Developmental suppression of schizophrenia-associated miR-137 alters sensorimotor function in zebrafish.

The neurodevelopmentally regulated microRNA miR-137 was strongly implicated as risk locus for schizophrenia in the most recent genome wide association study coordinated by the Psychiatric Genome Consortium (PGC). This molecule is highly conserved in vertebrates enabling the investigation of its function in the developing zebrafish. We utilized this model system to achieve overexpression and suppression of miR-137, both transiently and stably through transgenesis. While miR-137 overexpression was not associated with an observable specific phenotype, downregulation by antisense morpholino and/or transgenic expression of miR-sponge RNA induced significant impairment of both embryonic and larval touch-sensitivity without compromising overall anatomical development. We observed miR-137 expression and activity in sensory neurons including Rohon-Beard neurons and dorsal root ganglia, two neuronal cell types that confer touch-sensitivity in normal zebrafish, suggesting a role of these cell types in the observed phenotype. The lack of obvious anatomical or histological pathology in these cells, however, suggested that subtle axonal network defects or a change in synaptic function and neural connectivity might be responsible for the behavioral phenotype rather than a change in the cellular morphology or neuroanatomy.

Increased rare duplication burden genomewide in patients with treatment-resistant schizophrenia.

BACKGROUND: A significant number of patients with schizophrenia fail to respond to antipsychotic medication. Although several studies have investigated associated patient characteristics, the emerging findings from genetic studies offer further scope for study. METHOD: In 612 schizophrenia patients with detailed clinical information, common genetic variants indexed by polygenic risk scores, and rare variants indexed by deletion and duplication burden genomewide, we explored potential genetic predictors alongside other established risk factors for treatment resistance. Clinical outcomes of treatment resistance were also calculated using lifetime measures of positive, negative/disorganized and mood symptoms as well as number of hospitalizations and suicide attempts. RESULTS: Logistic regression models identified a significant relationship between treatment resistance and total duplication burden genomewide, years of formal schooling and age at onset. Clinically, treatment-resistant patients were characterized by greater negative/disorganized and positive symptoms and greater number of hospitalizations. CONCLUSIONS: Taken together, these findings suggest genetic information, specifically the genomewide burden of rare copy number variants, may increase our understanding and clinical management of patients with treatment-resistant schizophrenia.

Executive functioning in schizophrenia: Unique and shared variance with measures of fluid intelligence.

OBJECTIVE: Patients with schizophrenia often display deficits on tasks thought to measure "executive" processes. Recently, it has been suggested that reductions in fluid intelligence test performance entirely explain deficits reported for patients with focal frontal lesions on classical executive tasks. For patients with schizophrenia, it is unclear whether deficits on executive tasks are entirely accountable by fluid intelligence and representative of a common general process or best accounted for by distinct contributions to the cognitive profile of schizophrenia. METHOD: In the current study, 50 patients with schizophrenia and 50 age, sex and premorbid intelligence matched controls were assessed using a broad neuropsychological battery, including tasks considered sensitive to executive abilities, namely the Hayling Sentence Completion Test (HSCT), word fluency, Stroop test, digit-span backwards, and spatial working memory. Fluid intelligence was measured using both the Matrix reasoning subtest from the Weschler Abbreviated Scale of Intelligence (WASI) and a composite score derived from a number of cognitive tests. RESULTS: Patients with schizophrenia were impaired on all cognitive measures compared with controls, except smell identification and the optimal betting and risk-taking measures from the Cambridge Gambling Task. After introducing fluid intelligence as a covariate, significant differences remained for HSCT suppression errors, and classical executive function tests such as the Stroop test and semantic/phonemic word fluency, regardless of which fluid intelligence measure was included. CONCLUSIONS: Fluid intelligence does not entirely explain impaired performance on all tests considered as reflecting "executive" processes. For schizophrenia, these measures should remain part of a comprehensive neuropsychological assessment alongside a measure of fluid intelligence.

Common genetic risk variants are associated with positive symptoms and decision-making ability in patients with schizophrenia.

Schizophrenia is a clinically heterogeneous disorder associated with broad deficits across cognitive domains. As large genomewide association studies uncover the genetic architecture of schizophrenia, the relationship between common genetic variants and clinical and cognitive characteristics will form part of an integrative approach to understanding genetic effects on the clinical phenotype. In the current study, association between common genetic risk variants and clinical and cognitive variables was investigated. Common risk variants were associated with positive symptoms and decision-making ability from the Cambridge Gambling Task with trends in other domains.

