Shared and specific susceptibility loci for schizophrenia and bipolar disorder: a dense genome scan in Eastern Quebec families

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

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

Symptom dimensions as alternative phenotypes to address genetic heterogeneity in schizophrenia and bipolar disorder

This study introduces a novel way to use the lifetime ratings of symptoms of psychosis, mania and depression in genetic linkage analysis of schizophrenia (SZ) and bipolar disorder (BP). It suggests using a latent class model developed for family data to define more homogeneous symptom subtypes that are influenced by a smaller number of genes that will thus be more easily detectable. In a two-step approach, we proposed: (i) to form homogeneous clusters of subjects based on the symptom dimensions and (ii) to use the information from these homogeneous clusters in linkage analysis. This framework was applied to a unique SZ and BP sample composed of 1278 subjects from 48 large kindreds from the Eastern Quebec population. The results suggest that our strategy has the power to increase linkage signals previously obtained using the diagnosis as phenotype and allows for a better characterization of the linkage signals. This is the case for a linkage signal, which we formerly obtained in chromosome 13q and enhanced using the dimension mania. The analysis also suggests that the methods may detect new linkage signals not previously uncovered by using diagnosis alone, as in chromosomes 2q (delusion), 15q (bizarre behavior), 7p (anhedonia) and 9q (delusion). In the case of the 15q and 2q region, the results coincide with linkage signals detected in other studies. Our results support the view that dissecting phenotypic heterogeneity by modeling symptom dimensions may provide new insights into the genetics of SZ and BP.

A role for Akt and glycogen synthase kinase-3 as integrators of dopamine and serotonin neurotransmission in mental health

Mental illnesses, such as bipolar disorder, attention-deficit/hyperactivity disorder, depression and schizophrenia are a major public health concern worldwide. Several pharmacologic agents acting on monoamine neurotransmission are used for the management of these disorders. However, there is still little understanding of the ultimate molecular mechanisms responsible for the therapeutic effects of these drugs or their relations with disease etiology. Here I provide an overview of recent advances on the involvement of the signalling molecules Akt and glycogen synthase kinase-3 (GSK3) in the regulation of behaviour by the monoamine neurotransmitters dopamine (DA) and serotonin (5-HT). I examine the possible participation of these signalling molecules to the effects of antidepressants, lithium and antipsychotics, as well as their possible contribution to mental disorders. Regulation of Akt and GSK3 may constitute an important signalling hub in the subcellular integration of 5-HT and DA neurotransmission. It may also provide a link between the action of these neurotransmitters and gene products, like disrupted in schizophrenia 1 (DISC1) and neuregulin (NRG), that are associated with increased risk for mental disorders. However, changes in Akt and GSK3 signalling are not restricted to a single disorder, and their contribution to specific behavioural symptoms or therapeutic effects may be modulated by broader changes in biologic contexts or signalling landscapes. Understanding these interactions may provide a better understanding of mental illnesses, leading to better efficacy of new therapeutic approaches.

Genome-wide searches for bipolar disorder genes

Whole-genome linkage and association studies of bipolar disorder are beginning to provide some compelling evidence for the involvement of several chromosomal regions and susceptibility genes in the pathogenesis of bipolar disorder. Developments in genotyping technology and efforts to combine data from different studies have helped in identifying chromosomes 6q16-q25, 13q, and 16p12 as probable susceptibility loci for bipolar disorder and confirmed CACNA1C and ANK3 as susceptibility genes for bipolar disorder. However, a lack of replication is still apparent in the literature. New studies focusing on copy number variants as well as new analytical approaches utilizing pathway analysis offer a new direction in the study of the genetics of bipolar disorder.

Verbal and visual memory impairments among young offspring and healthy adult relatives of patients with schizophrenia and bipolar disorder: selective generational patterns indicate different developmental trajectories

OBJECTIVE

Memory deficits have been shown in patients affected by schizophrenia (SZ) and bipolar (BP)/mood disorder. We recently reported that young high-risk offspring of an affected parent were impaired in both verbal episodic memory (VEM) and visual episodic memory (VisEM). Understanding better the trajectory of memory impairments from childhood to adult clinical status in risk populations is crucial for early detection and prevention. In multigenerational families densely affected by SZ or BP, our aim was to compare the memory impairments observed in young nonaffected offspring with memory functioning in nonaffected adult relatives and patients.

METHODS

For 20 years, we followed up numerous kindreds in the Eastern Québec population. After having characterized the Diagnostic and Statistical Manual of Mental Disorders phenotypes, we assessed cognition (N = 381) in 3 subsamples in these kindreds and in controls: 60 young offspring of a parent affected by SZ or BP, and in the adult generations, 92 nonaffected adult relatives and 40 patients affected by SZ or BP. VEM was assessed with the California Verbal Learning Test and VisEM with the Rey figures.

RESULTS

The VEM deficits observed in the offspring were also found in adult relatives and patients. In contrast, the VisEM impairments observed in the young offspring were present only in patients, not in the adult relatives.

CONCLUSION

Implications for prevention and genetic mechanisms can be drawn from the observation that VEM and VisEM would show distinct generational trajectories and that the trajectory associated with VisEM may offer a better potential than VEM to predict future risk of developing the disease.

Molecular mechanisms underlying activity-dependent GABAergic synapse development and plasticity and its implications for neurodevelopmental disorders

GABAergic interneurons are critical for the normal function and development of neural circuits, and their dysfunction is implicated in a large number of neurodevelopmental disorders. Experience and activity-dependent mechanisms play an important role in GABAergic circuit development, also recent studies involve a number of molecular players involved in the process. Emphasizing the molecular mechanisms of GABAergic synapse formation, in particular basket cell perisomatic synapses, this paper draws attention to the links between critical period plasticity, GABAergic synapse maturation, and the consequences of its dysfunction on the development of the nervous system.

Young offspring at genetic risk of adult psychoses: the form of the trajectory of IQ or memory may orient to the right dysfunction at the right time

Objective

Neurocognitive dysfunctions analogous to those of adult patients have been detected in children at risk of schizophrenia and bipolar disorder. This led to the following developmental question: Do IQ and memory impairments exhibit different developmental courses from childhood to young adulthood in terms of stability or fluctuations?

Methods

In a high risk sample, we used a step by step sampling approach to narrow-down the early disease mechanisms. Upstream, we started with a 20-year follow-up of 48 densely affected multigenerational kindreds, including 1500 clinically characterized adult members. We then identified 400 adult members affected by a DSM-IV schizophrenia or bipolar disorder. Downstream, we finally focused on 65 offspring (of an affected parent) aged 7 to 22, who were administered a neuropsychological battery. We then constructed cross-sectional trajectories that were compared to those of controls.

Results

The childhood IQ deficit displayed a stability until young adulthood. The delay in visual memory exhibited a non-linear two-stage trajectory: a lagging period during childhood followed by a recuperation period from adolescence until adulthood, as supported by a significant Group x Age Periods interaction. No data suggested deterioration between 7 and 22.

Conclusion

In these offspring at genetic risk, the developmental trajectory of global IQ impairment may not apply to specific domains of cognition such as episodic memory. Different cognitive dysfunctions would mark different developmental courses. The shape of the trajectories might itself have a meaning and provide empirical leads for targeting the right dysfunction at the right time in future prevention research.

