Sex differences in neurodevelopmental trajectories in children with different levels of autistic traits.

AIM: Little is known about early manifestations of autism spectrum disorders (ASD) in females, including those who may be overlooked by the current diagnostic criteria. We longitudinally explored sex differences in the trajectories of cognitive and motor functions and adaptive behaviors in children with different levels of autistic traits. METHODS: The participants were 824 children from the Hamamatsu Birth Cohort for Mothers and Children (HBC Study), Japan, who were classified into three autistic trait groups-low, moderate, and high-based on the Social Responsiveness Scale-Second Edition. Cognitive and motor functions were measured at seven time-points from 0.5 to 3.5 years of age using the Mullen Scales of Early Learning. Adaptive behaviors were measured at five time-points from 2.7 to 9 years of age using the Vineland Adaptive Behavior Scales-Second Edition. Trajectories were depicted using latent growth curve modeling. RESULTS: Sex-specific trajectories were observed in the high-autistic-trait group, with only males showing a temporary decline in expressive language around the age of 2 years and a slight improvement thereafter. They also showed a slight improvement around 3 years in the adaptive behavior communication domain but a gradual downward trend later. Females in the high-autistic-trait group showed no distinct manifestation before the age of 3 years but showed a downward trend after 3.5 years in the adaptive behavior communication domain. CONCLUSION: Females and males with higher autistic traits than their same-sex peers, independent of clinical diagnosis, may have different phenotypes in certain neurodevelopmental domains during infancy and early childhood.

Elevated risk of attention deficit hyperactivity disorder (ADHD) in Japanese children with higher genetic susceptibility to ADHD with a birth weight under 2000 g.

BACKGROUND: Both genetic and pre- and perinatal factors, including birth weight, have been implicated in the onset of attention deficit hyperactivity disorder (ADHD) traits among children. This study aimed to elucidate to what extent the genetic risk of ADHD moderates the association between birth weight and ADHD traits among Japanese children. METHODS: We conducted a longitudinal birth cohort study (Hamamatsu Birth Cohort for Mother and Children Study) to investigate the association of genetic risk for ADHD and low birth weight with ADHD traits among Japanese children. Out of 1258 children, we included 796 who completed follow-ups at 8 to 9 years of age. Birth weight was categorized as <2000 g, 2000-2499 g, and ≥2500 g. Polygenic risk score for ADHD was generated using the summary data of a large-scale genome-wide association study. The Rating Scale IV (ADHD-RS) assessed ADHD traits (inattention and hyperactivity/impulsivity) based on parental reports. Following previous studies, sex, birth order of the child, gestational age at birth, mother's age at delivery, educational attainment, pre-pregnancy body mass index, pre-pregnancy or during pregnancy smoking status, alcohol consumption during pregnancy, father's age, education, and annual family income were considered as covariates. Multivariable negative binomial regression was applied to evaluate the association between birth weight and ADHD traits, while adjusting for potential covariates. The interaction term between birth weight categories and binary polygenic risk was added to the model. RESULTS: Birth weight of 2000-2499 g was not associated with ADHD traits. Birth weight under 2000 g was significantly associated with both inattention and hyperactivity. When accounting for higher and lower genetic risk for ADHD, only those with higher genetic risk and birth weight < 2000 g were associated with inattention (rate ratio [RR] 1.56, 95% CI 1.07-2.27) and hyperactivity (RR 1.87, 95% CI 1.14-3.06). CONCLUSIONS: Birth weight under 2000 g, together with the genetic risk of ADHD, contributes to higher levels of ADHD traits among Japanese children aged 8 to 9 years. The suggested association between low birth weight and ADHD is confined to children with a genetic susceptibility to ADHD, indicating the relevance of genetic-environmental interactions in the etiology.

Neurodevelopmental Trajectory During Infancy and Diagnosis of Autism Spectrum Disorder as an Outcome at 32 Months of Age.

