Disruption of the neurexin 1 gene is associated with schizophrenia.

Deletions within the neurexin 1 gene (NRXN1; 2p16.3) are associated with autism and have also been reported in two families with schizophrenia. We examined NRXN1, and the closely related NRXN2 and NRXN3 genes, for copy number variants (CNVs) in 2977 schizophrenia patients and 33 746 controls from seven European populations (Iceland, Finland, Norway, Germany, The Netherlands, Italy and UK) using microarray data. We found 66 deletions and 5 duplications in NRXN1, including a de novo deletion: 12 deletions and 2 duplications occurred in schizophrenia cases (0.47%) compared to 49 and 3 (0.15%) in controls. There was no common breakpoint and the CNVs varied from 18 to 420 kb. No CNVs were found in NRXN2 or NRXN3. We performed a Cochran-Mantel-Haenszel exact test to estimate association between all CNVs and schizophrenia (P = 0.13; OR = 1.73; 95% CI 0.81-3.50). Because the penetrance of NRXN1 CNVs may vary according to the level of functional impact on the gene, we next restricted the association analysis to CNVs that disrupt exons (0.24% of cases and 0.015% of controls). These were significantly associated with a high odds ratio (P = 0.0027; OR 8.97, 95% CI 1.8-51.9). We conclude that NRXN1 deletions affecting exons confer risk of schizophrenia.

Neuregulin-1 genotypes and eye movements in schizophrenia.

Neuregulin-1 (NRG-1) is a putative susceptibility gene for schizophrenia but the neurocognitive processes that may involve NRG-1 in schizophrenia are unknown. Deficits in antisaccade (AS) and smooth pursuit eye movements (SPEM) are promising endophenotypes, which may be associated with brain dysfunctions underlying the pathophysiology of schizophrenia. The aim of this study was to investigate the associations of NRG-1 genotypes with AS and SPEM in schizophrenia patients and healthy controls. Patients (N = 113) and controls (N = 106) were genotyped for two NRG-1 single nucleotide polymorphisms (SNPs); SNP8NRG222662, a surrogate marker for the originally described Icelandic NRG-1 risk haplotype, and SNP8NRG243177, which has recently been associated with individual differences in brain function. Subjects underwent infrared oculographic assessment of AS and SPEM. The study replicates previous findings of impaired AS and SPEM performance in schizophrenia patients (all P < 0.005; all d = 0.5-1.5). SNP8NRG243177 risk allele carriers had marginally increased variability of AS spatial error (P = 0.050, d = 0.3), but there were no significant genotype effects on other eye movement variables and no significant diagnosis-by-genotype interactions. Generally, risk allele carriers (G allele for SNP8NRG222662 and T allele for SNP8NRG243177) had numerically worse performance than non-carriers on most AS and SPEM variables. The results do not suggest that NRG-1 genotype significantly affects AS and SPEM task performance. However, the power of the sample to identify small effects is limited and the possibility of a type II error must be kept in mind. Larger samples may be needed to reliably investigate such gene effects on oculomotor endophenotypes.

Validity of K-SADS-PL (Schedule for Affective Disorders and Schizophrenia for School-Age Children--Present and Lifetime Version) depression diagnoses in an adolescent clinical population.

BACKGROUND: Validity studies of the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS) interview are modest in number given the international acceptance and extensive use of this instrument in epidemiological and treatment research. The results are somewhat mixed and limited, particularly for adolescent depression. AIMS: The objective of this study was to assess the convergent-divergent validity of the screen criteria and depression diagnoses (major depressive episode) generated with the diagnostic interview Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL). METHODS: Participants were 86 consecutively admitted inpatients aged 12-17 years and their parents. Both convergent and divergent validity of the depression diagnoses were assessed against 11 standard self-report or parent-report rating scales, all of which had been translated, adapted and in most cases validated in Iceland. A total of 25 subscales were included in calculations. RESULTS: Convergent validity was confirmed, with adolescents who screened positive or met criteria for major depressive episode scoring higher than other patients did on scales assessing depressive symptoms. However, divergent validity was only partially supported in this highly comorbid inpatient sample. Severity based on number of diagnostic criteria met had a generally substantial correlation with the rating scales. CONCLUSIONS: This study provides a substantial additional amount of convergent-divergent validity data related to this extensively used diagnostic instrument.

