Taishi Miyachi

Two genetic variants of CD38 in subjects with autism spectrum disorder and controls.

The neurobiological basis of autism spectrum disorder (ASD) remains poorly understood. Given the role of CD38 in social recognition through oxytocin (OT) release, we hypothesized that CD38 may play a role in the etiology of ASD. Here, we first examined the immunohistochemical expression of CD38 in the hypothalamus of post-mortem brains of non-ASD subjects and found that CD38 was colocalized with OT in secretory neurons. In studies of the association between CD38 and autism, we analyzed 10 single nucleotide polymorphisms (SNPs) and mutations of CD38 by re-sequencing DNAs mainly from a case-control study in Japan, and Caucasian cases mainly recruited to the Autism Genetic Resource Exchange (AGRE). The SNPs of CD38, rs6449197 (p<0.040) and rs3796863 (p<0.005) showed significant associations with a subset of ASD (IQ>70; designated as high-functioning autism (HFA)) in the U.S. 104 AGRE family trios, but not with Japanese 188 HFA subjects. A mutation that caused tryptophan to replace arginine at amino acid residue 140 (R140W; (rs1800561, 4693C>T)) was found in 0.6-4.6% of the Japanese population and was associated with ASD in the smaller case-control study. The SNP was clustered in pedigrees in which the fathers and brothers of T-allele-carrier probands had ASD or ASD traits. In this cohort OT plasma levels were lower in subjects with the T allele than in those without. One proband with the T allele who was taking nasal OT spray showed relief of symptoms. The two variant CD38 poloymorphysms tested may be of interest with regard of the pathophysiology of ASD.

Genetic influences on the broad spectrum of autism: study of proband-ascertained twins.

An investigation of genetic structures underlying autistic traits was performed with samples from twins for which at least one proband had been ascertained as having autism spectrum disorders (ASDs) in our catchment area. In order to adjust for recent concepts of autism, we employed criteria for the broad spectrum of disease and the childhood autism rating scale (CARS) for quantitative assessment. The CARS test was performed on 45 twin pairs (19 monozygotic, 26 dizygotic) detected with a regional routine screening system. The obtained CARS scores were subjected to structural equation modeling (SEM), incorporating sex differences for each causal influence ascertainment correction, using the Mx software. A best fitting model of causal influences on autistic traits measured continuously, incorporating additive genetic (A) and non‐shared environmental influences (E), was generated. With this AE model, the estimated heritability was 0.73 for males and 0.87 for females, based on the continuous CARS scores. There was no evidence for the existence of sex‐specific genetic influences. Autistic traits were highly heritable in twins with even broad spectrum of autism, corresponding to the results of early studies based on classical autism. Additive genetic factors were more influential in females than males.

Genetic analyses of Roundabout (ROBO) axon guidance receptors in autism

Autism is a pervasive developmental disorder diagnosed in early childhood. Abnormalities of serotonergic neurotransmission have been reported in autism. Serotonin transporter (SERT) modulates serotonin levels, and is a major therapeutic target in autism. Factors that regulate SERT expression might be implicated in the pathophysiology of autism. One candidate SERT regulatory protein is the roundabout axon guidance molecule, ROBO. SerT expression in Drosophila is regulated by robo; it plays a vital role in mammalian neurodevelopment also. Here, we examined the associations of ROBO3 and ROBO4 with autism, in a trio association study using DNA from 252 families recruited to AGRE. Four SNPs of ROBO3 (rs3923890, P = 0.023; rs7925879, P = 0.017; rs4606490, P = 0.033; and rs3802905, P = 0.049) and a single SNP of ROBO4 (rs6590109, P = 0.009) showed associations with autism; the A/A genotype of rs3923890 showed lower ADI‐R_A scores, which reflect social interaction. Significant haplotype associations were also observed for ROBO3 and ROBO4. We further compared the mRNA expressions of ROBO1, ROBO2, ROBO3, and ROBO4 in the lymphocytes of 19 drug‐naïve autistic patients and 20 age‐ and sex‐matched controls. Expressions of ROBO1 (P = 0.018) and ROBO2 (P = 0.023) were significantly reduced in the autistic group; the possibility of using the altered expressions of ROBO as peripheral markers for autism, may be explored. In conclusion, we suggest a possible role of ROBO in the pathogenesis of autism. Abnormalities of ROBO may lead to autism either by interfering with serotonergic system, or by disrupting neurodevelopment. To the best of our knowledge, this is the first report relating ROBO with autism.

