Autistic traits as predictors of persistent depression.

Persistent depression has been suggested to be associated with autistic traits in people of working age. This study aimed to clarify which autistic characteristics at the initial visit were associated with persistent depression at the 12 week follow-up in a primary care setting. Newly depressed outpatients aged 24-59 years with no history of autism were asked to complete the 50-item autism spectrum quotient (AQ) and the Beck depression inventory (BDI) at baseline and 12 week follow-up (N = 123, males: 48%, age: 37.7 ± 9.15 years). Nearly 40% of participants had an AQ score ≥ 26. Significant differences were observed between the group with remitted depression (N = 43) and those with persistent depression (N = 80) in educational years and AQ "attention switching" and "attention to detail" subscale scores. In addition, a statistically significant decrease in the total AQ and the "communication" and "imagination" scores were observed in the remitted group, while no such change was observed in the group with persistent depression. It remains unclear whether the self-perceived severity of communication and imagination traits in persistent depression was due to the state of persistent depression or a kind of premorbid autistic trait. The results suggest that high levels of autistic traits are frequently present in adults with depression. High "attention switching" and "attention to detail" scores in AQ screening at the first visit might predict the persistence of depressive symptoms after 12 weeks in adults with depression, while total AQ scores, especially for "communication" and "imagination" items, might be state-dependent.

Psychosocial characteristics of alcoholic and non-alcoholic liver disease recipient candidates in liver transplantation: a prospective observational study.

BACKGROUND: There are long-standing controversies about the transplant indications for alcoholic liver disease (ALD), because of the recognition that ALD is fundamentally self-inflicted. However, it is unclear whether psychosocial characteristics of ALD are different from that of non-alcoholic liver disease (NALD) in the selection of liver transplantation (LT) recipients. We aimed to clarify the psychosocial characteristics of ALD recipients (ALD-R)/ALD recipient candidates (ALD-RC) and NALD recipients (NALD-R)/ NALD recipient candidates (NALD-RC). METHODS: From 2011 to 2019, 75 patients were enrolled in this prospective observational study (ALD-RC, n = 19; NALD-RC, n = 56), LT were carried out as follow; ALD-R, n = 6; NALD-R, n = 52. We evaluated psychosocial characteristics in the preoperative period and 3, 12 months after LT (ALD-R, n = 3/3; NALD-R, n = 28/25). The following scales were used to evaluate psychosocial characteristics: Visual Analogue Scale, Alcohol Use Disorders Identification Test, Hospital Anxiety and Depression Scale, Beck Depression Inventory, Brief Evaluation of Medication Influences and Beliefs, Social Support Questionnaire (SSQ), Temperament and Character Inventory, Parental Bonding Instrument (PBI), the Short Form Health Survey (SF-36). RESULTS: When evaluating on the basis of abstinence rule, a comparison of ALD-RC and NALD-RC in the preoperative period identified similar patterns of psychosocial characteristics, except that the NALD-RC scored higher on the PBI item "overprotection from mother" (P < 0.05). The only significant difference between ALD-R and NALD-R after liver transplantation was in SSQ scores at 3 months. CONCLUSION: The psychosocial characteristics of ALD-RC and NALD-RC may be similar when evaluated on the basis of Japan's abstinence rule. This result also imply that the psychosocial characteristics of ALD-RC may differ from the previously reported psychosocial characteristics of alcohol dependent patients. These findings have the potential to provide helpful information for the evaluation of ALD-RC.

Generation and analysis of novel Reln-deleted mouse model corresponding to exonic Reln deletion in schizophrenia.

