Heritable anisotropy associated with cognitive impairments among patients with schizophrenia and their non-psychotic relatives in multiplex families

BACKGROUND

To test the functional implications of impaired white matter (WM) connectivity among patients with schizophrenia and their relatives, we examined the heritability of fractional anisotropy (FA) measured on diffusion tensor imaging data acquired in Pittsburgh and Philadelphia, and its association with cognitive performance in a unique sample of 175 multigenerational non-psychotic relatives of 23 multiplex schizophrenia families and 240 unrelated controls (total = 438).

METHODS

We examined polygenic inheritance (h2r) of FA in 24 WM tracts bilaterally, and also pleiotropy to test whether heritability of FA in multiple WM tracts is secondary to genetic correlation among tracts using the Sequential Oligogenic Linkage Analysis Routines. Partial correlation tests examined the correlation of FA with performance on eight cognitive domains on the Penn Computerized Neurocognitive Battery, controlling for age, sex, site and mother's education, followed by multiple comparison corrections.

RESULTS

Significant total additive genetic heritability of FA was observed in all three-categories of WM tracts (association, commissural and projection fibers), in total 33/48 tracts. There were significant genetic correlations in 40% of tracts. Diagnostic group main effects were observed only in tracts with significantly heritable FA. Correlation of FA with neurocognitive impairments was observed mainly in heritable tracts.

CONCLUSIONS

Our data show significant heritability of all three-types of tracts among relatives of schizophrenia. Significant heritability of FA of multiple tracts was not entirely due to genetic correlations among the tracts. Diagnostic group main effect and correlation with neurocognitive performance were mainly restricted to tracts with heritable FA suggesting shared genetic effects on these traits.

Rare variants in Protein tyrosine phosphatase, receptor type A (PTPRA) in schizophrenia: Evidence from a family based study

The contribution of both common and rare risk variants to the genetic architecture of schizophrenia (SZ) has been documented in genome-wide association studies, whole exome and whole genome sequencing approaches. As SZ is highly heritable and segregates in families, highly penetrant rare variants are more likely to be identified through analyses of multiply affected families. Further, much of the gene mapping studies in SZ have utilized individuals of Caucasian ancestry. Analysis of other ethnic groups may be informative. In this study, we aimed at identification of rare, penetrant risk variants utilizing whole exome sequencing (WES) in a three-generation Indian family with multiple members affected. Filtered data from WES, combined with in silico analyses revealed a novel heterozygous missense variant (NM_080841:c.1730C>G:p.T577R; exon18) in Protein tyrosine phosphatase, receptor type A (PTPRA 20p13). The variant was located in an evolutionarily conserved position and predicted to be damaging. Screening for variants in this gene in the WES data of an independent SZ cohort (n = 350) of matched ethnicity, identified five additional rare missense variants with MAF < 0.003, which were also predicted to be damaging. In conclusion, the rare missense variants in PTPRA identified in this study could confer risk for SZ. This has also derived support from concordant data from prior linkage and association, as well as animal studies which indicated a role for PTPRA in glutamate function.

Possible role of rare variants in Trace amine associated receptor 1 in schizophrenia

Schizophrenia (SZ) is a chronic mental illness with behavioral abnormalities. Recent common variant based genome wide association studies and rare variant detection using next generation sequencing approaches have identified numerous variants that confer risk for SZ, but etiology remains unclear propelling continuing investigations. Using whole exome sequencing, we identified a rare heterozygous variant (c.545G>T; p.Cys182Phe) in Trace amine associated receptor 1 gene (TAAR1 6q23.2) in three affected members in a small SZ family. The variant predicted to be damaging by 15 prediction tools, causes breakage of a conserved disulfide bond in this G-protein-coupled receptor. On screening this intronless gene for additional variant(s) in ~800 sporadic SZ patients, we identified six rare protein altering variants (MAF<0.001) namely p.Ser47Cys, p.Phe51Leu, p.Tyr294Ter, p.Leu295Ser in four unrelated north Indian cases (n=475); p.Ala109Thr and p.Val250Ala in two independent Caucasian/African-American patients (n=310). Five of these variants were also predicted to be damaging. Besides, a rare synonymous variant was observed in SZ patients. These rare variants were absent in north Indian healthy controls (n=410) but significantly enriched in patients (p=0.036). Conversely, three common coding SNPs (rs8192621, rs8192620 and rs8192619) and a promoter SNP (rs60266355) tested for association with SZ in the north Indian cohort were not significant (P>0.05). TAAR1 is a modulator of monoaminergic pathways and interacts with AKT signaling pathways. Substantial animal model based pharmacological and functional data implying its relevance in SZ are also available. However, this is the first report suggestive of the likely contribution of rare variants in this gene to SZ.

Genetic and morphological features of human iPSC-derived neurons with chromosome 15q11.2 (BP1-BP2) deletions

BACKGROUND

Copy number variation on chromosome 15q11.2 (BP1-BP2) causes deletion of CYFIP1, NIPA1, NIPA2 and TUBGCP5; it also affects brain structure and elevates risk for several neurodevelopmental disorders that are associated with dendritic spine abnormalities. In rodents, altered cyfip1 expression changes dendritic spine morphology, motivating analyses of human neuronal cells derived from iPSCs (iPSC-neurons).

METHODS

iPSCs were generated from a mother and her offspring, both carrying the 15q11.2 (BP1-BP2) deletion, and a non-deletion control. Gene expression in the deletion region was estimated using quantitative real-time PCR assays. Neural progenitor cells (NPCs) and iPSC-neurons were characterized using immunocytochemistry.

RESULTS

CYFIP1, NIPA1, NIPA2 and TUBGCP5 gene expression was lower in iPSCs, NPCs and iPSC-neurons from the mother and her offspring in relation to control cells. CYFIP1 and PSD95 protein levels were lower in iPSC-neurons derived from the CNV bearing individuals using Western blot analysis. At 10 weeks post-differentiation, iPSC-neurons appeared to show dendritic spines and qualitative analysis suggested that dendritic morphology was altered in 15q11.2 deletion subjects compared with control cells.

