Contribution of copy number variants to schizophrenia from a genome-wide study of 41,321 subjects

Polygenic risk for schizophrenia predicting Big Five personality traits in individuals without non-affective psychosis

BACKGROUND

A high genetic risk for schizophrenia, in complex interplay with environmental factors, has been suggested to explain population-level variation in personality traits among individuals who do not develop schizophrenia-spectrum disorders. We investigated, first, whether polygenic risk for schizophrenia (PRSscz) predicts Big Five personality traits in individuals, who have not developed non-affective psychosis. Second, we examined whether any observed associations are specific to PRSscz or evident also for PRS for major depression (PRSDEP).

STUDY DESIGN

The participants came from the population-based, prospective Young Finns Study (n = 1328-1874 in the final analyses). Diagnoses of non-affective psychoses were obtained from the Finnish hospital care register. Personality traits were assessed with the five-factor model including Neuroticism, Conscientiousness, Openness, Agreeableness, and Extraversion. Covariates included age, sex, adulthood educational level, and quality of early family environment (adverse socioeconomic circumstances, unfavorable emotional family atmosphere, and stressful life events).

RESULTS

In those without non-affective psychosis, PRSscz had a positive linear effect on Openness (B = 0.029, 95%CI = 0.006;0.052, p = 0.014) and a quadratic effect on Extraversion (B = -0.018, 95%CI = -0.033;-0.002, p = 0.024), indicating higher levels of Extraversion in those with low/high levels of PRSscz. The PRSscz did not account for other personality traits. The results held after adding covariates or after controlling for PRSDEP. PRSDEP was not associated with any of the personality traits.

CONCLUSIONS

Individuals with high PRS for schizophrenia, who have not developed non-affective psychosis, may still develop mildly different personality traits, including higher Openness and lower Extraversion. These findings seem to be specific to PRSscz and are not observed for PRSDEP.

Neural excitation/inhibition imbalance and neurodevelopmental pathology in human copy number variant syndromes: a systematic review

Cumulative evidence suggests neurodevelopmental disorders are closely related. The risk of these disorders is increased by a series of copy number variant syndromes - phenotypically heterogeneous genetic disorders, present in a minority of the population. Recent models suggest that a disruption in the balance between excitatory and inhibitory neural activity may contribute to the aetiology of neurodevelopmental disorders, and may be additionally disturbed in copy number variant syndromes. In this systematic review, the databases PubMed, Embase, and Scopus were searched for studies of excitation/inhibition imbalance in relation to neurodevelopmental disorders in human copy number variant samples. A total of 53 studies were included, representing a variety of copy number variants and research methodologies. The resulting data suggests excitation/inhibition balance is indeed disrupted in different copy number variant populations, providing insight into a putative mechanism of both idiopathic and genetic neurodevelopmental disorders. However, the high level of heterogeneity in the data set, alongside emerging techniques for excitation/inhibition assessment, prompts further investigation of this field.

DLG2 rs11607886 polymorphism associated with schizophrenia and precuneus functional changes

BACKGROUND AND HYPOTHESIS

Schizophrenia (SZ) is a severe mental disorder with high heritability. DLG2 encodes the postsynaptic scaffolding protein DLG2 (PSD93, Postsynaptic Density Protein 93), and its variants were associated with an increased risk of SZ. However, the role of DLG2 locus variation in SZ remains elusive. This study aims to investigate the association between DLG2 gene polymorphisms and SZ susceptibility and the relationship between DLG2 and altered brain function and clinical symptoms in SZ patients.

STUDY DESIGN

Single nucleotide polymorphisms (SNPs) rs11607886 and rs7479949 were genotyped in 350 SZ patients and 407 healthy controls (HCs). 47 SZ patients and 79 HCs were genotyped into two groups: the risk A allele carrier group and the GG-pure group. Functional magnetic resonance imaging (fMRI) indices were further analyzed. Subsequently, data from different brain regions were correlated with clinical symptom assessment.

STUDY RESULTS

DLG2 rs11607886 was significantly associated with SZ. Significant main effects were found in the ALFF and ReHo, especially for the left precuneus gyrus (PCu). A significant interaction between genotype and diagnosis had a significant effect on FC, which was increased between the left PCu and the right middle temporal gyrus in carriers of the A allele with SZ (r = -0.336, Pun-corrected = 0.042) and negatively correlated with spatial breadth scores (r = 0.444, PFDR-corrected = 0.002).

CONCLUSIONS

The rs11607886 polymorphism in DLG2 may influence the pathogenesis of SZ and have potential effects on cognitive function. The present study emphasizes DLG2 as a candidate gene for SZ and suggests an important role for PCu in SZ.

Recent Advances in Schizophrenia Genomics and Emerging Clinical Implications

The conceptualization of schizophrenia has evolved from Emil Kraepelin's identification of "dementia praecox" as a distinct illness characterized by cognitive and functional deficits to the modern understanding of its complex nature. Recent research, including the "deficit syndrome," highlights enduring negative symptoms that correlate with poor functional outcomes. Genetic epidemiologic studies reveal a strong heritable basis (60%-80%) for schizophrenia, with its polygenic architecture overlapping with various mental health disorders. This complexity raises questions about targeted precision medicine. Recent advancements in biobanks and neurogenomics research are providing valuable insights that aim to improve patient outcomes through enhanced genomic understanding.

Tourette Syndrome and Chronic Tic Disorders

Tourette syndrome (TS) and chronic tic disorder (CTD) are characterized by persistent verbal and motor tics of varying severity. We describe modern genetic studies of TS/CTD focused on common and rare variation, which quantify genetic risk per patient and identify risk genes such as NRXN1 and CELSR3. In general, the burden of TS/CTD genetic risk correlates with tic severity and the likelihood of a case belonging to a multiplex family. These findings do not immediately alter patient treatment, though they may in some cases help better define sources of patient risk.

Identification of Transdiagnostic Childhood Externalizing Pathology Within an Electronic Medical Records Database and Application to the Analysis of Rare Copy Number Variation

Externalizing traits and behaviors are broadly defined by impairments in self-regulation and impulse control that typically begin in childhood and adolescence. Externalizing behaviors, traits, and symptoms span a range of traditional psychiatric diagnostic categories. In this study, we sought to generate an algorithm that could reliably identify transdiagnostic childhood-onset externalizing cases and controls within a university hospital electronic health record (EHR) database. Within the Vanderbilt University Medical Center (VUMC) EHR, our algorithm identified cases with a clinician-validated positive predictive value of 90% and controls with a negative predictive value of 88%. In individuals of genetically defined European ancestry (CEU-clustered; Ncase = 487, Ncontrol = 5638), case status was significantly associated with psychiatric comorbidity and with elevated externalizing polygenic scores (OR: 1.20; 95% CI: 1.09-1.33; p = 1.14 × 10-3; based on published genome-wide association data). To test whether our cohort definitions could be applied to generate novel genetic insights, we examined rare (allele frequency < 0.5%) copy number variation. An association (OR: 9.70; CI: 3.24-29.0) was identified in the CEU-clustered cohort on chromosome 2 (chr2: 45,408,678-45,551,530; duplication), although the statistical strength of this association was modest (p = 0.052). We also examined the role of an externalizing burden score based on the number of externalizing diagnoses present in cases and found similar results to our case-control analysis. This analysis identified several other statistically significant CNV region associations. This study provides a framework for identifying childhood externalizing case-control cohorts within an EHR. Future work should validate this framework within other health systems. A broadly applicable algorithm, like this one, may allow for detection of rare outcomes or outcomes in populations historically excluded from genomic research through meta-analysis of data across health care systems.

A review of antipsychotic therapy effectiveness and tolerability among individuals with copy number variants relevant to schizophrenia

Although numerous copy number variants (CNVs) are considered pathogenic with respect to the development of schizophrenia, only eight loci have reached genome-wide significance. Reviews/studies characterizing antipsychotic use in this context exist for only three corresponding CNV syndromes. As these disorders also predispose to neurodevelopmental anomalies and various medical comorbidities, affected individuals may be particularly sensitive to the side effects of antipsychotic medications. As such, this review sought to identify and describe all reports of antipsychotic use among individuals with the other genome-wide significant schizophrenia risk CNVs (2p16.3 deletions/ NRXN1 variants, 15q13.3 and 16p11.2 deletions, 7q11.23 duplications, and 1q21.1 deletions or duplications). Only 10 eligible articles describing 29 individuals were included. While treatment response was reasonably good for most individuals, despite variability existing across the specific CNV syndromes, side effects were rarely reported. Above all, this review highlights the need for more case reports/series to be published.

