Common polygenic variation and risk for childhood-onset schizophrenia.

Childhood-onset schizophrenia (COS) is a rare and severe form of the disorder, with more striking abnormalities with respect to prepsychotic developmental disorders and abnormities in the brain development compared with later-onset schizophrenia. We previously documented that COS patients, compared with their healthy siblings and with adult-onset patients (AOS), carry significantly more rare chromosomal copy number variations, spanning large genomic regions (>100 kb) (Ahn et al. 2014). Here, we interrogated the contribution of common polygenic variation to the genetic susceptibility for schizophrenia. We examined the association between a direct measure of genetic risk of schizophrenia in 130 COS probands and 103 healthy siblings. Using data from the schizophrenia and autism GWAS of the Psychiatric Genomic Consortia, we selected three risk-related sets of single nucleotide polymorphisms from which we conducted polygenic risk score comparisons for COS probands and their healthy siblings. COS probands had higher genetic risk scores of both schizophrenia and autism than their siblings (P<0.05). Given the small sample size, these findings suggest that COS patients have more salient genetic risk than do AOS.

Hippocampal volume change relates to clinical outcome in childhood-onset schizophrenia.

BACKGROUND: Fixed hippocampal volume reductions and shape abnormalities are established findings in schizophrenia, but the relationship between hippocampal volume change and clinical outcome has been relatively unexplored in schizophrenia and other psychotic disorders. In light of recent findings correlating hippocampal volume change and clinical outcome in first-episode psychotic adults, we hypothesized that fewer decreases in hippocampal volume would be associated with better functional outcome and fewer psychotic symptoms in our rare and chronically ill population of childhood-onset schizophrenia (COS) patients. METHOD: We prospectively obtained 114 structural brain magnetic resonance images (MRIs) from 27 COS subjects, each with three or more scans between the ages of 10 and 30 years. Change in hippocampal volume, measured by fit slope and percentage change, was regressed against clinical ratings (Children's Global Assessment Scale, Scale for the Assessment of Positive Symptoms, Scale for the Assessment of Negative Symptoms) at last scan (controlling for sex, time between scans and total intracranial volume). RESULTS: Fewer negative symptoms were associated with less hippocampal volume decrease (fit slope: p = 0.0003, and percentage change: p = 0.005) while positive symptoms were not related to hippocampal change. There was also a relationship between improved clinical global functioning and maintained hippocampal volumes (fit slope: p = 0.025, and percentage change: p = 0.043). CONCLUSIONS: These results suggest that abnormal hippocampal development in schizophrenia can be linked to global functioning and negative symptoms. The hippocampus can be considered a potential treatment target for future therapies.

Clinical utility of neuronal cells directly converted from fibroblasts of patients for neuropsychiatric disorders: studies of lysosomal storage diseases and channelopathy.

Methodologies for generating functional neuronal cells directly from human fibroblasts [induced neuronal (iN) cells] have been recently developed, but the research so far has only focused on technical refinements or recapitulation of known pathological phenotypes. A critical question is whether this novel technology will contribute to elucidation of novel disease mechanisms or evaluation of therapeutic strategies. Here we have addressed this question by studying Tay-Sachs disease, a representative lysosomal storage disease, and Dravet syndrome, a form of severe myoclonic epilepsy in infancy, using human iN cells with feature of immature postmitotic glutamatergic neuronal cells. In Tay-Sachs disease, we have successfully characterized canonical neuronal pathology, massive accumulation of GM2 ganglioside, and demonstrated the suitability of this novel cell culture for future drug screening. In Dravet syndrome, we have identified a novel functional phenotype that was not suggested by studies of classical mouse models and human autopsied brains. Taken together, the present study demonstrates that human iN cells are useful for translational neuroscience research to explore novel disease mechanisms and evaluate therapeutic compounds. In the future, research using human iN cells with well-characterized genomic landscape can be integrated into multidisciplinary patient-oriented research on neuropsychiatric disorders to address novel disease mechanisms and evaluate therapeutic strategies.

High rate of disease-related copy number variations in childhood onset schizophrenia.