BACKGROUND: Little is known about the extent to which neurodevelopmental trajectories in infancy predict a later diagnosis of autism spectrum disorder (ASD). METHODS: We investigated the association between the neurodevelopmental trajectory classes identified using a latent class growth analysis and the distal clinical outcome. Participants included 952 infants from the Hamamatsu Birth Cohort for Mothers and Children (HBC study). Neurodevelopment was measured using the Mullen Scales of Early Learning, which contains five subscales (gross motor, fine motor, visual reception, receptive language, and expressive language), at seven time points from 1 to 24 months of age. ASD was diagnosed in 3.1% of the children at 32 months of age. The clinical outcome was included in our analysis model. RESULTS: Five neurodevelopmental classes were identified: high normal (11.5%), normal (49.2%), low normal (21.2%), delayed (14.1%), and markedly delayed (4.0%). The probability of a diagnosis of ASD in the markedly delayed class was highest (32.6%) when compared with the other classes. The probabilities of receiving a diagnosis of ASD in the delayed and low normal classes were 6.4% and 4.0%, respectively, whereas the probabilities in the normal and high normal classes were both 0%. CONCLUSIONS: A diagnosis of ASD may be predicted by the neurodevelopmental trajectories during infancy, which can be evaluated both routinely and objectively in clinical settings. In this representative population, children diagnosed with ASD showed early signs in neurodevelopmental domains during the first 2 years of life.

Reliability and validity of the Japan Ijime Scale and estimated prevalence of bullying among fourth through ninth graders: A large-scale school-based survey.

AIM: The present study aimed at developing a novel scale, the Japan Ijime Scale (JaIS), to measure bullying in Japan with substantial reliability and validity, with which we estimated the prevalence of bullying among children and adolescents of school age. METHODS: The JaIS is a self-report questionnaire and consists of three parts: subscales measuring victimization and witnessing, and an item measuring perpetration. To test the reliability and validity of the two subscales, the authors analyzed responses to the JaIS from 2334 school students (Grades 4-9) in six elementary and three junior high schools in a middle-sized industrial city in central Japan, using exploratory factor analysis, item response theory, and examination of the external validity of the items. The prevalence of bullying victimization, witnessing, and perpetration was estimated. RESULTS: Item response theory models revealed that both the Victimization and Witness subscales have sufficient discrimination power and measurement precision, and the external validity of each scale has been confirmed. Using the JaIS, we found that 35.8% of students had been victims of bullying every 2-3 months (27.6% were solely victims and 8.3% were bully/victims), 32.8% had witnessed some type of bullying act, and 11.8% had perpetrated some type of bullying (3.5% as perpetrators, and 8.3% as bully/victims). CONCLUSION: The JaIS is a reliable and valid measure. Using this scale, we found a high prevalence of bullying victimization in Japanese schools.

Comparison between placental gene expression of 11ß-hydroxysteroid dehydrogenases and infantile growth at 10 months of age.

AIM: The local expression of two isoenzymes of 11ß-hydroxysteroid dehydrogenase, type 1 (11ßHSD-1) and type 2 (11ßHSD-2), regulates the access of glucocorticoid hormones to their target cells. Reports on the association between the placental expression of 11ßHSD and infantile growth are limited. The aim of the present study was to investigate if the placental gene expression of 11ßHSD affects infantile growth at 10 months of age. METHODS: Placentas and umbilical venous cord blood were obtained from 42 singleton cases of cesarean deliveries between 31 and 40 weeks of gestation at Hamamatsu University Hospital between March 2009 and June 2010. The gene expression of both 11ßHSD-1 and 11ßHSD-2 was measured by quantitative reverse transcription polymerase chain reaction. Adiponectin and leptin levels in umbilical cord blood were measured using enzyme-linked immunoassay. RESULTS: 11ßHSD-1 and 11ßHSD-2 gene expression in human placentas did not correlate with bodyweight or the ponderal index (PI) at 10 months of age, whereas the gene expression of 11ßHSD-1, but not 11ßHSD-2, correlated with birthweight as well as PI at birth. Adiponectin levels in umbilical cord blood significantly correlated with the placental gene expression of 11ßHSD-1 as well as bodyweight and PI at 10 months of age, although no direct correlation was observed between them. CONCLUSION: No direct correlation was observed between the placental gene expression of 11ßHSD and infantile growth at 10 months of age. However, the placental gene expression of 11ßHSD-1 may be indirectly connected with infantile growth via adiponectin-associated metabolic regulation represented by adiponectin levels in umbilical cord blood.