The Eating Disorders Genetics Initiative 2 (EDGI2): study protocol

BACKGROUND

The Eating Disorders Genetics Initiative 2 (EDGI2) is designed to explore the role of genes and environment in anorexia nervosa, bulimia nervosa, binge-eating disorder, and avoidant/restrictive food intake disorder (ARFID) with a focus on broad population representation and severe and/or longstanding illness.

METHODS

A total of 20,000 new participants (18,700 cases and 1,300 controls) will be ascertained from the United States (US), Mexico (MX), Australia (AU), Aotearoa New Zealand (NZ), Sweden (SE), and Denmark (DK). Comprehensive phenotyping and genotyping will be performed for participants in US, MX, AU, NZ, and SE using the EDGI2 questionnaire battery and participant saliva samples. In DK, case identification and genotyping will be through the National Patient Register and bloodspots archived near birth. Case-control and case-case genome-wide association studies will be conducted within EDGI2 and enhanced via meta-analysis with external data from the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED). Additional analyses will explore genetic correlations between eating disorders (EDs) and other psychiatric and metabolic traits, calculate polygenic risk scores (PRS), and leverage functional biology to evaluate clinical outcomes. Moreover, analyzing PRS for patient stratification and linking identified risk loci to clinically relevant phenotypes highlight the potential of EDGI2 for clinical translation.

DISCUSSION

EDGI2 is a global expansion of the EDGI study to increase sample size, increase participant representation across multiple ancestral backgrounds, and to include ARFID. ED genetics research has historically lagged behind other psychiatric disorders, and EDGI2 is designed to rapidly advance the study of the genetics of the major EDs. Exploring EDs at both the diagnostic level and the symptom level will provide an unprecedented look at the genetic architecture underlying EDs.

TRIAL REGISTRATION

EDGI2 is a registered clinical trial: clinicaltrials.gov NCT06594913. https://clinicaltrials.gov/study/NCT06594913 (posted September 19, 2024).

Penetrance of neurodevelopmental copy number variants is associated with variations in cortical morphology

BACKGROUND

Copy number variants (CNVs) increase risk for neurodevelopmental conditions. The neurobiological mechanisms linking these high-risk genetic variants to clinical phenotypes are largely unknown. An important question is whether brain abnormalities in individuals carrying CNVs are associated with their degree of penetrance.

METHODS

We investigated if increased CNV-penetrance for schizophrenia and other developmental disorders was associated with variations in cortical and subcortical morphology. We pooled T1-weighted brain magnetic resonance imaging and genetic data from 22 cohorts from the ENIGMA-CNV consortium. In the main analyses, we included 9,268 individuals (aged 7 to 90 years, 54% females), from which we identified 398 carriers of 36 neurodevelopmental CNVs at 20 distinct loci. A secondary analysis was performed including additional neuroimaging data from the ENIGMA-22q consortium, including 274 carriers of the 22q11.2 deletion and 291 non-carriers. CNV-penetrance was estimated through penetrance scores that were previously generated from large cohorts of patients and controls. These scores represent the probability risk to develop either schizophrenia or other developmental disorders (including developmental delay, autism spectrum disorder and congenital malformations).

RESULTS

For both schizophrenia and developmental disorders, increased penetrance scores were associated with lower surface area in the cerebral cortex and lower intracranial volume. For both conditions, associations between CNV-penetrance scores and cortical surface area were strongest in regions of the occipital lobes, specifically in the cuneus and lingual gyrus.

CONCLUSIONS

Our findings link global and regional cortical morphometric features with CNV-penetrance, providing new insights into neurobiological mechanisms of genetic risk for schizophrenia and other developmental disorders.

An ace in the hole? Opportunities and limits of using mice to understand schizophrenia neurobiology

In applying model organisms to study the neurobiology of mental disorders, rodents offer unique potential for probing, with high spatiotemporal resolution, the neural and molecular mechanisms underlying behavior in a mammalian system. Furthermore, investigators can wield exceptional power to manipulate genes, molecules, and circuits in mice to pin down causal relationships. While these advantages have allowed us to understand much more deeply than ever before the brain mechanisms regulating complex behaviors, the impact of rodent models on developing therapeutic strategies for psychiatric disorders has remained thus far limited. Herein, we will discuss the opportunities and limits of using mouse models in the context of schizophrenia, a complex psychiatric disorder with strong genetic basis that poses various unmet clinical needs calling out for basic science research. We review approaches for employing behavioral, genetic, and circuit-based methods in rodents to inform schizophrenia symptomatology, pathophysiology, and, ultimately, treatment.

Body fluid biomarkers and psychosis risk in The Accelerating Medicines Partnership® Schizophrenia Program: design considerations

Advances in proteomic assay methodologies and genomics have significantly improved our understanding of the blood proteome. Schizophrenia and psychosis risk are linked to polygenic scores for schizophrenia and other mental disorders, as well as to altered blood and saliva levels of biomarkers involved in hormonal signaling, redox balance, and chronic systemic inflammation. The Accelerating Medicines Partnership® Schizophrenia (AMP®SCZ) aims to ascertain biomarkers that both predict clinical outcomes and provide insights into the biological processes driving clinical outcomes in persons meeting CHR criteria. AMP®SCZ will follow almost 2000 CHR and 640 community study participants for two years, assessing biomarkers at baseline and two-month follow-up including the collection of blood and saliva samples. The following provides the rationale and methods for plans to utilize polygenic risk scores for schizophrenia and other disorders, salivary cortisol levels, and a discovery-based proteomic platform for plasma analyses. We also provide details about the standardized methods used to collect and store these biological samples, as well as the study participant metadata and quality control measures related to preanalytical factors that could influence the values of the biomarkers. Finally, we discuss our plans for analyzing the results of blood- and saliva-based biomarkers. Watch Dr. Perkins discuss their work and this article: https://vimeo.com/1062879582?share=copy#t=0 .

Genomics of schizophrenia, bipolar disorder and major depressive disorder

Schizophrenia, bipolar disorder and major depressive disorder - which are the most common adult disorders requiring psychiatric care - contribute substantially to premature mortality and morbidity globally. Treatments for these disorders are suboptimal, there are no diagnostic pathologies or biomarkers and their pathophysiologies are poorly understood. Novel therapeutic and diagnostic approaches are thus badly needed. Given the high heritability of psychiatric disorders, psychiatry has potentially much to gain from the application of genomics to identify molecular risk mechanisms and to improve diagnosis. Recent large-scale, genome-wide association studies and sequencing studies, together with advances in functional genomics, have begun to illuminate the genetic architectures of schizophrenia, bipolar disorder and major depressive disorder and to identify potential biological mechanisms. Genomic findings also point to the aetiological relationships between different diagnoses and to the relationships between adult psychiatric disorders and childhood neurodevelopmental conditions.

A foundational neuronal protein network model unifying multimodal genetic, transcriptional, and proteomic perturbations in schizophrenia

Schizophrenia (SCZ) is a complex psychiatric disorder with a diverse genetic landscape, involving common regulatory variants, rare protein-coding mutations, structural genomic rearrangements, and transcriptional dysregulation. A critical challenge in developing rationally designed therapeutics is understanding how these various factors converge to disrupt cellular networks in the human brain, ultimately contributing to SCZ. Towards this aim, we generated multimodal data, including SCZ-specific protein-protein interactions in stem-cell-derived neuronal models and adult postmortem cortex, integrated with genetic and transcriptomic datasets from individuals with psychiatric disorders. We identified three distinct neuron-specific SCZ protein networks, or modules, significantly enriched for genetic and transcriptional perturbations associated with SCZ. The relevance of these modules was validated through whole-cell proteomics in patient-derived neurons, revealing their disruption in 22q11.2 deletion carriers diagnosed with SCZ. We demonstrated their therapeutic potential by showing that these modules are targets of GSK3 inhibition using phosphoproteomics. Our findings present a foundational model that integrates genetic, transcriptional, and proteomic perturbations in SCZ. This model provides a cohesive framework for understanding how polygenic and multimodal perturbations affect neuronal pathways in the human brain, as well as a data-driven pathway resource for identifying potential drug targets to reverse disruptions observed in these neuronal networks.