AIM: A Japanese individual with schizophrenia harboring a novel exonic deletion in RELN was recently identified by genome-wide copy-number variation analysis. Thus, the present study aimed to generate and analyze a model mouse to clarify whether Reln deficiency is associated with the pathogenesis of schizophrenia. METHODS: A mouse line with a novel RELN exonic deletion (Reln-del) was established using the CRISPR/Cas9 method to elucidate the underlying molecular mechanism. Subsequently, general behavioral tests and histopathological examinations of the model mice were conducted and phenotypic analysis of the cerebellar granule cell migration was performed. RESULTS: The phenotype of homozygous Reln-del mice was similar to that of reeler mice with cerebellar atrophy, dysplasia of the cerebral layers, and abrogated protein levels of cerebral reelin. The expression of reelin in heterozygous Reln-del mice was approximately half of that in wild-type mice. Conversely, behavioral analyses in heterozygous Reln-del mice without cerebellar atrophy or dysplasia showed abnormal social novelty in the three-chamber social interaction test. In vitro reaggregation formation and neuronal migration were severely altered in the cerebellar cultures of homozygous Reln-del mice. CONCLUSION: The present results in novel Reln-del mice modeled after our patient with a novel exonic deletion in RELN are expected to contribute to the development of reelin-based therapies for schizophrenia.

Possible involvement of a cell adhesion molecule, Migfilin, in brain development and pathogenesis of autism spectrum disorders.

Migfilin, encoded by FBLIM1 at the 1p36 locus, is a multi-domain adaptor protein essential for various cellular processes such as cell morphology and migration. Small deletions and duplications at the 1p36 locus, monosomy of which results in neurodevelopmental disorders and multiple congenital anomalies, have also been identified in patients with autism spectrum disorder (ASD). However, the impact of FBLIM1, the gene within 1p36, on the pathogenesis of ASD is unknown. In this study, we performed morphological analyses of migfilin to elucidate its role in brain development. Migfilin was detected specifically in the embryonic and perinatal stages of the mouse brain. Either silencing or overexpression of migfilin in embryos following in utero electroporation disrupted Neocortical neuronal migration. Additionally, neurite elongation was impaired when migfilin was silenced in cultured mouse hippocampal neurons. We then screened FBLIM1 for rare exonic deletions/duplications in 549 Japanese ASD patients and 824 controls, detecting one case of ASD and intellectual delay that harbored a 26-kb deletion at 1p36.21 that solely included the C-terminal exon of FBLIM1. The FBLIM1 mRNA expression level in this case was reduced compared to levels in individuals without FBLIM1 deletion. Our findings indicate that tightly regulated expression of migfilin is essential for neuronal development and that FBLIM1 disruption may be related to the phenotypes associated with ASD and related neurodevelopmental disorders.

Investigation of single-nucleotide variants in MBD5 associated with autism spectrum disorders and schizophrenia phenotypes.

MBD5 (Methyl-CpG-binding domain 5) is a critical gene for normal development. While deletion or duplication of MBD5 may contribute to a genetic predisposition to autism spectrum disorders (ASD), intellectual disability, or epilepsy, the impact of rare MBD5 single nucleotide variants (SNVs) on neurodevelopmental features, particularly features with late onset, has not been fully explored. In this study, we conducted exon-targeted resequencing of MBD5 with next-generation sequencing technology in 562 Japanese patients (192 with idiopathic ASD and 370 with schizophrenia (SCZ)) and detected 16 MBD5 SNVs with allele frequencies of ≤1%. We then performed phenotype analyses with 12 novel variants of these 16 SNVs. SCZ patients with these variants exhibited mainly within normal development ranges until the first psychosis and ASD patients with SNVs did not precisely overlap with the core characteristics described in previous literature as being associated with MBD5 SNVs. Our results suggested that MBD5 variants might contribute to a broad spectrum of neurodevelopmental pathophysiology. Further research and assessment of clinical diagnostic screening are necessary for understanding the burden of rare MBD5 SNVs for these neurodevelopmental disorders.

Machine learning algorithm-based estimation model for the severity of depression assessed using Montgomery-Asberg depression rating scale.