Convergent functional genomic studies of ω-3 fatty acids in stress reactivity, bipolar disorder and alcoholism

Omega-3 fatty acids have been proposed as an adjuvant treatment option in psychiatric disorders. Given their other health benefits and their relative lack of toxicity, teratogenicity and side effects, they may be particularly useful in children and in females of child-bearing age, especially during pregnancy and postpartum. A comprehensive mechanistic understanding of their effects is needed. Here we report translational studies demonstrating the phenotypic normalization and gene expression effects of dietary omega-3 fatty acids, specifically docosahexaenoic acid (DHA), in a stress-reactive knockout mouse model of bipolar disorder and co-morbid alcoholism, using a bioinformatic convergent functional genomics approach integrating animal model and human data to prioritize disease-relevant genes. Additionally, to validate at a behavioral level the novel observed effects on decreasing alcohol consumption, we also tested the effects of DHA in an independent animal model, alcohol-preferring (P) rats, a well-established animal model of alcoholism. Our studies uncover sex differences, brain region-specific effects and blood biomarkers that may underpin the effects of DHA. Of note, DHA modulates some of the same genes targeted by current psychotropic medications, as well as increases myelin-related gene expression. Myelin-related gene expression decrease is a common, if nonspecific, denominator of neuropsychiatric disorders. In conclusion, our work supports the potential utility of omega-3 fatty acids, specifically DHA, for a spectrum of psychiatric disorders such as stress disorders, bipolar disorder, alcoholism and beyond.

Structural and functional impairments of polysialic acid by a mutated polysialyltransferase found in schizophrenia

Polysialic acid (polySia), a unique acidic glycan modifying neural cell adhesion molecule (NCAM), is known to regulate embryonic neural development and adult brain functions. Polysialyltransferase STX is responsible for the synthesis of polySia, and two single nucleotide polymorphisms (SNPs) of the coding region of STX are reported from schizophrenic patients: SNP7 and SNP9, respectively, giving STX(G421A) with E141K and STX(C621G) with silent mutations. In this study, we focused on these mutations and a binding activity of polySia to neural materials, such as brain-derived neurotrophic factor (BDNF). Here we describe three new findings. First, STX(G421A) shows a dramatic decrease in polySia synthetic activity on NCAM, whereas STX(C621G) does not. The STX(G421A)-derived polySia-NCAM contains a lower amount of polySia with a shorter chain length. Second, polySia shows a dopamine (DA) binding activity, which is a new function of polySia as revealed by frontal affinity chromatography for measuring the polySia-neurotransmitter interactions. Interestingly, the STX(G421A)-derived polySia-NCAM completely loses the DA binding activity, whereas it greatly diminishes but does not lose the BDNF binding activity. Third, an impairment of the polySia structure with an endosialidase modulates the DA-mediated Akt signaling. Taken together, impairment of the amount and quality of polySia may be involved in psychiatric disorders through impaired binding to BDNF and DA, which are deeply involved in schizophrenia and other psychiatric disorders, such as depression and bipolar disorder.

Familial 3q29 microdeletion syndrome providing further evidence of involvement of the 3q29 region in bipolar disorder

The 3q29 microdeletion syndrome is caused by a recurrent 1.6 Mb deletion of the 3q subtelomeric region. Though sometimes visible on routine microscopy, the deletion is detected more reliably using subtelomeric fluorescence in-situ hybridization (FISH) or molecular karyotyping. The clinical features associated with a 3q29 microdeletion are variable and include developmental delay, autistic features, skeletal abnormalities and dysmorphic facial features with a relatively long face, long nose with a high bridge and broad tip, short philtrum and large ears. Orofacial clefting, cardiac defects, ocular anomalies and genitourinary malformations have been reported occasionally. We report a three generation family where four individuals were confirmed to have a 3q29 microdeletion and compare their clinical features to those of previously reported patients. This family shows that the learning difficulties associated with a 3q29 deletion may be relatively mild. The history of a severe depressive disorder commencing in adulthood in the affected grandmother also supports previous studies linking the 3q29 region to bipolar disorder and links with the observation of Digilio et al. (2009) who also reported a history of depression in an adult woman with a similar deletion.

Coming to grips with complex disorders: genetic risk prediction in bipolar disorder using panels of genes identified through convergent functional genomics

We previously proposed and provided proof of principle for the use of a complementary approach, convergent functional genomics (CFG), combining gene expression and genetic data, from human and animal model studies, as a way of mining the existing GWAS datasets for signals that are there already, but did not reach significance using a genetics-only approach [Le-Niculescu et al., 2009b]. CFG provides a fit-to-disease prioritization of genes that leads to generalizability in independent cohorts, and counterbalances the fit-to-cohort prioritization inherent in classic genetic-only approaches, which have been plagued by poor reproducibility across cohorts. We have now extended our previous work to include more datasets of GWAS, and more recent evidence from other lines of work. In essence our analysis is the most comprehensive integration of genetics and functional genomics to date in the field of bipolar disorder. Biological pathway analyses identified top canonical pathways, and epistatic interaction testing inside these pathways has identified genes that merit future follow-up as direct interactors (intra-pathway epistasis, INPEP). Moreover, we have put together a panel of best P-value single nucleotide polymorphisms (SNPs), based on the top candidate genes we identified. We have developed a genetic risk prediction score (GRPS) based on our panel, and demonstrate how in two independent test cohorts the GRPS differentiates between subjects with bipolar disorder and normal controls, in both European-American and African-American populations. Lastly, we describe a prototype of how such testing could be used to categorize disease risk in individuals and aid personalized medicine approaches, in psychiatry and beyond.

The effect of a functional NOS1 promoter polymorphism on impulsivity is moderated by platelet MAO activity

RATIONALE

Platelet monoamine oxidase (MAO) activity is associated with impulsivity in clinical samples. Recently, a functional promoter polymorphism of neuronal nitric oxide synthase (NOS1) termed NOS1 ex1f-VNTR was found to have an effect on impulsivity-related traits and resulting psychopathology.

OBJECTIVE

The study aims to explore the effect of both platelet MAO activity and NOS1 ex1f-VNTR genotype on impulsivity in a population-derived sample.

METHODS

This study was on a non-clinical sample of adult male subjects, previously used to investigate the effect of platelet MAO activity on impulsivity-related behaviour (Paaver et al., Psychopharmacology 186:32-40, 2006). Six hundred thirty-seven male subjects were genotyped for the NOS1 ex1f-VNTR promoter polymorphism. Impulsivity was self-reported. Effects of age and smoking, known to affect platelet MAO activity, were controlled for.

RESULTS

No main effect of either NOS1 genotype or platelet MAO activity was present. However, significant interactions were found between effects of the NOS1 genotype and platelet MAO activity on impulsivity measures. Impulsivity and in particular the aspects of adaptive impulsivity (e.g. fast decision-making and excitement-seeking behaviour) were higher in subjects with the NOS1 ex1f-VNTR short/short genotype if they belonged to the platelet MAO medium activity (interquartile) range.

CONCLUSIONS

This study supports evidence for higher impulsivity in the NOS1 short/short genotype subjects and further suggests that this is present in the subset of subjects who have close to average platelet MAO activity.

Cytosolic protein interactions of the schizophrenia susceptibility gene dysbindin

Using immunoprecipitation, mass spectrometry, and western blot analysis we investigated cytosolic protein interactions of the schizophrenia susceptibility gene dysbindin in mammalian cells. We identified novel interactions with members of the exocyst, dynactin and chaperonin containing T-complex protein complexes, and we confirmed interactions reported previously with all members of the biogenesis of lysosome-related organelles complex-1 and the adaptor-related protein complex 3. We report interactions between dysbindin and the exocyst and dynactin complex that confirm a link between two important schizophrenia susceptibility genes: dysbindin and disrupted-in-schizophrenia-1. To expand upon this network of interacting proteins we also investigated protein interactions for members of the exocyst and dynactin complexes in mammalian cells. Our results are consistent with the notion that impairment of aspects of the synaptic vesicle life cycle may be a pathogenic mechanism in schizophrenia.