CONCLUSIONS

The 15q11.2 (BP1-BP2) deletion is associated with reduced expression of four genes in iPSC-derived neuronal cells; it may also be associated altered iPSC-neuron dendritic morphology.

Elevated serum measures of lipid peroxidation and abnormal prefrontal white matter in euthymic bipolar adults: toward peripheral biomarkers of bipolar disorder

Diffusion tensor imaging (DTI) studies consistently reported abnormalities in fractional anisotropy (FA) and radial diffusivity (RD), measures of the integrity of white matter (WM), in bipolar disorder (BD), that may reflect underlying pathophysiologic processes. There is, however, a pressing need to identify peripheral measures that are related to these WM measures, to help identify easily obtainable peripheral biomarkers of BD. Given the high lipid content of axonal membranes and myelin sheaths, and that elevated serum levels of lipid peroxidation are reported in BD, these serum measures may be promising peripheral biomarkers of underlying WM abnormalities in BD. We used DTI and probabilistic tractography to compare FA and RD in ten prefrontal-centered WM tracts, 8 of which are consistently shown to have abnormal FA (and/or RD) in BD, and also examined serum lipid peroxidation (lipid hydroperoxides, LPH and 4-hydroxy-2-nonenal, 4-HNE), in 24 currently euthymic BD adults (BDE) and 19 age- and gender-matched healthy adults (CONT). There was a significant effect of group upon FA in these a priori WM tracts (BDECONT: F[1,41]=10.3; P=0.003), and a significant between-group difference in LPH (BDE>CONT: t[40]=2.4; P=0.022), but not in 4-HNE. Multivariate multiple regression analyses revealed that LPH variance explained, respectively, 59 and 51% of the variance of FA and RD across all study participants. This is the first study to examine relationships between measures of WM integrity and peripheral measures of lipid peroxidation. Our findings suggest that serum LPH may be useful in the development of a clinically relevant, yet easily obtainable and inexpensive, peripheral biomarkers of BD.

A comparative study of health locus of control in patients with schizophrenia and their first degree relatives

BACKGROUND AND AIMS

An individual's behaviour may be predicted from their beliefs about their locus of control (attribution). A person's "locus" can be internal or external. The present study aimed at comparing the locus of control as measured by Multidimensional Health Locus of Control Scale (MHLC) in patients with schizophrenia and their healthy first degree relatives. We hypothesized that persons with schizophrenia have different locus of control than their first degree relatives.

METHOD

Multidimensional Health Locus of Control Scale (MHLC) was first translated and validated in Hindi by bilingual students (N = 71). Consecutive patients affected with schizophrenia (SZ) (N = 125) and their siblings/offsprings (N = 119) were recruited. Diagnostic Interview for Genetic Studies and MHLC Scale were administered after written informed consent.

RESULTS

There was moderate intra-class correlation between Hindi and English versions of MHLC Scale. Schizophrenia patients were found to have more of 'chance' locus of control (F 6.625, p = 0.011) whereas their first degree relatives have more of 'internal' locus of control (F 6.760, p = 0.010).

CONCLUSION

Patients with SZ attributed their health to external factors which has been found to be associated with poor or late recovery. These findings may provide a theoretical base for developing intervention strategies to promote behavioural changes in patients.

Persistent infection with neurotropic herpes viruses and cognitive impairment

BACKGROUND

Herpes virus infections can cause cognitive impairment during and after acute encephalitis. Although chronic, latent/persistent infection is considered to be relatively benign, some studies have documented cognitive impairment in exposed persons that is untraceable to encephalitis. These studies were conducted among schizophrenia (SZ) patients or older community dwellers, among whom it is difficult to control for the effects of co-morbid illness and medications. To determine whether the associations can be generalized to other groups, we examined a large sample of younger control individuals, SZ patients and their non-psychotic relatives (n=1852). Method Using multivariate models, cognitive performance was evaluated in relation to exposures to herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2) and cytomegalovirus (CMV), controlling for familial and diagnostic status and sociodemographic variables, including occupation and educational status. Composite cognitive measures were derived from nine cognitive domains using principal components of heritability (PCH). Exposure was indexed by antibodies to viral antigens.

RESULTS

PCH1, the most heritable component of cognitive performance, declines with exposure to CMV or HSV-1 regardless of case/relative/control group status (p = 1.09 × 10-5 and 0.01 respectively), with stronger association with exposure to multiple herpes viruses (β = -0.25, p = 7.28 × 10-10). There were no significant interactions between exposure and group status.

CONCLUSIONS

Latent/persistent herpes virus infections can be associated with cognitive impairments regardless of other health status.

Heritability of functioning in families with schizophrenia in relation to neurocognition

The role of daily functioning is an integral part of the schizophrenia (SZ) phenotype and deficits in this trait appear to be present in both affected persons and some unaffected relatives; hence we have examined its heritability in our cohort of African American schizophrenia families. There is now ample evidence that deficits in cognitive function can impact family members who are not themselves diagnosed with SZ; there is some, but less evidence that role function behaves likewise. We evaluate whether role function tends to "run in families" who were ascertained because they contain an African American proband diagnosed with SZ.

METHODS

We analyzed heritability for selected traits related to daily function, employment, living situation, marital status, and Global Assessment Scale (GAS) score; modeling age, gender, along with neurocognition and diagnosis as covariates in a family based African-American sample (N=2488 individuals including 979 probands).

RESULTS

Measures of role function were heritable in models including neurocognitive domains and factor analytically derived neurocognitive summary scores and demographics as covariates; the most heritable estimate was obtained from the current GAS scores (h2=0.72). Neurocognition was not a significant contributor to heritability of role function.

CONCLUSIONS

Commonly assessed demographic and clinical indicators of functioning are heritable with a global rating of functioning being the most heritable. Measures of neurocognition had little impact on heritability of functioning overall. The family covariance for functioning, reflected in its heritability, supports the concept that interventions at the family level, such as evidenced-based family psychoeducation may be beneficial in schizophrenia.