Highly demarcated structural alterations in the brain and impaired social incentive learning in Tbx1 heterozygous mice

Copy number variants (CNVs) are robustly associated with psychiatric disorders and changes in brain structures. However, because CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how each gene encoded in the 22q11.2 region contributes to structural alterations, associated mental illnesses, and their dimensions. Our previous studies identified Tbx1, a T-box family transcription factor encoded in the 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes and behavioral alterations relevant to affected structures in congenic Tbx1 heterozygous mice. Our data showed that the volumes of the anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were most robustly reduced in Tbx1 heterozygous mice. In an amygdala-dependent task, Tbx1 heterozygous mice were impaired in their ability to learn the incentive value of a social partner. The volumes of the primary and secondary auditory cortexes were increased, and acoustic, but not non-acoustic, sensorimotor gating was impaired in Tbx1 heterozygous mice. Our findings identify the brain's regional volume alterations and their relevant behavioral dimensions associated with Tbx1 heterozygosity.

Genome-wide copy number variation association study in anorexia nervosa

This study represents the first large-scale investigation of rare (<1% population frequency) copy number variants (CNVs) in anorexia nervosa (AN). Large, rare CNVs are reported to be causally associated with anthropometric traits, neurodevelopmental disorders, and schizophrenia, yet their role in the genetic basis of AN is unclear. Using genome-wide association study (GWAS) array data from the Anorexia Nervosa Genetics Initiative (ANGI), which included 7414 AN case and 5044 controls, we investigated the association of 67 well-established syndromic CNVs and 178 pleiotropic disease-risk dosage-sensitive CNVs with AN. To identify novel CNV regions (CNVRs) that increase the risk of AN, we conducted genome-wide association studies with a focus on rare CNV-breakpoints (CNV-GWAS). We found no net enrichment of rare CNVs, either deletions or duplications, in AN, and none of the well-established syndromic or pleiotropic CNVs had a significant association with AN status. However, the CNV-GWAS found 21 nominally associated CNVRs that contribute to AN risk, covering protein-coding genes implicated in synaptic function, metabolic/mitochondrial factors, and lipid characteristics, like the CD36 (7q21.11) gene, which transports long-chain fatty acids into cells. CNVRs intersecting genes previously related to neurodevelopmental traits include deletions of NRXN1 intron 5 (2p16.3), IMMP2L (7q31.1), and PTPRD (9p23). Overall, given that our study is well powered to detect the CNV burden level reported for schizophrenia, we can conclude that rare CNVs have a limited role in the etiology of AN, as reported for bipolar disorder. Our nominal associations for the 21 discovered CNVRs are consistent with AN being a metabo-psychiatric trait, as demonstrated by the common genetic architecture of AN, and we provide association results to allow for replication in future research.

Cortical differences across psychiatric disorders and associated common and rare genetic variants

Genetic studies have identified common and rare variants increasing the risk for neurodevelopmental and psychiatric disorders (NPDs). These risk variants have also been shown to influence the structure of the cerebral cortex. However, it is unknown whether cortical differences associated with genetic variants are linked to the risk they confer for NPDs. To answer this question, we analyzed cortical thickness (CT) and surface area (SA) for common and rare variants associated with NPDs, in ~33000 individuals from the general population and clinical cohorts, as well as ENIGMA summary statistics for 8 NPDs. Rare and common genetic variants increasing risk for NPDs were preferentially associated with total SA, while NPDs were preferentially associated with mean CT. Larger effects on mean CT, but not total SA, were observed in NPD medicated subgroups. At the regional level, genetic variants were preferentially associated with effects in sensorimotor areas, while NPDs showed higher effects in association areas. We show that schizophrenia- and bipolar-disorder-associated SNPs show positive and negative effect sizes on SA suggesting that their aggregated effects cancel out in additive polygenic models. Overall, CT and SA differences associated with NPDs do not relate to those observed across individual genetic variants and may be linked with critical non-genetic factors, such as medication and the lived experience of the disorder.

Genotyping sequence-resolved copy number variation using pangenomes reveals paralog-specific global diversity and expression divergence of duplicated genes

Copy number variant (CNV) genes are important in evolution and disease, yet sequence variation in CNV genes remains a blind spot in large-scale studies. We present ctyper, a method that leverages pangenomes to produce allele-specific copy numbers with locally phased variants from next-generation sequencing (NGS) reads. Benchmarking on 3,351 CNV genes, including HLA, SMN, and CYP2D6, and 212 challenging medically relevant (CMR) genes that are poorly mapped by NGS, ctyper captures 96.5% of phased variants with ≥99.1% correctness of copy number on CNV genes and 94.8% of phased variants on CMR genes. Applying alignment-free algorithms, ctyper requires 1.5 hours per genome on a single CPU. The results improve prediction of gene expression compared to known expression quantitative trait loci (eQTL) variants. Allele-specific expression quantified divergent expression on 7.94% of paralogs and tissue-specific biases on 4.68% of paralogs. We found reduced expression of SMN-2 due to SMN1 conversion, potentially affecting spinal muscular atrophy, and increased expression of translocated duplications of AMY2B. Overall, ctyper enables biobank-scale genotyping of CNV and CMR genes.

Genetic modulation of brain dynamics in neurodevelopmental disorders: the impact of copy number variations on resting-state EEG

Research has shown that many copy number variations (CNVs) increase the risk of neurodevelopmental disorders (e.g., autism, ADHD, schizophrenia). However, little is known about the effects of CNVs on brain development and function. Resting-state electroencephalography (EEG) is a suitable method to study the disturbances of neuronal functioning in CNVs. We aimed to determine whether there are resting-state EEG signatures that are characteristic of children with pathogenic CNVs. EEG resting-state brain activity of 109 CNV carriers (66 deletion carriers, 43 duplication carriers) aged 3 to 17 years was recorded for 4 minutes. To better account for developmental variations, EEG indices (power spectral density and functional connectivity) were corrected with a normative model estimated from 256 Healthy Brain Network controls. Results showed a decreased exponent of the aperiodic activity and a reduced alpha peak frequency in CNV carriers. Additionally, the study showed altered periodic components and connectivity in several frequency bands. Deletion and duplication carriers exhibited a similar overall pattern of deviations in spectral and connectivity measures, although the significance and effect sizes relative to the control group varied across frequency bands. Deletion and duplication carriers can be differentiated by their periodic power in the gamma band and connectivity in the low alpha band, with duplication carriers showing more disrupted alterations than deletion carriers. The distinctive alterations in spectral patterns were found to be most prominent during adolescence. The results suggest that CNV carriers show electrophysiological alterations compared to neurotypical controls, regardless of the gene dosage effect and their affected genomic region. At the same time, while duplications and deletions share common electrophysiological alterations, each exhibits distinct brain alteration signatures that reflect gene dosage-specific effects.

Phenotypic complexities of rare heterozygous neurexin-1 deletions

Given the large number of genes significantly associated with risk for neuropsychiatric disorders, a critical unanswered question is the extent to which diverse mutations-sometimes affecting the same gene-will require tailored therapeutic strategies. Here we consider this in the context of rare neuropsychiatric disorder-associated copy number variants (2p16.3) resulting in heterozygous deletions in NRXN1, which encodes a presynaptic cell-adhesion protein that serves as a critical synaptic organizer in the brain. Complex patterns of NRXN1 alternative splicing are fundamental to establishing diverse neurocircuitry, vary between the cell types of the brain and are differentially affected by unique (non-recurrent) deletions1. We contrast the cell-type-specific effect of patient-specific mutations in NRXN1 using human-induced pluripotent stem cells, finding that perturbations in NRXN1 splicing result in divergent cell-type-specific synaptic outcomes. Through distinct loss-of-function (LOF) and gain-of-function (GOF) mechanisms, NRXN1+/- deletions cause decreased synaptic activity in glutamatergic neurons, yet increased synaptic activity in GABAergic neurons. Reciprocal isogenic manipulations causally demonstrate that aberrant splicing drives these changes in synaptic activity. For NRXN1 deletions, and perhaps more broadly, precision medicine will require stratifying patients based on whether their gene mutations act through LOF or GOF mechanisms, to achieve individualized restoration of NRXN1 isoform repertoires by increasing wild-type and/or ablating mutant isoforms. Given the increasing number of mutations predicted to engender both LOF and GOF mechanisms in brain disorders, our findings add nuance to future considerations of precision medicine.

Clozapine Use Among Individuals With Schizophrenia Occurring on the Background of Intellectual Disability and Rare Genetic Variation: A Retrospective Chart Review

BACKGROUND

Treatment resistance in schizophrenia is associated with both intellectual disability and rare genetic variation. Information pertaining to the use of clozapine in this context has primarily come from case reports and small case series. Given the frequent occurrence of comorbid medical issues in various genetic disorders and the heightened sensitivity to antipsychotic medications among intellectually disabled individuals, additional information regarding the effectiveness and tolerability of clozapine in this population is needed, particularly in light of its unique side effect profile.