Copy number variants (CNVs) are risk factors in neurodevelopmental disorders, including autism, epilepsy, intellectual disability (ID) and schizophrenia. Childhood onset schizophrenia (COS), defined as onset before the age of 13 years, is a rare and severe form of the disorder, with more striking array of prepsychotic developmental disorders and abnormalities in brain development. Because of the well-known phenotypic variability associated with pathogenic CNVs, we conducted whole genome genotyping to detect CNVs and then focused on a group of 46 rare CNVs that had well-documented risk for adult onset schizophrenia (AOS), autism, epilepsy and/or ID. We evaluated 126 COS probands, 69 of which also had a healthy full sibling. When COS probands were compared with their matched related controls, significantly more affected individuals carried disease-related CNVs (P=0.017). Moreover, COS probands showed a higher rate than that found in AOS probands (P<0.0001). A total of 15 (11.9%) subjects exhibited at least one such CNV and four of these subjects (26.7%) had two. Five of 15 (4.0% of the sample) had a 2.5-3 Mb deletion mapping to 22q11.2, a rate higher than that reported for adult onset (0.3-1%) (P<0.001) or autism spectrum disorder and, indeed, the highest rate reported for any clinical population to date. For one COS subject, a duplication found at 22q13.3 had previously only been associated with autism, and for four patients CNVs at 8q11.2, 10q22.3, 16p11.2 and 17q21.3 had only previously been associated with ID. Taken together, these findings support the well-known pleiotropic effects of these CNVs suggesting shared abnormalities early in brain development. Clinically, broad CNV-based population screening is needed to assess their overall clinical burden.

Neurodevelopmental model of schizophrenia: update 2012.

The neurodevelopmental model of schizophrenia, which posits that the illness is the end state of abnormal neurodevelopmental processes that started years before the illness onset, is widely accepted, and has long been dominant for childhood-onset neuropsychiatric disorders. This selective review updates our 2005 review of recent studies that have impacted, or have the greatest potential to modify or extend, the neurodevelopmental model of schizophrenia. Longitudinal whole-population studies support a dimensional, rather than categorical, concept of psychosis. New studies suggest that placental pathology could be a key measure in future prenatal high-risk studies. Both common and rare genetic variants have proved surprisingly diagnostically nonspecific, and copy number variants (CNVs) associated with schizophrenia are often also associated with autism, epilepsy and intellectual deficiency. Large post-mortem gene expression studies and prospective developmental multi-modal brain imaging studies are providing critical data for future clinical and high-risk developmental brain studies. Whether there can be greater molecular specificity for phenotypic characterization is a subject of current intense study and debate, as is the possibility of neuronal phenotyping using human pluripotent-inducible stem cells. Biological nonspecificity, such as in timing or nature of early brain development, carries the possibility of new targets for broad preventive treatments.

Transcriptome profiling of UPF3B/NMD-deficient lymphoblastoid cells from patients with various forms of intellectual disability.

The nonsense-mediated mRNA decay (NMD) pathway was originally discovered by virtue of its ability to rapidly degrade aberrant mRNAs with premature termination codons. More recently, it was shown that NMD also directly regulates subsets of normal transcripts, suggesting that NMD has roles in normal biological processes. Indeed, several NMD factors have been shown to regulate neurological events (for example, neurogenesis and synaptic plasticity) in numerous vertebrate species. In man, mutations in the NMD factor gene UPF3B, which disrupts a branch of the NMD pathway, cause various forms of intellectual disability (ID). Using Epstein Barr virus-immortalized B cells, also known as lymphoblastoid cell lines (LCLs), from ID patients that have loss-of-function mutations in UPF3B, we investigated the genome-wide consequences of compromised NMD and the role of NMD in neuronal development and function. We found that ~5% of the human transcriptome is impacted in UPF3B patients. The UPF3B paralog, UPF3A, is stabilized in all UPF3B patients, and partially compensates for the loss of UPF3B function. Interestingly, UPF3A protein, but not mRNA, was stabilised in a quantitative manner that inversely correlated with the severity of patients' phenotype. This suggested that the ability to stabilize the UPF3A protein is a crucial modifier of the neurological symptoms due to loss of UPF3B. We also identified ARHGAP24, which encodes a GTPase-activating protein, as a canonical target of NMD, and we provide evidence that deregulation of this gene inhibits axon and dendrite outgrowth and branching. Our results demonstrate that the UPF3B-dependent NMD pathway is a major regulator of the transcriptome and that its targets have important roles in neuronal cells.