Strong genetic evidence for a selective influence of GABAA receptors on a component of the bipolar disorder phenotype

Despite compelling evidence for a major genetic contribution to risk of bipolar mood disorder, conclusive evidence implicating specific genes or pathophysiological systems has proved elusive. In part this is likely to be related to the unknown validity of current phenotype definitions and consequent aetiological heterogeneity of samples. In the recent Wellcome Trust Case Control Consortium genome-wide association analysis of bipolar disorder (1868 cases, 2938 controls) one of the most strongly associated polymorphisms lay within the gene encoding the GABA(A) receptor beta1 subunit, GABRB1. Aiming to increase biological homogeneity, we sought the diagnostic subset that showed the strongest signal at this polymorphism and used this to test for independent evidence of association with other members of the GABA(A) receptor gene family. The index signal was significantly enriched in the 279 cases meeting Research Diagnostic Criteria for schizoaffective disorder, bipolar type (P=3.8 x 10(-6)). Independently, these cases showed strong evidence that variation in GABA(A) receptor genes influences risk for this phenotype (independent system-wide P=6.6 x 10(-5)) with association signals also at GABRA4, GABRB3, GABRA5 and GABRR3. [corrected] Our findings have the potential to inform understanding of presentation, pathogenesis and nosology of bipolar disorders. Our method of phenotype refinement may be useful in studies of other complex psychiatric and non-psychiatric disorders.

Retinal response to light in young nonaffected offspring at high genetic risk of neuropsychiatric brain disorders

BACKGROUND

In neuropsychiatric brain disorders, such as schizophrenia (SZ) and bipolar disorder (BD), the biased effect of chronic drug therapy and the toxic effect of illness once installed constitute obstacles to the identification of valid biomarkers. Such biomarkers could lie at the level of retinal function where anomalies have already been reported in adults suffering from neuropsychiatric disorders. Here, we report a specific electroretinographic (ERG) anomaly in young nonaffected and nonmedicated offspring at high genetic risk (HR) of these disorders.

METHODS

Electroretinography was performed in 29 HR offspring having one parent affected by DSM-IV SZ or BD (mean age: 20.8 years, SD 4.4) and 29 healthy control subjects (mean age: 20.6 years, SD 4.2). The HRs' parents descended from multigenerational families affected by SZ or BD.

RESULTS

Rod ERG (b-wave amplitude at V(max)) in HRs was significantly lower than control subjects (p < .0001; effect size of -1.47), whereas the cone ERG V(max) showed no difference (p = .27). No effects of gender, age, and seasons of testing were observed. The anomaly in retinal response (rod V(max) b-wave amplitude) was observed independently of parents' diagnosis (SZ; p = .007, effect size of -1.09; BD: p < .0001, effect size of -1.88) and was present in both the younger and older HRs (effect size of -1.6 and -1.8, respectively).

CONCLUSIONS

A rod retinal response anomaly before the age of the disease incidence may represent an early and specific biomarker of risk with meaning for further genetic and prevention research.

GABRB2 in schizophrenia and bipolar disorder: disease association, gene expression and clinical correlations

The SCZ (schizophrenia)-associated GABA(A) receptor (gamma-aminobutyric acid type A receptor) beta(2) subunit gene GABRB2 was recently associated with BPD (bipolar disorder). Although weaker than its association with SCZ, significant association of GABRB2 with BPD was found in both German and Chinese, especially for the haplotypes rs1816071-rs187269 and rs1816072-rs187269 for which the M-M variants showed higher frequency in disease than the control. Significant genotype-dependent reduction in GABRB2 expression was shown for BPD, but to a lesser extent than that for SCZ. Temporal effects on GABRB2 expression were observed. Moreover, for the homozygous major genotypes of rs1816071, rs1816072 and rs187269, expression increased with time in CON but decreased in SCZ and BPD. The genotypes of these three SNPs (single nucleotide polymorphisms) were further correlated with antipsychotics dosage in SCZ cohorts. The findings highlight the importance of GABRB2 in neuropsychiatric disease aetiology, with respect to haplotype association, as well as reduction of and temporal effects on gene expression in both SCZ and BPD, but to a lesser extent in the latter, supporting the suggestion that functional psychosis can be conceptualized as a continuous spectrum of clinical phenotypes rather than as distinct categories.

Positive association between ALDH1A2 and schizophrenia in the Chinese population

Vitamin A (retinol), in the biologically active form of retinoic acid (RA), has been proposed as involved in the pathogenesis of schizophrenia. We hypothesized that genetic basis of genes encoding RA metabolism enzymes, which control the cellular RA level, might be associated with this disease. This cascade genetic association model, using markers in genes of synthesis and degradation enzymes within the retinoid cascade, would better fit the biological character of the retinoid hypothesis than the single gene strategy. In the present study we chose to investigate 7 genes involved in the synthesis, degradation and transportation of RA, ALDH1A1, ALDH1A2, ALDH1A3, CYP26A1, CYP26B1, CYP26C1 and Transthyretin (TTR), for their roles in the development of schizophrenia. We genotyped 18 single nucleotide polymorphisms (SNPs) in the regulatory and coding regions of these 7 genes using LDR technology in the 617 Chinese Han subjects. Case-control analyses were performed to detect association of these 7 genes with schizophrenia. Association analyses using both allelic and genotypic single-locus tests revealed no significant association between the risk for each of investigated gene and schizophrenia. However, analyses of multiple-locus haplotypes indicated that the overall frequency of rs4646642-rs4646580 of ALDH1A2 gene showed significant difference between patients and control subjects (p=0.0055). We also employed multifactor dimensionality reduction method to detect multilocus effects. In summary, in this work we show multiple candidate genes involved in retinoid cascade in schizophrenics. In addition, our results suggest a positive association between ALDH1A2 and schizophrenics in the Chinese population and support the retinoid hypothesis of schizophrenia.

Shared neurocognitive dysfunctions in young offspring at extreme risk for schizophrenia or bipolar disorder in eastern quebec multigenerational families

BACKGROUND

Adult patients having schizophrenia (SZ) or bipolar disorder (BP) may have in common neurocognitive deficits. Former evidence suggests impairments in several neuropsychological functions in young offspring at genetic risk for SZ or BP. Moreover, a dose-response relation may exist between the degree of familial loading and cognitive impairments. This study examines the cognitive functioning of high-risk (HR) offspring of parents having schizophrenia (HRSZ) and high-risk offspring of parents having bipolar disorder (HRBP) descending from densely affected kindreds.

METHODS

The sample consisted of 45 young offspring (mean age of 17.3 years) born to a parent having SZ or BP descending from large multigenerational families of Eastern Québec that are densely affected by SZ or BP and followed up since 1989. The offspring were administered a lifetime best-estimate diagnostic procedure (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition [DSM-IV]) and an extensive standard neuropsychological battery. Raw scores were compared with age- and gender-matched controls.

RESULTS

The offspring displayed differences in memory and executive functions when compared with controls. Moderate to large effect sizes (Cohen d) ranging from 0.65 to 1.25 (for IQ and memory) were observed. Several of the cognitive dysfunctions were present in both HRSZ and HRBP, even when considering DSM-IV clinical status.

CONCLUSIONS

HRSZ and HRBP shared several aspects of their cognitive impairment. Our data suggest that the extremely high genetic and familial loading of these HRs may have contributed to a quantitatively increased magnitude of the cognitive impairments in both HR subgroups, especially in memory. These offspring at heightened risk present difficulties in processing information that warrant preventive research.