METHODS

This retrospective review of 1200 charts, which took place at a subspecialty psychiatry clinic, sought to characterize the use of clozapine in individuals with schizophrenia (or psychotic symptoms, generally speaking) and intellectual disability occurring on the background of rare genetic variation, a difficult to study and underserved patient population.

RESULTS

Twelve hundred charts were reviewed and 10 eligible individuals were identified, all of whom had been prescribed clozapine and carried a diagnosis of schizophrenia on the background of intellectual disability and rare genetic variation. Six of these 10 individuals harbored presumed pathogenic variants.

IMPLICATIONS

This study affirms what is known about clozapine treatment in 22q11.2 deletion syndrome, adds to the scarce literature on Usher syndrome in this context, and provides the first accounts of clozapine use in 22q11.2 microduplication syndrome and DCX variant-related heterotopia.

A burden of rare copy number variants in obsessive-compulsive disorder

Current genetic research on obsessive-compulsive disorder (OCD) supports contributions to risk specifically from common single nucleotide variants (SNVs), along with rare coding SNVs and small insertion-deletions (indels). The contribution to OCD risk from rare copy number variants (CNVs), however, has not been formally assessed at a similar scale. Here we describe an analysis of rare CNVs called from genotype array data in 2248 deeply phenotyped OCD cases and 3608 unaffected controls from Sweden and Norway. Cases carry an elevated burden of CNVs ≥30 kb in size (OR = 1.12, P = 1.77 × 10-3). The excess rate of these CNVs in cases versus controls was around 0.07 (95% CI 0.02-0.11, P = 2.58 × 10-3). This signal was largely driven by CNVs overlapping protein-coding regions (OR = 1.19, P = 3.08 × 10-4), particularly deletions impacting loss-of-function intolerant genes (pLI >0.995, OR = 4.12, P = 2.54 × 10-5). We did not identify any specific locus where CNV burden was associated with OCD case status at genome-wide significance, but we noted non-random recurrence of CNV deletions in cases (permutation P = 2.60 × 10-3). In cases where sufficient clinical data were available (n = 1612) we found that carriers of neurodevelopmental duplications were more likely to have comorbid autism (P < 0.001), and that carriers of deletions overlapping neurodevelopmental genes had lower treatment response (P = 0.02). The results demonstrate a contribution of rare CNVs to OCD risk, and suggest that studies of rare coding variation in OCD would have increased power to identify risk genes if this class of variation were incorporated into formal tests.

Genetic advances in neurodevelopmental disorders

Neurodevelopmental disorders (NDDs) are a group of highly heterogeneous diseases that affect children's social, cognitive, and emotional functioning. The etiology is complicated with genetic factors playing an important role. During the past decade, large-scale whole exome sequencing (WES) and whole genome sequencing (WGS) have vastly advanced the genetic findings of NDDs. Various forms of variants have been reported to contribute to NDDs, such as de novo mutations (DNMs), copy number variations (CNVs), rare inherited variants (RIVs), and common variation. By far, over 200 high-risk NDD genes have been identified, which are involved in biological processes including synaptic function, transcriptional and epigenetic regulation. In addition, monogenic, oligogenic, polygenetic, and omnigenic models have been proposed to explain the genetic architecture of NDDs. However, the majority of NDD patients still do not have a definitive genetic diagnosis. In the future, more types of risk factors, as well as noncoding variants, are await to be identified, and including their interplay mechanisms are key to resolving the etiology and heterogeneity of NDDs.

Contribution of Rare and Potentially Functionally Relevant Sequence Variants in Schizophrenia Risk-Locus Xq28,distal

Duplications of the Xq28,distal locus have been described in male and female patients with schizophrenia (SCZ) or intellectual disability. The Xq28,distal locus spans eight protein-coding genes (F8, CMC4, MTCP1, BRCC3, VBP1, FUNDC2, CLIC2, and RAB39B) and is flanked by recurrent genomic breakpoints. Thus, the issue of which gene/s at this locus is/are relevant in terms of SCZ pathogenesis remains unclear. The aim of this study was to investigate the contribution of rare and potentially functionally relevant sequence variants within the Xq28,distal locus to SCZ risk using the single-molecule molecular inversion probes (smMIP) method. Targeted sequencing was performed in a cohort of 1935 patients with SCZ and 1905 controls of European ancestry. The consecutive statistical analysis addressed two main areas. On the level of the individual variants, allele counts in the patient and control cohort were systematically compared with a Fisher's exact test: (i) for the entire present study cohort; (ii) for patients and controls separated by sex; and (iii) in combination with data published by the Schizophrenia Exome Meta-Analysis (SCHEMA) consortium. On the gene-wise level, a burden analysis was performed using the X-chromosomal model of the Optimal Unified Sequence Kernel Association Test (SKAT-O), with adjustment for possible sex-specific effects. Targeted sequencing identified a total of 13 rare and potentially functional variants in four patients and 11 controls. However, neither at the level of individual rare and potentially functional variants nor at the level of the eight protein-coding genes at the Xq28,distal locus was a statistically significant enrichment in patients compared to controls observed. Although inconclusive, the present findings represent a step toward improved understanding of the contribution of X-chromosomal risk factors in neuropsychiatric disorder development, which is an underrepresented aspect of genetic studies in this field.

Unresolved ethical issues of genetic counseling and testing in clinical psychiatry

OBJECTIVE

This position article discusses current major ethical and social issues related to genetic counseling and testing in clinical psychiatry (PsyGCT).

METHODS

To address these complex issues in the context of clinical psychiatry relevant to PsyGCT, the interdisciplinary and pan-European expert Network EnGagE (Enhancing Psychiatric Genetic Counseling, Testing, and Training in Europe; CA17130) was established in 2018. We conducted an interdisciplinary, international workshop at which we identified gaps across European healthcare services and research in PsyGCT; the workshop output was summarized and systematized for this position article.

RESULTS

Four main unresolved ethical topics were identified as most relevant for the implementation of PsyGCT: (1) the problematic dualism between somatic and psychiatric disorders, (2) the impact of genetic testing on stigma, (3) fulfilling professional responsibilities, and (4) ethical issues in public health services. We provide basic recommendations to inform psychiatrists and other healthcare professionals involved in the clinical implementation of PsyGCT and conclude by pointing to avenues of future ethics research in PsyGCT.

CONCLUSION

This article draws attention to a set of unresolved ethical issues relevant for mental health professionals, professionals within clinical genetics, patients and their family members, and society as a whole and stresses the need for more interdisciplinary exchange to define standards in psychiatric counseling as well as in public communication. The use of PsyGCT may, in the future, expand and include genetic testing for additional psychiatric diagnoses. We advocate the development of pan-European ethical standards addressing the four identified areas of ethical-practical relevance in PsyGCT.

Rare mutations implicate CGE interneurons as a vulnerable axis of cognitive deficits across psychiatric disorders

Neuropsychiatric disorders such as autism spectrum disorder (ASD) and schizophrenia (SCZ) share genetic risk factors, including rare high penetrance single nucleotide variants and copy number variants (CNVs), and exhibit both overlapping and distinct clinical phenotypes. Cognitive deficits and intellectual disability-critical predictors of long-term outcomes-are common to both conditions. To investigate shared and disorder-specific neurobiological impact of highly penetrant rare mutations in ASD and SCZ, we analyzed human single-nucleus whole-brain sequencing data to identify strongly affected brain cell types. Our analysis revealed Caudal Ganglionic Eminence (CGE)-derived GABAergic interneurons as a key nexus for cognitive deficits across these disorders. Notably, genes within 22q11.2 deletions, known to confer a high risk of SCZ, ASD, and cognitive impairment, showed a strong expression bias toward vasoactive intestinal peptide-expressing cells (VIP+) among CGE subtypes. To explore VIP+ GABAergic interneuron perturbations in the 22q11.2 deletion syndrome in vivo , we examined their activity in the Df(16)A +/- mouse model during a spatial navigation task and observed reduced activity along with altered responses to random rewards. At the population level, VIP+ interneurons exhibited impaired spatial encoding and diminished subtype-specific activity suggesting deficient disinhibition in CA1 microcircuits in the hippocampus, a region essential for learning and memory. Overall, these results demonstrate the crucial role of CGE-derived interneurons in mediating cognitive processes that are disrupted across a range of psychiatric and neurodevelopmental disorders.

