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.

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.

Validation and factor analysis of the parental bonding instrument in Japanese pregnant women.

The Parental Bonding Instrument (PBI) evaluates parental attitudes derived from an individual's childhood experiences with their parents. The factor structure of the PBI differs depending on variables such as psychosocial factors including culture, race, sex, and psychological and social conditions of participants. Although previous studies of the relationships between perinatal depression and parenting experiences have used the factor structures of the PBI from the general population, it is unclear whether the same factor structures are appropriate in the highly variable perinatal period. In this study, complete responses to the PBI and the Edinburgh Postnatal Depression Scale (EPDS) were received from 932 primiparas at 25 weeks of gestation and at 1 month postpartum. An exploratory factor analysis was performed on half of the responses, and it was confirmed that the three factors were care, interference, and autonomy. Confirmatory factor analysis of the remaining half of the answers showed comprehensible fitness. Each factor showed a high degree of internal consistency, and each factor of the PBI correlated with the EPDS, indicating construct validity. The reliability and validity of the PBI in perinatal Japanese women were confirmed, and it was found that the PBI had a three-factor structure.

Perceived Social Support Partially Mediates the Impact of Temperament and Character on Postpartum Depression.

INTRODUCTION: Temperament and character of pregnant women, especially harm avoidance (HA) and self-directedness (SD) have been identified as risk factors for postpartum depression, in addition to poor social support. However, the relationship between these personality traits and social support for depressive symptoms after delivery has not been examined. METHODS: Data were extracted from a prospective cohort survey on pregnant women conducted in Nagoya, Japan that included the Temperament and Character Inventory (TCI), the Social Support Questionnaire (J-SSQ), and the Edinburgh Postnatal Depression Scale (EPDS) at approximately week 25 and 1 month postpartum. A mediation analysis using structural equation modeling (SEM) was used to test if social support in pregnancy is a mediator between personality traits and postpartum depressive symptoms. RESULTS: Thousand five hundred and fifty-nine women were included in the analysis. Both harm avoidance and SD were significantly associated with depressive symptoms (total effect: ß [SE], 0.298 [0.041], P < 0.001 for harm avoidance; total effect: ß [SE], -0.265 [0.067], P < 0.001 for SD). Mediation analysis showed that the effect of harm avoidance on depressive symptoms was partially mediated by low social support (direct effect: ß [SE], 0.193 [0.004], P < 0.001; indirect effect: ß [SE], 0.082 [0.034], P = 0.015). Self-directedness on depressive symptoms was not found to be mediated by low social support. CONCLUSION: Results indicate that poor social support worsens depressive symptoms in women with high HA during pregnancy. Limitations include a possible selection bias due to the limited target facilities; most variables being evaluated based on self-report questionnaires, and different number of samples available for analysis between harm avoidance and SD.

Perinatal depression and anxiety of primipara is higher than that of multipara in Japanese women.

The proportion of women who experience a depressive state after delivery differs between primiparas and multiparas, so it is important to clarify the different factors related to depression between the two groups. In this study, we confirmed the differences in depressive states, the perinatal period, and social support between primiparas and multiparas, and clarified their characteristics. Data were extracted from a prospective cohort questionnaire survey conducted on pregnant women in Japan that included sociodemographic questions, the Edinburgh Postnatal Depression Scale, and the Japanese version of the Social Support Questionnaire. We carried out the chi-square test, Student's t-test, and analysis of covariance to compare responses between primiparas and multiparas. A total of 1138 primiparas and 380 multiparas provided valid responses. We found that primiparas had higher rates of experiencing maternity blues and postpartum depression than multiparas. We also found that primiparas had higher anxiety scores than multiparas. Primiparas with postpartum depression perceived a lower number of persons available to provide social support than primiparas without postpartum depression. These findings suggest that it is important to provide pregnant women, especially for primiparas, with information that allows them to increase the number of people who can provide them with support.

The Risk Factors Predicting Suicidal Ideation Among Perinatal Women in Japan.

