Normal Face Detection Over a Range of Luminance Contrasts in Adolescents With Autism Spectrum Disorder.

Face recognition is impaired in autism spectrum disorders (ASDs), but the reason for this remains unclear. One possibility is that impairments in the ability to visually detect faces might be a factor. As a preliminary study in this vein, we measured face detection ability as a function of visual contrast level in 13 individuals with ASD, aged 13-18, and 18 neurotypical controls (NCs) in the same age range. We also measured contrast sensitivity, using sinusoidal grating stimuli, as a control task. Individuals with ASD did not differ from controls in face detection (p > 0.9) or contrast detection (p > 0.2) ability. Performance on contrast and face detection was significantly correlated in ASD but not in NC. Results suggest that the ability to visually detect faces is not altered in ASD overall, but that alterations in basic visual processing may affect face detection ability in some individuals with ASD.

Targeted Treatment of Individuals With Psychosis Carrying a Copy Number Variant Containing a Genomic Triplication of the Glycine Decarboxylase Gene.

BACKGROUND: The increased mutational burden for rare structural genomic variants in schizophrenia and other neurodevelopmental disorders has so far not yielded therapies targeting the biological effects of specific mutations. We identified two carriers (mother and son) of a triplication of the gene encoding glycine decarboxylase, GLDC, presumably resulting in reduced availability of the N-methyl-D-aspartate receptor coagonists glycine and D-serine and N-methyl-D-aspartate receptor hypofunction. Both carriers had a diagnosis of a psychotic disorder. METHODS: We carried out two double-blind, placebo-controlled clinical trials of N-methyl-D-aspartate receptor augmentation of psychotropic drug treatment in these two individuals. Glycine was used in the first clinical trial, and D-cycloserine was used in the second one. RESULTS: Glycine or D-cycloserine augmentation of psychotropic drug treatment each improved psychotic and mood symptoms in placebo-controlled trials. CONCLUSIONS: These results provide two independent proof-of-principle demonstrations of symptom relief by targeting a specific genotype and explicitly link an individual mutation to the pathophysiology of psychosis and treatment response.

New insights into tardive dyskinesia genetics: Implementation of whole-exome sequencing approach.

Tardive dyskinesia (TD) is an adverse movement disorder induced by chronic treatment with antipsychotics drugs. The contribution of common genetic variants to TD susceptibility has been investigated in recent years, but with limited success. The aim of the current study was to investigate the potential contribution of rare variants to TD vulnerability. In order to identify TD risk genes, we performed whole-exome sequencing (WES) and gene-based collapsing analysis focusing on rare (allele frequency < 1%) and putatively deleterious variants (qualifying variants). 82 Jewish schizophrenia patients chronically treated with antipsychotics were included and classified as having severe TD or lack of any abnormal movements based on a rigorous definition of the TD phenotype. First, we performed a case-control, exome-wide collapsing analysis comparing 39 schizophrenia patients with severe TD to 3118 unrelated population controls. Then, we checked the potential top candidate genes among 43 patients without any TD manifestations. All the genes that were found to harbor one or more qualifying variants in patients without any TD features were excluded from the final list of candidate genes. Only one gene, regulating synaptic membrane exocytosis 2 (RIMS2), showed significant enrichment of qualifying variants in TD patients compared with unrelated population controls after correcting for multiple testing (Fisher's exact test p = 5.32E-08, logistic regression p = 2.50E-08). Enrichment was caused by a single variant (rs567070433) due to a frameshift in an alternative transcript of RIMS2. None of the TD negative patients had qualifying variants in this gene. In a validation cohort of 140 schizophrenia patients assessed for TD, the variant was also not detected in any individual. Some potentially suggestive TD genes were detected in the TD cohort and warrant follow-up in future studies. No significant enrichment in previously reported TD candidate genes was identified. To the best of our knowledge, this is the first WES study of TD, demonstrating the potential role of rare loss-of-function variant enrichment in this pharmacogenetic phenotype.

Auditory steady state response deficits are associated with symptom severity and poor functioning in patients with psychotic disorder.