Psychosocial determinants of mistimed and unwanted pregnancy: the Hamamatsu Birth Cohort (HBC) study.

The terms mistimed pregnancy (MP) and unwanted pregnancy (UWP) refer to a woman's intentions regarding childbearing. Determinants for each type of pregnancy have not been well understood. The present study aims to investigate whether MP and UWP have different sets of psychosocial determinants compared to intended pregnancy, with a particular emphasis on any difference in the history of maternal psychiatric diagnosis. Using an ongoing birth cohort study, we consecutively enrolled parturients who were at mid-pregnancy (n = 780) and were expected to give birth at either of our two research sites. MP and UWP were defined according to previous studies. To avoid multiple testing, we adopted multinomial logistic regression to estimate the independent contribution of the determinants while simultaneously allowing for other variables. The dependent variable in the model had three classes: Intended pregnancy, MP and UWP. Determinants of MP included younger age (<25 years: OR = 2.6), currently working (OR = 1.6), and history of major depression (OR = 2.0). Determinants for UWP were multiparity (OR = 3.9), short (≤12 years, OR = 1.7) and long period of education (≥17 years, OR = 3.3), history of anxiety disorder (OR = 2.5), currently working (OR = 0.6) and high income (≥8 million JPY, OR = 0.4). Different sets of psychosocial determinants contribute to formulate MP and UWP. A history of mental illness plays a role in predicting pregnancy intention.

Identification of neurodevelopmental transition patterns from infancy to early childhood and risk factors predicting descending transition.

It is unclear whether neurodevelopmental progress from infancy to early childhood remains stable. Moreover, little is known about the risk factors, if any, affecting neurodevelopmental descending transition patterns and the relationship between these patterns and later childhood adaptive behaviours. We used data of 875 children from the Hamamatsu Birth Cohort Study in Japan. Children's neurodevelopment at 18 and 32 months and adaptive behaviours at 40 months were evaluated. Perinatal factors and infant overweight status at 18 months were investigated to identify descending-transition-associated risk factors. In the latent transition analysis, ultimately, three classes were identified for each time-point, resulting in nine transition patterns; among them, 10.4% of children showed descending class shifts (normal to delayed class). Such decelerated growth was predicted by maternal pre-pregnancy overweight status (odds ratio [OR] 2.49; 95% confidence interval [CI] 1.23, 5.02), low maternal educational history (OR 1.20; 95% CI 1.04, 1.36), and infant overweight status at 18 months (OR 5.89; 95% CI 1.26, 27.45). Children with descending transition showed poor functioning in adaptive behaviours at the age of 40 months. To prevent subsequent poor adaptive functioning, it may be necessary to consider that a certain percentage of children show decelerated growth.

Jiko-shisen-kyofu (fear of one's own glance), but not taijin-kyofusho (fear of interpersonal relations), is an east Asian culture-related specific syndrome.

OBJECTIVE: According to the DSM-IV-TR, the concept of taijin-kyofusho (fear of interpersonal relations) is both unique to East Asia and a culture-bound syndrome. In the indigenous diagnostic classification system in Japan, taijin-kyofusho consists of four subtypes, i.e. sekimen-kyofu (phobia of blushing), shubo-kyofu (phobia of a deformed face/body), jiko-shu-kyofu (phobia of one's own foul body odour), and jiko-shisen-kyofu (phobia of one's own glance). Each subtype except for phobia of one's own glance can be adequately assigned to a respective existing category in the DSM-IV-TR. The aim of the study was to introduce clinical features of phobia of one's own glance to western psychiatrists. METHODS: Description of a series of cases with jiko-shisen-kyofu (phobia of one's own glance). RESULTS: All of our cases shared the unique feature that they suffered from the preoccupation that their own glance was offensive to others, and as a result were socially withdrawn themselves. CONCLUSIONS: To our best knowledge, no cases with a clear picture of phobia of one's own glance have been reported in the West to date. The controversial issue of the classification of phobia of one's own glance as an east Asian culture-related specific syndrome was addressed.