INTRODUCTION: The aim of the present study was to elucidate the foreseeable risk factors for suicidal ideation among Japanese perinatal women. METHODS: This cohort study was conducted in Nagoya, Japan, from July 2012 to March 2018. The Edinburgh Postnatal Depression Scale (EPDS) questionnaire was conducted at four time points: early pregnancy, late pregnancy, 5 days postpartum, and 1 month postpartum. A total of 430 women completed the questionnaires. A logistic regression analysis was performed using the presence of suicidal ideation on the EPDS as an objective variable. The explanatory variables were age, presence of physical or mental disease, smoking and drinking habits, education, hospital types, EPDS total score in early pregnancy, bonding, and quality and amount of social support, as well as the history of major depressive disorder (MDD). RESULTS: The rate of participants who were suspected of having suicidal ideation at any of the four time points was 11.6% (n=52), with the highest (n=25, 5.8%) at late pregnancy. For suicidal ideation, education level (OR: 1.19; 95% CI: 1.00-1.41; p=0.047), EPDS total points in the pregnancy period (OR: 1.25; 95% CI: 1.16-1.34; p < 0.000), a history of MDD (OR: 2.16; 95% CI: 1.00-4.79; p=0.049), and presence of mental disease (OR: 2.39; 95% CI: 1.00-5.70; p=0.049) were found to be risk factors for suicidal ideation. Age [odds ratio (OR): 0.88; 95% confidence interval (CI): 0.80-0.95; p=.002] and quality of social support (OR: 0.77; 95% CI: 0.60-0.99; p=.041) were found to be protective factors. CONCLUSION: Based on these results, effective preventive interventions, such as increasing the quality of social support and confirming the history of depression, should be carried out in pregnant depressive women at the early stage of the perinatal period.

Validation and factor structure of the Japanese version of the inventory to diagnose depression, lifetime version for pregnant women.

INTRODUCTION: A history of major depressive disorder before pregnancy is one risk factor for peripartum depression. Therefore, the purpose of the present study was to examine the validation and factor structure of the Japanese version of the Inventory to Diagnose Depression, Lifetime version (IDDL) for pregnant women. METHODS: The study participants were 556 pregnant women. Factor analysis was performed to identify the factor structure, construct validity was examined based on the results of the factor analysis, and reliability was examined using Cronbach's α coefficient. RESULTS: Based on the results of the factor analysis of the IDDL, a bifactor model composed of a single general dimension along with the following five factors was extracted: (1) depression, anxiety, and irritability (items 1, 2, 8-10, and 19-21); (2) retardation, decreased concentration, indecisiveness, and insomnia (items 4, 11, 12, and 17); (3) decrease in appetite/significant weight loss (items 13 and 14); (4) increase in appetite/significant weight gain (items 15 and 16); and (5) diminished interest, pleasure, and libido (items 5-7). Cronbach's α coefficients for these five factors were as follows: 0.910, 0.815, 0.780, 0.683, and 0.803, respectively. CONCLUSIONS: The reliability, construct validity, and factor structure of the Japanese version of the IDDL were confirmed in pregnant women.

Relation Between Perinatal Depressive Symptoms, Harm Avoidance, and a History of Major Depressive Disorder: A Cohort Study of Pregnant Women in Japan.

Introduction: The relationship between perinatal depressive symptoms, harm avoidance (HA), and a history of major depressive disorder (MDD) was examined in a prospective cohort study. Methods: This study was conducted from May 1, 2011, to December 31, 2016. A history of MDD was evaluated using the Inventory to Diagnose Depression, Lifetime version during pregnancy. Depressive state and HA were evaluated during pregnancy and at 1 month postnatal using the Edinburgh Postnatal Depression Scale (EPDS) and Temperament and Character Inventory, respectively. The relationship between these variances was examined using structural equation modeling. Results: A total of 338 participants with complete data were included in the present study. Pregnant women with compared with those without a history of MDD were observed to have a significantly higher intensity of HA and more severe depressive symptoms in both the prenatal and postnatal periods. A history of MDD affected the severity of depressive symptoms [standardized path coefficient (SPC) = 0.25, p < 0.001] and the intensity of HA during pregnancy (SPC = 0.36, p < 0.001). The intensity of HA during pregnancy affected that at 1 month postnatal (SPC = 0.78, p < 0.001), while the severity of depressive symptoms as assessed by the EPDS during pregnancy affected that at 1 month postnatal (SPC = 0.41, p < 0.001). The SPC for perinatal HA to postnatal depressive symptoms (SPC = 0.13, p = 0.014) was significant and higher than that for perinatal depressive symptoms to postnatal HA (SPC = 0.06, p = 0.087). Conclusion: The present results suggest that early intervention in pregnant women with a history of MDD or a high intensity of HA is important to prevent postnatal depressive symptoms.

Methylation analysis for postpartum depression: a case control study.