OBJECTIVES: Gamma oscillation is important for cortico-cortical coordination and the integration of information across neural networks. The 40 Hz auditory steady-state response (ASSR), which reflects neural synchrony in the gamma band (30-100 Hz), is abnormal in patients with schizophrenia (SZ). The present study used the ASSR at multiple frequencies to examine (1) gamma dysfunction in patients with SZ, schizoaffective (SA), and bipolar disorder (BD) compared with controls, (2) the relationship between ASSR measures and clinical symptom severity, and (3) the relationship between ASSR measures and real-life community functioning. METHODS: EEG was recorded from 75 controls, 52 SZ, 55 SA, and 89 BD patients during 20-30-40-Hz binaural click trains. ANCOVA was used to compare ASSR measures between groups controlling for age, sex, and education. Associations between ASSR measures, symptom severity, and community functioning were examined using linear regression and Pearson partial correlations. RESULTS: ASSR deficits at gamma frequency were observed in all patient groups. SA patients showed additional specific deficit in the 20 Hz ASSR. Severity of manic, depressive, and anxiety symptoms mediated ASSR deficits. Severity of hallucinatory symptom and community functioning, particularly independent living/meaningful activity, were significantly and independently associated with the 40 Hz ASSR. CONCLUSIONS: SZ, SA and BD patients are likely to share the same abnormalities in neural processes that generate gamma oscillations. 40 Hz ASSR are associated with community functioning across patients and may serve as a biomarker for predicting functional outcome.

Marker chromosome genomic structure and temporal origin implicate a chromoanasynthesis event in a family with pleiotropic psychiatric phenotypes.

Small supernumerary marker chromosomes (sSMC) are chromosomal fragments difficult to characterize genomically. Here, we detail a proband with schizoaffective disorder and a mother with bipolar disorder with psychotic features who present with a marker chromosome that segregates with disease. We explored the architecture of this marker and investigated its temporal origin. Array comparative genomic hybridization (aCGH) analysis revealed three duplications and three triplications that spanned the short arm of chromosome 9, suggestive of a chromoanasynthesis-like event. Segregation of marker genotypes, phased using sSMC mosaicism in the mother, provided evidence that it was generated during a germline-level event in the proband's maternal grandmother. Whole-genome sequencing (WGS) was performed to resolve the structure and junctions of the chromosomal fragments, revealing further complexities. While structural variations have been previously associated with neuropsychiatric disorders and marker chromosomes, here we detail the precise architecture, human life-cycle genesis, and propose a DNA replicative/repair mechanism underlying formation.

Patient-derived hiPSC neurons with heterozygous CNTNAP2 deletions display altered neuronal gene expression and network activity.

Variants in CNTNAP2, a member of the neurexin family of genes that function as cell adhesion molecules, have been associated with multiple neuropsychiatric conditions such as schizophrenia, autism spectrum disorder and intellectual disability; animal studies indicate a role for CNTNAP2 in axon guidance, dendritic arborization and synaptogenesis. We previously reprogrammed fibroblasts from a family trio consisting of two carriers of heterozygous intragenic CNTNAP2 deletions into human induced pluripotent stem cells (hiPSCs) and described decreased migration in the neural progenitor cells (NPCs) differentiated from the affected CNTNAP2 carrier in this trio. Here, we report the effect of this heterozygous intragenic deletion in CNTNAP2 on global gene expression and neuronal activity in the same cohort. Our findings suggest that heterozygous CNTNAP2 deletions affect genes involved in neuronal development and neuronal activity; however, these data reflect only one family trio and therefore more deletion carriers, with a variety of genetic backgrounds, will be needed to understand the molecular mechanisms underlying CNTNAP2 deletions.

Thought Disorder in Schizophrenia and Bipolar Disorder Probands, Their Relatives, and Nonpsychiatric Controls.

