[Role of glycogen synthase kinase-3β in the pathogenesis of mental disorders]

The literature review contains data about functions of glycogen synthase kinase-313 (GSK-313) in the cell and its role in the functioning of the nervous tissue, an analysis of current research on the participation of GSK-313 in the pathogenesis of affective disorders and schizophrenia and effect of psychotropic drugs on the activity of the kinase.

The role of FKBP5 in mood disorders: action of FKBP5 on steroid hormone receptors leads to questions about its evolutionary importance

Research on the FKBP5 gene and FKBP51 protein has more than doubled since the discovery that polymorphisms in this gene could alter treatment outcomes and depressive behavior in humans. This coincided with other data suggesting that the stress hormone axis contributes to the development of numerous mental illnesses. As a result, FKBP51 now lies at the heart of the research of many stress related psychiatric disorders, which has led to advances in the understanding of this protein and its role in humans and in animal models. Specifically, FKBP5-/- mice and a naturally existing overexpression of FKBP5 in 3 genera of new world monkeys have helped understand the effects of FKBP5 in vivo. This review will highlight these finding as well as discuss the current evolutionary need for the FKBP5 gene.

[Circadian rhythm and mood disorder]

Mood disorders show a common feature of distorted cycling of biological systems, manifesting, for example, as diurnal mood variation in depression, phasic time course in bipolar disorder, and seasonal mood swing in seasonal affective disorder. Accordingly, circadian dysfunction has been supposed to play an etiological role in mood disorders. Increasing evidence indicates that circadian misalignment between neuroendocrinological rhythm and the timing of sleep correlates with the severity of symptoms. In addition, several genetic studies have suggested that certain clock gene variants play a role in vulnerability to these disorders, and especially bipolar disorders. However, the role of circadian phenotypes and circadian genes in mood spectrum disorders remains unclear, although currently seem to have a pathoplastic rather than a pathogenetic effect.

The roles of DNA methylation of NR3C1 and 11β-HSD2 and exposure to maternal mood disorder in utero on newborn neurobehavior

Exposure to maternal mood disorder in utero may program infant neurobehavior via DNA methylation of the glucocorticoid receptor (NR3C1) and 11β-hydroxysteroid dehydrogenase type 2 ( 11β-HSD-2), two placental genes that have been implicated in perturbations of the hypothalamic pituitary adrenocortical (HPA) axis. We tested the relations among prenatal exposure to maternal depression or anxiety, methylation of exon 1F of NR3C1 and 11β-HSD-2, and newborn neurobehavior. Controlling for relevant covariates, infants whose mothers reported depression during pregnancy and showed greater methylation of placental NR3C1 CpG2 had poorer self-regulation, more hypotonia, and more lethargy than infants whose mothers did not report depression. On the other hand, infants whose mothers reported anxiety during pregnancy and showed greater methylation of placental 11β-HSD-2 CpG4 were more hypotonic compared with infants of mothers who did not report anxiety during pregnancy. Our results support the fetal programming hypothesis and suggest that fetal adjustments to cues from the intrauterine environment, in this case an environment that could be characterized by increased exposure to maternal cortisol, may lead to poor neurodevelopmental outcomes.

Epigenetic basis for the development of depression in children

The growing field of epigenetics and human behavior affords an unprecedented opportunity to discover molecular underpinnings of mental health disorders and pave the way for the development of preventive intervention programs. Maternal depression during pregnancy is a serious public health issue and leads to a 4-fold increase in the likelihood that the child will develop depression. We describe how mood disorders, particularly depression, may be shaped by early life stress, programming, and epigenetic processes and pathways showing how these processes could lead to depression in childhood. Implications of this approach to the study of mental health disorders for preventive interventions are discussed.

Human biomarkers of rapid antidepressant effects

Mood disorders such as major depressive disorder and bipolar disorder--and their consequent effects on the individual and society--are among the most disabling and costly of all medical illnesses. Although a number of antidepressant treatments are available in clinical practice, many patients still undergo multiple and lengthy medication trials before experiencing relief of symptoms. Therefore a tremendous need exists to improve current treatment options and to facilitate more rapid, successful treatment in patients suffering from the deleterious neurobiological effects of ongoing depression. Toward that end, ongoing research is exploring the identification of biomarkers that might be involved in prevention, diagnosis, treatment response, severity, or prognosis of depression. Biomarkers evaluating treatment response will be the focus of this review, given the importance of providing relief to patients in a more expedient and systematic manner. A novel approach to developing such biomarkers of response would incorporate interventions with a rapid onset of action--such as sleep deprivation or intravenous drugs (e.g., ketamine or scopolamine). This alternative translational model for new treatments in psychiatry would facilitate shorter studies, improve feasibility, and increase higher compound throughput testing for these devastating disorders.

