A total of 1018 and 812 first degree relatives (FDR) of schizoprencies and controls respectively, were studied to find out the psychiatric morbidity in the families of paranoid and non-paranoid schizophrenia patients. The risk of schizophrenia and affective disorders was found to be independent of the probands subtype diagnosis. The risk for schizoid-schizotypal and paranoid personality disorders was found to be increased in the first degree relatives of paranoid schizophrenic, as compared to non-paranoid schizophrenic, thus suggesting that the psychopathology in the FDR may differ with the subtype diagnosis of the proband.
We aim to replicate AKT1 gene variants studies using Malaysian samples. Seven AKT1 single nucleotide polymorphisms (SNPs) were studied in 417 patients and 429 controls. Haplotype showed significant association (p=0.036) with schizophrenia, especially in Malays and Indians. Meta-analysis of rs2494732 showed significant association worldwide (p=0.018) and in Asians (p=0.023).
We contrasted demographic and clinical characteristics in transethnic schizophrenia populations from Australia (n=821), India (n=520) and Sarawak, Malaysia (n=298) and proposed cultural explanations for identified site differences. From these we aimed to identify candidate variables free from significant cultural confounding that are hence suitable for inclusion in genetic analyses. We observed five phenomena: (1) more individuals were living alone in Australia than India or Sarawak; (2) drug use was lower in India than Australia or Sarawak; (3) duration of untreated psychosis (DUP) was longer in India than Australia or Sarawak; (4) the rate of schizoaffective disorder was lower in India than Australia or Sarawak; and (5) age at psychosis onset (AAO) was older in Sarawak than Australia or India. We suggest that site differences for living arrangements, drug use and DUP are culturally confounded. The schizoaffective site difference likely results from measurement bias. The AAO site difference, however, has no obvious cultural or measurement bias explanation. Therefore, this may be an ideal candidate for use in genetic studies, given that genetic variants affecting AAO have already been proposed.
Molecular components of the dopamine D3 receptor (DRD3) may play an important role in the pathophysiology of schizophrenia. Previous studies have demonstrated an association between DRD3 Ser9Gly and cathechol-o-methyltransferase (COMT, SNP = rs165656) polymorphisms and schizophrenia but the results were inconclusive. We investigated this apparent association between Ser9Gly (A/G) polymorphism and an intronic SNP (dbSNP or rs165656) in 261 Malay patients diagnosed with schizophrenia and 216 controls, using PCR-RFLP. The genotype distribution of the polymorphism DRD3 Ser9Gly was in Hardy-Weinberg equilibrium (HWE) for patients (P = 0.1251) and out of HWE for controls (P = 0.0137). However, both healthy controls and schizophrenia patients were out of HWE for the polymorphism COMT rs165656. Based on allele and genotype frequencies in both groups, we found no significant association of DRD3 Ser9Gly polymorphisms and COMT (rs165656) with schizophrenia in Malays. Further studies should examine the association between other dopamine-related genes and the behavioral phenotypes of schizophrenia.
Variations in the gene for dopamine D2 receptor (DRD2) might have an influence on the outcome of antipsychotic treatment in schizophrenia. The objective of this study was to investigate the influence of DRD2 polymorphisms on treatment outcomes in patients with schizophrenia.
Neuregulin-1 is widely investigated due to its hypothesised association with schizophrenia. Single-nucleotide polymorphisms rs764059, rs2954041 and rs3924999 were investigated (417 patients with schizophrenia and 429 controls). We failed to demonstrate a significant association between rs2954041 and rs3924999 with schizophrenia in the three ethnic groups studied (Malay, Chinese, and Indian), while rs764059 was found to be monomorphic.
Schizophrenics (n = 250) and normal controls (n = 90) were studied to investigate and compare their dermatoglyphic patterns. Their fingerprint patterns were studied. The frequency of arches in the patient and control groups was similar. The frequency of loops in the control group was higher than in the patient group, and the trend was consistent in all the digits. The whorls in the patient group showed an increase over the control group in all the digits, although this finding was not statistically significant.
The correlation of clinical and demographic variables of thought disorder was studied in 45 Research Diagnostic Criteria (RDC) schizophrenics. Thought disorder was assessed by the scale for the assessment of Thought, Language and Communication (TLC). Negative thought disorder was significantly correlated with the rural background. Individual TLC items like Distractible speech, Illogicality, Clanging, Neologisms, etc. were correlated with the literate group and perseveration with the illiterate group. No significant correlation was noted between thought disorder and clinical variables.