BACKGROUND: Postpartum depression (PPD) is a major depressive disorder that occurs after childbirth. Objective diagnostic and predictive methods for PPD are important for early detection and appropriate intervention. DNA methylation has been recognized as a potential biomarker for major depressive disorder. In this study, we used methylation analysis and peripheral blood to search for biomarkers that could to lead to the development a predictive method for PPD. METHODS: Study participants included 36 pregnant women (18 cases and 18 controls determined after childbirth). Genome-wide DNA methylation profiles were obtained by analysis with an Infinium Human Methylation 450BeadChip. The association of DNA methylation status at each DNA methylation site with PPD was assessed using linear regression analysis. We also conducted functional enrichment analysis of PPD using The Database for Annotation, Visualization and Integrated Discovery 6.8 to explore enriched functional-related gene groups for PPD. RESULTS: In the analysis with postpartum depressed state as an independent variable, the difference in methylation frequency between the postpartum non-depressed group and the postpartum depressed group was small, and sites with genome-wide significant differences were not confirmed. After analysis by The Database for Annotation, Visualization and Integrated Discovery 6.8, we revealed four gene ontology terms, including axon guidance, related to postpartum depression. CONCLUSIONS: These findings may help with the development of an objective predictive method for PPD.

Changes in tryptophan metabolism during pregnancy and postpartum periods: Potential involvement in postpartum depressive symptoms.

BACKGROUND: Many women experience depressive symptoms during pregnancy and postpartum periods. These depressive symptoms are often accompanied by other inflammatory morbidities present during pregnancy. Tryptophan (TRP) metabolism has attracted considerable attention due to its influence on the onset of depression via induction of inflammation. We examined the changes in plasma levels of TRP metabolites in pregnant women with depressive symptoms during pregnancy and/or the postpartum period. METHODS: In line with a previous analysis using the Edinburgh Postnatal Depression Scale (EPDS), participants were divided into a non-depressive (ND) group, a postpartum depressive (PD) group, a temporary gestational depressive (TG) group, and a continuous depressive (CD) group. Blood samples were collected before and 1 month after delivery. The concentrations of plasma TRP metabolites were measured using high-performance liquid chromatography (HPLC). RESULTS: There are differences in plasma levels of TRP metabolites during pregnancy and postpartum periods between the ND group and the PD group, but not the TG or CD group. In the PD group, plasma levels of kynurenine (KYN) and kynurenic acid (KA), and KYN/TRP and KA/KYN ratio during the pregnancy period were higher and 3-hydroxyanthranilic acid (3HAA) during the postpartum period was lower than those in the ND group. LIMITATIONS: Histories regarding mood disorders before pregnancy were not assessed. CONCLUSIONS: The higher plasma levels of KYN and KA, and KYN/TRP and KA/KYN ratio during pregnancy period and lower plasma level of 3HAA during the postpartum period could be useful predictive and diagnostic markers of postpartum depressive symptoms.

Author Correction: Proteomic analysis of lymphoblastoid cell lines from schizophrenic patients.

The original Article required a few updates; one co-author name, which was given as Hiroki Kiumura, has been updated to Hiroki Kimura. Furthermore, supplementary information has been updated, and grant numbers have been added. These updates have been made to both the PDF and HTML versions of this Article.

Proteomic analysis of lymphoblastoid cell lines from schizophrenic patients.

Although a number of studies have identified several convincing candidate genes or molecules, the pathophysiology of schizophrenia (SCZ) has not been completely elucidated. Therapeutic optimization based on pathophysiology should be performed as early as possible to improve functional outcomes and prognosis; to detect useful biomarkers for SCZ, which reflect pathophysiology and can be utilized for timely diagnosis and effective therapy. To explore biomarkers for SCZ, we employed fluorescence two-dimensional differential gel electrophoresis (2D-DIGE) of lymphoblastoid cell lines (LCLs) (1st sample set: 30 SCZ and 30 CON). Differentially expressed proteins were sequenced by liquid chromatography tandem-mass spectrometry (LC-MS/MS) and identified proteins were confirmed by western blotting (WB) (1st and 2nd sample set: 60 SCZ and 60 CON). Multivariate logistic regression analysis was performed to identify an optimal combination of biomarkers to create a prediction model for SCZ. Twenty protein spots were differentially expressed between SCZ and CON in 2D-DIGE analysis and 22 unique proteins were identified by LC-MS/MS. Differential expression of eight of 22 proteins was confirmed by WB. Among the eight candidate proteins (HSPA4L, MX1, GLRX3, UROD, MAPRE1, TBCB, IGHM, and GART), we successfully constructed logistic regression models comprised of 4- and 6-markers with good discriminative ability between SCZ and CON. In both WB and gene expression analysis of LCL, MX1 showed reproducibly significant associations. Moreover, Mx1 and its related proinflamatory genes (Mx2, Il1b, and Tnf) were also up-regulated in poly I:C-treated mice. Differentially expressed proteins might be associated with molecular pathophysiology of SCZ, including dysregulation of immunological reactions and potentially provide diagnostic and prognostic biomarkers.