Disability certificates in India: a challenge to health privacy

A "disability certificate" is necessary to access benefits afforded under the Persons with Disabilities Act (1995) in India. This paper analyses this requirement and concludes that it constitutes a major challenge to maintaining privacy of health information especially for persons with mental health disabilities in India and recommends modifications in the certificate's format and use, to reduce the magnitude of privacy infringement for those using the disability certificate to access benefits to which they are legally entitled.

Imprinting in the schizophrenia candidate gene GABRB2 encoding GABA(A) receptor β(2) subunit

Schizophrenia is a complex genetic disorder, the inheritance pattern of which is likely complicated by epigenetic factors yet to be elucidated. In this study, transmission disequilibrium tests with family trios yielded significant differences between paternal and maternal transmissions of the disease-associated single-nucleotide polymorphism (SNP) rs6556547 and its haplotypes. The minor allele (T) of rs6556547 was paternally undertransmitted to male schizophrenic offsprings, and this parent-of-origin effect strongly suggested that GABRB2 is imprinted. 'Flipping' of allelic expression in heterozygotes of SNP rs2229944 (C/T) in GABRB2 or rs2290732 (G/A) in the neighboring GABRA1 was compatible with imprinting effects on gene expression. Clustering analysis of GABRB2 mRNA expressions suggested that imprinting brought about the observed two-tiered distribution of expression levels in controls with heterozygous genotype at the disease-associated SNP rs1816071 (A/G). The deficit of upper-tiered expressions accounted for the lowered expression levels in the schizophrenic heterozygotes. The occurrence of a two-tiered distribution furnished support for imprinting, and also pointed to the necessity of differentiating between two kinds of heterozygotes of different parental origins in disease association studies on GABRB2. Bisulfite sequencing revealed hypermethylation in the neighborhood of SNP rs1816071, and methylation differences between controls and schizophrenia patients. Notably, the two schizophrenia-associated SNPs rs6556547 and rs1816071 overlapped with a CpG dinucleotide, thereby opening the possibility that CpG methylation status of these sites could have an impact on the risk of schizophrenia. Thus multiple lines of evidence pointed to the occurrence of imprinting in the GABRB2 gene and its possible role in the development of schizophrenia.

Imprinting in the schizophrenia candidate gene GABRB2

Imprinting, characterized by unequal expression of the offspring's genes in a parent-of-origin dependent manner, has been functionally implicated in brain development and in psychiatric disorders. In this study, unambiguous distortion in paternal but not maternal transmission of the disease-associated single-nucleotide polymorphism (SNP) rs6556547 (T/G) clearly indicated the presence of parent-of-origin effect (POE) in the GABAA receptor β2 subunit gene (GABRB2). ‘Flipping’ of allelic mRNA expression in heterozygotes of SNP rs2229944 (C/T) and the observed two-tiered distribution of mRNA expression levels in heterozygotes of the disease-associated SNP rs1816071 (G/A) furnished important support for the occurrence of imprinting at GABRB2. Imprinting in effect introduced heterozygotes from different parents-of-origin endowed with dissimilar mRNA expression capabilities. The deficit of upper-tiered expressions accounted for the lowered mRNA expression levels in the schizophrenic heterozygotes. This pointed to the necessity of differentiating between two kinds of heterozygotes of different parental origins in disease association studies on GABRB2. Bisulfite sequencing revealed hypermethylation in the neighborhood of SNP rs1816071, and methylation differences between controls and schizophrenia patients. Notably, allele-specific methylation was observed at the disease-associated SNPs rs6556547 and rs1816071. These findings raised the possibility that CpG methylation status of these sites could have an impact on the expression of GABRB2 and the risk of schizophrenia. Furthermore, the occurrence of imprinting and allele-specific methylation in the schizophrenia candidate gene GABRB2 was compatible with the epigenetic hypothesis for schizophrenia pathophysiology, thereby calling for the need to explore the role of epigenetic factors in mediating susceptibility to schizophrenia.

Executive functions and cognitive deficits in schizophrenia: comparisons between probands, parents and controls in India

BACKGROUND

Cognitive impairment is said to be a core feature of schizophrenia. Executive function is an important cognitive domain.

AIM

This study was undertaken to assess cognitive impairment among Indian patients with schizophrenia (Sz) or schizoaffective disorder (SzA), compared with their parents and unaffected individuals (controls).

SETTINGS AND DESIGN

Executive functions as measured by Trail-making Test (TMT), of patients and their parents were compared with controls. The patients were recruited from the Outpatients' Department (OPD) of a government hospital.

MATERIALS AND METHODS

Patients diagnosed as Sz or SzA (n=172) and their parents (n=196: families n=132, 119 fathers and 77 mothers) participated. We also included 120 persons with no history of psychiatric illness. Cognitive function was assessed with the TMT. The Information Score of the Post Graduate Institute Battery of Brain Dysfunction test, developed in India for Indian subjects was used as a proxy for general fixed knowledge.

STATISTICAL ANALYSIS

Logistic and linear regression was used to compare cognitive deficits of cases, parents and controls.

RESULTS

Cases and their parents took significantly more time than controls on Part B of the TMT. There were no statistically significant differences between cases and parents on any of the TMT parameters. Using regression analysis, the most significant correlates of all TMT parameters among cases were with occurrence of auditory hallucinations and current age.

CONCLUSION

Cases, as well as their parents showed more cognitive impairment than controls on the TMT.

Privacy and the Right to Information Act, 2005

Privacy is a key component of individual autonomy, and a voluminous literature has established both its practical value in healthcare contexts and its status as a fundamental, but not absolute ethical right. Because the Right to Information Act (2005) permits citizens to gain information under government control, it might be thought to threaten the privacy of patients and research subjects, especially those in government institutions. It is important for clinicians, administrators, information officers, patients, and research subjects to understand that the RTI Act generally does not require or permit disclosure of personal health information to third parties. Only under unusual circumstances when the larger public interest is properly certified to warrant it, would information shared or created within the fiduciary relationships of clinical care or research be required to be disclosed. Against this background concerning the right to privacy and the RTI Act, we consider a 2007 legal case that used the RTI Act to expose patient information of a public official and argue that the "public interest" claimed in this case did not justify disclosure of the official's private health information. We conclude that the provisions of the RTI Act, when properly interpreted, are compatible with the important value of safeguarding patient privacy.