[Recent progress of epidemiological research in search of the aetiology of autism].

Autism and autism spectrum disorders (ASDs) are neurodevelopmental disorders characterised by the behavioral traits of impaired social cognition and communication, and repetitive and/or obsessive behaviour and interests. Studies point towards increased prevalence of autism/ASD. However, no treatment or prevention for the disorder has been established, since the aetiological pathway of this disorder remains largely unknown. Considering this lack of knowledge, epidemiological studies are expected to give clues for a better understanding of the disorder. As such, advanced paternal age at birth and low birthweight (or intrauterine growth retardation) have been reported to be candidate risk factors. These findings allow us to propose novel research strategies in search of the aetiology of autism/ASD. Following this trend, the authors initiated a research project, "the Hamamatsu Birth Cohort for Mothers and Children (HBC)", seeking risk factors for autism/ASD extensively. The HBC is expected to enroll 1,200 dyads of mother and child and to follow them until the child becomes 4 years of age.

Association Between Genetic Risks for Obesity and Working Memory in Children.

Introduction: Obesity is highly heritable, and recent evidence demonstrates that obesity is associated with cognitive deficits, specifically working memory. However, the relationship between genetic risks for obesity and working memory is not clear. In addition, whether the effect of these genetic risks on working memory in children is mediated by increased body mass index (BMI) has not been elucidated. Methods: In order to test whether the polygenic risk score (PRS) for obesity in adulthood (adulthood-BMI-PRS) is associated with working memory at 8 years of age, and whether the effect is mediated by childhood BMI, in children from the general population, participants in the Hamamatsu Birth Cohort for Mothers and Children (HBC) study in Hamamatsu, Japan, underwent testing for association of adulthood-BMI-PRS with working memory. HBC data collection began in December 2007 and is ongoing. Adulthood-BMI-PRS values were generated using summary data from the recent genome-wide association study (GWAS) undertaken in Japan, and the significance of thresholds was calculated for each outcome. Outcomes measured included the working memory index (WMI) of Weschler Intelligence Scale-4 (WISC-IV) scores and the BMI at 8 years of age. Gene-set enrichment analysis was conducted to clarify the molecular basis common to adulthood-BMI and childhood-WMI. Mediation analysis was performed to assess whether childhood-BMI of children mediated the association between adulthood-BMI-PRS and working memory. Results: A total of 734 participants (377 males, 357 females) were analyzed. Adulthood-BMI-PRS was associated with lower childhood-WMI (ß[SE], -1.807 [0.668]; p = 0.010, corrected) of WISC-IV. Gene-set enrichment analyses found that regulation of neurotrophin Trk receptor signaling (ß[SE], -2.020 [6.39]; p = 0.002, corrected), negative regulation of GTPase activity (ß[SE], 2.001 [0.630]; p = 0.002, corrected), and regulation of gene expression epigenetic (ß[SE], -2.119 [0.664]; p = 0.002, corrected) were enriched in BMI in adulthood and WMI in childhood. Mediation analysis showed that there is no mediation effect of childhood-BMI between the adulthood-BMI-PRS and working memory deficits in children. Conclusion: Adulthood-BMI-PRS was associated with working memory among children in the general population. These genetic risks were not mediated by the childhood-BMI itself and were directly associated with working memory deficits.

Metabolite alterations in the hippocampus of high-functioning adult subjects with autism.

The aim of the present study was to investigate metabolite alterations in the hippocampal formation as they relate to aggression in high-functioning adults with autism. We measured concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), and creatine plus phosphocreatine (Cr+PCr) in the hippocampal formation by proton magnetic resonance spectroscopy in 12 non-medicated male subjects with autism and 12 age- and sex-matched controls. Aggression was scored in the autistic subjects using the Buss-Perry Aggression Questionnaire. The concentrations of Cho and Cr+PCr in the hippocampal formation in autistic subjects were significantly higher than the corresponding values in control subjects, and a significant positive correlation was observed between the concentrations of these metabolites in the hippocampal formation and scores on the Buss-Perry Aggression Questionnaire in autistic subjects. Results suggest that high-functioning adult subjects with autism have abnormal metabolite concentrations in the hippocampal formation, which may in part account for their aggression.