Copy number deletion burden is associated with cognitive, structural, and resting-state network differences in patients with schizophrenia.

Total burden of copy number deletions has been implicated in schizophrenia risk and has been associated with reduced cognitive functioning. The current study aims to replicate the cognitive findings and investigate regional grey and white matter volumes. Moreover, it will explore resting-state networks for correlations between functional connectivity and total deletion burden. All imaging differences will be investigated for correlations with cognitive differences. Seventy-eight patients with chronic schizophrenia, who formed a subset of a large genome-wide association study (GWAS), were assessed for intelligence, 34 had structural magnetic resonance imaging, 33 had resting-state functional magnetic resonance imaging, and 32 had diffusion tensor imaging (DTI). Total deletion burden was negatively associated with IQ performance and positively associated with regional volumes in the striatum bilaterally and in the right superior temporal gyrus and white-matter in the corpus callosum. Correlations were identified between deletion burden and both hyper and hypoconnectivity within the default-mode network and hypoconnectivity within the cognitive control network. The functional connectivity correlations with deletion burden were also correlated with the IQ differences identified. Total deletion burden affects regional volumes and resting-state functional connectivity in key brain networks in patients with schizophrenia. Moreover, effects of deletions on cognitive functioning in may be due to inefficiency of key brain networks as identified by dysconnectivity in resting-state networks.

Theory of mind and the social brain: implications for understanding the genetic basis of schizophrenia.

Genome-wide association studies in schizophrenia have recently made significant progress in our understanding of the complex genetic architecture of this disorder. Many genetic loci have been identified and now require functional investigation. One approach involves studying their correlation with neuroimaging and neurocognitive endophenotypes. Theory of Mind (ToM) deficits are well established in schizophrenia and they appear to fulfill criteria for being considered an endophenotype. We aim to review the behavioral and neuroimaging-based studies of ToM in schizophrenia, assess its suitability as an endophenotype, discuss current findings, and propose future research directions. Suitable research articles were sourced from a comprehensive literature search and from references identified through other studies. ToM deficits are repeatable, stable, and heritable: First-episode patients, those in remission and unaffected relatives all show deficits. Activation and structural differences in brain regions believed important for ToM are also consistently reported in schizophrenia patients at all stages of illness, although no research to date has examined unaffected relatives. Studies using ToM as an endophenotype are providing interesting genetic associations with both single nucleotide polymorphisms (SNPs) and specific copy number variations (CNVs) such as the 22q11.2 deletion syndrome. We conclude that ToM is an important cognitive endophenotype for consideration in future studies addressing the complex genetic architecture of schizophrenia, and may help identify more homogeneous clinical sub-types for further study.

The emerging spectrum of allelic variation in schizophrenia: current evidence and strategies for the identification and functional characterization of common and rare variants.

After decades of halting progress, recent large genome-wide association studies (GWAS) are finally shining light on the genetic architecture of schizophrenia. The picture emerging is one of sobering complexity, involving large numbers of risk alleles across the entire allelic spectrum. The aims of this article are to summarize the key genetic findings to date and to compare and contrast methods for identifying additional risk alleles, including GWAS, targeted genotyping and sequencing. A further aim is to consider the challenges and opportunities involved in determining the functional basis of genetic associations, for instance using functional genomics, cellular models, animal models and imaging genetics. We conclude that diverse approaches will be required to identify and functionally characterize the full spectrum of risk variants for schizophrenia. These efforts should adhere to the stringent standards of statistical association developed for GWAS and are likely to entail very large sample sizes. Nonetheless, now more than any previous time, there are reasons for optimism and the ultimate goal of personalized interventions and therapeutics, although still distant, no longer seems unattainable.

Schizophrenia-associated HapICE haplotype is associated with increased NRG1 type III expression and high nucleotide diversity.

