CI=1.124-1.592, P=0.001; T vs. A: OR=1.300, 95% CI=1.124-1.504, P<0.000; for rs821597: AA+AG vs. GG: OR=1.508, 95% CI=1.268-1.794, P<0.001; A vs. G: OR=1.345, 95% CI=1.184-1.527, P<0.001). A positive correlation was also observed between the single marker rs821616 and SCZ among the Japanese population in the recessive model (TT vs. AT+AA: OR=1.524, 95% CI=1.185-1.959, P=0.001). There was no significant relationship between other DISC1 polymorphisms (rs3738401, rs2273890, rs3738398, rs3738402, rs2492367, rs843979, rs3737597, rs4658971, rs1538979, rs1000731 and rs3738399) and SCZ.

CONCLUSIONS

DISC1 polymorphisms increased a risk of SCZ, especially in the Chinese population. In order to further corroborate our findings, large well-designed epidemiological studies are needed.