The interplay between genomic copy number variants, sleep, and cognition in the general population

Genomic Copy Number variants (CNVs) increase risk for neurodevelopmental disorders (NDDs) and affect cognition, but their impact on sleep remains understudied despite the well-established link between sleep disturbances, NDDs, and cognition. We investigated the relationship between CNVs, sleep traits, cognitive ability, and executive function in 498,852 individuals from an unselected population in the UK Biobank. We replicated the U-shape relationship between measures of cognitive ability and sleep duration. The effects of CNVs on sleep duration were evident at the genome-wide level; CNV-burden analyses showed that overall, CNVs with an increasing number of intolerant genes were associated with increased or decreased sleep duration in a U-shape pattern (p < 2e-16), but did not increase risk of insomnia. Sleep duration only marginally mediated the robust association between CNVs and poorer cognitive performance, suggesting that sleep and cognitive phenotypes may result from pleiotropic effects of CNVs with minimal causal relationship.

Neurodevelopmental impact of CNV models in ASD: Recent advances and future directions

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social communication impairments and restricted, repetitive behaviors. ASD exhibits a strong genetic basis, with rare and common genetic variants contributing to its etiology. Copy number variations (CNVs), deletions or duplications of chromosomal segments, have emerged as key contributors to ASD risk. Rare CNVs often demonstrate large effect sizes and can directly cause ASD, while common variants collectively exert subtle influences. Recent advances have identified numerous ASD-associated CNVs, including recurrent loci such as 1q21.1, 2p16.3, 7q11.23, 15q11.2, 15q11-q13, 16p11.2 and 22q11.2. Mouse models carrying these CNVs have provided profound insights into the underlying neurobiological mechanisms. Recent studies integrating transcriptomic, proteomic, and functional imaging approaches have revealed alterations in synaptic function, neuronal differentiation, myelination, metabolic pathways, and circuit connectivity. Notably, investigations leveraging conditional knockout models, high magnetic field MRI, and single-cell analyses highlight disruptions in excitatory-inhibitory balance, white matter integrity, and dynamic gene regulatory networks. Parallel human-based approaches, including iPSC-derived neurons, cerebral organoids, and large-scale single-nucleus sequencing, are combined with animal model data. These integrative strategies promise to refine our understanding of ASD's genetic architecture, bridging the gap between fundamental discoveries in model organisms and clinically relevant biomarkers, subtypes, and therapeutic targets in humans. This review summarizes key findings from recent CNV mouse model studies and highlights emerging technologies applied to human ASD samples. Finally, we outline prospects for translating findings from mouse studies to humans. By illuminating both unique and convergent genetic mechanisms, these advances offer a critical framework for unraveling etiological complexity in ASD.

Transcriptomic and genetic analysis suggests a role for mitochondrial dysregulation in schizophrenia

Schizophrenia is an often devastating disorder characterized by persistent and idiopathic cognitive deficits, delusions and hallucinations. Schizophrenia has been associated with impaired nervous system development and an excitation/inhibition imbalance in the prefrontal cortex. On a molecular level, schizophrenia is moderately heritable and genetically complex. Hundreds of risk genes have been identified, spanning a heterogeneous landscape dominated by loci that confer relatively small risk. Bioinformatic analyses of genetic associations point to a limited set of neurons, mainly excitatory cortical neurons, but other analyses suggest the importance of astrocytes and microglia. To understand different cell type roles in schizophrenia and reveal novel cell-type specific aetiologically relevant perturbations in schizophrenia, our study integrated genetic analysis with single nucleus RNA-seq of 536,618 nuclei from postmortem samples of dorsal prefrontal cortex (Brodmann Area 8/9) of 43 cases with schizophrenia and 42 neurotypical controls. We found no significant difference in cell type abundance. Gene expression in excitatory layer 2-3 intra-telencephalic neurons had the greatest number of differentially expressed transcripts and, together with excitatory deep layer intra-telencephalic neurons, conferred most of the genetic risk for schizophrenia. Most differential expression of genes was found in specific cell types and was dominated by down-regulated transcripts. Down-regulated transcripts were enriched in gene sets including transmembrane transport, mitochondrial function, protein folding, and cell-cell signaling whereas up-regulated transcripts were enriched in gene sets related to RNA processing, including RNA splicing in neurons. Co-regulation network analysis identified 40 schizophrenia-relevant programs across 13 cell types. A gene program largely shared between neuronal subtypes, astrocytes, and oligodendrocytes was significantly enriched for schizophrenia risk, supporting an aetiological role for perturbed protein modification, ion transport, and mitochondrial function. These results were largely consistent with cell-type expression quantitative trait locus and transcriptome-wide association analyses. Moreover, single-cell RNA sequencing results, most prominently mitochondrial dysfunction, had multiple points of convergence with proteomic and long-read RNA sequencing results from samples from the same donors. Our study integrates genetic analysis with transcriptomics to reveal novel cell-type specific aetiologically relevant perturbations in schizophrenia.

Early Manifestations of Neurodevelopmental Copy Number Variants in Children: A Population-Based Investigation

BACKGROUND

There is clinical interest in recognizing copy number variants (CNVs) in children because many have immediate and long-term health implications. Neurodevelopmental (ND) CNVs are associated with intellectual disability, autism spectrum disorder (ASD), and attention-deficit/hyperactivity disorder (ADHD), conditions typically diagnosed by medical practitioners. However, ND CNVs may have additional, early developmental impacts that have yet to be examined in unselected populations.

METHODS

Carriers of known ND CNVs were identified in 2 UK birth cohorts: ALSPAC (Avon Longitudinal Study of Parents and Children) (carriers = 144, controls = 6217) and MCS (Millennium Cohort Study) (carriers = 151, controls = 6559). In ALSPAC, we assessed associations between CNV carrier status and birth complications; preschool development; cognitive ability; ND conditions (ASD, ADHD, reading, language, and motor difficulties); and psychiatric, social, and educational outcomes. Corresponding phenotypes were identified in MCS and meta-analyzed, where available.

RESULTS

In ALSPAC, ND CNVs were associated with low cognitive ability, ADHD, and ASD. ND CNV carriers showed a greater likelihood of preterm birth, fine and gross motor delay, difficulties in motor coordination, language, and reading, and special educational needs (SEND). Meta-analysis with available measures in MCS identified elevated likelihood of ASD, ADHD, low birth weight, reading difficulties, SEND, and peer problems.

CONCLUSIONS

ND CNVs are associated with a broad range of developmental impacts. While clinicians who see children with intellectual disability, ASD, or ADHD may be aware of the impacts of CNVs and consider genetic testing, our investigation suggests that this training and awareness may need to extend to other professional groups (e.g., speech and language therapists).

Synaptic-dependent developmental dysconnectivity in 22q11.2 deletion syndrome

Chromosome 22q11.2 deletion increases the risk of neuropsychiatric disorders like autism and schizophrenia. Disruption of large-scale functional connectivity in 22q11 deletion syndrome (22q11DS) has been widely reported, but the biological factors driving these changes remain unclear. We used a cross-species design to uncover the developmental trajectory and neural underpinnings of brain dysconnectivity in 22q11DS. In LgDel mice, a model for 22q11DS, we found age-specific patterns of brain dysconnectivity, with widespread fMRI hyperconnectivity in juvenile mice reconfiguring to hippocampal hypoconnectivity over puberty. These changes correlated with developmental alterations in dendritic spine density, and both were transiently normalized by GSK3β inhibition, suggesting a synaptic origin for this phenomenon. Notably, analogous pubertal hyperconnectivity-to-hypoconnectivity reconfiguration occurs in human 22q11DS, affecting cortical regions enriched for GSK3β-associated synaptic genes and autism-relevant transcripts. This dysconnectivity also predicts age-dependent social alterations in 22q11DS individuals. These results suggest that synaptic mechanisms underlie developmental brain dysconnectivity in 22q11DS.