Excitement and controversy have followed neuregulin (NRG1) since its discovery as a putative schizophrenia susceptibility gene; however, the mechanism of action of the associated risk haplotype (HapICE) has not been identified, and specific genetic variations, which may increase risk to schizophrenia have remained elusive. Using a postmortem brain cohort from 37 schizophrenia cases and 37 controls, we resequenced upstream of the type I-IV promoters, and the HapICE repeat regions in intron 1. Relative abundance of seven NRG1 mRNA transcripts in the prefrontal cortex were determined and compared across diagnostic and genotypic groups. We identified 26 novel DNA variants and showed an increased novel variant load in cases compared with controls (χ(2)=7.815; P=0.05). The average nucleotide diversity (θ = 10.0 × 10(-4)) was approximately twofold higher than that previously reported for BDNF, indicating that NRG1 may be particularly prone to genetic change. A greater nucleotide diversity was observed in the HapICE linkage disequilibrium block in schizophrenia cases (θ((case)) = 13.2 × 10(-4); θ((control)) = 10.0 × 10(-4)). The specific HapICE risk haplotype was associated with increased type III mRNA (F = 3.76, P = 0.028), which in turn, was correlated with an earlier age of onset (r = -0.343, P = 0.038). We found a novel intronic five-SNP haplotype ~730 kb upstream of the type I promoter and determined that this region functions as transcriptional enhancer that is suppressed by SRY. We propose that the HapICE risk haplotype increases expression of the most brain-abundant form of NRG1, which in turn, elicits an earlier clinical presentation, thus providing a novel mechanism through which this genetic association may increase risk of schizophrenia.

Meta-analysis of 32 genome-wide linkage studies of schizophrenia.

A genome scan meta-analysis (GSMA) was carried out on 32 independent genome-wide linkage scan analyses that included 3255 pedigrees with 7413 genotyped cases affected with schizophrenia (SCZ) or related disorders. The primary GSMA divided the autosomes into 120 bins, rank-ordered the bins within each study according to the most positive linkage result in each bin, summed these ranks (weighted for study size) for each bin across studies and determined the empirical probability of a given summed rank (P(SR)) by simulation. Suggestive evidence for linkage was observed in two single bins, on chromosomes 5q (142-168 Mb) and 2q (103-134 Mb). Genome-wide evidence for linkage was detected on chromosome 2q (119-152 Mb) when bin boundaries were shifted to the middle of the previous bins. The primary analysis met empirical criteria for 'aggregate' genome-wide significance, indicating that some or all of 10 bins are likely to contain loci linked to SCZ, including regions of chromosomes 1, 2q, 3q, 4q, 5q, 8p and 10q. In a secondary analysis of 22 studies of European-ancestry samples, suggestive evidence for linkage was observed on chromosome 8p (16-33 Mb). Although the newer genome-wide association methodology has greater power to detect weak associations to single common DNA sequence variants, linkage analysis can detect diverse genetic effects that segregate in families, including multiple rare variants within one locus or several weakly associated loci in the same region. Therefore, the regions supported by this meta-analysis deserve close attention in future studies.

Genomewide linkage scan of schizophrenia in a large multicenter pedigree sample using single nucleotide polymorphisms.

A genomewide linkage scan was carried out in eight clinical samples of informative schizophrenia families. After all quality control checks, the analysis of 707 European-ancestry families included 1615 affected and 1602 unaffected genotyped individuals, and the analysis of all 807 families included 1900 affected and 1839 unaffected individuals. Multipoint linkage analysis with correction for marker-marker linkage disequilibrium was carried out with 5861 single nucleotide polymorphisms (SNPs; Illumina version 4.0 linkage map). Suggestive evidence for linkage (European families) was observed on chromosomes 8p21, 8q24.1, 9q34 and 12q24.1 in nonparametric and/or parametric analyses. In a logistic regression allele-sharing analysis of linkage allowing for intersite heterogeneity, genomewide significant evidence for linkage was observed on chromosome 10p12. Significant heterogeneity was also observed on chromosome 22q11.1. Evidence for linkage across family sets and analyses was most consistent on chromosome 8p21, with a one-LOD support interval that does not include the candidate gene NRG1, suggesting that one or more other susceptibility loci might exist in the region. In this era of genomewide association and deep resequencing studies, consensus linkage regions deserve continued attention, given that linkage signals can be produced by many types of genomic variation, including any combination of multiple common or rare SNPs or copy number variants in a region.

Genetic variation in South Indian castes: evidence from Y-chromosome, mitochondrial, and autosomal polymorphisms.