Systematic resequencing of X-chromosome synaptic genes in autism spectrum disorder and schizophrenia.

Autism spectrum disorder (ASD) and schizophrenia (SCZ) are two common neurodevelopmental syndromes that result from the combined effects of environmental and genetic factors. We set out to test the hypothesis that rare variants in many different genes, including de novo variants, could predispose to these conditions in a fraction of cases. In addition, for both disorders, males are either more significantly or more severely affected than females, which may be explained in part by X-linked genetic factors. Therefore, we directly sequenced 111 X-linked synaptic genes in individuals with ASD (n = 142; 122 males and 20 females) or SCZ (n = 143; 95 males and 48 females). We identified >200 non-synonymous variants, with an excess of rare damaging variants, which suggest the presence of disease-causing mutations. Truncating mutations in genes encoding the calcium-related protein IL1RAPL1 (already described in Piton et al. Hum Mol Genet 2008) and the monoamine degradation enzyme monoamine oxidase B were found in ASD and SCZ, respectively. Moreover, several promising non-synonymous rare variants were identified in genes encoding proteins involved in regulation of neurite outgrowth and other various synaptic functions (MECP2, TM4SF2/TSPAN7, PPP1R3F, PSMD10, MCF2, SLITRK2, GPRASP2, and OPHN1).

Common functional polymorphisms of DISC1 and cortical maturation in typically developing children and adolescents.

Disrupted-in-schizophrenia-1 (DISC1), contains two common non-synonymous single-nucleotide polymorphisms (SNPs)--Leu607Phe and Ser704Cys--that modulate (i) facets of DISC1 molecular functioning important for cortical development, (ii) fronto-temporal cortical anatomy in adults and (iii) risk for diverse psychiatric phenotypes that often emerge during childhood and adolescence, and are associated with altered fronto-temporal cortical development. It remains unknown, however, if Leu607Phe and Ser704Cys influence cortical maturation before adulthood, and whether each SNP shows unique or overlapping effects. Therefore, we related genotype at Leu607Phe and Ser704Cys to cortical thickness (CT) in 255 typically developing individuals aged 9-22 years on whom 598 magnetic resonance imaging brain scans had been acquired longitudinally. Rate of cortical thinning varied with DISC1 genotype. Specifically, the rate of cortical thinning was attenuated in Phe-carrier compared with Leu-homozygous groups (in bilateral superior frontal and left angular gyri) and accelerated in Ser-homozygous compared with Cys-carrier groups (in left anterior cingulate and temporal cortices). Both SNPs additively predicted fixed differences in right lateral temporal CT, which were maximal between Phe-carrier/Ser-homozygous (thinnest) vs Leu-homozygous/Cys-carrier (thickest) groups. Leu607Phe and Ser704Cys genotype interacted to predict the rate of cortical thinning in right orbitofrontal, middle temporal and superior parietal cortices, wherein a significantly reduced rate of CT loss was observed in Phe-carrier/Cys-carrier participants only. Our findings argue for further examination of Leu607Phe and Ser704Cys interactions at a molecular level, and suggest that these SNPs might operate (in concert with other genetic and environmental factors) to shape risk for diverse phenotypes by impacting on the early maturation of fronto-temporal cortices.

Rare mutations in N-methyl-D-aspartate glutamate receptors in autism spectrum disorders and schizophrenia.

Pharmacological, genetic and expression studies implicate N-methyl-D-aspartate (NMDA) receptor hypofunction in schizophrenia (SCZ). Similarly, several lines of evidence suggest that autism spectrum disorders (ASD) could be due to an imbalance between excitatory and inhibitory neurotransmission. As part of a project aimed at exploring rare and/or de novo mutations in neurodevelopmental disorders, we have sequenced the seven genes encoding for NMDA receptor subunits (NMDARs) in a large cohort of individuals affected with SCZ or ASD (n=429 and 428, respectively), parents of these subjects and controls (n=568). Here, we identified two de novo mutations in patients with sporadic SCZ in GRIN2A and one de novo mutation in GRIN2B in a patient with ASD. Truncating mutations in GRIN2C, GRIN3A and GRIN3B were identified in both subjects and controls, but no truncating mutations were found in the GRIN1, GRIN2A, GRIN2B and GRIN2D genes, both in patients and controls, suggesting that these subunits are critical for neurodevelopment. The present results support the hypothesis that rare de novo mutations in GRIN2A or GRIN2B can be associated with cases of sporadic SCZ or ASD, just as it has recently been described for the related neurodevelopmental disease intellectual disability. The influence of genetic variants appears different, depending on NMDAR subunits. Functional compensation could occur to counteract the loss of one allele in GRIN2C and GRIN3 family genes, whereas GRIN1, GRIN2A, GRIN2B and GRIN2D appear instrumental to normal brain development and function.