Whole-genome association study of bipolar disorder

We performed a genome-wide association scan in 1461 patients with bipolar (BP) 1 disorder, 2008 controls drawn from the Systematic Treatment Enhancement Program for Bipolar Disorder and the University College London sample collections with successful genotyping for 372,193 single nucleotide polymorphisms (SNPs). Our strongest single SNP results are found in myosin5B (MYO5B; P=1.66 x 10(-7)) and tetraspanin-8 (TSPAN8; P=6.11 x 10(-7)). Haplotype analysis further supported single SNP results highlighting MYO5B, TSPAN8 and the epidermal growth factor receptor (MYO5B; P=2.04 x 10(-8), TSPAN8; P=7.57 x 10(-7) and EGFR; P=8.36 x 10(-8)). For replication, we genotyped 304 SNPs in family-based NIMH samples (n=409 trios) and University of Edinburgh case-control samples (n=365 cases, 351 controls) that did not provide independent replication after correction for multiple testing. A comparison of our strongest associations with the genome-wide scan of 1868 patients with BP disorder and 2938 controls who completed the scan as part of the Wellcome Trust Case-Control Consortium indicates concordant signals for SNPs within the voltage-dependent calcium channel, L-type, alpha 1C subunit (CACNA1C) gene. Given the heritability of BP disorder, the lack of agreement between studies emphasizes that susceptibility alleles are likely to be modest in effect size and require even larger samples for detection.

Correlates of hallucinations in schizophrenia: A cross-cultural evaluation

INTRODUCTION

Demographic, clinical and familial factors may plausibly influence the manifestation of hallucinations. It is unclear if the pattern of the effects is similar in different environmental/cultural settings.

AIMS

To evaluate factors associated with hallucination from a demographic, clinical and familial perspective in two distinct cultural settings.

METHODS

Patients with a clinical diagnosis of schizophrenia (SZ) or schizoaffective disorder (SZA) were diagnosed systematically using DSM IV criteria. Two independent samples were recruited in India and USA using identical inclusion/exclusion criteria and assessment procedures (n=1287 patients total; 807 Indian and 480 US participants). The association of key demographic and clinical factors with hallucinations of different modalities was examined. To evaluate the impact of familial factors, we separately analyzed correlations among affected sibling pairs (ASPs, n=136, Indian; n=77, US).

RESULTS

The prevalence of different modalities of hallucinations differed in the Indian and US samples, though the rank order of frequency was similar. The pattern of associations between selected variables and the risk of hallucinations was different across cultures, except for some correlations with indices of severity. No significant concordance was observed among the ASPs after correcting for multiple comparisons.

CONCLUSIONS

The factors associated with hallucinations vary across environments. Our results are consistent with a multi-factorial etiology of psychopathology, but re-direct attention to endophenotypic features in the causal chain that precede the symptoms themselves.

Brain morphological changes associated with exposure to HSV1 in first-episode schizophrenia

Infectious agents have been proposed as one of the risk factors for schizophrenia. However, the data on the association of infectious agents with in vivo brain changes are scant. We evaluated the association of serological evidence of exposure to herpes simplex virus 1 (HSV1) with in vivo brain structural variations among first-episode antipsychotic-naive schizophrenia/schizoaffective disorder patients and control subjects. We assayed HSV1 immunoglobulin G (IgG) antibody in serum samples from 30 patients and 44 healthy subjects and obtained structural magnetic resonance imaging scans from the same individuals. There were proportionately more patients with elevated HSV1 antibody ratios than healthy comparison subjects (chi2=3.98, 1 df, P=0.046) and patients had significantly higher HSV1 IgG antibody ratios compared with healthy subjects. Using optimized voxel-based morphometry, we examined diagnosis by HSV1 serological status interaction followed by within- and between-group comparison across the serological status. We observed a diagnosis by HSV1 serological status interaction and a significant main effect of HSV1 serological status in the prefrontal gray matter. Patients exposed to HSV1 had decreased gray matter in Brodmann area 9 (dorsolateral prefrontal cortex) and 32 (anterior cingulate cortex) compared with patients without serological evidence of exposure to HSV1. HSV1-associated differences in brain structure were not detected among healthy subjects. These findings suggest that HSV1 exposure in schizophrenia is associated with specific regional gray matter differences that may not be attributable to medications, illness chronicity or comorbid substance use. This study provides suggestive evidence for a link between HSV1 exposure and some of the cerebral morphological changes often reported in schizophrenia.

Genetic susceptibility to Tardive Dyskinesia in chronic schizophrenia subjects: V. Association of CYP1A2 1545 C>T polymorphism

Tardive dyskinesia (TD) is an iatrogenic disorder observed in approximately 20-30% of schizophrenia patients on long-term treatment with typical antipsychotic drugs. CYP1A2 is involved in the metabolism of atypical antipsychotic drugs such as clozapine and olanzapine. It is not directly involved in the metabolism of typical antipsychotic drugs, but gains importance when the schizophrenia patients are under long-term chronic treatment, acting as a low-affinity high-capacity metabolizing enzyme. In this study, we have completely sequenced the coding region to ascertain the presence of common coding polymorphisms and their role if any in susceptibility to TD and schizophrenia. Four previously reported polymorphisms, CYP1A2*1F (intron A), rs2472304 & rs3743484 (intron D) and rs2470890 (CYP1A2 1545 C>T) in exon 7 were identified. We further investigated whether the CYP1A2 1545 C>T polymorphism has any role to play in susceptibility to TD and in schizophrenia per se. Association of this single nucleotide polymorphism with TD (P=0.03) and schizophrenia (P=0.04) was observed, but was rendered insignificant after corrections for multiple comparisons.