Contrasting genetic predisposition and diagnosis in psychiatric disorders: A multi-omic single-nucleus analysis of the human OFC

Psychiatric disorders like schizophrenia, bipolar disorder, and major depressive disorder exhibit substantial genetic and clinical overlap. However, their molecular architecture remains elusive due to their polygenic nature and complex brain cell interactions. We integrated clinical data with genetic susceptibility to investigate gene expression and chromatin accessibility in the orbitofrontal cortex of 92 postmortem human brain samples at the single-nucleus (sn) level. Using snRNA-seq and snATAC-seq, we analyzed ~800,000 and 400,000 nuclei, respectively. We observed cell-type-specific dysregulation related to clinical diagnosis and genetic risk. Dysregulation in gene expression and chromatin accessibility associated with diagnosis was pronounced in excitatory neurons. Conversely, genetic risk predominantly affected glial and endothelial cells. Notably, INO80E and HCN2 genes exhibited dysregulation in excitatory neurons' superficial layers 2/3 influenced by schizophrenia polygenic risk. This study unveils the complex genetic and epigenetic landscape of psychiatric disorders, emphasizing the importance of cell-type-specific analyses in understanding their pathogenesis and contrasting genetic predisposition with clinical diagnosis.

Inter-chromosomal insertions at Xq27.1 associated with retinal dystrophy induce dysregulation of LINC00632 and CDR1as/ciRS-7

In two unrelated families with X-linked inherited retinal dystrophy, identification of the causative variants was elusive. Interrogation of the next-generation sequencing (NGS) data revealed a "dark" intergenic region on Xq27.1 with poor coverage. Long-range PCR and DNA walking across this region revealed different inter-chromosomal insertions into the human-specific palindrome on Xq27.1: a 58 kb insertion of 9p24.3 [der(X)dir ins(X;9)(q27.1;p24.3)] in family 1 and a 169 kb insertion of 3p14.2 [der(X)inv ins(X;3)(q27.1;p14.2)] in family 2. To explore the functional consequence of these structural variants in genomic and cellular contexts, induced pluripotent stem cells were derived from affected and control fibroblasts and differentiated to retinal organoids (ROs) and retinal pigment epithelium. Transcriptional dysregulation was evaluated using RNA sequencing (RNA-seq) and RT-qPCR. A downstream long non-coding RNA, LINC00632 (Xq27.1), was upregulated in ROs from both families compared to control samples. In contrast, the circular RNA CDR1as/ciRS-7 (circular RNA sponge for miR-7), spliced from linear LINC00632, was downregulated. To investigate this tissue-specific dysregulation, we interrogated the landscape of the locus using Hi-C and cleavage under targets and tagmentation sequencing (CUT&Tag). This revealed active retinal enhancers within the insertions within a topologically associated domain that also contained the upstream promoter of LINC00632, permitting ectopic contact. Furthermore, CDR1as/ciRS-7 acts as a "sponge" for miR-7, and target genes of miR-7 were also dysregulated in ROs derived from both families. We describe a new genomic mechanism for retinal dystrophy, and our data support a convergent tissue-specific mechanism of altered regulation of LINC00632 and CDR1as/ciRS-7 as a consequence of the insertions within the palindrome on Xq27.1.

Gene-level analysis reveals the genetic aetiology and therapeutic targets of schizophrenia

Genome-wide association studies (GWASs) have reported multiple risk loci for schizophrenia (SCZ). However, the majority of the associations were from populations of European ancestry. Here we conducted a large-scale GWAS in Eastern Asian populations (29,519 cases and 44,392 controls) and identified ten Eastern Asian-specific risk loci, two of which have not been previously reported. A further cross-ancestry GWAS meta-analysis (96,806 cases and 492,818 controls) including populations from diverse ancestries identified 61 previously unreported risk loci. Systematic variant-level analysis, including fine mapping, functional genomics and expression quantitative trait loci, prioritized potential causal variants. Gene-level analyses, including transcriptome-wide association study, proteome-wide association study and Mendelian randomization, nominated the potential causal genes. By integrating evidence from layers of different analyses, we prioritized the most plausible causal genes for SCZ, such as ACE, CNNM2, SNAP91, ABCB9 and GATAD2A. Finally, drug repurposing showed that ACE, CA14, MAPK3 and MAPT are potential therapeutic targets for SCZ. Our study not only showed the power of cross-ancestry GWAS in deciphering the genetic aetiology of SCZ, but also uncovered new genetic risk loci, potential causal variants and genes and therapeutic targets for SCZ.

Genome-wide association testing beyond SNPs

Decades of genetic association testing in human cohorts have provided important insights into the genetic architecture and biological underpinnings of complex traits and diseases. However, for certain traits, genome-wide association studies (GWAS) for common SNPs are approaching signal saturation, which underscores the need to explore other types of genetic variation to understand the genetic basis of traits and diseases. Copy number variation (CNV) is an important source of heritability that is well known to functionally affect human traits. Recent technological and computational advances enable the large-scale, genome-wide evaluation of CNVs, with implications for downstream applications such as polygenic risk scoring and drug target identification. Here, we review the current state of CNV-GWAS, discuss current limitations in resource infrastructure that need to be overcome to enable the wider uptake of CNV-GWAS results, highlight emerging opportunities and suggest guidelines and standards for future GWAS for genetic variation beyond SNPs at scale.

Real-World Treatment of Schizophrenia in Adults With a 22q11.2 Microdeletion: Traitement dans le monde réel de la schizophrénie chez des adultes atteints du syndrome de microdélétion 22q11.2

OBJECTIVE

One in every 4 individuals born with a 22q11.2 microdeletion will develop schizophrenia. Thirty years of clinical genetic testing capability have enabled detection of this major molecular susceptibility for psychotic illness. However, there is limited literature on the treatment of schizophrenia in individuals with a 22q11.2 microdeletion, particularly regarding the issue of treatment resistance.

METHODS

From a large, well-characterized adult cohort with a typical 22q11.2 microdeletion followed for up to 25 years at a specialty clinic, we studied all 107 adults (49 females, 45.8%) meeting the criteria for schizophrenia or schizoaffective disorder. We performed a comprehensive review of lifetime (1,801 patient-years) psychiatric records to determine treatments used and the prevalence of treatment-resistant schizophrenia (TRS). We used Clinical Global Impression-Improvement (CGI-I) scores to compare within-individual responses to clozapine and nonclozapine antipsychotics. For a subgroup with contemporary data (n = 88, 82.2%), we examined antipsychotics and dosage at the last follow-up.

RESULTS

Lifetime treatments involved on average 4 different antipsychotic medications per individual. Sixty-three (58.9%) individuals met the study criteria for TRS, a significantly greater proportion than for a community-based comparison (42.9%; χ2 = 10.38, df = 1, p < 0.01). The non-TRS group was enriched for individuals with genetic diagnosis before schizophrenia diagnosis. Within-person treatment response in TRS was significantly better for clozapine than for nonclozapine antipsychotics (p < 0.0001). At the last follow-up, clozapine was the most common antipsychotic prescribed, followed by olanzapine, risperidone, and paliperidone. Total antipsychotic chlorpromazine equivalent dosages were in typical clinical ranges (median: 450 mg; interquartile range: 300, 750 mg).

CONCLUSION

The results for this large sample indicate that patients with 22q11.2 microdeletion have an increased propensity to treatment resistance. The findings provide evidence about how genetic diagnosis can inform clinical psychiatric management and could help reduce treatment delays. Further research is needed to shed light on the pathophysiology of antipsychotic response and on strategies to optimize outcomes.

PLAIN LANGUAGE SUMMARY TITLE

Real-world treatment of schizophrenia in adults with a 22q11.2 microdeletion.

Contribution of copy number variations to education, socioeconomic status and cognition from a genome-wide study of 305,401 subjects

Educational attainment (EA), socioeconomic status (SES) and cognition are phenotypically and genetically linked to health outcomes. However, the role of copy number variations (CNVs) in influencing EA/SES/cognition remains unclear. Using a large-scale (n = 305,401) genome-wide CNV-level association analysis, we discovered 33 CNV loci significantly associated with EA/SES/cognition, 20 of which were novel (deletions at 2p22.2, 2p16.2, 2p12, 3p25.3, 4p15.2, 5p15.33, 5q21.1, 8p21.3, 9p21.1, 11p14.3, 13q12.13, 17q21.31, and 20q13.33, as well as duplications at 3q12.2, 3q23, 7p22.3, 8p23.1, 8p23.2, 17q12 (105 kb), and 19q13.32). The genes identified in gene-level tests were enriched in biological pathways such as neurodegeneration, telomere maintenance and axon guidance. Phenome-wide association studies further identified novel associations of EA/SES/cognition-associated CNVs with mental and physical diseases, such as 6q27 duplication with upper respiratory disease and 17q12 (105 kb) duplication with mood disorders. Our findings provide a genome-wide CNV profile for EA/SES/cognition and bridge their connections to health. The expanded candidate CNVs database and the residing genes would be a valuable resource for future studies aimed at uncovering the biological mechanisms underlying cognitive function and related clinical phenotypes.