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

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

Chromosome 8p as a potential hub for developmental neuropsychiatric disorders: implications for schizophrenia, autism and cancer

Defects in genetic and developmental processes are thought to contribute susceptibility to autism and schizophrenia. Presumably, owing to etiological complexity identifying susceptibility genes and abnormalities in the development has been difficult. However, the importance of genes within chromosomal 8p region for neuropsychiatric disorders and cancer is well established. There are 484 annotated genes located on 8p; many are most likely oncogenes and tumor-suppressor genes. Molecular genetics and developmental studies have identified 21 genes in this region (ADRA1A, ARHGEF10, CHRNA2, CHRNA6, CHRNB3, DKK4, DPYSL2, EGR3, FGF17, FGF20, FGFR1, FZD3, LDL, NAT2, NEF3, NRG1, PCM1, PLAT, PPP3CC, SFRP1 and VMAT1/SLC18A1) that are most likely to contribute to neuropsychiatric disorders (schizophrenia, autism, bipolar disorder and depression), neurodegenerative disorders (Parkinson's and Alzheimer's disease) and cancer. Furthermore, at least seven nonprotein-coding RNAs (microRNAs) are located at 8p. Structural variants on 8p, such as copy number variants, microdeletions or microduplications, might also contribute to autism, schizophrenia and other human diseases including cancer. In this review, we consider the current state of evidence from cytogenetic, linkage, association, gene expression and endophenotyping studies for the role of these 8p genes in neuropsychiatric disease. We also describe how a mutation in an 8p gene (Fgf17) results in a mouse with deficits in specific components of social behavior and a reduction in its dorsomedial prefrontal cortex. We finish by discussing the biological connections of 8p with respect to neuropsychiatric disorders and cancer, despite the shortcomings of this evidence.

Neuropsychological performance as endophenotypes in extended schizophrenia families from the Central Valley of Costa Rica

OBJECTIVE

The understanding of complex heritable psychiatric disorders such as schizophrenia could be clarified by examining endophenotypes within genetically isolated populations, such as the one found in the Central Valley of Costa Rica. The reduction of familial variability within a sample could allow the relationship between the cognitive and symptomatic manifestations of the illness and the genetic underpinnings to become more observable. This study investigates the neuropsychological test performances of 41 family members from four extended multiplex families within the Spanish origin population of the Central Valley of Costa Rica as potential endophenotypes for genetic studies.

METHODS

Individuals with a diagnosis of schizophrenia or schizoaffective disorder were compared with unaffected relatives and 15 unrelated controls with no family history of schizophrenia.

RESULTS

Although the sample size is small, the results confirm previous reports in the literature of deficits in working memory, executive function, processing speed, and verbal fluency in individuals with schizophrenia compared with controls and intermediate performance in nonpsychotic family members compared with controls. We also found several suggestive quantitative cognitive trait loci with log of the odds greater than 1.75.

CONCLUSION

These findings suggest that the cognitive deficits in schizophrenia are consistent aspects of the illness, although their usefulness as endophenotypes for genetic studies remains unclear.

A genome screen of 35 bipolar affective disorder pedigrees provides significant evidence for a susceptibility locus on chromosome 15q25-26

Bipolar affective disorder is a heritable, relatively common, severe mood disorder with lifetime prevalence up to 4%. We report the results of a genome-wide linkage analysis conducted on a cohort of 35 Australian bipolar disorder families which identified evidence of significant linkage on chromosome 15q25-26 and suggestive evidence of linkage on chromosomes 4q, 6q and 13q. Subsequent fine-mapping of the chromosome 15q markers, using allele frequencies calculated from our cohort, gave significant results with a maximum two-point LOD score of 3.38 and multipoint LOD score of 4.58 for marker D15S130. Haplotype analysis based on pedigree-specific, identical-by-descent allele sharing, supported the location of a bipolar susceptibility gene within the Z(max-1) linkage confidence interval of 17 cM, or 6.2 Mb, between markers D15S979 and D15S816. Non-parametric and affecteds-only linkage analysis further verified the linkage signal in this region. A maximum NPL score of 3.38 (P=0.0008) obtained at 107.16 cM (near D15S130), and a maximum two-point LOD score of 2.97 obtained at marker D15S1004 (affecteds only), support the original genome-wide findings on chromosome 15q. These results are consistent with four independent positive linkage studies of mood and psychotic disorders, and raise the possibility that a common gene for susceptibility to bipolar disorder, and other psychiatric disorders may lie in this chromosome 15q25-26 region.

Genome-wide association studies in ADHD

Attention-deficit/hyperactivity disorder, ADHD, is a common and highly heritable neuropsychiatric disorder that is seen in children and adults. Although heritability is estimated at around 76%, it has been hard to find genes underlying the disorder. ADHD is a multifactorial disorder, in which many genes, all with a small effect, are thought to cause the disorder in the presence of unfavorable environmental conditions. Whole genome linkage analyses have not yet lead to the identification of genes for ADHD, and results of candidate gene-based association studies have been able to explain only a tiny part of the genetic contribution to disease, either. A novel way of performing hypothesis-free analysis of the genome suitable for the identification of disease risk genes of considerably smaller effect is the genome-wide association study (GWAS). So far, five GWAS have been performed on the diagnosis of ADHD and related phenotypes. Four of these are based on a sample set of 958 parent-child trio's collected as part of the International Multicentre ADHD Genetics (IMAGE) study and genotyped with funds from the Genetic Association Information Network (GAIN). The other is a pooled GWAS including adult patients with ADHD and controls. None of the papers reports any associations that are formally genome-wide significant after correction for multiple testing. There is also very limited overlap between studies, apart from an association with CDH13, which is reported in three of the studies. Little evidence supports an important role for the 'classic' ADHD genes, with possible exceptions for SLC9A9, NOS1 and CNR1. There is extensive overlap with findings from other psychiatric disorders. Though not genome-wide significant, findings from the individual studies converge to paint an interesting picture: whereas little evidence-as yet-points to a direct involvement of neurotransmitters (at least the classic dopaminergic, noradrenergic and serotonergic pathways) or regulators of neurotransmission, some suggestions are found for involvement of 'new' neurotransmission and cell-cell communication systems. A potential involvement of potassium channel subunits and regulators warrants further investigation. More basic processes also seem involved in ADHD, like cell division, adhesion (especially via cadherin and integrin systems), neuronal migration, and neuronal plasticity, as well as related transcription, cell polarity and extracellular matrix regulation, and cytoskeletal remodeling processes. In conclusion, the GWAS performed so far in ADHD, though far from conclusive, provide a first glimpse at genes for the disorder. Many more (much larger studies) will be needed. For this, collaboration between researchers as well as standardized protocols for phenotyping and DNA-collection will become increasingly important.

Convergent functional genomics of genome-wide association data for bipolar disorder: comprehensive identification of candidate genes, pathways and mechanisms

Given the mounting convergent evidence implicating many more genes in complex disorders such as bipolar disorder than the small number identified unambiguously by the first-generation Genome-Wide Association studies (GWAS) to date, there is a strong need for improvements in methodology. One strategy is to include in the next generation GWAS larger numbers of subjects, and/or to pool independent studies into meta-analyses. We propose and provide proof of principle for the use of a complementary approach, convergent functional genomics (CFG), as a way of mining the existing GWAS datasets for signals that are there already, but did not reach significance using a genetics-only approach. With the CFG approach, the integration of genetics with genomics, of human and animal model data, and of multiple independent lines of evidence converging on the same genes offers a way of extracting signal from noise and prioritizing candidates. In essence our analysis is the most comprehensive integration of genetics and functional genomics to date in the field of bipolar disorder, yielding a series of novel (such as Klf12, Aldh1a1, A2bp1, Ak3l1, Rorb, Rora) and previously known (such as Bdnf, Arntl, Gsk3b, Disc1, Nrg1, Htr2a) candidate genes, blood biomarkers, as well as a comprehensive identification of pathways and mechanisms. These become prime targets for hypothesis driven follow-up studies, new drug development and personalized medicine approaches.