An affective disorder in zebrafish with mutation of the glucocorticoid receptor

Upon binding of cortisol, the glucocorticoid receptor (GR) regulates the transcription of specific target genes, including those that encode the stress hormones corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone. Dysregulation of the stress axis is a hallmark of major depression in human patients. However, it is still unclear how glucocorticoid signaling is linked to affective disorders. We identified an adult-viable zebrafish mutant in which the negative feedback on the stress response is disrupted, due to abolition of all transcriptional activity of GR. As a consequence, cortisol is elevated, but unable to signal through GR. When placed into an unfamiliar aquarium ('novel tank'), mutant fish become immobile ('freeze'), show reduced exploratory behavior and do not habituate to this stressor upon repeated exposure. Addition of the antidepressant fluoxetine to the holding water and social interactions restore normal behavior, followed by a delayed correction of cortisol levels. Fluoxetine does not affect the overall transcription of CRH, the mineralocorticoid receptor (MR), the serotonin transporter (Serta) or GR itself. Fluoxetine, however, suppresses the stress-induced upregulation of MR and Serta in both wild-type fish and mutants. Our studies show a conserved, protective function of glucocorticoid signaling in the regulation of emotional behavior and reveal novel molecular aspects of how chronic stress impacts vertebrate brain physiology and behavior. Importantly, the zebrafish model opens up the possibility of high-throughput drug screens in search of new classes of antidepressants.

Variants within the GABA transaminase (ABAT) gene region are associated with somatosensory evoked EEG potentials in families at high risk for affective disorders

BACKGROUND

Depression frequently co-occurs with somatization, and somatic complaints have been reported as a vulnerability marker for affective disorders observable before disease onset. Somatization is thought to result from an increased attention to somatic sensations, which should be reflected in long-latency somatosensory evoked electroencephalogram (EEG) potentials (SSEPs) at the physiological level. Previous studies revealed that SSEPs are altered in depressed patients and suggested late SSEP components as vulnerability markers for affective disorders. Neurotransmitters such as serotonin, γ-aminobutyric acid (GABA) and the neuropeptide substance P may play an important role for both affective disorders and somatosensory processing. Method We investigated the associations between SSEPs and polymorphisms within candidate genes of the serotonergic, GABAergic as well as the substance P system in subjects at high risk for affective disorders. The sample was composed of high-risk families participating in the Munich Vulnerability Study and genetic association analyses were calculated using qfam (family-based association tests for quantitative traits) implemented in PLINK 1.05.

RESULTS

We observed significant associations (false discovery rate <0.05) withstanding correction for multiple testing between late SSEP components (response strength 170-370 ms after stimulation) and four single nucleotide polymorphisms within the GABA transaminase (ABAT) gene region coding for a protein responsible for GABA degradation. No effects were found with the classical disease trait approach, suggesting SSEP marker specificity of the observed associations.

CONCLUSIONS

Our findings point to a possible role of ABAT gene-regulated GABA catabolism for an altered processing of somatosensory stimuli as a potential vulnerability marker for affective disorders.

Thought disorder in mid-childhood as a predictor of adulthood diagnostic outcome: findings from the New York High-Risk Project

BACKGROUND

Thought disorder has been proposed as an indicator of schizotypy, which is considered to be necessary but not sufficient for the development of schizophrenia. It is unclear whether thought disorder is an indicator of susceptibility (i.e. an endophenotype) for schizophrenia. The goal of the present study was to elucidate the role of thought disorder in relation to schizotypy by examining its presence in high-risk individuals during mid-childhood. Method The sample consisted of 265 subjects drawn from the New York High-Risk Project. Individuals at high risk for schizophrenia (i.e. offspring of parents with schizophrenia) were compared with individuals at low risk for schizophrenia (i.e. offspring of parents with affective disorder or offspring of psychiatrically normal parents). Videotaped interviews were rated for thought disorder using the Scale for the Assessment of Thought, Language, and Communication (TLC). The same subjects were administered diagnostic interviews in late adolescence/early adulthood.