Over 3000 candidate gene association studies have been performed to elucidate the genetic underpinnings of schizophrenia. However, a comprehensive evaluation of these studies' findings has not been undertaken since the decommissioning of the schizophrenia gene (SzGene) database in 2011. As such, we systematically identified and carried out random-effects meta-analyses for all polymorphisms with four or more independent studies in schizophrenia along with a series of expanded meta-analyses incorporating published and unpublished genome-wide association (GWA) study data. Based on 550 meta-analyses, 11 SNPs in eight linkage disequilibrium (LD) independent loci showed Bonferroni-significant associations with schizophrenia. Expanded meta-analyses identified an additional 10 SNPs, for a total of 21 Bonferroni-significant SNPs in 14 LD-independent loci. Three of these loci (MTHFR, DAOA, ARVCF) had never been implicated by a schizophrenia GWA study. In sum, the present study has provided a comprehensive summary of the current schizophrenia genetics knowledgebase and has made available all the collected data as a resource for the research community.
Evidence has shown that attempted suicide in psychiatric disorders is a complex interplay of genes and environment. Noradrenergic dysfunction due to abnormalities in the tyrosine hydroxylase (TH) gene has been implicated in the pathogenesis of suicidal behavior in mood disorders. However, suicide is a leading cause of mortality in schizophrenia too. Recent evidence suggests that TH gene variants may also increase the risk of suicide attempts in schizophrenia patients, although the interaction with established clinical risk factors is unclear. This study aimed to identify TH gene variants conferring risk for suicide attempt in schizophrenia while accounting for the interaction between this gene and clinical risk factors. We performed analysis on four TH SNPs (rs11564717, rs11042950, rs2070762, rs689) and the common TCAT repeat (UniSTS:240639) for 234 schizophrenia patients (51 suicide attempters and 183 non-attempters). Clinical risk factors and ethnic stratification were included as covariates. Single marker analysis identified the SNP rs11564717 (p=0.042) and the TCAT(6) (p=0.004) as risk variants for suicide attempt. We also identified the haplotype A-A-A-G as a risk factor for suicide attempt (p=0.0025). In conclusion, our findings suggest that TH polymorphisms may contribute to the risk of attempted suicide in schizophrenia even after accounting for established clinical risk factors and ethnic stratification. Further larger scale studies are needed to confirm these findings and to understand the mechanisms underlying the role of TH gene variants in suicide attempt in schizophrenia.
Transcription factor 4 (TCF4) gene plays an important role in nervous system development and it always associated with the risk of schizophrenia. Since miRNAs regulate targetgenes by binding to 3'UTRs of target mRNAs, the functional variants located in 3'UTR of TCF4 are highly suggested to affect the gene expressions in schizophrenia. To test the hypothesis regarding the effects of the variants located in 3'UTR of TCF4, we conducted an in silico analysis to identify the functional variants and their predicted functions. In this study, we sequenced the 3'UTR of TCF4 in 13 multiplex schizophrenia families and 14 control families. We found two functional variants carried by three unrelated patients. We determined that the C allele of rs1272363 and the TC insert of rs373174214 might suppress post- transcriptional expression. Secondly, we cloned the region that flanked these two variants into a dual luciferase reporter system and compared the luciferase activities between the pmirGLO-TCF4 (control), pmirGLO-TCF4-rs373174214 and pmirGLO-TCF4-rs1273263. Both pmirGLO-TCF4-rs373174214 and pmirGLO-TCF4-rs1273263 caused lower reporter gene activities, as compared to the control. However, only the C allele of rs1272363 reduced the luciferase activity significantly (p = 0.0231). Our results suggested that rs1273263 is a potential regulator of TCF4 expression, and might be associated with schizophrenia.
First-degree relatives (FDRs) of 162 schizophrenic and 106 control probands were investigated [corrected]. Psychiatric morbidity was present in 34.8% of FDRs of schizophrenic probands and in 9.2% of FDRs of controls. There was significantly more psychiatric illness in the siblings and parents than in the offspring of both schizophrenic and control subjects. The morbidity risks for schizoid-schizotypal personality disorders, cannabis-use disorder and paranoid personality disorder were significantly higher in the FDRs of schizophrenic patients than in those of controls, suggesting a biological relationship.
A validated study of the Self-Reporting Questionnaire (SRQ-20) of the World Health Organization against ICD-9 was found to have good validation indices at the cut-off point of 5/6. The sensitivity was 84.8% and specificity 83.7%. However, SRQ-24 had poor validation indices and are too sensitive to detect psychotic illness. Twenty-three per cent of 264 schizophrenic relatives who had been staying together with them and or actively involved in their care for at least one year had neurotic disorders compared with 1% who had latent schizophrenia. The prevalence of psychiatric morbidity was higher in the first-degree relatives compared with non-first degree relatives.