Measuring School Climate among Japanese Students-Development of the Japan School Climate Inventory (JaSC).

School climate is a significant determinant of students' behavioral problems and academic achievement. In this study, we developed the Japan School Climate Inventory (JaSC) to see whether it measures school climate properly. To do so, we investigated whether or not the measurement with JaSC varies across sub-groups of varying grade and of gender and examined the relationship between the perception of school climate and the psychological and behavioral traits at individual levels in a sample of Japanese elementary and junior high school students (n = 1399; grade 4-9). The results showed that the measurement was consistent, since single-factor structures, factor loadings and thresholds of the items were found not to vary across sub-groups of the participants. The participants' perception of school climate was associated positively with quality of life, especially in school (ß = 0.152, p < 0.001) and associated negatively with involvement in ijime (bullying) as "victim" and "bully/victim" (ß = -0.098, p = 0.001; ß = -0.188, p = 0.001, respectively) and peer relationship problems (ß = -0.107, p = 0.025). JaSC was found to measure school climate consistently among varying populations of Japanese students, with satisfactory validity.

Polygenic risk score analysis revealed shared genetic background in attention deficit hyperactivity disorder and narcolepsy.

Attention deficit hyperactive disorder (ADHD) is a highly heritable neurodevelopmental disorder, and excessive daytime sleepiness is frequently observed in ADHD patients. Excessive daytime sleepiness is also a core symptom of narcolepsy and essential hypersomnia (EHS), which are also heritable conditions. Psychostimulants are effective for the symptomatic control of ADHD (primary recommended intervention) and the two sleep disorders (frequent off-label use). However, the common biological mechanism for these disorders has not been well understood. Using a previously collected genome-wide association study of narcolepsy and EHS, we calculated polygenic risk scores (PRS) for each individual. We investigated a possible genetic association between ADHD and narcolepsy traits in the Hamamatsu Birth Cohort for mothers and children (HBC study) (n = 876). Gene-set enrichment analyses were used to identify common pathways underlying these disorders. Narcolepsy PRS were significantly associated with ADHD traits both in the hyperactivity domain (e.g., P-value threshold < 0.05, ß [SE], 5.815 [1.774]; P = 0.002) and inattention domain (e.g., P-value threshold < 0.05, ß [SE], 5.734 [1.761]; P = 0.004). However, EHS PRS was not significantly associated with either domain of ADHD traits. Gene-set enrichment analyses revealed that pathways related to dopaminergic signaling, immune systems, iron metabolism, and glial cell function involved in both ADHD and narcolepsy. Findings indicate that ADHD and narcolepsy are genetically related, and there are possible common underlying biological mechanisms for this relationship. Future studies replicating these findings would be warranted to elucidate the genetic vulnerability for daytime sleepiness in individuals with ADHD.

Association of Genetic Risks With Autism Spectrum Disorder and Early Neurodevelopmental Delays Among Children Without Intellectual Disability.