RESULTS

Although positive thought disorder was equally present in subjects with affective and non-affective psychoses, negative thought disorder (namely, poverty of speech and poverty of content of speech) was elevated only in subjects with schizophrenia-related psychosis. Logistic regression analyses revealed that negative thought disorder added to the prediction of schizophrenia-related psychosis outcomes over and above positive thought disorder.

CONCLUSIONS

These findings suggest that negative thought disorder may have a specific association with schizotypy, rather than a more general association with psychosis. The findings also support consideration of negative thought disorder as an endophenotypic indicator of a schizophrenia diathesis.

Risk markers for affective disorder, a seven-years follow up study of a twin cohort at low and high risk for affective disorder

This study aims to investigate whether: familial history of affective disorder, subclinical depressive symptoms and life events (LEs) are predictive of a later development of mood disorder (onset). In a high-risk study, 234 healthy monozygotic and dizygotic twins with and without a co-twin history of affective disorder (high and low risk twins, respectively) were identified through nationwide registers and assessed from 2002 to 2005. Participants were followed longitudinally at 6-months intervals for up to nine years and finally reassessed with a personal interview to obtain information on whether they had an onset. During the follow-up period (mean time 7.0 years), 36 participants (15.4%) developed onset. Onset was significantly associated with risk status (Hazard ratio (HR) = 1.38, 95% CI 1.08-1.76), female sex, HR = 2.70, 95% CI 1.19-6.97, age HR = 0.97, 95% CI 0.93-0.99), and also with baseline Hamilton 17 score (HR = 1.30, 95% CI 1.13-1.48), Becks Depression Inventory 21 (HR = 1.14, 95% CI, 1.05-1.24) and neuroticism (HR = 1.08, 95% 1.02-1.12). Finally, the experience of LEs lifetime before baseline predicted onset (HR = 1.20, 95% CI 1.01-1.46) and the experience of LEs during follow-up also predicted onset (HR = 1.06, 95% CI 1.01-1.11). These findings suggest that young individuals at familial risk of affective disorders are at enhanced risk of onset and at further risk when having female sex and more subclinical depressive symptoms at baseline. Further, they seem to experience more LEs and to be more vulnerable to these.

Genome-wide scan of job-related exhaustion with three replication studies implicate a susceptibility variant at the UST gene locus

Job-related exhaustion is the core dimension of burnout, a work-related stress syndrome that has several negative health consequences. In this study, we explored the molecular genetic background of job-related exhaustion. A genome-wide analysis of job-related exhaustion was performed in the GENMETS subcohort (n = 1256) of the Finnish population-based Health 2000 study. Replication analyses included an analysis of the strongest associations in the rest of the Health 2000 sample (n = 1660 workers) and in three independent populations (the FINRISK population cohort, n = 10 753; two occupational cohorts, total n = 1451). Job-related exhaustion was ascertained using a standard self-administered questionnaire (the Maslach Burnout Inventory (MBI)-GS exhaustion scale in the Health 2000 sample and the occupational cohorts) or a single question (FINRISK). A variant located in an intron of UST, uronyl-2-sulfotransferase (rs13219957), gave the strongest statistical evidence in the initial genome-wide study (P = 1.55 × 10(-7)), and was associated with job-related exhaustion in all the replication sets (P < 0.05; P = 6.75 × 10(-7) from the meta-analysis). Consistent with studies of mood disorders, individual common genetic variants did not have any strong effect on job-related exhaustion. However, the nominally significant signals from the allelic variant of UST in four separate samples suggest that this variant might be a weak risk factor for job-related exhaustion. Together with the previously reported associations of other dermatan/chondroitin sulfate genes with mood disorders, these results indicate a potential molecular pathway for stress-related traits and mark a candidate region for further studies of job-related and general exhaustion.