Attention-deficit/hyperactivity disorder is characterized by a delay in cortical maturation.

There is controversy over the nature of the disturbance in brain development that underpins attention-deficit/hyperactivity disorder (ADHD). In particular, it is unclear whether the disorder results from a delay in brain maturation or whether it represents a complete deviation from the template of typical development. Using computational neuroanatomic techniques, we estimated cortical thickness at >40,000 cerebral points from 824 magnetic resonance scans acquired prospectively on 223 children with ADHD and 223 typically developing controls. With this sample size, we could define the growth trajectory of each cortical point, delineating a phase of childhood increase followed by adolescent decrease in cortical thickness (a quadratic growth model). From these trajectories, the age of attaining peak cortical thickness was derived and used as an index of cortical maturation. We found maturation to progress in a similar manner regionally in both children with and without ADHD, with primary sensory areas attaining peak cortical thickness before polymodal, high-order association areas. However, there was a marked delay in ADHD in attaining peak thickness throughout most of the cerebrum: the median age by which 50% of the cortical points attained peak thickness for this group was 10.5 years (SE 0.01), which was significantly later than the median age of 7.5 years (SE 0.02) for typically developing controls (log rank test chi(1)(2) = 5,609, P < 1.0 x 10(-20)). The delay was most prominent in prefrontal regions important for control of cognitive processes including attention and motor planning. Neuroanatomic documentation of a delay in regional cortical maturation in ADHD has not been previously reported.

Neuregulin 1 (8p12) and childhood-onset schizophrenia: susceptibility haplotypes for diagnosis and brain developmental trajectories.

Childhood-onset schizophrenia (COS), defined as onset of psychosis by the age of 12, is a rare and malignant form of the illness, which may have more salient genetic influence. Since the initial report of association between neuregulin 1 (NRG1) and schizophrenia in 2002, numerous independent replications have been reported. In the current study, we genotyped 56 markers (54 single-nucleotide polymorphisms (SNPs) and two microsatellites) spanning the NRG1 locus on 78 COS patients and their parents. We used family-based association analysis for both diagnostic (extended transmission disequilibrium test) and quantitative phenotypes (quantitative transmission disequilibrium test) and mixed-model regression. Most subjects had prospective anatomic brain magnetic resonance imaging (MRI) scans at 2-year intervals. Further, we genotyped a sample of 165 healthy controls in the MRI study to examine genetic risk effects on normal brain development. Individual markers showed overtransmission of alleles to affecteds (P=0.009-0.05). Further, several novel four-marker haplotypes demonstrated significant transmission distortion. There was no evidence of epistasis with SNPs in erbB4. The risk allele (0) at 420M9-1395 was associated with poorer premorbid social functioning. Further, possession of the risk allele was associated with different trajectories of change in lobar volumes. In the COS group, risk allele carriers had greater total gray and white matter volume in childhood and a steeper rate of subsequent decline in volume into adolescence. By contrast, in healthy children, possession of the risk allele was associated with different trajectories in gray matter only and was confined to frontotemporal regions, reflecting epistatic or other illness-specific effects mediating NRG1 influence on brain development in COS. This replication further documents the role of NRG1 in the abnormal brain development in schizophrenia. This is the first demonstration of a disease-specific pattern of gene action in schizophrenia.

Association of the dopamine receptor D4 (DRD4) gene 7-repeat allele with children with attention-deficit/hyperactivity disorder (ADHD): an update.