Are neurologic examination abnormalities heritable? A preliminary study

BACKGROUND

Neurologic examination abnormalities (NEA) are more prevalent among patients with schizophrenia as well as their unaffected relatives when compared with healthy controls, suggesting that NEA may be endophenotypes for schizophrenia. We estimated the heritability of NEA in moderately sized pedigrees. We also evaluated correlations between NEA and cognitive performance in order to examine their construct validity.

METHODS

Members of eight extended families, each consisting of two first degree relatives with schizophrenia/schizoaffective disorders, as well as available first- to fifth-degree relatives were examined (n=96 participants). A modification of the Neurological Evaluation Scale (NES) was employed, augmented with localizing signs. Where feasible, we used untransformed data such as error counts and completion time, rather than ordinal measures. Heritability was estimated using the variance component method, implemented in SOLAR.

RESULTS

Statistically significant heritability (h2) estimates were obtained for several measures (p<0.05, h2+/-standard error: rapid alternating movements, right-sided completion time, 0.99+/-0.19; alternating fist-palm test, completion time, 0.77+/-0.19 s, errors, 0.70+/-0.32; fist-ring test, right-sided completion time, 0.53+/-0.23 s, left-sided completion time, 0.70+/-0.21 s; go-no go task, correct responses, 0.93+/-0.33; audio-visual integration, correct responses, 0.79+/-0.54). For most items, heritability analysis was hampered by insufficient data variability (infrequent errors). Correlational analyses show some degree of divergence among types of NEA, repetitive motor tasks being associated with most domains of cognitive functioning other than executive functioning, and cognitive-perceptual tasks being associated with memory and executive functioning.

CONCLUSIONS

Significant familial influences on certain aspects of neurologic performance were detected. These heritable measures were also correlated with heritable neurocognitive measures.

DNA pooling: a comprehensive, multi-stage association analysis of ACSL6 and SIRT5 polymorphisms in schizophrenia

Many candidate gene association studies have evaluated incomplete, unrepresentative sets of single nucleotide polymorphisms (SNPs), producing non-significant results that are difficult to interpret. Using a rapid, efficient strategy designed to investigate all common SNPs, we tested associations between schizophrenia and two positional candidate genes: ACSL6 (Acyl-Coenzyme A synthetase long-chain family member 6) and SIRT5 (silent mating type information regulation 2 homologue 5). We initially evaluated the utility of DNA sequencing traces to estimate SNP allele frequencies in pooled DNA samples. The mean variances for the DNA sequencing estimates were acceptable and were comparable to other published methods (mean variance: 0.0008, range 0-0.0119). Using pooled DNA samples from cases with schizophrenia/schizoaffective disorder (Diagnostic and Statistical Manual of Mental Disorders edition IV criteria) and controls (n=200, each group), we next sequenced all exons, introns and flanking upstream/downstream sequences for ACSL6 and SIRT5. Among 69 identified SNPs, case-control allele frequency comparisons revealed nine suggestive associations (P<0.2). Each of these SNPs was next genotyped in the individual samples composing the pools. A suggestive association with rs 11743803 at ACSL6 remained (allele-wise P=0.02), with diminished evidence in an extended sample (448 cases, 554 controls, P=0.062). In conclusion, we propose a multi-stage method for comprehensive, rapid, efficient and economical genetic association analysis that enables simultaneous SNP detection and allele frequency estimation in large samples. This strategy may be particularly useful for research groups lacking access to high throughput genotyping facilities. Our analyses did not yield convincing evidence for associations of schizophrenia with ACSL6 or SIRT5.

Association study of eight circadian genes with bipolar I disorder, schizoaffective disorder and schizophrenia

We hypothesize that circadian dysfunction could underlie, at least partially, the liability for bipolar 1 disorder (BD1). Our hypothesis motivated tests for the association between the polymorphisms of genes that mediate circadian function and liability for BD1. The US Caucasian patients with BD1 (DSM-IV criteria) and available parents were recruited from Pittsburgh and surrounding areas (n = 138 cases, 196 parents) and also selected from the NIMH Genetics Collaborative Initiative (n = 96 cases, 192 parents). We assayed 44 informative single-nucleotide polymorphisms (SNPs) from eight circadian genes in the BD1 samples. A population-based sample, specifically cord blood samples from local live births, served as community-based controls (n = 180). It was used as a contrast for genotype and haplotype distributions with those of patients. US patients with schizophrenia/schizoaffective disorder (SZ/SZA, n = 331) and available parents from Pittsburgh (n = 344) were assayed for a smaller set of SNPs based on the results from the BD1 samples. Modest associations with SNPs at ARNTL (BmaL1) and TIMELESS genes were observed in the BD1 samples. The associations were detected using family-based and case-control analyses, albeit with different SNPs. Associations with TIMELESS and PERIOD3 were also detected in the Pittsburgh SZ/SZA group. Thus far, evidence for association between specific SNPs at the circadian gene loci and BD1 is tentative. Additional studies using larger samples are required to evaluate the associations reported here.

Genetic polymorphisms of the RGS4 and dorsolateral prefrontal cortex morphometry among first episode schizophrenia patients

Polymorphisms of the gene encoding the regulator of G-protein signaling subtype 4 (RGS4) may confer risk for schizophrenia.(1) DNA microarray studies of postmortem brain samples have shown RGS4 underexpression in the dorsolateral prefrontal cortex (DLPFC, area 9), motor and visual cortices in schizophrenia patients relative to control subjects.(2) Underexpression of RGS4 in DLPFC is pathophysiologically significant because DLPFC pathology in schizophrenia has been supported by neurocognitive,(3,4) structural(5) and functional(6,7) imaging, postmortem,(8) cellular(9,10) and molecular(11) pathological studies. For these reasons, we examined the association of DLPFC gray matter volume with RGS4 polymorphisms in a series of antipsychotic-naive first-episode schizophrenia patients and control subjects. We hypothesized that volumetric alterations of the DLPFC would be associated with RGS4 polymorphisms and that these differences would be more pronounced in patients than in controls. We observed robust volumetric differences across the genotypes in the pooled sample of patients and control subjects; when separately analyzed, we observed differences within the patient group (n = 30) but not in control subject (n = 27) group. The findings suggest that RGS4 polymorphisms may contribute to structural alterations in the DLPFC.