Candidate gene studies of a promising intermediate phenotype: failure to replicate

Many candidate gene studies use 'intermediate phenotypes' instead of disease diagnoses. It has been proposed that intermediate phenotypes have simpler genetic architectures such that individual alleles account for a larger percentage of trait variance. This implies that smaller samples can be used to identify genetic associations. Pharmacogenomic drug challenge studies may be an especially promising class of intermediate phenotype. We previously conducted a series of 12 candidate gene analyses of acute subjective and physiological responses to amphetamine in 99-162 healthy human volunteers (ADORA2A, SLC6A3, BDNF, SLC6A4, CSNK1E, SLC6A2, DRD2, FAAH, COMT, OPRM1). Here, we report our attempt to replicate these findings in over 200 additional participants ascertained using identical methodology. We were unable to replicate any of our previous findings. These results raise critical issues related to non-replication of candidate gene studies, such as power, sample size, multiple testing within and between studies, publication bias and the expectation that true allelic effect sizes are similar to those reported in genome-wide association studies. Many of these factors may have contributed to our failure to replicate our previous findings. Our results should instill caution in those considering similarly designed studies.

A large-scale candidate gene analysis of mood disorders: evidence of neurotrophic tyrosine kinase receptor and opioid receptor signaling dysfunction

BACKGROUND

Despite proven heritability, little is known about the genetic architecture of mood disorders. Although a number of family and case-control studies have examined the genetics of mood disorders, none have carried out joint linkage-association studies and sought to validate the results with gene expression analyses in an independent cohort.

METHODS

We present findings from a large candidate gene study that combines linkage and association analyses using families and singletons, providing a systematic candidate gene investigation of mood disorder. For this study, 876 individuals were recruited, including 83 families with 313 individuals and 563 singletons. This large-scale candidate gene analysis included 130 candidate genes implicated in addictive and other psychiatric disorders. These data showed significant genetic associations for 28 of these candidate genes, although none remained significant after correction for multiple testing. To evaluate the functional significance of these 28 candidate genes in mood disorders, we examined the transcriptional profiles of these genes within the dorsolateral prefrontal cortex and anterior cingulate for 21 cases with mood disorders and 25 nonpsychiatric controls, and carried out a pathway analysis to identify points of high connectivity suggestive of particular molecular pathways that may be dysregulated.

RESULTS

Two primary gene candidates were supported by the linkage-association, gene expression profiling, and network analysis: neurotrophic tyrosine kinase receptor, type 2 (NTRK2), and the opioid receptor, κ1 (OPRK1).

CONCLUSION

This study supports a role for NTRK2 and OPRK1 signaling in the pathophysiology of mood disorder. The unique approach incorporating evidence from multiple experimental and computational modalities enhances confidence in these findings.

Brain dopamine-serotonin vesicular transport disease and its treatment

We describe a disease encompassing infantile-onset movement disorder (including severe parkinsonism and nonambulation), mood disturbance, autonomic instability, and developmental delay, and we describe evidence supporting its causation by a mutation in SLC18A2 (which encodes vesicular monoamine transporter 2 [VMAT2]). VMAT2 translocates dopamine and serotonin into synaptic vesicles and is essential for motor control, stable mood, and autonomic function. Treatment with levodopa was associated with worsening, whereas treatment with direct dopamine agonists was followed by immediate ambulation, near-complete correction of the movement disorder, and resumption of development.

Empathy and emotion recognition in people with autism, first-degree relatives, and controls

Empathy is the lens through which we view others' emotion expressions, and respond to them. In this study, empathy and facial emotion recognition were investigated in adults with autism spectrum conditions (ASC; N=314), parents of a child with ASC (N=297) and IQ-matched controls (N=184). Participants completed a self-report measure of empathy (the Empathy Quotient [EQ]) and a modified version of the Karolinska Directed Emotional Faces Task (KDEF) using an online test interface. Results showed that mean scores on the EQ were significantly lower in fathers (p<0.05) but not mothers (p>0.05) of children with ASC compared to controls, whilst both males and females with ASC obtained significantly lower EQ scores (p<0.001) than controls. On the KDEF, statistical analyses revealed poorer overall performance by adults with ASC (p<0.001) compared to the control group. When the 6 distinct basic emotions were analysed separately, the ASC group showed impaired performance across five out of six expressions (happy, sad, angry, afraid and disgusted). Parents of a child with ASC were not significantly worse than controls at recognising any of the basic emotions, after controlling for age and non-verbal IQ (all p>0.05). Finally, results indicated significant differences between males and females with ASC for emotion recognition performance (p<0.05) but not for self-reported empathy (p>0.05). These findings suggest that self-reported empathy deficits in fathers of autistic probands are part of the 'broader autism phenotype'. This study also reports new findings of sex differences amongst people with ASC in emotion recognition, as well as replicating previous work demonstrating empathy difficulties in adults with ASC. The use of empathy measures as quantitative endophenotypes for ASC is discussed.