Importance: Autism spectrum disorder (ASD) is highly heritable, and modest contributions of common genetic variants to ASD have been reported. However, the association of genetic risks derived from common risk variants with ASD traits in children from the general population is not clear, and the association of these genetic risks with neurodevelopment in infants has not been well understood. Objective: To test whether a polygenic risk score (PRS) for ASD is associated with neurodevelopmental progress at age 18 months and ASD traits at age 6 years among children from the general population. Design, Setting, and Participants: In this cohort study, 876 children in the Hamamatsu Birth Cohort for Mothers and Children in Hamamatsu, Japan, underwent testing for the association of an ASD PRS with neurodevelopmental progress and ASD traits. Data collection began in December 2007 and is ongoing. Data analysis was conducted from April to December 2019. Main Outcomes and Measures: Summary data from the largest genome-wide association study were used to generate ASD PRSs, and significance of thresholds was calculated for each outcome. The Autism Diagnostic Observation Schedule 2 was used to measure ASD traits at age 6 years, and the Mullen Scales of Early Learning was used to measure neurodevelopmental progress at age 18 months. Results: Of 876 participants (mean [SD] gestational age at birth, 38.9 [1.6] weeks; 438 [50.0%] boys; 868 [99.1%] Japanese), 734 were analyzed. The ASD PRS was associated with ASD traits (R2 = 0.024; ß, 0.71; SE, 0.24; P = .03). The association of ASD PRS with infant neurodevelopment was most pronounced in gross motor (R2 = 0.015; ß, -1.25; SE, 0.39; P = .01) and receptive language (R2 = 0.014; ß, -1.19; SE, 0.39; P = .02) scores on the Mullen Scales of Early Learning. Gene set enrichment analyses found that several pathways, such as cell maturation (R2 = 0.057; ß, -5.28; SE, 1.40; P < .001) and adenylyl cyclase activity and cyclic adenosine monophosphate concentration (R2 = 0.064; ß, -5.30; SE 1.30; P < .001), were associated with ASD traits. Gene sets associated with inflammation were commonly enriched with ASD traits and gross motor skills (eg, chemokine motif ligand 2 production: R2 = 0.051; ß, -6.04; SE, 1.75; P = .001; regulation of monocyte differentiation: R2 = 0.052; ß, -6.63; SE, 1.90; P = .001; and B-cell differentiation: R2 = 0.051; ß, 7.37; SE, 2.15; P = .001); glutamatergic signaling-associated gene sets were commonly enriched with ASD traits and receptive language skills (eg, regulation of glutamate secretion: R2 = 0.052; ß, -5.82; SE, 1.68; P = .001; ionotropic glutamate receptor signaling pathway: R2 = 0.047; ß, 3.54; SE, 1.09; P = .001; and negative regulation of glutamate secretion: R2 = 0.045; ß, -5.38; SE, 1.74; P = .002). Conclusions and Relevance: In this study, the ASD PRS was associated with ASD traits among children from the general population. Genetic risks for ASD might be associated with delays in some neurodevelopmental domains, such as gross motor and receptive language skills.

Methamphetamine causes microglial activation in the brains of human abusers.

Methamphetamine is a popular addictive drug whose use is associated with multiple neuropsychiatric adverse events and toxic to the dopaminergic and serotonergic systems of the brain. Methamphetamine-induced neuropathology is associated with increased expression of microglial cells that are thought to participate in either pro-toxic or protective mechanisms in the brain. Although reactive microgliosis has been observed in animal models of methamphetamine neurotoxicity, no study has reported on the status of microglial activation in human methamphetamine abusers. The present study reports on 12 abstinent methamphetamine abusers and 12 age-, gender-, and education-matched control subjects who underwent positron emission tomography using a radiotracer for activated microglia, [(11)C](R)-(1-[2-chlorophenyl]-N-methyl-N-[1-methylpropyl]-3-isoquinoline carboxamide) ([(11)C](R)-PK11195). Compartment analysis was used to estimate quantitative levels of binding potentials of [(11)C](R)-PK11195 in brain regions with dopaminergic and/or serotonergic innervation. The mean levels of [(11)C](R)-PK11195 binding were higher in methamphetamine abusers than those in control subjects in all brain regions (>250% higher; p < 0.01 for all). In addition, the binding levels in the midbrain, striatum, thalamus, and orbitofrontal and insular cortices (p < 0.05) correlated inversely with the duration of methamphetamine abstinence. These results suggest that chronic self-administration of methamphetamine can cause reactive microgliosis in the brains of human methamphetamine abusers, a level of activation that appears to subside over longer periods of abstinence.

Association studies and gene expression analyses of the DISC1-interacting molecules, pericentrin 2 (PCNT2) and DISC1-binding zinc finger protein (DBZ), with schizophrenia and with bipolar disorder.