Thought disorder (TD) has long been associated with schizophrenia (SZ) and is now widely recognized as a symptom of mania and other psychotic disorders as well. Previous studies have suggested that the TD found in the clinically unaffected relatives of SZ, schizoaffective and bipolar probands is qualitatively similar to that found in the probands themselves. Here, we examine which quantitative measures of TD optimize the distinction between patients with diagnoses of SZ and bipolar disorder with psychotic features (BP) from nonpsychiatric controls (NC) and from each other. In addition, we investigate whether these same TD measures also distinguish their respective clinically unaffected relatives (RelSZ, RelBP) from controls as well as from each other. We find that deviant verbalizations are significantly associated with SZ and are co-familial in clinically unaffected RelSZ, but are dissociated from, and are not co-familial for, BP disorder. In contrast, combinatory thinking was nonspecifically associated with psychosis, but did not aggregate in either group of relatives. These results provide further support for the usefulness of TD for identifying potential non-penetrant carriers of SZ-risk genes, in turn enhancing the power of genetic analyses. These findings also suggest that further refinement of the TD phenotype may be needed in order to be suitable for use in genetic studies of bipolar disorder.

Divergent Levels of Marker Chromosomes in an hiPSC-Based Model of Psychosis.

In the process of generating presumably clonal human induced pluripotent stem cells (hiPSCs) from two carriers of a complex structural rearrangement, each having a psychotic disorder, we also serendipitously generated isogenic non-carrier control hiPSCs, finding that the rearrangement occurs as an extrachromosomal marker (mar) element. All confirmed carrier hiPSCs and differentiated neural progenitor cell lines were found to be mosaic. We caution that mar elements may be difficult to functionally evaluate in hiPSC cultures using currently available methods, as it is difficult to distinguish cells with and without mar elements in live mosaic cultures.

Increased Nigral SLC6A3 Activity in Schizophrenia Patients: Findings From the Toronto-McLean Cohorts.

SLC6A3, which encodes the primary regulator of extracellular dopamine (DA) concentration, the DA transporter, has been implicated in schizophrenia (SCZ). However, the details of its genetic effect on risk remain largely unknown. The purpose of this candidate gene study was to identify a specificSLC6A3activity associated with SCZ by using functional genetic approaches. We first examined gene activity in DA neurons isolated from case-control postmortem nigral tissue and found that the averageSLC6A3mRNA level in controls was only 0.37-fold of that in cases (P= .0034). To understand this expression difference, we examined the association of 10 genetic markers, mostly located in the promoter region, with SCZ in 1717 subjects collected from Toronto and McLean cohorts, including 881 controls and 836 cases and identified the 5' promoter SNP rs1478435 as having a significant association signal (uncorrectedPvalue: .00462; adjustedPvalue: .0319) in unrelated Caucasians. Allele T was over-represented in controls (OR = .75); T-carrier controls had decreased mRNA levels in nigral DA neurons, contributing to the reduced activity in the controls. In vitro functional analysis confirmed that T carriers displayed attenuated enhancement of promoter activity. These findings collectively suggest that increased nigralSLC6A3activity may be a risk factor for SCZ, and may help to explain high rates of comorbidity with substance abuse.

Quantitative Measures of Craniofacial Dysmorphology in a Family Study of Schizophrenia and Bipolar Illness.

Several laboratories, including ours, have reported an overrepresentation of craniofacial (CF) anomalies in schizophrenia (SZ). How might this dysmorphology arise in a brain-based disorder? Because the brain and face derive from shared embryologic primordia and morphogenetic forces, maldevelopmental processes may result in both CF and brain dysmorphology.Our approach is 2-pronged. First, we have employed, for the first time in the study of psychiatric disorders, objective measures of CF morphology that utilize an extensive normative database, permitting computation of standardized scores for each subject. Second, we have rendered these findings biologically interpretable by adopting principles of embryology in the analysis of dysmorphology.Dependent measures in this investigation focused on derivatives of specific embryonic primordia and were contrasted among probands with psychotic disorders, their first-degree relatives, and normal controls (NC). Subject groups included patients with a diagnosis of SZ (N = 39) or bipolar (BP) disorder with psychotic features (N = 32), their clinically unaffected relatives (N = 82 and N = 41, respectively), and NC (N = 95) subjects.Anomalies involving derivatives of frontonasal and mandibular embryonic primordia showed a clear association with psychotic illness, as well as familial aggregation in relatives in both diagnostic groups. In contrast, one class of CF anomalies emerged only among SZ probands and their first-degree relatives: dysmorphology arising along the junction of the frontonasal and maxillary prominence derivatives, manifested as marked asymmetries. This class was not overrepresented among the BP patients nor among their relatives, indicating that this dysmorphology appears to be specific to SZ and not a generalized feature of psychosis. We discuss these findings in light of embryologic models that relate brain regions to specific CF areas.