A new clinical evidence-based gene-environment interaction model of depression

In our current understanding of mood disorders, the role of genes is diverse including the mediation of the effects of provoking and protective factors. Different or partially overlapping gene sets play a major role in the development of personality traits including also affective temperaments, in the mediation of the effects of environmental factors, and in the interaction of these elements in the development of depression. Certain genes are associated with personality traits and temperaments including e.g., neuroticism, impulsivity, openness, rumination and extroversion. Environmental factors consist of external (early and provoking life events, seasonal changes, social support etc.) and internal factors (hormones, biological rhythm generators, comorbid disorders etc). Some of these environmental factors, such as early life events and some prenatal events directly influence the development of personality traits and temperaments. In the NEWMOOD cohort polymorphisms of the genes of the serotonin transporter, 5-HT1A, 5-HT1B and 5-HT2A and endocannabinoid CB1 receptors, tryptophan hydroxylase, CREB1, BDNF and GIRK provide evidence for the involvement of these genes in the development of depression. Based on their role in this process they could be assigned to different gene sets. The role of certain genes, such as promoter polymorphisms of the serotonin transporter (5-HTTLPR) and CB1 receptor has been shown in more than one of the above factors. Furthermore, gene-gene interactions of these promoters associated with anxiety suggest the application of these polymorphisms in personalized medicine. In this review we introduce a new model including environmental factors, genes, trait and temperament markers based on human genetic studies.

Analysis of copy number variations in brain DNA from patients with schizophrenia and other psychiatric disorders

BACKGROUND

Clinical studies have identified several regions of the genome with copy number variations (CNVs) associated with diverse neurodevelopmental behavioral disorders.

METHODS

We analyzed 1 million (M) single nucleotide polymorphism genotype arrays for evidence of previously reported recurrent CNVs and enriched genome-wide CNV burden in DNA from 600 brains, including 441 individuals with various psychiatric diagnoses. We explored gene expression in the dorsolateral prefrontal cortex in selected cases with CNVs and in other subjects with Illumina BeadArrays (568 subjects in total) and additionally in 66-92 subjects with quantitative real-time polymerase chain reaction.

RESULTS

The CNVs in previously reported genomic regions were identified in 4 of 193 patients with the diagnosis of schizophrenia (1q21.1, 11q25, 15q11.2, 22q11), 4 of 238 patients with mood disorders (11q25, 15q11.2, 22q11), and 1 of 10 patients with autism (2p16.3). No evidence of increased genome-wide CNV burden was observed in cases with schizophrenia or mood disorders, although the study is underpowered to observe rare events. Messenger RNA expression patterns suggested incomplete molecular penetrance of observed CNVs.

CONCLUSIONS

Our data confirm in brain DNA the presence of certain recurrent CNVs in a small percentage of patients with psychiatric diagnoses.

Genome-wide association uncovers shared genetic effects among personality traits and mood states

Measures of personality and psychological distress are correlated and exhibit genetic covariance. We conducted univariate genome-wide SNP (~2.5 million) and gene-based association analyses of these traits and examined the overlap in results across traits, including a prediction analysis of mood states using genetic polygenic scores for personality. Measures of neuroticism, extraversion, and symptoms of anxiety, depression, and general psychological distress were collected in eight European cohorts (n ranged 546-1,338; maximum total n = 6,268) whose mean age ranged from 55 to 79 years. Meta-analysis of the cohort results was performed, with follow-up associations of the top SNPs and genes investigated in independent cohorts (n = 527-6,032). Suggestive association (P = 8 × 10(-8)) of rs1079196 in the FHIT gene was observed with symptoms of anxiety. Other notable associations (P < 6.09 × 10(-6)) included SNPs in five genes for neuroticism (LCE3C, POLR3A, LMAN1L, ULK3, SCAMP2), KIAA0802 for extraversion, and NOS1 for general psychological distress. An association between symptoms of depression and rs7582472 (near to MGAT5 and NCKAP5) was replicated in two independent samples, but other replication findings were less consistent. Gene-based tests identified a significant locus on chromosome 15 (spanning five genes) associated with neuroticism which replicated (P < 0.05) in an independent cohort. Support for common genetic effects among personality and mood (particularly neuroticism and depressive symptoms) was found in terms of SNP association overlap and polygenic score prediction. The variance explained by individual SNPs was very small (up to 1%) confirming that there are no moderate/large effects of common SNPs on personality and related traits.