Association and linkage analysis of RGS4 polymorphisms with schizophrenia and bipolar disorder in Brazil

Linkage and association studies in five independently ascertained samples have suggested that polymorphisms of the regulator of G-protein signaling 4 (RGS4) may confer risk for schizophrenia (SCZ). Suggestive evidence for association with bipolar disorder (BD) has also been presented. However, the associated alleles and haplotypes have differed among the samples. Data from other independent samples may clarify the putative associations. Hence, we investigated an independent, ethnically diverse Brazilian population comprising patients with SCZ (n=271) or BD1 (n=306), who were contrasted with 576 community-based controls. Parents of 49 SCZ cases and 44 BD cases were available for transmission disequilibrium tests (TDTs). Four RGS4 single-nucleotide polymorphisms (SNPs) 1, 4, 7 and 18 putatively associated with SCZ were investigated. In the SCZ samples, significant case-control differences were not observed for individual SNPs or haplotypes, though the TDT suggested transmission distortion similar to that observed in the initial report. For the BD sample, case-control comparisons revealed no significant differences for individual SNPs, but an omnibus test suggested differences in the overall distribution of haplotypes bearing all four SNPs (SNP-EM Omnibus likelihood ratio test; P=0.003). The TDT revealed over-transmission of allele A at SNP7 (P=0.016), as well as haplotypes incorporating this allele. However, global tests incorporating all haplotypes yielded only suggestive trends for association (P=0.19). In conclusion, association with SCZ was not detected in the present analyses. The failure to detect an association may be related to inadequate power or to confounds related to ethnic admixture. Suggestive associations with BD detected here require further investigation in a larger sample.

Association analysis of NOTCH 4 polymorphisms with schizophrenia among two independent family based samples

The present study investigated polymorphisms of the NOTCH 4 gene in two independent samples from India and USA, consisting of patients with schizophrenia and their parents (n = 182, and n = 148 'trios,' respectively). Five DNA markers, namely (GAAG)(n), (TAA)(n), SNP1, SNP2, and (CTG)(n) were evaluated. Transmission distortion, consistent with a modest association was detected among both samples. Additional association studies at this locus are warranted.

Clinical and familial correlates of tardive dyskinesia in India and Israel

BACKGROUND

Antipsychotic drugs are widely used for the treatment of psychosis, especially schizophrenia. Their long-term use can result at times in serious side-effects such as Tardive Dyskinesia (TD). Since over 80% of schizophrenia sufferers (lifetime prevalence 1%) receive long-term antipsychotic drug treatment, the extent of the problem is potentially large. Increasing age is the most consistently demonstrated risk factor for TD.

AIMS

To assess effect of different clinical factors and demographic variables in India and Israel and sib pair concordance of Tardive Dyskinesia (TD) in India.

SETTINGS AND DESIGN

The study was conducted simultaneously among Indian and Israeli subjects: ascertainment was family-based in India and hospital-based in Israel.

METHODS AND MATERIAL

In India the instruments used were: Diagnostic Interview for Genetic Studies (DIGS), Positive and Negative Syndrome Scale (PANSS), Abnormal Involuntary Movement Scale (AIMS), and Simpson Angus Scale (SAS). The last three instruments were also used in Israel.

STATISTICAL ANALYSIS

Regression analysis and Pearson's correlation.

RESULTS AND CONCLUSIONS

TD symptoms were present in 40.4% of 151 Israeli subjects and 28.7% of 334 Indian subjects. While age at onset and total scores on PANSS were significant predictors of TD in both the samples, lower scores on the Global Assessment of Functioning Scale (GAF), diagnostic sub-group and male gender were significant predictors among Indians. There was no concordance of TD symptoms among 33 affected sib-pairs from India.

Gender and procreation among patients with schizophrenia

OBJECTIVE

Reduced procreation among men with schizophrenia has been reported consistently when compared with female patients, but the cause is unknown. Reports on Caucasian individuals predominate in the published literature. Therefore, analyses were conducted concurrently among independent Indian and US samples in the present study.

METHOD

Individuals with schizophrenia or schizoaffective disorder (DSM-IV criteria) were ascertained and interviewed at New Delhi and in the northeastern United States using identical procedures (n=224 and 144, respectively). Selected indices of fertility and fecundity were compared among men and women at each site.

RESULTS

In the smaller US sample, male cases were significantly more likely to be single and childless compared with female cases. They also had fewer children. In contrast, there were no significant gender differences in the larger Indian sample with regard to the reproductive indices. Multivariate analyses revealed that the indices of reproduction were associated with different variables in the US and Indian samples. Fertility (the presence or absence of offspring) was associated with gender and age in the US sample while in the Indian sample conjugal status and age were significant predictors. Fecundity (the number of offspring) was associated with gender, conjugal status and educational status in the US sample while in the Indian sample conjugal status and educational status were both significant.

CONCLUSIONS

The reproductive deficit observed among US males was not observed among the Indian men. Conjugal status was a significant covariate for reproduction in both samples. The reproductive deficit may be due to difficulties in establishing long-term conjugal relationships among the US men. The differences may also reflect underlying cultural variations related to marital practices in these two countries. Our analyses suggest that the male reproductive deficit in schizophrenia is variable and may be overcome.

A systematic genomewide linkage study in 353 sib pairs with schizophrenia

We undertook a genomewide linkage study in a total of 353 affected sib pairs (ASPs) with schizophrenia. Our sample consisted of 179 ASPs from the United Kingdom, 134 from Sweden, and 40 from the United States. We typed 372 microsatellite markers at approximately 10-cM intervals. Our strongest finding was a LOD score of 3.87 on chromosome 10q25.3-q26.3, with positive results being contributed by all three samples and a LOD-1 interval of 15 cM. This finding achieved genomewide significance (P<.05), on the basis of simulation studies. We also found two regions, 17p11.2-q25.1 (maximum LOD score [MLS] = 3.35) and 22q11 (MLS = 2.29), in which the evidence for linkage was highly suggestive. Linkage to all of these regions has been supported by other studies. Moreover, we found strong evidence for linkage (genomewide P<.02) to 17p11.2-q25.1 in a single pedigree with schizophrenia. In our view, the evidence is now sufficiently compelling to undertake detailed mapping studies of these three regions.