COMT val(158)met genotype and smooth pursuit eye movements in schizophrenia.

The association between the catechol-O-methyltransferase (COMT) val(158)met polymorphism (rs4680) and smooth pursuit eye movements (SPEM) was investigated in 110 schizophrenia patients and 96 controls. Patients had lower steady-state pursuit gain and made more frequent saccades than controls. Genotype was not associated with schizophrenia or SPEM, in either group or the combined sample. SPEM deficits in schizophrenia appear to be determined by genotypes other than rs4680, although the study may have lacked power to detect small effects.

An Icelandic version of the Kiddie-SADS-PL: translation, cross-cultural adaptation and inter-rater reliability.

The development of structured diagnostic instruments has been an important step for research in child and adolescent psychiatry, but the adequacy of a diagnostic instrument in a given culture does not guarantee its reliability or validity in another population. The objective of the study was to describe the process of cross-cultural adaptation into Icelandic of the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (Kiddie-SADS-PL) and to test the inter-rater reliability of the adapted version. To attain cross-cultural equivalency, five important dimensions were addressed: semantic, technical, content, criterion and conceptual. The adapted Icelandic version was introduced into an inpatient clinical setting, and inter-rater reliability was estimated both at the symptom and diagnoses level, for the most frequent diagnostic categories in both international diagnostic classification systems (DSM-IV and ICD-10). The cross-cultural adaptation has provided an Icelandic version allowing similar understanding among different raters and has achieved acceptable cross-cultural equivalence. This initial study confirmed the quality of the translation and adaptation of Kiddie-SADS-PL and constitutes the first step of a larger validation study of the Icelandic version of the instrument.

Support for involvement of the AHI1 locus in schizophrenia.

Recently, markers in the Abelson Helper Integration Site 1 (AHI1) region were shown to be associated with schizophrenia in a family sample of Israeli-Arabs. Here, we report a study evaluating the relevance of the AHI1 region to schizophrenia in an Icelandic sample. Seven markers shown to confer risk in the previous report were typed in 608 patients diagnosed with broad schizophrenia and 1,504 controls. Odds ratios for the overtransmitted alleles in the Israeli-Arab families ranged from 1.15 to 1.29 in the Icelandic sample. After Bonferroni correction for the seven markers tested, two markers were significantly associated with schizophrenia. Thus, our results are in general agreement with the previous report, with the strongest association signal observed in a region upstream of the AHI1 gene.

Genome scan of pedigrees multiply affected with bipolar disorder provides further support for the presence of a susceptibility locus on chromosome 12q23-q24, and suggests the presence of additional loci on 1p and 1q.

OBJECTIVE: To localize genes conferring susceptibility to bipolar affective disorder. METHODS: Seven families were selected on the basis of containing multiple cases of bipolar affective disorder present in three or more generations, an absence of schizophrenia and unilineal transmission. DNA samples from these families were genotyped with 365 microsatellite markers spaced at approximately 10 cM intervals across the whole genome. All markers were subjected to initial two-point and three-point analyses using LOD score and model-free analysis. All regions producing a result significant at P<0.01 were then subjected to four-point LOD score analysis under the assumption of heterogeneity. RESULTSA four-point LOD score of 2.8 was obtained using a dominant model and including unipolar cases as affected in the region of D12S342. Four-point LOD scores of 2 were obtained around D1S243, D1S251 and D3S1265. The positive results around D1S243 were accounted for by a LOD score of 3.1 occurring in a single pedigree. CONCLUSIONS: Since there has been previous strong support for linkage to the region of 12q23-q24 around D12S342, it now seems very probable that it does indeed contain a gene influencing susceptibility to bipolar affective disorder. Some evidence for linkage in the region of 1q near to D1S251 has been reported in one previous study. It therefore seems that this region of 1q and the region of 1p close to D1S243 may also harbour susceptibility genes.

Candidate gene analysis of the human natural killer-1 carbohydrate pathway and perineuronal nets in schizophrenia: B3GAT2 is associated with disease risk and cortical surface area.