A t(1;11) translocation linked to schizophrenia and affective disorders gives rise to aberrant chimeric DISC1 transcripts that encode structurally altered, deleterious mitochondrial proteins

Disrupted-In-Schizophrenia 1 (DISC1) was identified as a risk factor for psychiatric illness through its disruption by a balanced chromosomal translocation, t(1;11)(q42.1;q14.3), that co-segregates with schizophrenia, bipolar disorder and depression. We previously reported that the translocation reduces DISC1 expression, consistent with a haploinsufficiency disease model. Here we report that, in lymphoblastoid cell lines, the translocation additionally results in the production of abnormal transcripts due to the fusion of DISC1 with a disrupted gene on chromosome 11 (DISC1FP1/Boymaw). These chimeric transcripts encode abnormal proteins, designated CP1, CP60 and CP69, consisting of DISC1 amino acids 1-597 plus 1, 60 or 69 amino acids, respectively. The novel 69 amino acids in CP69 induce increased α-helical content and formation of large stable protein assemblies. The same is predicted for CP60. Both CP60 and CP69 exhibit profoundly altered functional properties within cell lines and neurons. Both are predominantly targeted to mitochondria, where they induce clustering and loss of membrane potential, indicative of severe mitochondrial dysfunction. There is currently no access to neural material from translocation carriers to confirm these findings, but there is no reason to suppose that these chimeric transcripts will not also be expressed in the brain. There is thus potential for the production of abnormal chimeric proteins in the brains of translocation carriers, although at substantially lower levels than for native DISC1. The mechanism by which inheritance of the translocation increases risk of psychiatric illness may therefore involve both DISC1 haploinsufficiency and mitochondrial deficiency due to the effects of abnormal chimeric protein expression. GenBank accession numbers: DISC1FP1 (EU302123), Boymaw (GU134617), der 11 chimeric transcript DISC1FP1 exon 2 to DISC1 exon 9 (JQ650115), der 1 chimeric transcript DISC1 exon 4 to DISC1FP1 exon 4 (JQ650116), der 1 chimeric transcript DISC1 exon 6 to DISC1FP1 exon 3a (JQ650117).

Identification of sialyltransferase 8B as a generalized susceptibility gene for psychotic and mood disorders on chromosome 15q25-26

We previously identified a significant bipolar spectrum disorder linkage peak on 15q25-26 using 35 extended families with a broad clinical phenotype, including bipolar disorder (types I and II), recurrent unipolar depression and schizoaffective disorder. However, the specific gene(s) contributing to this signal had not been identified. By a fine mapping association study in an Australian case-control cohort (n = 385), we find that the sialyltransferase 8B (ST8SIA2) gene, coding for an enzyme that glycosylates proteins involved in neuronal plasticity which has previously shown association to both schizophrenia and autism, is associated with increased risk to bipolar spectrum disorder. Nominal single point association was observed with SNPs in ST8SIA2 (rs4586379, P = 0.0043; rs2168351, P = 0.0045), and a specific risk haplotype was identified (frequency: bipolar vs controls = 0.41 vs 0.31; χ(2) = 6.46, P = 0.011, OR = 1.47). Over-representation of the specific risk haplotype was also observed in an Australian schizophrenia case-control cohort (n = 256) (χ(2) = 8.41, P = 0.004, OR = 1.82). Using GWAS data from the NIMH bipolar disorder (n = 2055) and NIMH schizophrenia (n = 2550) cohorts, the equivalent haplotype was significantly over-represented in bipolar disorder (χ(2) = 5.91, P = 0.015, OR = 1.29), with the same direction of effect in schizophrenia, albeit non-significant (χ(2) = 2.3, P = 0.129, OR = 1.09). We demonstrate marked down-regulation of ST8SIA2 gene expression across human brain development and show a significant haplotype×diagnosis effect on ST8SIA2 mRNA levels in adult cortex (ANOVA: F(1,87) = 6.031, P = 0.016). These findings suggest that variation the ST8SIA2 gene is associated with increased risk to mental illness, acting to restrict neuronal plasticity and disrupt early neuronal network formation, rendering the developing and adult brain more vulnerable to secondary genetic or environmental insults.