BACKGROUND: Major population movements, social structure, and caste endogamy have influenced the genetic structure of Indian populations. An understanding of these influences is increasingly important as gene mapping and case-control studies are initiated in South Indian populations. RESULTS: We report new data on 155 individuals from four Tamil caste populations of South India and perform comparative analyses with caste populations from the neighboring state of Andhra Pradesh. Genetic differentiation among Tamil castes is low (RST = 0.96% for 45 autosomal short tandem repeat (STR) markers), reflecting a largely common origin. Nonetheless, caste- and continent-specific patterns are evident. For 32 lineage-defining Y-chromosome SNPs, Tamil castes show higher affinity to Europeans than to eastern Asians, and genetic distance estimates to the Europeans are ordered by caste rank. For 32 lineage-defining mitochondrial SNPs and hypervariable sequence (HVS) 1, Tamil castes have higher affinity to eastern Asians than to Europeans. For 45 autosomal STRs, upper and middle rank castes show higher affinity to Europeans than do lower rank castes from either Tamil Nadu or Andhra Pradesh. Local between-caste variation (Tamil Nadu RST = 0.96%, Andhra Pradesh RST = 0.77%) exceeds the estimate of variation between these geographically separated groups (RST = 0.12%). Low, but statistically significant, correlations between caste rank distance and genetic distance are demonstrated for Tamil castes using Y-chromosome, mtDNA, and autosomal data. CONCLUSION: Genetic data from Y-chromosome, mtDNA, and autosomal STRs are in accord with historical accounts of northwest to southeast population movements in India. The influence of ancient and historical population movements and caste social structure can be detected and replicated in South Indian caste populations from two different geographic regions.

A reanalysis of 409 European-Ancestry and African American schizophrenia pedigrees reveals significant linkage to 8p23.3 with evidence of locus heterogeneity.

The detection and replication of schizophrenia risk loci can require substantial sample sizes, which has prompted various collaborative efforts for combining multiple samples. However, pooled samples may comprise sub-samples with substantial population genetic differences, including allele frequency differences. We investigated the impact of population differences via linkage reanalysis of Molecular Genetics of Schizophrenia 1 (MGS1) affected sibling-pair data, comprising two samples of distinct ancestral origin: European (EA: 263 pedigrees) and African-American (AA: 146 pedigrees). To exploit the linkage information contained within these distinct continental samples, we performed separate analyses of the individual samples, allowing for within-sample locus heterogeneity, and the pooled sample, allowing for both within-sample and between-sample heterogeneity. Significance levels, corrected for the multiple tests, were determined empirically. For all suggestive peaks, stronger linkage evidence was obtained in either the EA or AA sample than the combined sample, regardless of how heterogeneity was modeled for the latter. Notably, we report genomewide significant linkage of schizophrenia to 8p23.3 and evidence for a second, independent susceptibility locus, reaching suggestive linkage, 29 cM away on 8p21.3. We also detected suggestive linkage on chromosomes 5p13.3 and 7q36.2. Many regions showed pronounced differences in the extent of linkage between the EA and AA samples. This reanalysis highlights the potential impact of population differences upon linkage evidence in pooled data and demonstrates a useful approach for the analysis of samples drawn from distinct continental groups.

Expression profiling in monozygotic twins discordant for bipolar disorder reveals dysregulation of the WNT signalling pathway.

To identify genes dysregulated in bipolar disorder (BD1), we carried out global gene expression profiling using whole-genome microarrays. To minimize genetic variation in gene expression levels between cases and controls, we compared expression profiles in lymphoblastoid cell lines from monozygotic twin pairs discordant for the disease. We identified 82 genes that were differentially expressed by >or=1.3-fold in three BD1 cases compared to their co-twins, and which were statistically (P

Polymorphisms in the vitamin D receptor and their associations with risk of schizophrenia and selected anthropometric measures.

The association between vitamin D levels and skeletal growth has long been recognized. However, exposure to low levels of vitamin D during early life is also known to alter brain development, and is a candidate risk factor for schizophrenia. This study examines the association between four polymorphisms in the vitamin D receptor (VDR) and 1) risk of schizophrenia, and 2) three anthropometric variables (height, head size, and head shape). Four single-nucleotide polymorphisms (SNPs; rs10735810/FokI, rs1544410/BsmI, rs7975232/ApaI, and rs731236/TaqI) in the VDR gene were genotyped in 179 individuals with schizophrenia and 189 healthy controls. No significant associations were detected between any of the four VDR SNPs and risk of schizophrenia. Patients were slightly but significantly shorter compared to controls. Of the four SNPs, only rs10735810/FokI was associated with any of the anthropometric measures: the M4 isoform of this SNP was significantly associated with larger head size (P = 0.002). In light of the evidence demonstrating a role for vitamin D during brain development, the association between polymorphisms in VDR and brain development warrants closer scrutiny.