BACKGROUND: The Human Natural Killer-1 carbohydrate (HNK-1) is involved in neurodevelopment and synaptic plasticity. Extracellular matrix structures called perineuronal nets, condensed around subsets of neurons and proximal dendrites during brain maturation, regulate synaptic transmission and plasticity. METHODS: Ten genes of importance for HNK-1 biosynthesis (B3GAT1, B3GAT2, and CHST10) or for the formation of perineuronal nets (TNR, BCAN, NCAN, HAPLN1, HAPLN2, HAPLN3, and HAPLN4) were investigated for potential involvement in schizophrenia (SCZ) susceptibility, by genotyping 104 tagSNPs in the Scandinavian Collaboration on Psychiatric Etiology sample (849 cases; 1602 control subjects). Genome-wide association study imputation data from the European SGENE-plus sample (2663 cases; 13,498 control subjects) were used for comparison. The effect of SCZ risk alleles on brain structure was investigated in a Norwegian subset (98 cases; 177 control subjects) with structural magnetic resonance imaging data. RESULTS: Five single nucleotide polymorphisms (SNPs), located in two adjacent estimated linkage disequilibrium blocks in the first intron of ß-1,3-glucuronyltransferase 2 (B3GAT2), were nominally associated with SCZ (.004 ≤ P(empirical) ≤ .05). The rs2460691 was significantly associated in the comparison sample and in the meta-analysis after correction for all 121 SNP/haplotype tests (P(raw) = 1 × 10(-4); P(corrected) = .018). Increased dosage of the rs2460691 SCZ risk allele was associated with decreased cortical area (p = .002) but not thickness or hippocampal volume. A second SNP (r(2) = .24 with rs10945275), which conferred the highest SCZ risk effect in the Norwegian subset, was also associated with cortical area. CONCLUSIONS: The present results suggest that effects on biosynthesis of the neuronal epitope HNK-1, through common B3GAT2 variation, could increase the risk of SCZ, possibly by decreasing cortical area.

At-risk variant in TCF7L2 for type II diabetes increases risk of schizophrenia.

BACKGROUND: Schizophrenia is associated with increased risk of type II diabetes and metabolic disorders. However, it is unclear whether this comorbidity reflects shared genetic risk factors, at-risk lifestyle, or side effects of antipsychotic medication. METHODS: Eleven known risk variants of type II diabetes were genotyped in patients with schizophrenia in a sample of 410 Danish patients, each matched with two healthy control subjects on sex, birth year, and month. Replication was carried out in a large multinational European sample of 4089 patients with schizophrenia and 17,597 controls (SGENE+) using Mantel-Haenszel test. RESULTS: One type II diabetes at-risk allele located in TCF7L2, rs7903146 [T], was associated with schizophrenia in the discovery sample (p = .0052) and in the replication with an odds ratio of 1.07 (95% confidence interval 1.01-1.14, p = .033). CONCLUSION: The association reported here with a well-known diabetes variant suggests that the observed comorbidity is partially caused by genetic risk variants. This study also demonstrates how genetic studies can successfully examine an epidemiologically derived hypothesis of comorbidity.

Maternally derived microduplications at 15q11-q13: implication of imprinted genes in psychotic illness.

OBJECTIVE: Rare copy number variants have been implicated in different neurodevelopmental disorders, with the same copy number variants often increasing risk of more than one of these phenotypes. In a discovery sample of 22 schizophrenia patients with an early onset of illness (10-15 years of age), the authors observed in one patient a maternally derived 15q11-q13 duplication overlapping the Prader-Willi/Angelman syndrome critical region. This prompted investigation of the role of 15q11-q13 duplications in psychotic illness. METHOD: The authors scanned 7,582 patients with schizophrenia or schizoaffective disorder and 41,370 comparison subjects without known psychiatric illness for copy number variants at 15q11-q13 and determined the parental origin of duplications using methylation-sensitive Southern hybridization analysis. RESULTS: Duplications were found in four case patients and five comparison subjects. All four case patients had maternally derived duplications (0.05%), while only three of the five comparison duplications were maternally derived (0.007%), resulting in a significant excess of maternally derived duplications in case patients (odds ratio=7.3). This excess is compatible with earlier observations that risk for psychosis in people with Prader-Willi syndrome caused by maternal uniparental disomy is much higher than in those caused by deletion of the paternal chromosome. CONCLUSIONS: These findings suggest that the presence of two maternal copies of a fragment of chromosome 15q11.2-q13.1 that overlaps with the Prader-Willi/Angelman syndrome critical region may be a rare risk factor for schizophrenia and other psychoses. Given that maternal duplications of this region are among the most consistent cytogenetic observations in autism, the findings provide further support for a shared genetic etiology between autism and psychosis.