AIM: Depressive disorder is often evaluated using established rating scales. However, consistent data collection with these scales requires trained professionals. In the present study, the "rater & estimation-system" reliability was assessed between consensus evaluation by trained psychiatrists and the estimation by 2 models of the AI-MADRS (Montgomery-Asberg Depression Rating Scale) estimation system, a machine learning algorithm-based model developed to assess the severity of depression. METHODS: During interviews with trained psychiatrists and the AI-MADRS estimation system, patients responded orally to machine-generated voice prompts from the AI-MADRS structured interview questions. The severity scores estimated from two models of the AI-MADRS estimation system, the max estimation model and the average estimation model, were compared with those by trained psychiatrists. RESULTS: A total of 51 evaluation interviews conducted on 30 patients were analyzed. Pearson's correlation coefficient with the scores evaluated by trained psychiatrists was 0.76 (95% confidence interval 0.62-0.86) for the max estimation model, and 0.86 (0.76-0.92) for the average estimation model. The ANOVA ICC rater & estimation-system reliability with the evaluation scores by trained psychiatrists was 0.51 (-0.09 to 0.79) for the max estimation model, and 0.75 (0.55-0.86) for the average estimation model. CONCLUSION: The average estimation model of AI-MADRS demonstrated substantially acceptable rater & estimation-system reliability with trained psychiatrists. Accumulating a broader training dataset and the refinement of AI-MADRS interviews are expected to improve the performance of AI-MADRS. Our findings suggest that AI technologies can significantly modernize and potentially revolutionize the realm of depression assessments.

Molecular diagnosis of 405 individuals with autism spectrum disorder.

Autism spectrum disorder (ASD) is caused by combined genetic and environmental factors. Genetic heritability in ASD is estimated as 60-90%, and genetic investigations have revealed many monogenic factors. We analyzed 405 patients with ASD using family-based exome sequencing to detect disease-causing single-nucleotide variants (SNVs), small insertions and deletions (indels), and copy number variations (CNVs) for molecular diagnoses. All candidate variants were validated by Sanger sequencing or quantitative polymerase chain reaction and were evaluated using the American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines for molecular diagnosis. We identified 55 disease-causing SNVs/indels in 53 affected individuals and 13 disease-causing CNVs in 13 affected individuals, achieving a molecular diagnosis in 66 of 405 affected individuals (16.3%). Among the 55 disease-causing SNVs/indels, 51 occurred de novo, 2 were compound heterozygous (in one patient), and 2 were X-linked hemizygous variants inherited from unaffected mothers. The molecular diagnosis rate in females was significantly higher than that in males. We analyzed affected sibling cases of 24 quads and 2 quintets, but only one pair of siblings shared an identical pathogenic variant. Notably, there was a higher molecular diagnostic rate in simplex cases than in multiplex families. Our simulation indicated that the diagnostic yield is increasing by 0.63% (range 0-2.5%) per year. Based on our simple simulation, diagnostic yield is improving over time. Thus, periodical reevaluation of ES data should be strongly encouraged in undiagnosed ASD patients.

A systematic review and network meta-analysis of antimanic drugs for the treatment of acute mania used in Japan.

This review aimed to clarify whether antimanic agents used in Japan are superior to placebo for the treatment of acute mania, based on reports of randomized controlled trials (RCTs) conducted in Japan and other East Asian countries. A literature search was conducted using the MEDLINE, PubMed, and Ichushi databases from their dates of inception to July 31, 2021, for studies written in English or Japanese with a primary diagnosis of bipolar I disorder, comparing any of the following active drugs to treat acute mania in adults: aripiprazole, carbamazepine, chlorpromazine, haloperidol, lithium, olanzapine, sultopride, timiperone, and zotepine. A random-effects network meta-analysis was performed within a frequentist framework. The quality of each included study was evaluated using the revised Cochrane risk-of-bias tool for randomized trials. The outcomes adopted were the response rate for efficacy and dropout rate for tolerability during 3 weeks from baseline. Eleven RCTs, totaling 1148 participants, were reviewed. The pooled odds ratio (OR) (±95% confidence interval [CI]) was calculated. Timiperone (OR = 4.53, CI 1.09-18.80), sultopride (OR = 3.76, CI 1.08-13.05), and aripiprazole (OR = 1.99, CI 1.22-3.24) were significantly more effective than placebo. Olanzapine (OR = 0.51, CI 0.29-0.90) was significantly superior in acceptability to placebo. The results showed no significant differences from placebo for carbamazepine, chlorpromazine, haloperidol, lithium, and olanzapine. These results suggest that noninferiority trials alone cannot always confirm the antimanic drug efficacy and that direct placebo-controlled trials are necessary to verify the antimanic efficacy of the drugs.