Identification of the semaphorin receptor PLXNA2 as a candidate for susceptibility to schizophrenia.

The discovery of genetic factors that contribute to schizophrenia susceptibility is a key challenge in understanding the etiology of this disease. Here, we report the identification of a novel schizophrenia candidate gene on chromosome 1q32, plexin A2 (PLXNA2), in a genome-wide association study using 320 patients with schizophrenia of European descent and 325 matched controls. Over 25,000 single-nucleotide polymorphisms (SNPs) located within approximately 14,000 genes were tested. Out of 62 markers found to be associated with disease status, the most consistent finding was observed for a candidate locus on chromosome 1q32. The marker SNP rs752016 showed suggestive association with schizophrenia (odds ratio (OR) = 1.49, P = 0.006). This result was confirmed in an independent case-control sample of European Americans (combined OR = 1.38, P = 0.035) and similar genetic effects were observed in smaller subsets of Latin Americans (OR = 1.26) and Asian Americans (OR = 1.37). Supporting evidence was also obtained from two family-based collections, one of which reached statistical significance (OR = 2.2, P = 0.02). High-density SNP mapping showed that the region of association spans approximately 60 kb of the PLXNA2 gene. Eight out of 14 SNPs genotyped showed statistically significant differences between cases and controls. These results are in accordance with previous genetic findings that identified chromosome 1q32 as a candidate region for schizophrenia. PLXNA2 is a member of the transmembrane semaphorin receptor family that is involved in axonal guidance during development and may modulate neuronal plasticity and regeneration. The PLXNA2 ligand semaphorin 3A has been shown to be upregulated in the cerebellum of individuals with schizophrenia. These observations, together with the genetic results, make PLXNA2 a likely candidate for the 1q32 schizophrenia susceptibility locus.

Separate and interacting effects within the catechol-O-methyltransferase (COMT) are associated with schizophrenia.

Several lines of evidence have implicated the catechol-O-methyltransferase (COMT) gene as a candidate for schizophrenia (SZ) susceptibility, not only because it encodes a key dopamine catabolic enzyme but also because it maps to the velocardiofacial syndrome region of chromosome 22q11 which has long been associated with SZ predisposition. The interest in COMT as a candidate SZ risk factor has led to numerous case-control and family-based studies, with the majority placing emphasis on examining a functional Val/Met polymorphism within this enzyme. Unfortunately, these studies have continually produced conflicting results. To assess the genetic contribution of other COMT variants to SZ susceptibility, we investigated three single-nucleotide polymorphisms (SNPs) (rs737865, rs4633, rs165599) in addition to the Val/Met variant (rs4680) in a highly selected sample of Australian Caucasian families containing 107 patients with SZ. The Val/Met and rs4633 variants showed nominally significant associations with SZ (P<0.05), although neither of the individual SNPs remained significant after adjusting for multiple testing (most significant P=0.1174). However, haplotype analyses showed strong evidence of an association; the most significant being the three-marker haplotype rs737865-rs4680-rs165599 (global P=0.0022), which spans more than 26 kb. Importantly, conditional analyses indicated the presence of two separate and interacting effects within this haplotype, irrespective of gender. In addition, our results indicate the Val/Met polymorphism is not disease-causing and is simply in strong linkage disequilibrium with a causative effect, which interacts with another as yet unidentified variant approximately 20 kb away. These results may help explain the inconsistent results reported on the Val/Met polymorphism and have important implications for future investigations into the role of COMT in SZ susceptibility.

Multicenter linkage study of schizophrenia loci on chromosome 22q.

The hypothesis of the existence of one or more schizophrenia susceptibility loci on chromosome 22q is supported by reports of genetic linkage and association, meta-analyses of linkage, and the observation of elevated risk for psychosis in people with velocardiofacial syndrome, caused by 22q11 microdeletions. We tested this hypothesis by evaluating 10 microsatellite markers spanning 22q in a multicenter sample of 779 pedigrees. We also incorporated age at onset and sex into the analysis as covariates. No significant evidence for linkage to schizophrenia or for linkage associated with earlier age at onset, gender, or heterogeneity across sites was observed. We interpret these findings to mean that the population-wide effects of putative 22q schizophrenia susceptibility loci are too weak to detect with linkage analysis even in large samples.

Polymorphisms in the 5'-untranslated region of the human serotonin receptor 1B (HTR1B) gene affect gene expression.