Genomewide association analyses of electrophysiological endophenotypes for schizophrenia and psychotic bipolar disorders: a preliminary report.

Several event-related potentials (ERP), including P3, sensory gating (P50), and gamma oscillation, are robustly impaired in patients with schizophrenia (SCZ) and bipolar disorder (BIP). Although these ERPs are known to be heritable, little is known about the specific genetic loci involved and the degree to which they overlap with loci influencing mood and psychotic disorders. In the present study, we conducted GWAS to a) identify common variants associated with ERP endophenotypes, and b) construct polygenic risk scores (PRS) to examine overlap between genetic components of ERPs and mood and psychotic disorders. The sample consisted of 271 patients with SCZ or psychotic BIP diagnosis and 128 controls for whom ERP and genomewide data were available. GWAS were conducted using the full sample. PRS, derived from the Psychiatric Genomics Consortium (PGC) analyses of SCZ, BIP, and major depressive disorder were applied to each ERP phenotype. We identified a region on chromosome 14 that was significantly associated with sensory gating (peak SNP rs10132223, P = 1.27 × 10(-9) ). This locus has not been previously associated with psychotic illness in PGC-GWAS. In the PRS analyses, patients with a higher load of SCZ risk alleles had reduced gamma response whereas patients with a higher load of BIP risk alleles had smaller P3 amplitude. We observed a genomewide significant locus on chromosome 14 for P50. This locus may influence P50 but not psychotic illness. Among patients with psychotic illness, PRS results indicated genetic overlap between SCZ loci and gamma oscillation and between BIP loci and P3 amplitude.

Characterization of molecular and cellular phenotypes associated with a heterozygous CNTNAP2 deletion using patient-derived hiPSC neural cells.

Neurodevelopmental disorders, such as autism spectrum disorders (ASD) and schizophrenia (SZ), are complex disorders with a high degree of heritability. Genetic studies have identified several candidate genes associated with these disorders, including contactin-associated protein-like 2 (CNTNAP2). Traditionally, in animal models or in vitro, the function of CNTNAP2 has been studied by genetic deletion or transcriptional knockdown, which reduce the expression of the entire gene; however, it remains unclear whether the mutations identified in clinical settings are sufficient to alter CNTNAP2 expression in human neurons. Here, using human induced pluripotent stem cells (hiPSCs) derived from two individuals with a large (289kb) and heterozygous deletion in CNTNAP2 (affecting exons 14-15) and discordant clinical outcomes, we have characterized CNTNAP2 expression patterns in hiPSC neural progenitor cells (NPCs), two independent populations of hiPSC-derived neurons and hiPSC-derived oligodendrocyte precursor cells (OPCs). First, we observed exon-specific changes in CNTNAP2 expression in both carriers; although the expression of exons 14-15 is significantly decreased, the expression of other exons is upregulated. Second, we observed significant differences in patterns of allele-specific expression in CNTNAP2 carriers that were consistent with clinical outcome. Third, we observed a robust neural migration phenotype that correlated with diagnosis and exon- and allele-specific CNTNAP2 expression patterns, but not with genotype. In all, our data highlight the importance of considering the nature, location and regulation of mutated alleles when attempting to connect GWAS studies to gene function.

Clozapine-induced agranulocytosis is associated with rare HLA-DQB1 and HLA-B alleles.