Exome sequencing of Japanese schizophrenia multiplex families supports the involvement of calcium ion channels.

BACKGROUND: Most sequencing studies of schizophrenia (SCZ) have focused on de novo genetic variants due to interpretability. However, investigating shared rare variants among patients in the same multiplex family is also important. Relatively large-scale analyses of SCZ multiplex families have been done in Caucasian populations, but whether detected variants are also pathogenic in the Japanese population is unclear because of ethnic differences in rare variants. MATERIALS AND METHODS: We performed whole-exome sequencing (WES) of 14 Japanese SCZ multiplex families. After quality control and filtering, we identified rare variants shared among affected persons within the same family. A gene ontology (GO) analysis was performed to identify gene categories possibly affected by these candidate variants. RESULTS: We found 530 variants in 486 genes as potential candidate variants from the 14 SCZ multiplex families examined. The GO analysis demonstrated significant enrichment in calcium channel activity. CONCLUSION: This study provides supporting evidence that calcium ion channel activity is involved in SCZ. WES of multiplex families is a potential means of identifying disease-associated rare variants for SCZ.

Investigation of OLIG2 as a candidate gene for schizophrenia and autism spectrum disorder.

A number of genomic mutations that are thought to be strongly involved in the development of schizophrenia (SCZ) and autism spectrum disorder (ASD) have been identified. Abnormalities involving oligodendrocytes have been reported in SCZ, and as a related gene, oligodendrocyte lineage transcription factor 2 (OLIG2) has been reported to be strongly associated with SCZ. In this study, based on the common disease-rare variant hypothesis, target sequencing of candidate genes was performed to identify rare mutations with a high effect size and the possibility that the identified mutations may increase the risks of SCZ and ASD in the Japanese population. In this study, the exon region of OLIG2 was targeted; 370 patients with SCZ and 192 with ASD were subjected to next-generation sequencing. As a result, one rare missense mutation (A33T) was detected. We used the Sanger method to validate this missense mutation with a low frequency (<1%), and then carried out a genetic association analysis involving 3299 unrelated individuals (1447 with SCZ, 380 with ASD, and 1472 healthy controls) to clarify whether A33T was associated with SCZ or ASD. A33T was not found in either case group, and in only one control. We did not find evidence that p.A33T is involved in the onset of ASD or SCZ; however, associations with this variant need to be evaluated in larger samples to confirm our results.

Exome sequencing analysis of Japanese autism spectrum disorder case-control sample supports an increased burden of synaptic function-related genes.

Autism spectrum disorder (ASD) is a highly heritable, complex disorder in which rare variants contribute significantly to disease risk. Although many genes have been associated with ASD, there have been few genetic studies of ASD in the Japanese population. In whole exomes from a Japanese ASD sample of 309 cases and 299 controls, rare variants were associated with ASD within specific neurodevelopmental gene sets, including highly constrained genes, fragile X mental retardation protein target genes, and genes involved in synaptic function, with the strongest enrichment in trans-synaptic signaling (p = 4.4 × 10-4, Q-value = 0.06). In particular, we strengthen the evidence regarding the role of ABCA13, a synaptic function-related gene, in Japanese ASD. The overall results of this case-control exome study showed that rare variants related to synaptic function are associated with ASD susceptibility in the Japanese population.