Proposal for a Novel Classification of Patients With Enlarged Ventricles and Cognitive Impairment Based on Data-Driven Analysis of Neuroimaging Results in Patients With Psychiatric Disorders

One of the challenges in diagnosing psychiatric disorders is that the results of biological and neuroscience research are not reflected in the diagnostic criteria. Thus, data-driven analyses incorporating biological and cross-disease perspectives, regardless of the diagnostic category, have recently been proposed. A data-driven clustering study based on subcortical volumes in 5604 subjects classified into four brain biotypes associated with cognitive/social functioning. Among the four brain biotypes identified in controls and patients with schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorder, and other psychiatric disorders, we further analyzed the brain biotype 1 subjects, those with an extremely small limbic region, for clinical utility. We found that the representative feature of brain biotype 1 is enlarged lateral ventricles. An enlarged ventricle, defined by an average z-score of left and right lateral ventricle volumes > 3, had a sensitivity of 99.1% and a specificity of 98.1% for discriminating brain biotype 1. However, the presence of an enlarged ventricle was not sufficient to classify patient subgroups, as 1% of the controls also had enlarged ventricles. Reclassification of patients with enlarged ventricles according to cognitive impairment resulted in a stratified subgroup that included patients with a high proportion of schizophrenia diagnoses, electroencephalography abnormalities, and rare pathological genetic copy number variations. Data-driven clustering analysis of neuroimaging data revealed subgroups with enlarged ventricles and cognitive impairment. This subgroup could be a new diagnostic candidate for psychiatric disorders. This concept and strategy may be useful for identifying biologically defined psychiatric disorders in the future.

Copy number variants and the tangential expansion of the cerebral cortex

The tangential expansion of the human cerebral cortex, indexed by its surface area (SA), occurs mainly during prenatal and early postnatal periods, and is influenced by genetic factors. Here we investigate the role of rare copy number variants (CNVs) in shaping SA, and the underlying mechanisms, by aggregating CNVs across the genome in community-based cohorts (N = 39,015). We reveal that genome-wide CNV deletions and duplications are associated with smaller SA. Subsequent analyses with gene expression in fetal cortex suggest that CNVs influence SA by interrupting the proliferation of neural progenitor cells during fetal development. Notably, the deletion of genes with strong (but not weak) coexpression with neural progenitor genes is associated with smaller SA. Follow up analyses reveal similar mechanisms at play in three clinical CNVs, 1q21.1, 16p11.2 and 22q11.2. Together, this study of rare CNVs expands our knowledge about genetic architecture of human cerebral cortex.

Understanding the Emergence of Schizophrenia in the Light of Human Evolution: New Perspectives in Genetics

Schizophrenia is a frequent and disabling disease. The persistence of the disorder despite its harmful consequences represents an evolutionary paradox. Based on recent discoveries in genetics, scientists have formulated the "price-to-pay" hypothesis: schizophrenia would be intimately related to human evolution, particularly to brain development and human-specific higher cognitive functions. The objective of the present work is to question scientific literature about the relationship between schizophrenia and human evolution from a genetic point of view. In the last two decades, research investigated the association between schizophrenia and a few genetic evolutionary markers: Human accelerated regions, segmental duplications, and highly repetitive DNA such as the Olduvai domain. Other studies focused on the action of natural selection on schizophrenia-associated genetic variants, also thanks to the complete sequencing of archaic hominins' genomes (Neanderthal, Denisova). Results suggested that a connection between human evolution and schizophrenia may exist; nonetheless, much research is still needed, and it is possible that a definitive answer to the evolutionary paradox of schizophrenia will never be found.

Behavioral Phenotypes and Comorbidity in 3q29 Deletion Syndrome: Results from the 3q29 Registry

3q29 deletion syndrome (3q29del) is associated with a significantly increased risk for neurodevelopmental and neuropsychiatric disorders. However, the full spectrum of behavioral phenotypes associated with 3q29del is still evolving. Individuals with 3q29del (n = 96, 60.42% male) or their guardian completed the Achenbach Child or Adult Behavior Checklist (CBCL/ABCL) via the online 3q29 registry (3q29deletion.org). Typically developing controls (n = 57, 49.12% male) were ascertained as a comparison group. We analyzed mean performance on the CBCL/ABCL for individuals with 3q29del and controls across composite, DSM-keyed, and developmental scales; and the relationship between CBCL/ABCL performance and clinical and developmental phenotypes for individuals with 3q29del. Individuals with 3q29del showed significantly elevated behavioral and developmental impairment relative to controls across CBCL/ABCL domains. A substantial proportion of study participants with 3q29del scored in the Borderline or Clinical range for composite and DSM-keyed scales, indicating significant behavioral problems that may require clinical evaluation. We found that the preschool CBCL DSM-keyed autism spectrum problems scale is a potential screening tool for autism spectrum disorder (ASD) for individuals with 3q29del; CBCL/ABCL DSM-keyed scales were not accurate screeners for anxiety disorders or attention-deficit/hyperactivity disorder (ADHD) in our study sample. We identified a high degree of psychiatric comorbidity in individuals with 3q29del, with 60.42% (n = 58) of individuals with 3q29del scoring in the Borderline or Clinical range on two or more DSM-keyed CBCL/ABCL scales. Finally, we found that the degree of developmental delay in participants with 3q29del does not explain the increased behavioral problems observed on the CBCL/ABCL. The CBCL/ABCL can be used as screening tools in populations such as 3q29del, even in the presence of substantial psychiatric comorbidity. These results expand our understanding of the phenotypic spectrum of 3q29del and demonstrate an effective method for recruiting and phenotyping a large sample of individuals with a rare genetic disorder.

The Contribution of Mosaic Chromosomal Alterations to Schizophrenia

BACKGROUND

Mosaic chromosomal alterations are implicated in neuropsychiatric disorders, but the contribution to schizophrenia (SCZ) risk for somatic copy number variations (sCNVs) emerging in early developmental stages has not been fully established.

METHODS

We analyzed blood-derived genotype arrays from 9715 patients with SCZ and 28,822 control participants of Chinese descent using a computational tool (MoChA) based on long-range chromosomal information to detect mosaic chromosomal alterations. We focused on probable early developmental sCNVs through stringent filtering. We assessed the burden of sCNVs across varying cell fraction cutoffs, as well as the frequency with which genes were involved in sCNVs. We integrated this data with the PGC (Psychiatric Genomics Consortium) dataset, which comprises 12,834 SCZ cases and 11,648 controls of European descent, and complemented it with genotyping data from postmortem brain tissue of 936 participants (449 cases and 487 controls).

RESULTS

Patients with SCZ had a significantly higher somatic losses detection rate than control participants (1.00% vs. 0.52%; odds ratio = 1.91; 95% CI, 1.47-2.49; two-sided Fisher's exact test, p = 1.49 × 10-6). Further analysis indicated that the odds ratios escalated proportionately (from 1.91 to 2.78) with the increment in cell fraction cutoffs. Recurrent sCNVs associated with SCZ (odds ratio > 8; Fisher's exact test, p < .05) were identified, including notable regions at 10q21.1 (ZWINT), 3q26.1 (SLITRK3), 1q31.1 (BRINP3) and 12q21.31-21.32 (MGAT4C and NTS) in the Chinese cohort, and some regions were validated with PGC data. Cross-tissue validation pinpointed somatic losses at loci like 1p35.3-35.2 and 19p13.3-13.2.

CONCLUSIONS

The study highlights the significant impact of mosaic chromosomal alterations on SCZ, suggesting their pivotal role in the disorder's genetic etiology.

Connecting genomic results for psychiatric disorders to human brain cell types and regions reveals convergence with functional connectivity

Identifying cell types and brain regions critical for psychiatric disorders and brain traits is essential for targeted neurobiological research. By integrating genomic insights from genome-wide association studies with a comprehensive single-cell transcriptomic atlas of the adult human brain, we prioritized specific neuronal clusters significantly enriched for the SNP-heritabilities for schizophrenia, bipolar disorder, and major depressive disorder along with intelligence, education, and neuroticism. Extrapolation of cell-type results to brain regions reveals the whole-brain impact of schizophrenia genetic risk, with subregions in the hippocampus and amygdala exhibiting the most significant enrichment of SNP-heritability. Using functional MRI connectivity, we further confirmed the significance of the central and lateral amygdala, hippocampal body, and prefrontal cortex in distinguishing schizophrenia cases from controls. Our findings underscore the value of single-cell transcriptomics in understanding the polygenicity of psychiatric disorders and suggest a promising alignment of genomic, transcriptomic, and brain imaging modalities for identifying common biological targets.