Parent-youth agreement on symptoms and diagnosis: assessment with a diagnostic interview in an adolescent inpatient clinical population.

Diagnostic information on adolescents may be elicited from both youths and their parents, especially for depressive and suicidal symptomatology. The objective of this study was to examine the degree of agreement between parent and adolescent reports of major psychiatric disorders, at the diagnostic and at the symptom level, in a severely affected inpatient clinical population. 64 parent-adolescent pairs were interviewed separately with the semi-structured diagnostic interview Kiddie-SADS-PL. Symptomatology was also assessed with 11 self-report and parent-report scales, all translated, adapted and in most cases validated in Iceland. A total of 25 subscales were included to assess emotional dimensions such as depression or anxiety and cognitive dimensions such as attention deficit or self-concept. Good agreement was found for social phobia and fair agreement for generalized anxiety disorder. Although parent-youth agreement was poor in most cases at the symptoms level, significant correlations indicated consistency for most severity scores, except those related to depressive symptomatology, attention deficit, separation anxiety or conduct disorder. The low agreement between reports of suicidal ideation is in line with results from previous studies and suggests that parents might under- or over-estimate this symptomatology. The combination of data obtained with diagnostic interviews and rating-scales confirmed results from prior empirical work, giving greater weight to parents' reports of observable behavior and to adolescents' reports of subjective experiences, especially depressive symptomatology. Our findings suggest that both parent and child informants are necessary to obtain adequate assessments in adolescents. Further research should explore the correspondence between discrepant diagnoses and external criteria such as parental psychopathology or parent-child relationships and attachment. Psychoanalysis could benefit from cognitive neuroscience and use cognitive assessments as interesting tools. Thus, cognitive assessments can show discrepant results according to parents' or adolescents' reports and can therefore shed light on the parent-child interaction and relational dynamics. Inversely, cognitive neuroscience could benefit from psychoanalysis by taking into account, when interpretating the scores, the relational dynamics and the personal history of the rater.

Catechol-O-methyltransferase Val 158 Met polymorphism and antisaccade eye movements in schizophrenia.

The catechol-O-methyltransferase (COMT) enzyme catabolizes dopamine. The val(158)met single nucleotide polymorphism (rs4680) in the COMT gene has received considerable attention as a candidate gene for schizophrenia as well as for frontally mediated cognitive functions. Antisaccade performance is a good measure of frontal lobe integrity. Deficits on the task are considered a trait marker for schizophrenia. The aim of this study was to investigate the association of COMT val(158)met polymorphism with antisaccade eye movements in schizophrenia patients and healthy controls. Schizophrenia patients (N = 105) and healthy controls (N = 95) underwent infrared oculographic assessment of antisaccades. Subjects were genotyped for COMT val(158)met and divided into 3 groups according to genotype (val/val, val/met, and met/met). Patients displayed significantly more reflexive errors, longer and more variable latency, and lower amplitude gain than controls (all P < 0.02). A greater number of val(158) alleles was associated with shorter (P = 0.045) and less variable (P = 0.028) antisaccade latency and, nonsignificantly, with lower reflexive error rate (P = 0.056). None of these variables showed a group-by-genotype interaction (P > 0.1). There were no significant associations of genotype with measures of amplitude gain or spatial error (P > 0.2). The results suggest that COMT val(158) carrier status is associated with better performance on the antisaccade task. Possible explanations of this finding are discussed.

Gene variants associated with schizophrenia in a Norwegian genome-wide study are replicated in a large European cohort.