Polymorphisms of the dopamine receptor D4 gene DRD4, 11p15.5, have previously been associated with attention-deficit/hyperactivity disorder (ADHD) [Bobb et al., 2005; Am J Med Genet B Neuropsychiatr Genet 132:109-125; Faraone et al., 2005; Biol Psychiatry 57:1313-1323; Thapar et al., 2005; Hum Mol Genet 14 Spec No. 2:R275-R282]. As a follow up to a pilot study [see Castellanos et al., 1998; Mol Psychiatry 3:431-434] consisting of 41 probands and 56 controls which found no significant association between the DRD4 7-repeat allele in exon 3 and ADHD, a greatly expanded study sample (cases n = 166 and controls n = 282) and long term follow-up (n = 107, baseline mean age n = 9, follow-up mean age of n = 15) prompted reexamination of this gene. The DRD4 7-repeat allele was significantly more frequent in ADHD cases than controls (OR = 1.2; P = 0.028). Further, within the ADHD group, the 7-repeat allele was associated with better cognitive performance (measured by the WISC-III) (P = 0.013-0.07) as well as a trend for association with better long-term outcome. This provides further evidence of the role of the DRD4 7-repeat allele in the etiology of ADHD and suggests that this allele may be associated with a more benign form of the disorder.

Segmental uniparental isodisomy on 5q32-qter in a patient with childhood-onset schizophrenia.

Schizophrenia is a severe mental disorder affecting approximately 1% of the world's population. Although the aetiology of schizophrenia is complex and multifactorial, with estimated heritabilities as high as 80%, genetic factors are the most compelling. Childhood-onset schizophrenia (COS), defined as onset of schizophrenia before the age of 13 years, is a rare and malignant form of the illness that may have more salient genetic influence. The first known case of paternal segmental uniparental isodisomy (iUPD) on 5q32-qter in a patient with COS is described, which adds to the previously known high rates of chromosomal abnormalities reported in this sample. iUPD is a rare genetic condition in which the offspring receives two chromosomal homologues from one parent. Segmental UPD is defined as UPD on a portion of a chromosome with biparental inheritance seen in the rest of the homologous pair. Complications owing to this abnormality may arise from malfunctioning imprinted genes or homozygosity of recessive disease-causing mutations. This aberration became apparent during whole-genomic screening of a COS cohort and is of particular interest because 5q has been implicated in schizophrenia by several genomewide linkage studies and positive gene associations. This report, therefore, presents more evidence that schizophrenia susceptibility gene, or genes, may be found on distal 5q.

Dysbindin (DTNBP1, 6p22.3) is associated with childhood-onset psychosis and endophenotypes measured by the Premorbid Adjustment Scale (PAS).

Straub et al. (2002) recently identified the 6p22.3 gene dysbindin (DTNBP1) through positional cloning as a schizophrenia susceptibility gene. We studied a rare cohort of 102 children with onset of psychosis before age 13. Standardized ratings of early development, medication response, neuropsychological and cognitive performance, premorbid dysfunction and clinical follow-up were obtained. Fourteen SNPs were genotyped in the gene DTNBP1. Family-based pairwise and haplotype transmission disequilibrium test (TDT) analysis with the clinical phenotype, and quantitative transmission disequilibrium test (QTDT) explored endophenotype relationships. One SNP was associated with diagnosis (TDT p=.01). The QTDT analyses showed several significant relationships. Four adjacent SNPs were associated (p values=.0009-.003) with poor premorbid functioning. These findings support the hypothesis that this and other schizophrenia susceptibility genes contribute to early neurodevelopmental impairment.

The neurodevelopmental model of schizophrenia: update 2005.