Clozapine is a particularly effective antipsychotic medication but its use is curtailed by the risk of clozapine-induced agranulocytosis/granulocytopenia (CIAG), a severe adverse drug reaction occurring in up to 1% of treated individuals. Identifying genetic risk factors for CIAG could enable safer and more widespread use of clozapine. Here we perform the largest and most comprehensive genetic study of CIAG to date by interrogating 163 cases using genome-wide genotyping and whole-exome sequencing. We find that two loci in the major histocompatibility complex are independently associated with CIAG: a single amino acid in HLA-DQB1 (126Q) (P=4.7 × 10(-14), odds ratio (OR)=0.19, 95% confidence interval (CI)=0.12-0.29) and an amino acid change in the extracellular binding pocket of HLA-B (158T) (P=6.4 × 10(-10), OR=3.3, 95% CI=2.3-4.9). These associations dovetail with the roles of these genes in immunogenetic phenotypes and adverse drug responses for other medications, and provide insight into the pathophysiology of CIAG.

A hierarchical finite mixture model that accommodates zero-inflated counts, non-independence, and heterogeneity.

A number of mixture modeling approaches assume both normality and independent observations. However, these two assumptions are at odds with the reality of many data sets, which are often characterized by an abundance of zero-valued or highly skewed observations as well as observations from biologically related (i.e., non-independent) subjects. We present here a finite mixture model with a zero-inflated Poisson regression component that may be applied to both types of data. This flexible approach allows the use of covariates to model both the Poisson mean and rate of zero inflation and can incorporate random effects to accommodate non-independent observations. We demonstrate the utility of this approach by applying these models to a candidate endophenotype for schizophrenia, but the same methods are applicable to other types of data characterized by zero inflation and non-independence.

Neurophysiologic effect of GWAS derived schizophrenia and bipolar risk variants.

Genome-wide association studies (GWAS) have identified multiple single nucleotide polymorphisms (SNPs) as disease associated variants for schizophrenia (SCZ), bipolar disorder (BPD), or both. Although these results are statistically robust, the functional effects of these variants and their role in the pathophysiology of SCZ or BPD remain unclear. Dissecting the effects of risk genes on distinct domains of brain function can provide important biological insights into the mechanisms by which these genes may confer illness risk. This study used quantitative event related potentials to characterize the neurophysiological effects of well-documented GWAS-derived SCZ/BPD susceptibility variants in order to map gene effects onto important domains of brain function. We genotyped 199 patients with DSM-IV diagnoses of SCZ or BPD and 74 healthy control subjects for 19 risk SNPs derived from previous GWAS findings and tested their association with five neurophysiologic traits (P3 amplitude, P3 latency, N1 amplitude, P2 amplitude, and P50 sensory gating responses) known to be abnormal in psychosis. The TCF4 SNP rs17512836 risk allele showed a significant association with reduced auditory P3 amplitude (P = 0.00016) after correction for multiple testing. The same allele was also associated with delayed P3 latency (P = 0.005). Our results suggest that a SCZ risk variant in TCF4 is associated with neurophysiologic traits thought to index attention and working memory abnormalities in psychotic disorders. These findings suggest a mechanism by which TCF4 may contribute to the neurobiological basis of psychotic illness.

Exome sequencing followed by large-scale genotyping suggests a limited role for moderately rare risk factors of strong effect in schizophrenia.

Schizophrenia is a severe psychiatric disorder with strong heritability and marked heterogeneity in symptoms, course, and treatment response. There is strong interest in identifying genetic risk factors that can help to elucidate the pathophysiology and that might result in the development of improved treatments. Linkage and genome-wide association studies (GWASs) suggest that the genetic basis of schizophrenia is heterogeneous. However, it remains unclear whether the underlying genetic variants are mostly moderately rare and can be identified by the genotyping of variants observed in sequenced cases in large follow-up cohorts or whether they will typically be much rarer and therefore more effectively identified by gene-based methods that seek to combine candidate variants. Here, we consider 166 persons who have schizophrenia or schizoaffective disorder and who have had either their genomes or their exomes sequenced to high coverage. From these data, we selected 5,155 variants that were further evaluated in an independent cohort of 2,617 cases and 1,800 controls. No single variant showed a study-wide significant association in the initial or follow-up cohorts. However, we identified a number of case-specific variants, some of which might be real risk factors for schizophrenia, and these can be readily interrogated in other data sets. Our results indicate that schizophrenia risk is unlikely to be predominantly influenced by variants just outside the range detectable by GWASs. Rather, multiple rarer genetic variants must contribute substantially to the predisposition to schizophrenia, suggesting that both very large sample sizes and gene-based association tests will be required for securely identifying genetic risk factors.