We present evidence of complex balancing regulation of HTR1B transcription by common polymorphisms in its promoter. Computational analysis of the HTR1B gene predicted that a 5' segment, spanning common DNA sequence variations, T-261G, A-161T, and -182INS/DEL-181, contained a putative functional promoter. Using a secreted alkaline phosphatase (SEAP) reporter gene system, we found that the haplotype -261G_-182INS-181_A-161 enhanced transcriptional activity 2.3-fold compared with the haplotype T-261_-182INS-181_A-161. Conversely, -161T reversed this, and the net effect when -261G and -161T were in the same haplotype (-261G_-182INS-181_-161T) was equivalent to the major haplotype (T-261_-182INS-181_A-161). Electrophoretic mobility shift experiments showed that -261G and -161T modify the binding of transcription factors (TFs): -261G generates a new AP2 binding site, while alleles A-161 and -161T exhibit different binding characteristics to AP1. T-261G and A-161T were found to be in linkage disequilibrium (LD) with G861C in a European ancestry population. Interestingly, G861C has been reported to be associated with several psychiatric disorders. Our results indicate that HTR1B is the target of substantial transcriptional genetic regulation by common haplotypes, which are in LD with the HTR1B single-nucleotide polymorphism (SNP) most commonly used in association studies.

Immunotoxicity of a standardized citrus polymethoxylated flavone extract.

Polymethoxylated flavones (PMFs) from citrus inhibit production of TNF-alpha and other pro-inflammatory cytokines. As TNF-alpha also modulates NK cell activity, the current studies were conducted to assess the potential for a standardized citrus PMF mixture to suppress humoral and innate immune functions. PMFs were isolated from orange peel oil using a procedure that obtained a consistent mixture of PMFs both in identity and proportion. The mixture consisted of nobiletin (30.7%), 3,3',4',5,6,7,8-heptamethoxyflavone (27.9%), trimethylscutellarein (14.5%), tangeretin (10.4%), sinensetin (5.8%), 5-demethyl-nobiletin (2.0%), hexa-O-methylquercetagetin (1.3%), 5-demethyl-tetramethylscutellarein (0.6%), and other flavonoids (2.7%). To assess the effect of the PMF mixture on humoral immune responses, female B(6)C(3)F(1) mice (n=8) were exposed to the PMF by gavage at 5, 50, 150 and 500 mg/kg/day for 28 days. On day 25, mice were sensitized to sRBC by tail vein injection and AFC response determined 4 days later. Humoral immunity was insensitive to suppression following exposure to all concentrations of the PMF mixture. Suppression of NK cell activity was observed only following 500 mg/kg/day for 28 days. Body weights were not affected by exposure to any concentration of the PMF mixture in sRBC immunized or non-immunized mice. However, in sRBC-immunized mice, higher concentrations of PMF were associated with a statistically insignificant increase in spleen weight (P>0.05). No change in spleen weight was observed in non-immunized mice. As anticipated, based on previously published in vitro observations, long-term, high-dose exposure to a standardized mixture of citrus PMFs caused a mild suppression of NK cell activity; however, humoral immunity was not sensitive to suppression at the same exposure levels.

Genetic diversity of the human serotonin receptor 1B (HTR1B) gene.

We systematically and comprehensively investigated polymorphisms of the HTR1B gene as well as their linkage disequilibrium and ancestral relationships. We have detected the following polymorphisms in our sample via denaturing gradient gel electrophoresis, database comparisons, and/or previously published assays: G-511T, T-261G, -182INS/DEL-181, A-161T, C129T, T371G, T655C, C705T, G861C, A1099G, G1120A, and A1180G. The results of the intermarker analyses showed strong linkage disequilibrium between the C129T and the G861C polymorphisms and revealed four common haplotypes: ancestral (via chimpanzee comparisons), 129T/861C, -161T, and -182DEL-181. The results of association tests with schizophrenia were negative, although A-161T had a nominal P = 0.04 via ASPEX/sib_tdt. The expressed missense substitutions, Phe124Cys, Phe219Leu, Ile367Val, and Glu374Lys, could potentially affect ligand binding or interaction with G proteins and thus modify drug response in carriers of these variants. On average, the human cSNPs and differences among other primates clustered in the more thermodynamically unstable regions of the mRNA, which suggests that the evolutionary survival of nucleotide sequence variation may be influenced by the mRNA structure of this gene.