Identification of ultra-rare disruptive variants in voltage-gated calcium channel-encoding genes in Japanese samples of schizophrenia and autism spectrum disorder.

Several large-scale whole-exome sequencing studies in patients with schizophrenia (SCZ) and autism spectrum disorder (ASD) have identified rare variants with modest or strong effect size as genetic risk factors. Dysregulation of cellular calcium homeostasis might be involved in SCZ/ASD pathogenesis, and genes encoding L-type voltage-gated calcium channel (VGCC) subunits Cav1.1 (CACNA1S), Cav1.2 (CACNA1C), Cav1.3 (CACNA1D), and T-type VGCC subunit Cav3.3 (CACNA1I) recently were identified as risk loci for psychiatric disorders. We performed a screening study, using the Ion Torrent Personal Genome Machine (PGM), of exon regions of these four candidate genes (CACNA1C, CACNA1D, CACNA1S, CACNA1I) in 370 Japanese patients with SCZ and 192 with ASD. Variant filtering was applied to identify biologically relevant mutations that were not registered in the dbSNP database or that have a minor allele frequency of less than 1% in East-Asian samples from databases; and are potentially disruptive, including nonsense, frameshift, canonical splicing site single nucleotide variants (SNVs), and non-synonymous SNVs predicted as damaging by five different in silico analyses. Each of these filtered mutations were confirmed by Sanger sequencing. If parental samples were available, segregation analysis was employed for measuring the inheritance pattern. Using our filter, we discovered one nonsense SNV (p.C1451* in CACNA1D), one de novo SNV (p.A36V in CACNA1C), one rare short deletion (p.E1675del in CACNA1D), and 14 NSstrict SNVs (non-synonymous SNV predicted as damaging by all of five in silico analyses). Neither p.A36V in CACNA1C nor p.C1451* in CACNA1D were found in 1871 SCZ cases, 380 ASD cases, or 1916 healthy controls in the independent sample set, suggesting that these SNVs might be ultra-rare SNVs in the Japanese population. The neuronal splicing isoform of Cav1.2 with the p.A36V mutation, discovered in the present study, showed reduced Ca2+-dependent inhibition, resulting in excessive Ca2+ entry through the mutant channel. These results suggested that this de novo SNV in CACNA1C might predispose to SCZ by affecting Ca2+ homeostasis. Thus, our analysis successfully identified several ultra-rare and potentially disruptive gene variants, lending partial support to the hypothesis that VGCC-encoding genes may contribute to the risk of SCZ/ASD.

Cross-Disorder Analysis of Genic and Regulatory Copy Number Variations in Bipolar Disorder, Schizophrenia, and Autism Spectrum Disorder.

BACKGROUND: We aimed to determine the similarities and differences in the roles of genic and regulatory copy number variations (CNVs) in bipolar disorder (BD), schizophrenia (SCZ), and autism spectrum disorder (ASD). METHODS: Based on high-resolution CNV data from 8708 Japanese samples, we performed to our knowledge the largest cross-disorder analysis of genic and regulatory CNVs in BD, SCZ, and ASD. RESULTS: In genic CNVs, we found an increased burden of smaller (<100 kb) exonic deletions in BD, which contrasted with the highest burden of larger (>500 kb) exonic CNVs in SCZ/ASD. Pathogenic CNVs linked to neurodevelopmental disorders were significantly associated with the risk for each disorder, but BD and SCZ/ASD differed in terms of the effect size (smaller in BD) and subtype distribution of CNVs linked to neurodevelopmental disorders. We identified 3 synaptic genes (DLG2, PCDH15, and ASTN2) as risk factors for BD. Whereas gene set analysis showed that BD-associated pathways were restricted to chromatin biology, SCZ and ASD involved more extensive and similar pathways. Nevertheless, a correlation analysis of gene set results indicated weak but significant pathway similarities between BD and SCZ or ASD (r = 0.25-0.31). In SCZ and ASD, but not BD, CNVs were significantly enriched in enhancers and promoters in brain tissue. CONCLUSIONS: BD and SCZ/ASD differ in terms of CNV burden, characteristics of CNVs linked to neurodevelopmental disorders, and regulatory CNVs. On the other hand, they have shared molecular mechanisms, including chromatin biology. The BD risk genes identified here could provide insight into the pathogenesis of BD.