Patterns of deficits in brain function in bipolar disorder and schizophrenia: a cluster analytic study.

Historically, bipolar disorder and schizophrenia have been considered distinct disorders with different etiologies. Growing evidence suggests that overlapping genetic influences contribute to risk for these disorders and that each disease is genetically heterogeneous. Using cluster analytic methods, we empirically identified homogeneous subgroups of patients, their relatives, and controls based on distinct neurophysiologic profiles. Seven phenotypes were collected from two independent cohorts at two institutions. K-means clustering was used to identify neurophysiologic profiles. In the analysis of all participants, three distinct profiles emerged: "globally impaired", "sensory processing", and "high cognitive". In a secondary analysis, restricted to patients only, we observed a similar clustering into three profiles. The neurophysiological profiles of the Schizophrenia (SZ) and Bipolar Disorder (BPD) patients did not support the Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic distinction between these two disorders. Smokers in the globally impaired group smoked significantly more cigarettes than those in the sensory processing or high cognitive groups. Our results suggest that empirical analyses of neurophysiological phenotypes can identify potentially biologically relevant homogenous subgroups independent of diagnostic boundaries. We hypothesize that each neurophysiology subgroup may share similar genotypic profiles, which may increase statistical power to detect genetic risk factors.

Comparison of putative intermediate phenotypes in schizophrenia patients with and without obsessive-compulsive disorder: examining evidence for the schizo-obsessive subtype.

Obsessive-compulsive symptoms or obsessive-compulsive disorder (OCD) is estimated to occur in up to 30% of patients with schizophrenia. Whether this subgroup of patients is cognitively, affectively, or physiologically distinct remains unclear. 204 schizophrenia patients, 15 who also met criteria for a diagnosis of OCD, and 147 healthy controls were examined on several intermediate phenotypes. The patient groups did not differ from each other except that the co-morbid group exhibited an elevated rate of eye-tracking dysfunction. Results suggest that OCD-co-morbid patients did not comprise a distinct subgroup based on the measures studied here, although systematic assessment of larger cohorts is warranted.

The effects of perceptual encoding on the magnitude of object working memory impairment in schizophrenia.

Deficits in the visual working memory (WM) system have been consistently reported in schizophrenia patients, but the relative contribution of initial perceptual encoding to these deficits remains unsettled. We assessed the role of visual perceptual encoding on performance on an object WM task. Schizophrenia patients (N=37) and nonpsychiatric control subjects (N=33) were tested on an object WM task involving three delay periods: 200 ms, 3s, and 10s. Schizophrenia patients performed significantly less accurately than controls on all three conditions. However, after controlling for the effect of perceptual encoding (accuracy on the 200 ms delay condition) on performance in the two memory load conditions, schizophrenia patients demonstrated intact WM in the 3s delay condition, and showed a weak trend for decreased accuracy on the 10s delay compared with controls. Analysis of individual differences in pattern of performance revealed that a distinct subgroup of poor encoder patients had a significantly greater reduction in accuracy at 3s than the other patient subgroups and controls. In contrast, among schizophrenia patients who performed poorly on the 10s delay, accuracy was equivalently reduced independent of encoding ability. WM deficits in controls were independent of encoding ability at both delay intervals. These results indicate that encoding ability titrates the magnitude of WM impairment in schizophrenia patients but not in controls, and that heterogeneity has to be taken into account to correctly estimate the effects of perceptual encoding on visual object WM deficits in schizophrenia.