Bipolar Disorder and Schizophrenia Working Group of the Psychiatric Genomics Consortium. Electronic address: douglas.ruderfer@vanderbilt.edu, Bipolar Disorder and Schizophrenia Working Group of the Psychiatric Genomics Consortium
Schizophrenia and bipolar disorder are two distinct diagnoses that share symptomology. Understanding the genetic factors contributing to the shared and disorder-specific symptoms will be crucial for improving diagnosis and treatment. In genetic data consisting of 53,555 cases (20,129 bipolar disorder [BD], 33,426 schizophrenia [SCZ]) and 54,065 controls, we identified 114 genome-wide significant loci implicating synaptic and neuronal pathways shared between disorders. Comparing SCZ to BD (23,585 SCZ, 15,270 BD) identified four genomic regions including one with disorder-independent causal variants and potassium ion response genes as contributing to differences in biology between the disorders. Polygenic risk score (PRS) analyses identified several significant correlations within case-only phenotypes including SCZ PRS with psychotic features and age of onset in BD. For the first time, we discover specific loci that distinguish between BD and SCZ and identify polygenic components underlying multiple symptom dimensions. These results point to the utility of genetics to inform symptomology and potential treatment.
Genome-wide association study (GWAS) evidence has identified the metabotropic glutamate receptor 3 (GRM3) gene as a potential harbor for schizophrenia risk variants. However, previous meta-analyses have refuted the association between GRM3 single-nucleotide polymorphisms (SNPs) and schizophrenia risk. To reconcile these conflicting findings, we conducted the largest and most comprehensive meta-analysis of 14 SNPs in GRM3 from a total of 11 318 schizophrenia cases, 13 820 controls and 486 parent-proband trios. We found significant associations for three SNPs (rs2237562: odds ratio (OR)=1.06, 95% confidence interval (CI)=1.02-1.11, P=0.017; rs13242038: OR=0.90, 95% CI=0.85-0.96, P=0.016 and rs917071: OR=0.94, 95% CI=0.91-0.97, P=0.003). Two of these SNPs (rs2237562, rs917071) were in strong-to-moderate linkage disequilibrium with the top GRM3 GWAS significant SNP (rs12704290) reported by the Schizophrenia Working Group of the Psychiatric Genomics Consortium. We also found evidence for population stratification related to rs2237562 in that the 'risk' allele was dependent on the population under study. Our findings support the GWAS-implicated link between GRM3 genetic variation and schizophrenia risk as well as the notion that alleles conferring this risk may be population specific.
A number of studies have pointed to the association of BDNF (brain-derived neurotrophic factor) and DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, 32 kDa) with schizophrenia. The purpose of this study was to determine whether these two genes are involved in the pathogenesis of schizophrenia in the Malay population. Two single nucleotide polymorphisms Val66Met of BDNF, -2036C>G and g.1238delG of DARPP-32 were genotyped in the Malay population in 200 patients with schizophrenia and 256 healthy controls. Analysis of allele and genotype frequencies in these two groups revealed no significant association of BDNF or DARPP-32 polymorphisms with schizophrenia in Malays. This is the first such association study in the Malay population.
The catechol-O-methyltransferase (COMT) gene is a candidate gene for schizophrenia as its encoded enzyme is involved in the metabolic inactivation of dopamine and noradrenaline. Several molecular genetic studies thus far have demonstrated that the COMT functional polymorphism of Val158Met is susceptible with schizophrenia. Hence, the present study aims to determine this genetic association of this SNP in the three major ethnic groups of the Malaysian population. A total of 317 patients (79 Malays, 154 Chinese and 84 Indians) meeting DSM-IV criteria for schizophrenia and 417 healthy subjects (160 Malays, 164 Chinese and 93 Indians) were recruited. A PCR-RFLP method was used to determine the genotypes and alleles present. We found a significant association of genotypes within the total pooled samples, as well as in the female subgroup, with a higher frequency of heterozygotes in schizophrenia subjects. However, there were no significant differences in allele and genotype frequency between the schizophrenic patients and normal controls in all three ethnic groups. Our current findings suggest that the Val158Met polymorphism has a weak association with schizophrenia in the Malaysian population and does not play a major role in conferring susceptibility to the schizophrenia in any of the three major local ethnicities.
The present study included a total 261 patients with schizophrenia and 261 healthy controls to replicate the genetic association between the cathechol-o-methyltransferase gene and schizophrenia using a haplotype block-based gene-tagging. The G-G-G haplotype was found to show a highly significant association with schizophrenia.