Psychotic symptoms in Alzheimer disease: evidence for a distinct phenotype

Though efforts to identify the genetic etiology of Alzheimer disease (AD) have made substantial progress, to date only some of the genes contributing to AD risk have been identified. Utilization of more etiologically homogeneous subphenotypes represents one strategy to facilitate the identification of novel risk genes in complex disorders. In this review, we evaluate the hypothesis that psychotic symptoms, such as delusions and hallucinations, define a suitable subphenotype in AD patients for gene-mapping efforts. Psychotic symptoms occur in 40-60% of patients with AD and are associated with more severe cognitive deficits and a more rapidly deteriorating course. The presence of psychotic symptoms in AD confers increased risk of similar symptoms to affected siblings. Candidate gene association analyses and initial linkage analysis have yielded significant results. We discuss possible genetic models of psychotic symptoms in AD, and suggest strategies for further investigation. Identification of such genetic factors may facilitate gene-mapping studies for both AD and idiopathic psychoses.

Can clinical features of bipolar-I disorder be assessed reliably on the telephone?

BACKGROUND

The reliability of telephone interviews for rating 25 selected individual items of the Diagnostic Interview for Genetic Studies (DIGS) was assessed among persons with remitted bipolar disorder I (BPD I, n = 20).

METHODS

The Diagnostic Interview for Genetic Studies (DIGS) was administered directly (with two raters present) and by telephone in random order to 20 adults with bipolar disorder I.

RESULTS

Telephone interviews achieved reliability comparable to direct interviews for 16 items (64%), but were considered unsatisfactory for seven others (28%). Two other items, which evaluated the overlap between substance abuse and mood disorder, were considered unreliable for both methods of interview.

LIMITATIONS

The presence of two interviewers for the in-person interview may have led to over-estimation of in-person reliability. Investigator bias in favor of phone interviews and a relatively small sample may have confounded the results.

CONCLUSIONS

Telephone interviews may be used to evaluate individuals with BPD I in remission, provided the limitations of this method are recognized. They have limited reliability for dissecting overlap between mood abnormalities and psychotic phenomena or substance abuse.

Linkage analysis of Alzheimer disease with psychosis

Although a portion of risk for late-onset AD (LOAD) is attributable to APOE, the search for other loci is ongoing. The authors hypothesize that psychotic symptoms with LOAD (LOAD+P) identify a potentially more etiologically homogeneous form of AD. Linkage analysis of families with LOAD+P identified one significant and several suggestive novel linkage signals, which bolsters the conjecture of greater etiologic homogeneity.

Increased familial risk of the psychotic phenotype of Alzheimer disease

BACKGROUND

Psychotic symptoms in patients with AD (AD with psychosis [AD+P]) define a phenotype characterized by more rapid cognitive and functional decline and a liability to aggressive behaviors.

OBJECTIVE

To determine if AD+P aggregates within families.

METHODS

Case-control study of AD+P frequency in 461 siblings of 371 probands diagnosed with AD. All siblings were ascertained as part of a genetic investigation and also were diagnosed with AD. Statistical analysis used Generalized Estimating Equations to adjust for clustering within families.

RESULTS

AD+P in probands was associated with a significantly increased risk for AD+P in family members (OR, 2.41; 95% CI 1.46-4.0; p = 0.0006). The correlation among siblings for AD+P status was modest: 0.16.

CONCLUSION

AD+P demonstrates familial aggregation. Further studies are required to investigate a possible genetic basis of AD+P.

Molecular genetics of schizophrenia: past, present and future

Schizophrenia is a severe neuropsychiatric disorder with a polygenic mode of inheritance which is also governed by non-genetic factors. Candidate genes identified on the basis of biochemical and pharmacological evidence are being tested for linkage and association studies. Neurotransmitters, especially dopamine and serotonin have been widely implicated in its etiology. Genome scan of all human chromosomes with closely spaced polymorphic markers is being used for linkage studies. The completion and availability of the first draft of Human Genome Sequence has provided a treasure-trove that can be utilized to gain insight into the so far inaccessible regions of the human genome. Significant technological advances for identification of single nucleo-tide polymorphisms (SNPs) and use of microarrays have further strengthened research methodologies for genetic analysis of complex traits. In this review, we summarize the evolution of schizophrenia genetics from the past to the present, current trends and future direction of research.

Association studies of cytosolic phospholipase A2 polymorphisms and schizophrenia among two independent family-based samples

An association between the cytosolic phospholipase A2 locus (cPLA2) and schizophrenia has been reported using two polymorphic DNA markers. In an attempt to replicate these results, two independent family-based samples were ascertained from the United States and India (86 and 159 families, respectively). No significant associations were detected in either sample.

Immune related genetic polymorphisms and schizophrenia among the Chinese

Genetic association studies were conducted among two independent cohorts of Chinese ethnicity. The samples consisted of cases and unrelated controls, ascertained from Guangzhou, China, and Singapore. The studies were prompted by our earlier report of an association between schizophrenia and HLA DQB1 alleles (HLA DQB1*0602 and HLA DQB1*0303) in the Singapore sample. Polymorphisms of HLA DQB1 and flanking markers on chromosome 6p21.3 were investigated in the first part of the study. A significant negative association with HLA DQB1*0402 was detected in the Guangzhou sample (Odds ratio, OR 0.26, 95% confidence intervals, CI 0.1, 0.6; p < 0.02, corrected for multiple comparisons). Additional analysis of the Guangzhou and Singapore samples revealed associations at three other anonymous markers flanking HLA DQB1. In the second part of the study, three polymorphisms at the Interleukin-1 gene cluster (IL-1, chromosome 2q13-q21) were investigated in both cohorts, since associations with schizophrenia have been reported in another sample. Persuasive evidence for an association at IL-1 was not detected in either sample. Our results suggest a susceptibility locus for schizophrenia in the HLA region among the Chinese, but further clarification is necessary.