Identifying blood biomarkers for mood disorders using convergent functional genomics

There are to date no objective clinical laboratory blood tests for mood disorders. The current reliance on patient self-report of symptom severity and on the clinicians' impression is a rate-limiting step in effective treatment and new drug development. We propose, and provide proof of principle for, an approach to help identify blood biomarkers for mood state. We measured whole-genome gene expression differences in blood samples from subjects with bipolar disorder that had low mood vs those that had high mood at the time of the blood draw, and separately, changes in gene expression in brain and blood of a mouse pharmacogenomic model. We then integrated our human blood gene expression data with animal model gene expression data, human genetic linkage/association data and human postmortem brain data, an approach called convergent functional genomics, as a Bayesian strategy for cross-validating and prioritizing findings. Topping our list of candidate blood biomarker genes we have five genes involved in myelination (Mbp, Edg2, Mag, Pmp22 and Ugt8), and six genes involved in growth factor signaling (Fgfr1, Fzd3, Erbb3, Igfbp4, Igfbp6 and Ptprm). All of these genes have prior evidence of differential expression in human postmortem brains from mood disorder subjects. A predictive score developed based on a panel of 10 top candidate biomarkers (five for high mood and five for low mood) shows sensitivity and specificity for high mood and low mood states, in two independent cohorts. Our studies suggest that blood biomarkers may offer an unexpectedly informative window into brain functioning and disease state.

Chromosome 13q13-q14 locus overlaps mood and psychotic disorders: the relevance for redefining phenotype

The nosology of major psychoses is challenged by the findings that schizophrenia (SZ) and bipolar disorder (BP) share several neurobiological, neuropsychological and clinical phenotypic characteristics. Moreover, several vulnerability loci or genes may be common to the two DSM disorders. We previously reported, in a sample of 21 kindreds (sample 1), a genome-wide suggestive linkage in 13q13-q14 with a common locus (CL) phenotype that crossed the diagnostic boundaries by combining SZ, BP and schizoaffective disorders. Our objectives were to test phenotype specificity in a separate sample (sample 2) of 27 kindreds from Eastern Quebec and to also analyze the combined sample of 48 kindreds (1274 family members). We performed nonparametric and parametric analyses and tested as phenotypes: SZ alone, BP alone, and a CL phenotype. We replicated in sample 2 our initial finding with CL with a maximum NPL(pair) score of 3.36 at D13S1272 (44 Mb), only 2.1 Mb telomeric to our previous maximum result. In the combined sample, the peak with CL was at marker D13S1297 (42.1 Mb) with a NPL(pair) score reaching 5.21, exceeding that obtained in each sample and indicating consistency across the two samples. Our data suggest a susceptibility locus in 13q13-q14 that is shared by schizophrenia and mood disorder. That locus would be additional to another well documented and more distal 13q locus where the G72/G30 gene is mapped.

Genetics of bipolar disorder: successful start to a long journey

Family and twin studies attest to the importance of genetic factors influencing susceptibility to bipolar disorder and to its genetic and phenotypic complexity. Although linkage and candidate gene association studies have repeatedly implicated some chromosome regions and certain genes, they have not produced the level of unambiguous support required to confirm the involvement of any specific gene or sequence variant in the pathogenesis of bipolar disorder. However, strong associations have recently been reported in meta-analyses of genome-wide association studies and the systematic study of structural variation is ongoing. These findings indicate that the study of large, phenotypically well-characterized samples will make an important contribution to delineating the etiology and pathogenesis of bipolar disorder and thereby pave the way for major improvements in clinical management.

Genome-wide association scan of quantitative traits for attention deficit hyperactivity disorder identifies novel associations and confirms candidate gene associations

Attention deficit hyperactivity disorder (ADHD) is a complex condition with environmental and genetic etiologies. Up to this point, research has identified genetic associations with candidate genes from known biological pathways. In order to identify novel ADHD susceptibility genes, 600,000 SNPs were genotyped in 958 ADHD proband-parent trios. After applying data cleaning procedures we examined 429,981 autosomal SNPs in 909 family trios. We generated six quantitative phenotypes from 18 ADHD symptoms to be used in genome-wide association analyses. With the PBAT screening algorithm, we identified 2 SNPs, rs6565113 and rs552655 that met the criteria for significance within a specified phenotype. These SNPs are located in intronic regions of genes CDH13 and GFOD1, respectively. CDH13 has been implicated previously in substance use disorders. We also evaluated the association of SNPs from a list of 37 ADHD candidate genes that was specified a priori. These findings, along with association P-values with a magnitude less than 10(-5), are discussed in this manuscript. Seventeen of these candidate genes had association P-values lower then 0.01: SLC6A1, SLC9A9, HES1, ADRB2, HTR1E, DDC, ADRA1A, DBH, DRD2, BDNF, TPH2, HTR2A, SLC6A2, PER1, CHRNA4, SNAP25, and COMT. Among the candidate genes, SLC9A9 had the strongest overall associations with 58 association test P-values lower than 0.01 and multiple association P-values at a magnitude of 10(-5) in this gene. In sum, these findings identify novel genetic associations at viable ADHD candidate genes and provide confirmatory evidence for associations at previous candidate genes. Replication of these results is necessary in order to confirm the proposed genetic variants for ADHD.

Evidence for association between the 5' flank of the NOS1 gene and schizophrenia in the Chinese population

Nitric oxide (NO) plays an important role in the dopaminergic and serotonergic system as the second messenger of the NMDA receptor and has possible roles in neurotransmission, neurosecretion, synaptic plasticity, and tissue injury in many neurological disorders, including schizophrenia. There is also genetic evidence to support the human NOS1 (neuronal nitric oxide synthase 1) gene as a promising candidate gene associated with schizophrenia. In this paper we conducted a case-control association study involving 1705 Chinese subjects and 12 genetic markers [11 single nucleotide polymorphisms (SNPs) and 1 microsatellite] mainly in the 5' flank region of the gene by direct sequencing and capillary electrophoresis. We identified SNP rs3782206 and several haplotypes derived from it as being significantly associated with schizophrenia and, specifically, in a paranoid subgroup. Our results strongly support a previous hypothesis that NOS1 contributes to the genetic risk of schizophrenia and suggest that further research on more NOS1 variants and its regular elements are warranted.