Peripheral biomarkers of attention-deficit hyperactivity disorder: Current status and future perspective.

Attention-deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders, characterized by a persistent pattern of inattention, hyperactivity, and impulsivity. Since the diagnosis of ADHD is defined by operational diagnostic criteria consisting of several clinical symptoms, a number of heterogeneous mechanisms have been considered to be implicated in its pathophysiology. Although no clinically reliable biomarkers are available for the diagnosis of ADHD, several plausible candidate biomarkers have been proposed based on recent advances in biochemistry and molecular biology. This review article summarizes potential peripheral biomarkers associated with ADHD, mainly from recently published case-control studies. These include 1) biochemical markers: neurotransmitters and their receptors, neurotrophic factors, serum electrolytes, and inflammation markers; 2) genetic and epigenetic markers: microRNA, mRNA expression, and peripheral DNA methylation; 3) physiological markers: eye movement and electroencephalography. It also discusses the limitations and future directions of these potential biomarkers for application in clinical practice.

Depressive mood changes are associated with self-perceptions of ADHD characteristics in adults.

Subjective attention deficit/hyperactivity disorder (ADHD) symptoms seen in adult depressive patients have often become a pathophysiological topic in recent years. Screening questionnaires are widely used for detecting ADHD; however, the risk of misdiagnosis exists. The present study examined whether self-perceptions of ADHD-related characteristics were consistent regardless of changes in the severity of depressive symptoms. Between April to October 2018, newly diagnosed depressed outpatients aged 24-59 years with good social functioning and without a history of ADHD were asked to fill out the Adult ADHD Self-Report Scale version 1.1 (ASRS) and the Beck Depression Inventory (BDI) at baseline (n = 726) and 12-week follow-up (n = 202). A statistically significant correlation was found between a change in BDI and ASRS scores (score at baseline minus score at the endpoint; r = .57). In addition, the higher the rate of improvement in BDI, the lower the frequency of positive screening for ADHD by ASRS. This study showed that subjective ADHD symptoms were correlated with depressive states. Diagnostic evaluation of comorbid ADHD using self-report scales in a primary care setting should be made with caution.

Establishment of in-hospital clinical network for patients with neurofibromatosis type 1 in Nagoya University Hospital.

Neurofibromatosis type 1 (NF1) is a genetic multisystem disorder. Clinicians must be aware of the diverse clinical features of this disorder in order to provide optimal care for it. We have set up an NF1 in-hospital medical care network of specialists regardless of patient age, launching a multidisciplinary approach to the disease for the first time in Japan. From January 2014 to December 2020, 246 patients were enrolled in the NF1 patient list and medical records. Mean age was 26.0 years ranging from 3 months to 80 years. The number of patients was higher as age at first visit was lower. There were 107 males (41%) and 139 females. After 2011, the number of patients has increased since the year when the medical care network was started. Regarding orthopedic signs, scoliosis was present in 60 cases (26%), and bone abnormalities in the upper arm, forearm, and tibia in 8 cases (3.5%). Neurofibromas other than cutaneous neurofibromas were present in 90 cases (39%), and MPNST in 17 cases (7.4%). We launched a multidisciplinary NF1 clinic system for the first time in Japan. For patients with NF1, which is a hereditary and systemic disease associated with a high incidence of malignant tumors, it will be of great benefit when the number of such clinics in Japan and the rest of Asia is increased.