Stable factor structure of the Edinburgh Postnatal Depression Scale during the whole peripartum period: Results from a Japanese prospective cohort study.

Early detection of perinatal depression is an urgent issue. Our study aimed to examine the construct validity and factor structure of the Japanese version of the Edinburgh Postnatal Depression Scale (EPDS) from a prospective cohort study from pregnancy to postpartum. A total of 1075 women completed all items of the EPDS at four time points: early pregnancy, late pregnancy, 5 days postpartum and 1 month postpartum. The participants were randomly divided into two sample sets. The first sample set (n = 304) was used for exploratory factor analysis, and the second sample set (n = 771) was used for confirmatory factor analysis. As a result, the Cronbach's alpha coefficients of the EPDS items were 0.762, 0.740, 0.765 and 0.772 at the four time points. From the confirmatory factor analysis of the EPDS in a sample set of Japanese women from pregnancy to postpartum, the following three factors were detected: depression (items 7, 9), anxiety (items 4, 5) and anhedonia (items 1, 2). In conclusion, the EPDS is a useful rating scale, and its factor structure is consistently stable during the whole peripartum period.

Comparative Analyses of Copy-Number Variation in Autism Spectrum Disorder and Schizophrenia Reveal Etiological Overlap and Biological Insights.

Compelling evidence in Caucasian populations suggests a role for copy-number variations (CNVs) in autism spectrum disorder (ASD) and schizophrenia (SCZ). We analyzed 1,108 ASD cases, 2,458 SCZ cases, and 2,095 controls in a Japanese population and confirmed an increased burden of rare exonic CNVs in both disorders. Clinically significant (or pathogenic) CNVs, including those at 29 loci common to both disorders, were found in about 8% of ASD and SCZ cases, which was significantly higher than in controls. Phenotypic analysis revealed an association between clinically significant CNVs and intellectual disability. Gene set analysis showed significant overlap of biological pathways in both disorders including oxidative stress response, lipid metabolism/modification, and genomic integrity. Finally, based on bioinformatics analysis, we identified multiple disease-relevant genes in eight well-known ASD/SCZ-associated CNV loci (e.g., 22q11.2, 3q29). Our findings suggest an etiological overlap of ASD and SCZ and provide biological insights into these disorders.

Impact of perceived rearing and social support on bonding failure and depression among mothers: A longitudinal study of pregnant women.

BACKGROUND: Although previous studies have reported associations between bonding failure, depression, social support among mothers, and perceived rearing, the causal relationships remain unclear. METHODS: A total of 855 women (mean age, 32.4 ±â€¯4.4 years) completed the Mother-Infant Bonding Questionnaire (MIBQ), the Edinburgh Postnatal Depression Scale (EPDS), the Japanese version of the Social Support Questionnaire, and the Parental Bonding Instrument in early pregnancy before week 25 (T1) and at 1 month after delivery (T2). We created a path model to clarify the causal relationships between perinatal bonding failure, depression, social support, and perceived rearing during pregnancy and at 1 month after delivery. The model was tested using structural equation modeling. RESULTS: Our recursive model showed acceptable fit (chi-squared statistic/degree of freedom = 2.1, comparative fit index = 0.98, root mean square error of approximation = 0.04). It was revealed that: (1) at T1, higher overprotection significantly predicted MIBQ scores; (2) at T1, poorer social support significantly predicted both MIBQ and EPDS scores; and (3) at T1, both MIBQ and EPDS scores significantly predicted respective scores at T2. CONCLUSIONS: These results showed that bonding failure in the postpartum period was significantly influenced by mothers' own perceived rearing and social support during pregnancy. In addition, depression in the postpartum period was strongly influenced by social support during pregnancy. These findings suggest that psychosocial interventions that focus on both mothers' recollections of their own upbringing and social support during pregnancy are effective for preventing bonding failure and depression in the postpartum period.

Postpartum depression among women in Nagoya indirectly exposed to the Great East Japan Earthquake.