Hypothesis: grandiosity and guilt cause paranoia; paranoid schizophrenia is a psychotic mood disorder; a review

Delusional paranoia has been associated with severe mental illness for over a century. Kraepelin introduced a disorder called "paranoid depression," but "paranoid" became linked to schizophrenia, not to mood disorders. Paranoid remains the most common subtype of schizophrenia, but some of these cases, as Kraepelin initially implied, may be unrecognized psychotic mood disorders, so the relationship of paranoid schizophrenia to psychotic bipolar disorder warrants reevaluation. To address whether paranoia associates more with schizophrenia or mood disorders, a selected literature is reviewed and 11 cases are summarized. Comparative clinical and recent molecular genetic data find phenotypic and genotypic commonalities between patients diagnosed with schizophrenia and psychotic bipolar disorder lending support to the idea that paranoid schizophrenia could be the same disorder as psychotic bipolar disorder. A selected clinical literature finds no symptom, course, or characteristic traditionally considered diagnostic of schizophrenia that cannot be accounted for by psychotic bipolar disorder patients. For example, it is hypothesized here that 2 common mood-based symptoms, grandiosity and guilt, may underlie functional paranoia. Mania explains paranoia when there are grandiose delusions that one's possessions are so valuable that others will kill for them. Similarly, depression explains paranoia when delusional guilt convinces patients that they deserve punishment. In both cases, fear becomes the overwhelming emotion but patient and physician focus on the paranoia rather than on underlying mood symptoms can cause misdiagnoses. This study uses a clinical, case-based, hypothesis generation approach that warrants follow-up with a larger representative sample of psychotic patients followed prospectively to determine the degree to which the clinical course observed herein is typical of all such patients. Differential diagnoses, nomenclature, and treatment implications are discussed because bipolar patients misdiagnosed with schizophrenia are severely misserved.

Genomic imprinting in the development and evolution of psychotic spectrum conditions

I review and evaluate genetic and genomic evidence salient to the hypothesis that the development and evolution of psychotic spectrum conditions have been mediated in part by alterations of imprinted genes expressed in the brain. Evidence from the genetics and genomics of schizophrenia, bipolar disorder, major depression, Prader-Willi syndrome, Klinefelter syndrome, and other neurogenetic conditions support the hypothesis that the etiologies of psychotic spectrum conditions commonly involve genetic and epigenetic imbalances in the effects of imprinted genes, with a bias towards increased relative effects from imprinted genes with maternal expression or other genes favouring maternal interests. By contrast, autistic spectrum conditions, including Kanner autism, Asperger syndrome, Rett syndrome, Turner syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome, commonly engender increased relative effects from paternally expressed imprinted genes, or reduced effects from genes favouring maternal interests. Imprinted-gene effects on the etiologies of autistic and psychotic spectrum conditions parallel the diametric effects of imprinted genes in placental and foetal development, in that psychotic spectrum conditions tend to be associated with undergrowth and relatively-slow brain development, whereas some autistic spectrum conditions involve brain and body overgrowth, especially in foetal development and early childhood. An important role for imprinted genes in the etiologies of psychotic and autistic spectrum conditions is consistent with neurodevelopmental models of these disorders, and with predictions from the conflict theory of genomic imprinting.

Replication of linkage with bipolar disorder on chromosome 16p in the Eastern Quebec population

In a previous study [Maziade et al. (2005); Mol Psychiatry 10:486-499], we provided evidence for linkage (parametric lod score of 4.05) on chromosome 16p for bipolar affective disorder (BP) in 21 kindreds from Eastern Quebec, a population characterized by a founder effect. Using a stringent design, we performed a replication study in a second sample of 27 kindreds (sample 2) collected from the same population and assessed with the same methodologies as in our original sample (sample 1), that is with the same diagnostic procedure and using a common set of 23 markers studied with model-based (parametric) and model-free (nonparametric) linkage analyses. We replicated our initial finding with P values <0.001. Indeed, maximum NPL(all) scores of 3.7 and 3.52 were found at marker D16S3060 in sample 2 for the narrow and broad BP phenotype definition, respectively. For the latter definition, the nonparametric score reached 3.87 in the combined sample, a value that exceeded the maximum NPL score obtained in each individual sample (NPL(all) = 2.32 in sample 1; NPL(all) = 3.52 in sample 2). Moreover, a refined phenotype restricted to BP associated with psychosis yielded significant evidence for linkage in each individual sample (NPL(all) = 2.38 in sample 1; NPL(all) = 2.72) while yielding the best result (NPL(all) score = 3.90) in the combined sample (samples 1 and 2), despite an important reduction in the number of affected individuals. It is also noteworthy that the use of the refined phenotype provided a location of the maximum linkage peak shared by both samples, that is, at marker D16S668 in 16p13.12, suggesting consistency across samples. Our study provided one of the strongest pieces of evidence for linkage with BP in 16p and illustrated the heuristic potential of a replication study in a second sample ascertained from the same population and using homogeneous methodologies.

Systematic of psychiatric disorders between categorical and dimensional approaches: Kraepelin's dichotomy and beyond

This paper describes basic principles of systematics for psychiatric disorders such as the categorical and dimensional approach. It summarises validity aspects of the traditional psychiatric nosology and syndromatology. The importance and limitations of the dichotomy of schizophrenia and affective disorders, first suggested by Kraepelin, is reviewed in the light of results from modern research in the field of classification, follow-up and neurobiological studies, especially neurochemical, neurogenetic and neuroimaging studies. Current developments towards DSM-V and ICD-11 are critically reflected. The conclusion is reached that there might be insufficient data to establish a new systematics of psychoses. Therefore it might be premature to leave the Kraepelinian dichotomy totally although it has to be modified in the light of new research.

No significant association between the genetic polymorphisms in the GSK-3 beta gene and schizophrenia in the Chinese population

The GSK-3 beta gene encodes a protein kinase which is abundant in the brain, and its product is involved in signal transduction cascades of neuronal cell development, energy metabolism and body pattern formation. Previous studies have suggested that GSK-3 beta might act as a potential candidate locus for schizophrenia susceptibility. We genotyped six SNPs within the gene and conducted a case-control study involving 329 schizophrenic patients and 288 healthy subjects in the Chinese population. We examined allele and genotype frequencies and haplotype distributions in the subtype of paranoid schizophrenic patients as well as schizophrenic subjects in general. Our results fail to replicate the association of the GSK-3 beta gene with susceptibility to schizophrenia in the Chinese population.

Phenomic, convergent functional genomic, and biomarker studies in a stress-reactive genetic animal model of bipolar disorder and co-morbid alcoholism

We had previously identified the clock gene D-box binding protein (Dbp) as a potential candidate gene for bipolar disorder and for alcoholism, using a Convergent Functional Genomics (CFG) approach. Here we report that mice with a homozygous deletion of DBP have lower locomotor activity, blunted responses to stimulants, and gain less weight over time. In response to a chronic stress paradigm, these mice exhibit a diametric switch in these phenotypes. DBP knockout mice are also activated by sleep deprivation, similar to bipolar patients, and that activation is prevented by treatment with the mood stabilizer drug valproate. Moreover, these mice show increased alcohol intake following exposure to stress. Microarray studies of brain and blood reveal a pattern of gene expression changes that may explain the observed phenotypes. CFG analysis of the gene expression changes identified a series of novel candidate genes and blood biomarkers for bipolar disorder, alcoholism, and stress reactivity.

Differential RNA expression between schizophrenic patients and controls of the dystrobrevin binding protein 1 and neuregulin 1 genes in immortalized lymphocytes

The dystrobrevin binding protein 1 (DTNBP1) and neuregulin 1 (NRG1) genes have been related to schizophrenia (SZ) and bipolar disorder (BP) by several whole-genome linkage and associations studies. Few expression studies in post-mortem brains have also reported a lower or a higher expression of DTNBP1 and NRG1, respectively, in SZ. Since the difficulty to access post-mortem brains, we evaluated RNA expression of DTNBP1 and NRG1 in immortalized lymphocytes of SZ patients and unrelated-family controls. An antipsychotic stimulation was also used to challenge the genetic background of the subjects and enhance differential expression. Immortalized lymphocytes of twelve SZ and twelve controls were grown individually in the presence or not of the antipsychotic olanzapine (Zyprexa; EliLilly). RNA was extracted and pooled in four groups of three SZ and four groups of three controls, and used to probe Agilent 18K microchips. Mean gene expression values were contrasted between SZ and control groups using a T-test. For DTNBP1, RNA expression was lower in SZ than in controls before (-28%; p=0.02) and after (-30%; p=0.01) olanzapine stimulation. Similarly, NRG1 GGF2 isoform showed a lower expression in SZ before (-29%; p=0.04) and after (-33%; p=0.02) olanzapine stimulation. In contrast, NRG1 GGF isoform showed no significant difference between SZ and controls (-7%; p=0.61, +3%; p=0.86, respectively), but was slightly repressed by olanzapine in controls (-8%; p=0.008) but not in SZ (+1%; p=0.91). These results are in agreement with those observed in post-mortem brain when the isoforms involved are considered.