We have performed a genome-wide association study (GWAS) of schizophrenia in a Norwegian discovery sample of 201 cases and 305 controls (TOP study) with a focused replication analysis in a larger European sample of 2663 cases and 13,780 control subjects (SGENE-plus study). Firstly, the discovery sample was genotyped with Affymetrix Genome-Wide Human SNP Array 6.0 and 572,888 markers were tested for schizophrenia association. No SNPs in the discovery sample attained genome-wide significance (P<8.7 x 10(-8)). Secondly, based on the GWAS data, we selected 1000 markers with the lowest P values in the discovery TOP sample, and tested these (or HapMap-based surrogates) for association in the replication sample. Sixteen loci were associated with schizophrenia (nominal P value<0.05 and concurring OR) in the replication sample. As a next step, we performed a combined analysis of the findings from these two studies, and the strongest evidence for association with schizophrenia was provided for markers rs7045881 on 9p21, rs433598 on 16p12 and rs10761482 on 10q21. The markers are located in PLAA, ACSM1 and ANK3, respectively. PLAA has not previously been described as a susceptibility gene, but 9p21 is implied as a schizophrenia linkage region. ACSM1 has been identified as a susceptibility gene in a previous schizophrenia GWAS study. The association of ANK3 with schizophrenia is intriguing in light of recent associations of ANK3 with bipolar disorder, thereby supporting the hypothesis of an overlap in genetic susceptibility between these psychopathological entities.

Eye movement deficits in schizophrenia: investigation of a genetically homogenous Icelandic sample.

BACKGROUND: Deficits in antisaccade (AS) and smooth pursuit eye movements (SPEM) are promising endophenotypes in genetic studies of schizophrenia. The Icelandic population lends itself ideally to genetic studies due to its ethnic homogeneity and well-documented genealogy. The primary aim of this study was to assess AS and SPEM performance in a large Icelandic sample. Additional aims were to investigate the relationship between AS and SPEM task performance and to assess internal consistency, within-session performance changes and effects of SPEM target velocity on performance. METHOD: Patients with schizophrenia (N = 118) and healthy controls (N = 109) matched for age and gender underwent infrared oculographic assessment of AS and SPEM (at target velocities of 12 degrees , 24 degrees and 36 degrees /s). RESULTS: On the AS task patients displayed significantly more reflexive errors, longer latency, increased intra-individual latency variability, and reduced amplitude gain compared to controls. On the SPEM task, patients had significantly lower velocity gain and more frequent saccades during pursuit at all velocities, but group differences in velocity gain increased with increasing target velocity. Internal consistency of performance was high for all variables in both groups (Cronbach's alpha >0.77 for AS and >0.85 for SPEM) except for AS spatial error in patients (alpha = 0.38). A moderate association was found between AS and SPEM performance. By and large, patients and controls showed similar patterns of systematic within-session performance changes. CONCLUSIONS: Our findings confirm the existence of robust eye movement deficits in schizophrenia in a large sample. These measures may be studied as endophenotypes in future studies of potential schizophrenia risk genotypes in the genetically homogenous Icelandic population.

Implementing the semi-structured interview Kiddie-SADS-PL into an in-patient adolescent clinical setting: impact on frequency of diagnoses.

BACKGROUND: Research is needed to establish the utility of diagnostic interviews in clinical settings. Studies comparing clinical diagnoses with diagnoses generated with structured instruments show generally low or moderate agreement and clinical diagnostic assignment (e.g. admission or chart diagnoses) are often considered to underdiagnose disorders. The objective of this study was to evaluate the impact of implementing the Schedule for Affective Disorders and Schizophrenia for School-Age Children - Present and Lifetime Version (Kiddie-SADS-PL) into an in-patient adolescent clinical setting. METHODS: Participants were all adolescents admitted through the years 2001-2004 (N = 333 admissions, age 12-17 years). The authors reviewed the charts of the previous three years of consecutive admissions, patients being evaluated using routine psychiatric evaluation, before the Kiddie-SADS-PL was introduced. They then reviewed the charts of all consecutive admissions during the next twelve months, patients being evaluated by adding the instrument to routine practice. RESULTS: The rates of several main diagnostic categories (depressive, anxiety, bipolar and disruptive disorders) increased considerably, suggesting that those disorders were likely underreported when using non-structured routine assessment procedures. The rate of co-morbidity increased markedly as the number of diagnoses assigned to each patient increased. CONCLUSION: The major differences in diagnostic assignment rates provide arguments for the utility of diagnostic interviews in inpatient clinical settings but need further research, especially on factors that affect clinical diagnostic assignment in "real world" settings.