This study aimed to assess the situation of postpartum depression and maternal bonding in Nagoya, a city distant from the epicenter of the Great East Japan Earthquake that occurred on March 11, 2011. Among the participants at 1 month after childbirth between March 11, 2010 and March 10, 2013 (n = 188), 152 fully responded to the Edinburgh Postnatal Depression Scale (EPDS) and Mother-Infant Bonding Questionnaire (MIBQ). They were divided into pre-quake (n = 58), and 0-6, 6-12, 12-18, and 18-24 months after the earthquake groups (n = 20, 26, 29, and 19, respectively). The rate of mothers who scored above the cutoff point for the EPDS increased from 12.1% in the pre-quake to 35.0% in the 0-6 months group (p = 0.022). The EPDS total and anxiety subscale scores (mean ± standard error) were also significantly different between the pre-quake and 0-6 months after the earthquake groups (4.45 ± 0.50 vs. 7.95 ± 1.47, p = 0.024; 2.16 ± 0.26 vs. 3.65 ± 0.57, p = 0.021, respectively). The EPDS total and anxiety scores were the highest for the 0-6 months group, followed by the 6-12, 12-18, 18-24 months groups (p = 0.019, p = 0.022). MIBQ scores did not differ between the pre-quake and 0-6 months groups. Depressive symptoms, mainly explained by anxiety, increased after the earthquake with no changes in maternal bonding.

The coping process of Japanese parents who experience violence from adult children with schizophrenia.

With the acceleration of deinstitutionalization might increase families' chances of suffering violence by patients. This study clarified parents' coping processes with violence experienced from patients with schizophrenia. The grounded theory approach was used, and 26 parents were interviewed. We identified a four-stage coping process: (1) hope for treatment, (2) living with violence, (3) trying to solve violence, and (4) last solution for violence. This coping process had two illness-related characteristics: (1) a process of coping with two main stressful events (the illness and violence), and (2) the need for long-term appraisal of violence because of its unclear causes.

Validation and Factor Analysis of the Japanese Version of the Highs Scale in Perinatal Women.

Background: The Highs scale has been developed to evaluate hypomanic symptoms in the first postpartum week. However, it has not been elucidated whether this scale is also applicable to pregnant women. To address this issue, we confirmed the factor structure, reliability, and validity of the Japanese version of the Highs scale for pregnant and postpartum women. Methods: 418 women provided effective responses to both the Highs scale and the Edinburgh Postnatal Depression Scale (EPDS) during early pregnancy (before week 25), late pregnancy (around week 36), at 5 days and at 1 month after delivery. Subjects were randomly divided into two groups, and exploratory and confirmatory factor analyses were performed for each group. Cronbach's alpha was calculated and the correlation of the Highs scale with EPDS was analyzed. The correlation between the subscales was analyzed at four time points, and the correlation of subscales between the four time points was confirmed. Results: This scale was found to have the two-factor structure with elation and agitation subscales. The two subscales had reasonable internal consistency at all time points (Cronbach's alpha range: Factor 1, 0.696-0.758; Factor 2, 0.553-0.694). The overall scale had reasonable internal consistency at all time points (Cronbach's alpha range: 0.672-0.738). Based on the correlation analysis of the two subscales and EPDS, discriminative and convergent validity were indicated at all time points, confirming the construct validity of the Highs scale. Subscale scores showed a significant correlation with EPDS at all time points (r = 0.388, 0.384, 0.498, and 0.442, p < 0.01). Conclusions: The Japanese version of the Highs scale is reliable and valid, and can be applied for evaluating the hypomanic symptoms during pregnancy and postpartum period.

Rare loss of function mutations in N-methyl-D-aspartate glutamate receptors and their contributions to schizophrenia susceptibility.

In schizophrenia (SCZ) and autism spectrum disorder (ASD), the dysregulation of glutamate transmission through N-methyl-D-aspartate receptors (NMDARs) has been implicated as a potential etiological mechanism. Previous studies have accumulated evidence supporting NMDAR-encoding genes' role in etiology of SCZ and ASD. We performed a screening study for exonic regions of GRIN1, GRIN2A, GRIN2C, GRIN2D, GRIN3A, and GRIN3B, which encode NMDAR subunits, in 562 participates (370 SCZ and 192 ASD). Forty rare variants were identified including 38 missense, 1 frameshift mutation in GRIN2C and 1 splice site mutation in GRIN2D. We conducted in silico analysis for all variants and detected seven missense variants with deleterious prediction. De novo analysis was conducted if pedigree samples were available. The splice site mutation in GRIN2D is predicted to result in intron retention by minigene assay. Furthermore, the frameshift mutation in GRIN2C and splice site mutation in GRIN2D were genotyped in an independent sample set comprising 1877 SCZ cases, 382 ASD cases, and 2040 controls. Both of them were revealed to be singleton. Our study gives evidence in support of the view that ultra-rare variants with loss of function (frameshift, nonsense or splice site) in NMDARs genes may contribute to possible risk of SCZ.