Clinical diagnoses in young offspring from eastern Québec multigenerational families densely affected by schizophrenia or bipolar disorder

OBJECTIVE

The follow-up since 1989 of a large sample of multigenerational families of eastern Québec that are densely affected by schizophrenia (SZ) or bipolar disorder (BP) has permitted to look at the rates of DSM diagnoses in the young offspring of a SZ parent (HRSZ) and of a BP parent (HRBP) who had an extremely loaded family history.

METHOD

The sample (average age of 17.5, SD 4.5) consisted of 54 high-risk offspring (HR) having one parent affected by a DSM-IV SZ or BP. The parents descended from 21 multigenerational families that constitute a quasi-total sample of such kindred in eastern Québec. The HRs were administered a lifetime best estimate DSM-IV diagnosis.

RESULTS

We observed that the rates, the diversity of diagnoses, the high comorbidity, the severity and the age of onset of the clinical diagnoses tended to be similar with those already reported in the offspring of affected parents with a low familial loading. Although the sample size was small, HRSZ and HRBP also tended to show similarities in their clinical status.

CONCLUSION

Overall, taking into account methodological limitations, the observation early in life of some shared characteristics among HRSZ and HRBP in terms of non-psychotic diagnosis may be congruent with the accumulating evidence that several phenotypic features are shared in adulthood by the two major psychoses.

Possible association of the pro-melanin-concentrating hormone gene with a greater body mass index as a side effect of the antipsychotic olanzapine

Following our report of a linkage at 12q24 with a phenotype of obesity under antipsychotics, we tested the pro-melanin-concentrating hormone (PMCH) candidate gene for a possible association in humans with the body mass index (BMI; kg/m2) in unrelated schizophrenic patients (SZ) receiving antipsychotics (N = 300) and in controls (CTL; N = 150). Subjects were classified in obese (OB) (BMI > or = 30 kg/m2), overweight (25 < or = BMI < 30 kg/m2), and normal weight (BMI < 25 kg/m2) groups. Single nucleotide polymorphisms (SNP) rs7973796 and rs11111201, located 5' at -4.5 kb and 3' at +1.8 kb, respectively, of PMCH were genotyped. Interaction effects of genotypes and antipsychotic treatment on BMI were tested in a covariance analysis with age and gender as covariates. Interaction effects on the prevalence of obesity were tested in a logistic regression analysis. For subjects under 50 years, the effect of the rs7973796 genotype on BMI differed between the SZ patients taking olanzapine and CTL group (interaction P = 0.025). Olanzapine-treated SZ patients carrying the ancestral homozygote genotype showed a higher BMI for rs7973796 (P = 0.016 with the LSMeans t-test) than the variant homozygotes. Accordingly, the ORs for obesity associated with rs7973796 genotypes differed in the SZ patients taking olanzapine compared to the CTL group (interaction P = 0.0094). The G allele was associated with an increase in the odds of obesity in SZ patients taking olanzapine. No association was observed for those over 50 years, or for rs11111201. These results suggest that the common allele of PMCH rs7973796 may be associated with a greater BMI in olanzapine-treated SZ patients.

Evidence for two schizophrenia susceptibility genes on chromosome 22q13

OBJECTIVE

Previous linkage scans and meta-analyses for schizophrenia susceptibility loci failed to include the most distal portion of chromosome 22q. Accordingly, 27 families having individuals affected with schizophrenia and schizophrenia-spectrum disorders were analyzed using a set of highly informative markers covering all of chromosome 22q.

METHODS

Microsatellite and single nucleotide polymorphism markers were evaluated by nonparametric linkage, parametric linkage, and transmission disequilibrium testing of 22q.

RESULTS

The maximum nonparametric logarithm of odd scores were 2.9 (P=0.0016) for schizophrenia and 2.7 (P=0.003) for a broader disease definition that included schizotypal personality disorder-both at 44.5 cM within the Sult4A1 locus. Parametric models assuming dominant modes of inheritance and genetic heterogeneity gave maximum multipoint logarithm of odd scores for the broader disease definition at the Sult4A1 locus of 3.3 (P=0.0006) and single point logarithm of odd scores of 3.1-4.8 for Sult4A1 markers (P=0.000015-0.0005). A distal locus, centered at 61 cM, shows a maximum nonparametric logarithm of odd scores of 1.5 (P=0.072) for the broader disease definition. Transmission disequilibrium testing for three adjacent microsatellite markers located near the distal linkage peak revealed significant values for marker D22s526 for schizophrenia (P=0.0016-0.14) and for broader disease definitions including schizotypal personality disorder (P=0.0002-0.0003), and both schizotypal personality disorder plus schizoaffective disorder (P=0.00001-0.000077).

CONCLUSION

At least two separable, but closely linked, loci within 22q13 influencing susceptibility to schizophrenia-spectrum disorders, might be possible.

The first genomewide interaction and locus-heterogeneity linkage scan in bipolar affective disorder: strong evidence of epistatic effects between loci on chromosomes 2q and 6q

We present the first genomewide interaction and locus-heterogeneity linkage scan in bipolar affective disorder (BPAD), using a large linkage data set (52 families of European descent; 448 participants and 259 affected individuals). Our results provide the strongest interaction evidence between BPAD genes on chromosomes 2q22-q24 and 6q23-q24, which was observed symmetrically in both directions (nonparametric LOD [NPL] scores of 7.55 on 2q and 7.63 on 6q; P<.0001 and P=.0001, respectively, after a genomewide permutation procedure). The second-best BPAD interaction evidence was observed between chromosomes 2q22-q24 and 15q26. Here, we also observed a symmetrical interaction (NPL scores of 6.26 on 2q and 4.59 on 15q; P=.0057 and .0022, respectively). We covered the implicated regions by genotyping additional marker sets and performed a detailed interaction linkage analysis, which narrowed the susceptibility intervals. Although the heterogeneity analysis produced less impressive results (highest NPL score of 3.32) and a less consistent picture, we achieved evidence of locus heterogeneity at chromosomes 2q, 6p, 11p, 13q, and 22q, which was supported by adjacent markers within each region and by previously reported BPAD linkage findings. Our results provide systematic insights in the framework of BPAD epistasis and locus heterogeneity, which should facilitate gene identification by the use of more-comprehensive cloning strategies.