Neurodevelopmental models of schizophrenia that identify longitudinal precursors of illness have been of great heuristic importance focusing most etiologic research over the past two decades. These models have varied considerably with respect to specificity and timing of hypothesized genetic and environmental 'hits', but have largely focused on insults to prenatal brain development. With heritability around 80%, nongenetic factors impairing development must also be part of the model, and any model must also account for the wide range of age of onset. In recent years, longitudinal brain imaging studies of both early and adult (to distinguish from late ie elderly) onset populations indicate that progressive brain changes are more dynamic than previously thought, with gray matter volume loss particularly striking in adolescence and appearing to be an exaggeration of the normal developmental pattern. This supports an extended time period of abnormal neurodevelopment in schizophrenia in addition to earlier 'lesions'. Many subtle cognitive, motor, and behavioral deviations are seen years before illness onset, and these are more prominent in early onset cases. Moreover, schizophrenia susceptibility genes and chromosomal abnormalities, particularly as examined for early onset populations (ie GAD1, 22q11DS), are associated with premorbid neurodevelopmental abnormalities. Several candidate genes for schizophrenia (eg dysbindin) are associated with lower cognitive abilities in both schizophrenic and other pediatric populations more generally. Postmortem human brain and developmental animal studies document multiple and diverse effects of developmental genes (including schizophrenia susceptibility genes), at sequential stages of brain development. These may underlie the broad array of premorbid cognitive and behavioral abnormalities seen in schizophrenia, and neurodevelopmental disorders more generally. Increased specificity for the most relevant environmental risk factors such as exposure to prenatal infection, and their interaction with susceptibility genes and/or action through phase-specific altered gene expression now both strengthen and modify the neurodevelopmental theory of schizophrenia.

GAD1 (2q31.1), which encodes glutamic acid decarboxylase (GAD67), is associated with childhood-onset schizophrenia and cortical gray matter volume loss.

Postmortem brain studies have shown deficits in the cortical gamma-aminobutyric acid (GABA) system in schizophrenic individuals. Expression studies have shown a decrease in the major GABA-synthesizing enzyme (glutamic acid decarboxylase (GAD67) mRNA levels in neurons in dorsolateral prefrontal cortex in schizophrenics relative to controls. In the present study, SNPs in and around the GAD1 gene, which encodes the protein GAD67, were tested on a rare, severely ill group of children and adolescents with childhood-onset schizophrenia (COS) (n=72), in a family-based association analysis. Compared to adult-onset samples, the COS sample has evidence for more salient familial, and perhaps genetic, risk factors for schizophrenia, as well as evidence for frontal cortical hypofunction, and greater decline in cortical gray matter volume on anatomic brain MRI scans during adolescence. We performed family-based TDT and haplotype association analyses of the clinical phenotype, as well as association analyses with endophenotypes using the QTDT program. Three adjacent SNPs in the 5' upstream region of GAD1 showed a positive pairwise association with illness in these families (P=0.022-0.057). Significant transmission distortion of 4-SNP haplotypes was also observed (P=0.003-0.008). Quantitative trait TDT analyses showed an intriguing association between several SNPs and increased rate of frontal gray matter loss. These observations, when taken together with the positive results reported recently in two independent adult-onset schizophrenia pedigree samples, suggest that the gene encoding GAD67 may be a common risk factor for schizophrenia.

Pedigree disequilibrium test (PDT) replicates association and linkage between DRD4 and ADHD in multigenerational and extended pedigrees from a genetic isolate.

Association/linkage between dopamine D4 receptor (DRD4) polymorphisms and attention-deficit/hyperactivity disorder (ADHD) has been suggested by case-control- and nuclear-family-based studies. Here, we present a candidate gene analysis for DRD4 using 14 extended and multigenerational families segregating ADHD derived from the 'Paisa' community of Antioquia, Colombia, a genetic isolate. Two DRD4 polymorphisms (a 120 bp tandem duplication at the promoter and a 48 bp-VNTR at exon 3), reported associated to ADHD, were genotyped. Parametric and non-parametric linkage analyses, and a family-based association test (FBAT), the pedigree disequilibrium test (PDT), were applied to search for evidence of association/linkage. Two-point LOD scores were significantly negative, with values ranging from -3.21 (P=0.011158) to -7.66 (P=0.000091 at theta=0). Non-parametrical analysis resulted in nonsignificant evidence for linkage. The PDT showed a moderate trend toward significance of association/linkage between the 7-repeat (7R) allele at the 48 bp VNTR and ADHD (P=0.0578). Furthermore, the haplotype analysis shows a significant association/linkage of the 7R-240 bp haplotype (P=0.0467) with ADHD. Results suggest that either a moderate DRD4 genetic effect, or linkage disequilibrium of DRD4 with an ADHD disease locus in the vicinity or the linkage to a phenotypic component of the ADHD spectrum could be underlying this association/linkage. These results provide further evidence for the association of ADHD to genetic variation in or near to DRD4 and replicate the previously reported association between ADHD and the 7R allele.