Disrupted-in-Schizophrenia 1 (DISC1) and its molecular cascade have been implicated in the pathophysiology of major psychoses. Previously, we identified pericentrin 2 (PCNT2) and DISC1-binding zinc finger protein (DBZ) as binding partners of DISC1; further, we observed elevated expression of PCNT2 in the postmortem brains and in the lymphocytes of bipolar disorder patients, compared to controls. Here, we examined the association of PCNT2 with schizophrenia in a case-control study of Japanese cohorts. We also examined the association of DBZ with schizophrenia and with bipolar disorder, and compared the mRNA levels of DBZ in the postmortem brains of schizophrenia, bipolar and control samples. DNA from 180 schizophrenia patients 201 controls were used for the association study of PCNT2 and DBZ with schizophrenia. Association of DBZ with bipolar disorder was examined in DNA from 238 bipolar patients and 240 age- and gender-matched controls. We observed significant allelic and genotypic associations of the PCNT2 SNPs, rs2249057, rs2268524, and rs2073380 (Ser/Arg) with schizophrenia; the association of rs2249057 (P = 0.002) withstand multiple testing correction. Several two SNP- and three SNP-haplotypes showed significant associations; the associations of haplotypes involving rs2249057 withstand multiple testing correction. No associations were observed for DBZ with schizophrenia or with bipolar disorder; further, there was no significant difference between the DBZ mRNA levels of control, schizophrenia and bipolar postmortem brains. We suggest a possible role of PCNT2 in the pathogenesis of schizophrenia. Abnormalities of PCNT2, the centrosomal protein essential for microtubule organization, may be suggested to lead to neurodevelopmental abnormalities.

Preliminary genome-wide association study of bipolar disorder in the Japanese population.

Recent progress in genotyping technology and the development of public databases has enabled large-scale genome-wide association tests with diseases. We performed a two-stage genome-wide association study (GWAS) of bipolar disorder (BD) in Japanese cohorts. First we used Affymetrix 100K GeneChip arrays in the analysis of 107 cases with bipolar I disorder and 107 controls, and selected markers that were nominally significant (P < 0.01) in at least one of the three models (1,577 markers in total). In the follow-up stage, we analyzed these markers using an Illumina platform (1,526 markers; 51 markers were not designable for the platform) and an independent sample set, which consisted of 395 cases (bipolar I + II) and 409 controls. We also assessed the population stratification of current samples using principal components analysis. After the two-stage analysis, 89 markers remained nominally significant (allelic P < 0.05) with the same allele being consistently over-represented in both the first and the follow-up stages. However, none of these were significant after correction for multiple-testing by false discovery rates. Sample stratification was virtually negligible. Collectively, this is the first GWAS of BD in the Japanese population. But given the small sample size and the limited genomic coverage, these results should be taken as preliminary.

Interaction effect of oxytocin receptor (OXTR) rs53576 genotype and maternal postpartum depression on child behavioural problems.

Previous studies have reported interaction effects of oxytocin receptor genotype (rs53576) and environmental factors on mental health in youth. However, the findings are mixed, especially regarding the type of allele (i.e., A vs. G), and it remains unanswered whether such an interaction presents at an early stage of development. Thus, using a unique longitudinal birth cohort sample in Japan (n = 568), we examined whether there was an effect of the interaction between the OXTR rs53576 genotype and maternal postpartum depression, as an environmental risk, on behavioural problems in children. Child behavioural problems (internalising and externalising problems) were ascertained using the Strengths and Difficulties Questionnaire when children were 6 years old. Maternal postpartum depression was measured using the Edinburgh Postnatal Depression Scale when children were at 2 months and 10 months of age. The results revealed a significant effect in the interaction between OXTR rs53576 genotype and maternal postpartum depression on externalising problems in children with AA genotype (ß = 0.136, 95% CI 0.032 to 0.240), but not in those with GG/GA genotype. This indicates that an interaction of vulnerable genotypes (i.e., A allele of OXTR rs53576) with an environmental burden (i.e. maternal postpartum depression) may be one of the potential elements that predisposes the infant to developing behavioural problems early in life. Hence, special attention needs to be paid to children exposed to environmental risks such as maternal postpartum depression, to facilitate the provision of appropriate care.