Conceptual and methodological issues in the design of clinical trials of antipsychotics for the treatment of schizophrenia

Schizophrenia is one of the most severe and disabling psychiatric disorders. Antipsychotic drugs offer considerable benefits in controlling symptoms and preventing relapse. The strategy for the present review of clinical trials was to ask 'What are the features of schizophrenia and the existing treatments of the illness that have implications for future clinical trials'? Six key facts were identified.First, schizophrenia is genetically 'complex'. Trials may benefit from designs including genetically related illnesses, by focussing on cross-cutting aspects of the phenotype such as psychosis or cognitive dysfunction, and by collecting information on possible moderators and mediators of treatment response.Second, schizophrenia affects multiple neurotransmitter systems. Multiple signalling pathways may need to be considered, with different time courses of response. Outcome measures from clinical trials could be collected at more frequent intervals, particularly in the early phase of response.Third, the clinical features used to define the illness are a mix of symptoms and social-occupational dysfunction, yet treatment response is often defined only by changes in symptoms. Multiple measures of functioning need to be collected at baseline and at the endpoint of trials. Consensus definitions for response, remission, relapse, recovery and recurrence need to be developed.Fourth, schizophrenia is often highly disabling. Linking treatment response in clinical trials to measures of quality-adjusted life-years will allow comparison with other medical illnesses using common metrics.Fifth, the general health and care of individuals with schizophrenia is often poor. 'Complex' interventions, which include, but are not limited to, antipsychotic medications, need to be designed and tested for the problems facing these patients.Finally, large gaps exist between clinical trials, practice guidelines and patterns of practice. Trials need to be designed to investigate widely used approaches such as antipsychotic polypharmacy, where actual practice diverges from evidence-based guidelines.

Genome-wide scan of bipolar disorder and investigation of population stratification effects on linkage: support for susceptibility loci at 4q21, 7q36, 9p21, 12q24, 14q24, and 16p13

Bipolar disorder (BPD) is a complex genetic disorder with cycling symptoms of depression and mania. Despite the extreme complexity of this psychiatric disorder, attempts to localize genes which confer vulnerability to the disorder have had some success. Chromosomal regions including 4p16, 12q24, 18p11, 18q22, and 21q21 have been repeatedly linked to BPD in different populations. Here we present the results of a whole genome scan for linkage to BPD in an Irish population. Our most significant result was at 14q24 which yielded a non-parametric LOD (NPL) score of 3.27 at the D14S588 marker with a nominal P-value of 0.0006 under a narrow (bipolar type I only) model of affection. We previously reported linkage to 14q22-24 in a subset of the families tested in this analysis. We also obtained suggestive evidence for linkage at 4q21, 9p21, 12q24, and 16p13, chromosomal regions that have all been previously linked to BPD. Additionally, we report on a novel approach to linkage analysis, STRUCTURE-Guided Linkage Analysis (SGLA), which is designed to reduce genetic heterogeneity and increase the power to detect linkage. Application of this technique resulted in more highly significant evidence for linkage of BPD to three regions including 16p13, a locus that has been repeatedly linked to numerous psychiatric disorders.

No evidence for association between 19 cholinergic genes and bipolar disorder

Cholinergic dysfunction has been proposed for the pathogenesis of bipolar disorder (BD), and we have therefore performed a systematic association study of cholinergic system genes in BD (including schizoaffective disorder bipolar type). We genotyped 93 single nucleotide polymorphisms (SNPs) in 19 genes (CHAT, CHRM1-5, CHRNA1-7, CHRNA9, CHRNA10, and CHRNB1-4) in two series of samples: the National Institute of Mental Health (NIMH) Genetics Initiative pedigrees with 474 samples from 152 families, and the Clinical Neurogenetics (CNG) pedigrees with 83 samples from 22 multiplex families. Sib-transmission/disequilibrium test (sib_TDT) analysis showed nominally significant transmission bias for four SNPs (CHRNA2: rs7017417, P = 0.024; CHRNA5: rs514743, P = 0.031; CHRNB1: rs2302762, P = 0.049; CHRNB4: rs1948, P = 0.031). Haploview analyses showed nominally significant transmission bias of several haplotypes in CHRNA2, CHRNA7, CHRNB1, and CHRNB4, respectively. However, none of these associations reached gene-wide significance after correction by permutation. Alcohol dependence (including alcohol abuse) was not a significant covariate in the present genetic association analysis. Thus, it is unlikely that these 19 cholinergic genes play a major role in the pre-disposition to BD in these pedigrees.

Association analysis of HSP90B1 with bipolar disorder

Pathophysiological role of endoplasmic reticulum (ER) stress response signaling has been suggested for bipolar disorder. The goal of this study was to test the genetic association between bipolar disorder and an ER chaperone gene, HSP90B1 (GRP94/gp96), which is located on a candidate locus, 12q23.3. We tested the genetic association between bipolar disorder and HSP90B1 by case-control studies in two independent Japanese sample sets and by a transmission disequilibrium test (TDT) in NIMH Genetics initiative bipolar trio samples (NIMH trios). We also performed gene expression analysis of HSP90B1 in lymphoblastoid cells. Among the 11 SNPs tested, rs17034977 showed significant association in both Japanese sample sets. The frequency of the SNP was lower in NIMH samples than in Japanese samples and there was no significant association in NIMH trios. Gene expression analysis of HSP90B1 in lymphoblastoid cells suggested a possible relationship between the associated SNP and mRNA levels. HSP90B1 may have a pathophysiological role in bipolar disorder in the Japanese population, though further study will be needed to understand the underlying functional mechanisms.

Schizoaffective disorder merges schizophrenia and bipolar disorders as one disease--there is no schizoaffective disorder

PURPOSE OF REVIEW

Schizoaffective disorder was named as a compromise diagnosis in 1933, and remains popular as judged by its place in the International Classification of Diseases and the Diagnostic and Statistical Manual of Mental Disorders, its frequent use in clinical practice, and its extensive discussion in the literature. Some, however, have questioned the validity of schizoaffective disorder as separate from psychotic mood disorder. We examined the literature to assess the rationale for the continuation of schizoaffective disorder as a legitimate diagnostic category.

RECENT FINDINGS

The diagnosis of schizoaffective disorder depends on the disease specificity of the diagnostic criteria for schizophrenia; however, the psychotic symptoms for schizophrenia, traditionally held as specific, can be accounted for by psychotic bipolar. Further, the interrater reliability for diagnosing schizoaffective disorder is very low. A recent and expanding body of comparative evidence from a wide range of clinical and basic science studies, especially genetic, reveals multiple similarities between schizoaffective disorder, schizophrenia and psychotic bipolar.

SUMMARY

Schizoaffective disorder unifies schizophrenia and bipolar, blurring the zones of rarity between them and suggesting that schizoaffective disorder is not a separate, 'bona-fide' disease. Patients diagnosed with schizoaffective disorder likely suffer from a psychotic mood disorder. The diagnosis of schizoaffective disorder, which can result in substandard treatment, should be eliminated from the diagnostic nomenclature.

A linkage and family-based association analysis of a potential neurocognitive endophenotype of bipolar disorder

The identification of the genetic variants underpinning bipolar disorder (BPD) has been impeded by a complex pattern of inheritance characterized by genetic and phenotypic heterogeneity, genetic epistasis, and gene-environment interactions. In this paper two strategies were used to ameliorate these confounding factors. A unique South African sample including 190 individuals of the relatively, reproductively isolated Afrikaner population was assessed with a battery of neuropsychological tests in an attempt to identify a BPD-associated quantitative trait or endophenotype. BPD individuals performed significantly worse than their unaffected relatives on visual and verbal memory tasks, a finding congruent with the literature. Afocused linkage and family-based association study was carried out using this memory-related endophenotype. In the largest 77-strong Afrikaner pedigree significant evidence for linkage was detected on chromosome 22q11, a region previously implicated in BPD. The quantitative transmission disequilibrium tests-based association analysis suggested that functional variants of the DRD4 and MAO-A genes modulate memory-related cognition. We speculate that polymorphisms at these loci may predispose to a subtype of BPD characterized by memory-related deficits.