NeuropsychopharmARCology: Shaping Neuroplasticity through Arc/ Arg3.1 Modulation

Activity-regulated cytoskeleton-associated protein (aka activity-regulated gene Arg3.1) belongs to the effector gene family of the immediate early genes. This family encodes effector proteins, which act directly on cellular homeostasis and function. Arc/Arg3.1 is localized at dendritic processes, allowing the protein local synthesis on demand, and it is considered a reliable index of activity- dependent synaptic changes. Evidence also exists showing the critical role of Arc/Arg3.1 in memory processes. The high sensitivity to changes in neuronal activity, its specific localization as well as its involvement in long-term synaptic plasticity indeed make this effector gene a potential, critical target of the action of psychotropic drugs. In this review, we focus on antipsychotic and antidepressant drugs as well as on psychostimulants, which belong to the category of drugs of abuse but can also be used as drugs for specific disorders of the central nervous system (i.e., Attention Deficit Hyperactivity Disorder). It is demonstrated that psychotropic drugs with different mechanisms of action converge on Arc/Arg3.1, providing a means whereby Arc/Arg3.1 synaptic modulation may contribute to their therapeutic activity. The potential translational implications for different neuropsychiatric conditions are also discussed, recognizing that the treatment of these disorders is indeed complex and involves the simultaneous regulation of several dysfunctional mechanisms.

Rare nonsynonymous germline and mosaic de novo variants in Japanese patients with schizophrenia

AIM

Whole-exome sequencing (WES) studies have revealed that germline de novo variants (gDNVs) contribute to the genetic etiology of schizophrenia. However, the contribution of mosaic DNVs (mDNVs) to the risk of schizophrenia remains to be elucidated. In the present study, we systematically investigated the gDNVs and mDMVs that contribute to the genetic etiology of schizophrenia in a Japanese population.

METHODS

We performed deep WES (depth: 460×) of 73 affected offspring and WES (depth: 116×) of 134 parents from 67 families with schizophrenia. Prioritized rare nonsynonymous gDNV and mDNV candidates were validated using Sanger sequencing and ultra-deep targeted amplicon sequencing (depth: 71,375×), respectively. Subsequently, we performed a Gene Ontology analysis of the gDNVs and mDNVs to obtain biological insights. Lastly, we selected DNVs in known risk genes for psychiatric and neurodevelopmental disorders.

RESULTS

We identified 62 gDNVs and 98 mDNVs. The Gene Ontology analysis of mDNVs implicated actin filament and actin cytoskeleton as candidate biological pathways. There were eight DNVs in known risk genes: splice region gDNVs in AKAP11 and CUL1; a frameshift gDNV in SHANK1; a missense gDNV in SRCAP; missense mDNVs in CTNNB1, GRIN2A, and TSC2; and a nonsense mDNV in ZFHX4.

CONCLUSION

Our results suggest the potential contributions of rare nonsynonymous gDNVs and mDNVs to the genetic etiology of schizophrenia. This is the first report of the mDNVs in schizophrenia trios, demonstrating their potential relevance to schizophrenia pathology.

Analysis of exonic deletions in a large population study provides novel insights into NRXN1 pathology

The NRXN1 locus is a hotspot for non-recurrent copy number variants and exon-disrupting NRXN1 deletions have been associated with increased risk of neurodevelopmental disorders in case-control studies. However, corresponding population-based estimates of prevalence and disease-associated risk are currently lacking. Also, most studies have not differentiated between deletions affecting exons of different NRXN1 splice variants nor considered intronic deletions. We used the iPSYCH2015 case-cohort sample to obtain unbiased estimates of the prevalence of NRXN1 deletions and their associated risk of autism, schizophrenia, depression, and ADHD. Most exon-disrupting deletions affected exons specific to the alpha isoform, and almost half of the non-exonic deletions represented a previously reported segregating founder deletion. Carriage of exon-disrupting NRXN1 deletions was associated with a threefold and twofold increased risk of autism and ADHD, respectively, whereas no significantly increased risk of depression or schizophrenia was observed. Our results highlight the importance of using population-based samples in genetic association studies.

Hearing problems in humans and mouse models with rare copy number variants associated with schizophrenia: a scoping review protocol

Background

Hearing loss is a risk factor for developing auditory hallucinations and other psychosis symptoms. To date, very little research has investigated hearing loss in individuals with a high genetic risk of developing schizophrenia and other types of psychosis. 13 copy number variant (CNV) loci are robustly associated with an increased risk of schizophrenia. Of these, microdeletions at 22q11.2 often lead to some hearing loss, and mouse models of this CNV display impaired auditory functioning. We hypothesise that individuals who have a high genetic risk of schizophrenia may also experience hearing problems. This scoping review will explore whether the 13 schizophrenia-associated CNVs are related to hearing problems, including peripheral hearing loss and other auditory problems, in humans and related mouse models.

Methods

Our scoping review will follow guidelines provided by the Joanna Briggs Institute and the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews. A systematic search will be completed using PubMed (MEDLINE), Embase, PsychINFO, and Cochrane Library databases, as well as other sources to identify relevant grey literature. Search terms will include all commonly used synonyms for hearing loss and problems with auditory perception, and both human and mouse studies that describe relevant CNVs will be included. Search lists will be screened by two authors independently, according to eligibility criteria, and data will be extracted and summarised using a narrative approach.

Conclusions

To our knowledge, this will be the first scoping review to explore auditory functioning across all CNVs that confer high schizophrenia risk. Looking ahead, if hearing problems are a clinical feature in these groups (including humans and related mouse models), they may serve as useful genetic models for future mechanistic studies.

Effects of gene dosage on cognitive ability: A function-based association study across brain and non-brain processes

Copy-number variants (CNVs) that increase the risk for neurodevelopmental disorders also affect cognitive ability. However, such CNVs remain challenging to study due to their scarcity, limiting our understanding of gene-dosage-sensitive biological processes linked to cognitive ability. We performed a genome-wide association study (GWAS) in 258,292 individuals, which identified-for the first time-a duplication at 2q12.3 associated with higher cognitive performance. We developed a functional-burden analysis, which tested the association between cognition and CNVs disrupting 6,502 gene sets biologically defined across tissues, cell types, and ontologies. Among those, 864 gene sets were associated with cognition, and effect sizes of deletion and duplication were negatively correlated. The latter suggested that functions across all biological processes were sensitive to either deletions (e.g., subcortical regions, postsynaptic) or duplications (e.g., cerebral cortex, presynaptic). Associations between non-brain tissues and cognition were driven partly by constrained genes, which may shed light on medical comorbidities in neurodevelopmental disorders.

Copy Number Variations and Human Well-Being: Integrating Psychiatric, Physical, and Socioeconomic Perspectives

Copy number variations (CNVs) have emerged as crucial genetic factors that influence a wide spectrum of human health outcomes, with particularly strong associations to psychiatric disorders. In this review, we present a synthesis of diverse impacts of psychiatric disorder-associated CNVs on neurodevelopment, brain function, and physical health across the lifespan. Large-scale studies have revealed that CNV carriers exhibit an increased risk for psychiatric disorders, cognitive deficits, sleep disturbances, neurological disorders, and other physical conditions, including cardiovascular diseases, diabetes, and renal disease, highlighting the wide-ranging impact of CNVs beyond the brain. Neuroimaging studies have revealed substantial CNV effects on brain structure, from cortical and subcortical alterations to white matter microstructure, with effect sizes often exceeding those observed in idiopathic psychiatric disorders. Cellular and animal models have begun to elucidate dynamic CNV effects on neurodevelopment, neuronal function, and cellular energy metabolism, while revealing complex CNV-environment interactions and cell type-specific responses, particularly in studies of 22q11.2 deletion syndrome. This review also explores the complex interplay between psychiatric and physical health conditions in CNV carriers and how these interactions contribute to adverse socioeconomic outcomes, including reduced educational attainment and income levels, creating a feedback loop that further impacts health outcomes. Finally, in this review, we also highlight research limitations and propose key priorities for clinical implementation, including the need for longitudinal studies, standardized guidelines for CNV result reporting and genetic counseling, and integrated care networks to provide a foundation for advancing the field of precision psychiatry.