Impact of overlapping recruitment on linkage analysis of complex disorders: simulation studies

Evidence for significant linkage in complexly inherited disorders usually necessitates independent, replicative studies. This study investigates the implications of including in the replicative studies families already used to suggest linkage in initial linkage analysis. We generated 1,000 unlinked replicates of 100 nuclear families with a complexly inherited disease but with no linkage to the markers analyzed. We then used a standard nonparametric linkage method to analyze these data. From the original 1,000 replicates of the original data set, one set was chosen as it yielded suggestive, but falsely positive, linkage results (LOD score = 3.4). Variable numbers of randomly selected families from this positive replicate (n = 100 families) were used to replace families in replicates of the original (unlinked) data set, and linkage analysis repeated. Overlap of families from the "positive data set" did increase the LOD scores for "unlinked data sets." While a small amount of overlap (replacement) between a positive linkage result and the replication sample is unlikely in practice to alter results, our study suggests that steps should be taken to ensure that overlap is minimized. The implications of this overlapping recruitment on replicative linkage studies are discussed.

Family-based association studies of monoaminergic gene polymorphisms among North Indians with schizophrenia

Associations between schizophrenia and four candidate genes were tested among Indian patients with schizophrenia and their parents (DSM-IV criteria, n = 179 families). Polymorphisms within the genes encoding the serotonin 2A receptor (HT2A), tryptophan hydroxylase (TPH), catechol-O-methyl transferase (COMT) and dopamine transporter (DAT) were thus investigated. Two polymorphisms each were analyzed at HT2A and TPH, enabling haplotype-based analyses using the transmission disequilibrium test (TDT) for these genes. No significant associations were detected. Pooled analysis of samples like ours may be necessary to definitively exclude putative allelic associations at these loci.

Schizophrenia and HLA: a review

A number of reports of genetic association of human leucocyte antigens (HLA) and alleles with schizophrenia have recently been published. A schizophrenia locus on chromosome 6p near the HLA region has also been reported, on the basis of linkage studies. We have therefore reviewed the investigations of association of HLA with schizophrenia published from 1974 to date, and have also briefly reviewed the chromosome 6p linkage studies. Two or more groups of investigators have reported association of each of the following HLA antigens or alleles with schizophrenia - A9 or its A24 subspecificity, A28, A10, DRB1*01 and DRw6. However, these results may represent Type I errors caused by small sample size, inappropriate diagnostic, laboratory and/or statistical methodology, and/or incorrectly chosen comparison subjects. Hypothesis-driven negative associations of DRB1*04 and DQB1*0602 with schizophrenia have also been reported. Taken together, however, HLA association investigations provide only weak evidence for the existence of either resistance or susceptibility loci for schizophrenia close to the HLA region at the 6p21.3 band and, indeed, recently reported investigations that controlled for most of these confounders found no evidence of association. Linkage studies suggest that a susceptibility locus may exist and that it may be within the HLA region, but again the evidence is far from conclusive. Further HLA association investigations should employ operational diagnostic criteria, comparison subjects screened for illness and HLA genotyping, and should include both association studies of candidate alleles and transmission disequilibrium and haplotype relative risk studies.

NURR1 mutations in cases of schizophrenia and manic-depressive disorder

Transgenic mice lacking the nuclear orphan transcription factor Nur-related receptor 1 (Nurr1) fail to develop mesencephalic dopamine neurons. There is a highly homologous NURR1 gene in humans (formerly known as NOT) which therefore constitutes a good candidate gene for neurologic and psychiatric disorders with an involvement of the dopamine neuron system, such as Parkinson's disease, schizophrenia, and manic-depression. By direct sequencing of genomic DNA, we found two different missense mutations in the third exon of NURR1 in two schizophrenic patients and another missense mutation in the same exon in an individual with manic-depressive disorder. All three mutations caused a similar reduction of in vitro transcriptional activity of NURR1 dimers of about 30-40%. Neither of these amino acid changes, nor any sequence changes whatsoever, were found in patients with Parkinson's disease or control DNA material of normal populations. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:808-813, 2000.

NURR1 mutations in cases of schizophrenia and manic-depressive disorder

Transgenic mice lacking the nuclear orphan transcription factor Nur-related receptor 1 (Nurr1) fail to develop mesencephalic dopamine neurons. There is a highly homologous NURR1 gene in humans (formerly known as NOT) which therefore constitutes a good candidate gene for neurologic and psychiatric disorders with an involvement of the dopamine neuron system, such as Parkinson's disease, schizophrenia, and manic-depression. By direct sequencing of genomic DNA, we found two different missense mutations in the third exon of NURR1 in two schizophrenic patients and another missense mutation in the same exon in an individual with manic-depressive disorder. All three mutations caused a similar reduction of in vitro transcriptional activity of NURR1 dimers of about 30-40%. Neither of these amino acid changes, nor any sequence changes whatsoever, were found in patients with Parkinson's disease or control DNA material of normal populations. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:808-813, 2000.

NURR1 mutations in cases of schizophrenia and manic-depressive disorder

Transgenic mice lacking the nuclear orphan transcription factor Nur-related receptor 1 (Nurr1) fail to develop mesencephalic dopamine neurons. There is a highly homologous NURR1 gene in humans (formerly known as NOT) which therefore constitutes a good candidate gene for neurologic and psychiatric disorders with an involvement of the dopamine neuron system, such as Parkinson's disease, schizophrenia, and manic-depression. By direct sequencing of genomic DNA, we found two different missense mutations in the third exon of NURR1 in two schizophrenic patients and another missense mutation in the same exon in an individual with manic-depressive disorder. All three mutations caused a similar reduction of in vitro transcriptional activity of NURR1 dimers of about 30-40%. Neither of these amino acid changes, nor any sequence changes whatsoever, were found in patients with Parkinson's disease or control DNA material of normal populations. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:808-813, 2000.