Association of neuregulin 1 with schizophrenia confirmed in a Scottish population.

Recently, we identified neuregulin 1 (NRG1) as a susceptibility gene for schizophrenia in the Icelandic population, by a combined linkage and association approach. Here, we report the first study evaluating the relevance of NRG1 to schizophrenia in a population outside Iceland. Markers representing a core at-risk haplotype found in Icelanders at the 5' end of the NRG1 gene were genotyped in 609 unrelated Scottish patients and 618 unrelated Scottish control individuals. This haplotype consisted of five SNP markers and two microsatellites, which all appear to be in strong linkage disequilibrium. For the Scottish patients and control subjects, haplotype frequencies were estimated by maximum likelihood, using the expectation-maximization algorithm. The frequency of the seven-marker haplotype among the Scottish patients was significantly greater than that among the control subjects (10.2% vs. 5.9%, P=.00031). The estimated risk ratio was 1.8, which is in keeping with our report of unrelated Icelandic patients (2.1). Three of the seven markers in the haplotype gave single-point P values ranging from .000064 to .0021 for the allele contributing to the at-risk haplotype. This direct replication of haplotype association in a second population further implicates NRG1 as a factor that contributes to the etiology of schizophrenia.

Neuregulin 1 and susceptibility to schizophrenia.

The cause of schizophrenia is unknown, but it has a significant genetic component. Pharmacologic studies, studies of gene expression in man, and studies of mouse mutants suggest involvement of glutamate and dopamine neurotransmitter systems. However, so far, strong association has not been found between schizophrenia and variants of the genes encoding components of these systems. Here, we report the results of a genomewide scan of schizophrenia families in Iceland; these results support previous work, done in five populations, showing that schizophrenia maps to chromosome 8p. Extensive fine-mapping of the 8p locus and haplotype-association analysis, supplemented by a transmission/disequilibrium test, identifies neuregulin 1 (NRG1) as a candidate gene for schizophrenia. NRG1 is expressed at central nervous system synapses and has a clear role in the expression and activation of neurotransmitter receptors, including glutamate receptors. Mutant mice heterozygous for either NRG1 or its receptor, ErbB4, show a behavioral phenotype that overlaps with mouse models for schizophrenia. Furthermore, NRG1 hypomorphs have fewer functional NMDA receptors than wild-type mice. We also demonstrate that the behavioral phenotypes of the NRG1 hypomorphs are partially reversible with clozapine, an atypical antipsychotic drug used to treat schizophrenia.

Genome scan meta-analysis of schizophrenia and bipolar disorder, part II: Schizophrenia.

Schizophrenia is a common disorder with high heritability and a 10-fold increase in risk to siblings of probands. Replication has been inconsistent for reports of significant genetic linkage. To assess evidence for linkage across studies, rank-based genome scan meta-analysis (GSMA) was applied to data from 20 schizophrenia genome scans. Each marker for each scan was assigned to 1 of 120 30-cM bins, with the bins ranked by linkage scores (1 = most significant) and the ranks averaged across studies (R(avg)) and then weighted for sample size (N(sqrt)[affected casess]). A permutation test was used to compute the probability of observing, by chance, each bin's average rank (P(AvgRnk)) or of observing it for a bin with the same place (first, second, etc.) in the order of average ranks in each permutation (P(ord)). The GSMA produced significant genomewide evidence for linkage on chromosome 2q (PAvgRnk<.000417). Two aggregate criteria for linkage were also met (clusters of nominally significant P values that did not occur in 1,000 replicates of the entire data set with no linkage present): 12 consecutive bins with both P(AvgRnk) and P(ord)<.05, including regions of chromosomes 5q, 3p, 11q, 6p, 1q, 22q, 8p, 20q, and 14p, and 19 consecutive bins with P(ord)<.05, additionally including regions of chromosomes 16q, 18q, 10p, 15q, 6q, and 17q. There is greater consistency of linkage results across studies than has been previously recognized. The results suggest that some or all of these regions contain loci that increase susceptibility to schizophrenia in diverse populations.