Clinical Features and Long-Term Outcomes of Living Donors of Liver Transplantation Who Developed Psychiatric Disorders.

BACKGROUND In the field of living donor liver transplantation (LDLT), it is important to ensure donor's psychological well-being. We report on clinical features and long-term outcomes of LDLT donors who developed psychiatric disorders after their donor operations. Additionally, we compare patient backgrounds, as well as surgical and perioperative aspects between LDLT donors with and without postoperative psychiatric complications. MATERIAL AND METHODS Between November 1998 and March 2018, we identified 254 LDLT donors at our hospital. Among these, we investigated those who had newly developed psychiatric complications and required psychiatric treatment after donor operation. RESULTS The median duration of follow-up was 4 years. Sixty-five donors were lost to follow-up. Eight donors (3.1%) developed postoperative psychiatric complications, including major depressive disorder in 4, panic disorder in 2, conversion disorder and panic disorder in 1, and adjustment disorder in 1. The median duration from donor surgery to psychiatric diagnosis was 104.5 days (range, 12 to 657 days) and the median treatment duration was 18 months (range, 3 to 168 months). Of those, 3 donors required psychiatric treatment over 10 years, and 4 donors remained under treatment. The duration of hospital stay after donor operation was significantly longer and perioperative complications with Clavien classification greater than grade IIIa were more frequent in donors with psychiatric complications than in those without psychiatric complications (P=0.02 and P=0.006, respectively). CONCLUSIONS Accurate diagnosis and appropriate treatment for psychiatric disorders by psychiatrists and psychologists are important during LDLT donor follow-up. Minimization of physiological complications might be important to prevent postoperative psychiatric complications in LDLT donors.

Functional characterization of rare NRXN1 variants identified in autism spectrum disorders and schizophrenia.

BACKGROUND: Rare genetic variants contribute to the etiology of both autism spectrum disorder (ASD) and schizophrenia (SCZ). Most genetic studies limit their focus to likely gene-disrupting mutations because they are relatively easier to interpret their effects on the gene product. Interpretation of missense variants is also informative to some pathophysiological mechanisms of these neurodevelopmental disorders; however, their contribution has not been elucidated because of relatively small effects. Therefore, we characterized missense variants detected in NRXN1, a well-known neurodevelopmental disease-causing gene, from individuals with ASD and SCZ. METHODS: To discover rare variants with large effect size and to evaluate their role in the shared etiopathophysiology of ASD and SCZ, we sequenced NRXN1 coding exons with a sample comprising 562 Japanese ASD and SCZ patients, followed by a genetic association analysis in 4273 unrelated individuals. Impact of each missense variant detected here on cell surface expression, interaction with NLGN1, and synaptogenic activity was analyzed using an in vitro functional assay and in silico three-dimensional (3D) structural modeling. RESULTS: Through mutation screening, we regarded three ultra-rare missense variants (T737M, D772G, and R856W), all of which affected the LNS4 domain of NRXN1α isoform, as disease-associated variants. Diagnosis of individuals with T737M, D772G, and R856W was 1ASD and 1SCZ, 1ASD, and 1SCZ, respectively. We observed the following phenotypic and functional burden caused by each variant. (i) D772G and R856W carriers had more serious social disabilities than T737M carriers. (ii) In vitro assay showed reduced cell surface expression of NRXN1α by D772G and R856W mutations. In vitro functional analysis showed decreased NRXN1α-NLGN1 interaction of T737M and D772G mutants. (iii) In silico 3D structural modeling indicated that T737M and D772G mutations could destabilize the rod-shaped structure of LNS2-LNS5 domains, and D772G and R856W could disturb N-glycan conformations for the transport signal. CONCLUSIONS: The combined data suggest that missense variants in NRXN1 could be associated with phenotypes of neurodevelopmental disorders beyond the diagnosis of ASD and/or SCZ.