Brain region-specific altered expression and association of mitochondria-related genes in autism

BackgroundMitochondrial dysfunction (MtD) has been observed in approximately five percent of children with autism spectrum disorders (ASD). MtD could impair highly energy-dependent processes such as neurodevelopment, thereby contributing to autism. Most of the previous studies of MtD in autism have been restricted to the biomarkers of energy metabolism, while most of the genetic studies have been based on mutations in the mitochondrial DNA (mtDNA). Despite the mtDNA, most of the proteins essential for mitochondrial replication and function are encoded by the genomic DNA; so far, there have been very few studies of those genes. Therefore, we carried out a detailed study involving gene expression and genetic association studies of genes related to diverse mitochondrial functions.MethodsFor gene expression analysis, postmortem brain tissues (anterior cingulate gyrus (ACG), motor cortex (MC) and thalamus (THL)) from autism patients (n=8) and controls (n=10) were obtained from the Autism Tissue Program (Princeton, NJ, USA). Quantitative real-time PCR arrays were used to quantify the expression of 84 genes related to diverse functions of mitochondria, including biogenesis, transport, translocation and apoptosis. We used the delta delta Ct (∆∆Ct) method for quantification of gene expression. DNA samples from 841 Caucasian and 188 Japanese families were used in the association study of genes selected from the gene expression analysis. FBAT was used to examine genetic association with autism.ResultsSeveral genes showed brain region-specific expression alterations in autism patients compared to controls. Metaxin 2 (MTX2), neurofilament, light polypeptide (NEFL) and solute carrier family 25, member 27 (SLC25A27) showed consistently reduced expression in the ACG, MC and THL of autism patients. NEFL (P = 0.038; Z-score 2.066) and SLC25A27 (P = 0.046; Z-score 1.990) showed genetic association with autism in Caucasian and Japanese samples, respectively. The expression of DNAJC19, DNM1L, LRPPRC, SLC25A12, SLC25A14, SLC25A24 and TOMM20 were reduced in at least two of the brain regions of autism patients.ConclusionsOur study, though preliminary, brings to light some new genes associated with MtD in autism. If MtD is detected in early stages, treatment strategies aimed at reducing its impact may be adopted.

Downregulation of the Expression of Mitochondrial Electron Transport Complex Genes in Autism Brains

Mitochondrial dysfunction (MtD) and abnormal brain bioenergetics have been implicated in autism, suggesting possible candidate genes in the electron transport chain (ETC). We compared the expression of 84 ETC genes in the post‐mortem brains of autism patients and controls. Brain tissues from the anterior cingulate gyrus, motor cortex, and thalamus of autism patients (n = 8) and controls (n = 10) were obtained from Autism Tissue Program, USA. Quantitative real‐time PCR arrays were used to quantify gene expression. We observed reduced expression of several ETC genes in autism brains compared to controls. Eleven genes of Complex I, five genes each of Complex III and Complex IV, and seven genes of Complex V showed brain region‐specific reduced expression in autism. ATP5A1 (Complex V), ATP5G3 (Complex V) and NDUFA5 (Complex I) showed consistently reduced expression in all the brain regions of autism patients. Upon silencing ATP5A1, the expression of mitogen‐activated protein kinase 13 (MAPK13), a p38 MAPK responsive to stress stimuli, was upregulated in HEK 293 cells. This could have been induced by oxidative stress due to impaired ATP synthesis. We report new candidate genes involved in abnormal brain bioenergetics in autism, supporting the hypothesis that mitochondria, critical for neurodevelopment, may play a role in autism.

Paternal age at birth and high-functioning autistic-spectrum disorder in offspring.

BACKGROUND Previous studies have reported the association between advanced paternal age at birth and the risk of autistic-spectrum disorder in offspring, including offspring with intellectual disability. AIMS To test whether an association between advanced paternal age at birth is found in offspring with high-functioning autistic-spectrum disorder (i.e. offspring without intellectual disability). METHOD A case-control study was conducted in Japan. The participants consisted of individuals with full-scale IQ>or=70, with a DSM-IV autistic disorder or related diagnosis. Unrelated healthy volunteers were recruited as controls. Parental ages were divided into tertiles (i.e. three age classes). Odds ratios and 95% confidence intervals were estimated using logistic regression analyses, with an adjustment for age, gender and birth order. RESULTS Eighty-four individuals with autistic-spectrum disorder but without intellectual disability and 208 healthy controls were enrolled. Increased paternal, but not maternal, age was associated with an elevated risk of high-functioning autistic-spectrum disorder. A one-level advance in paternal age class corresponded to a 1.8-fold increase in risk, after adjustment for covariates. CONCLUSIONS Advanced paternal age is associated with an increased risk for high-functioning autistic-spectrum disorder.

Evaluation of the Japanese version of the Developmental Coordination Disorder Questionnaire as a screening tool for clumsiness of Japanese children.

Developmental Coordination Disorder (DCD) is characterized by clumsiness and coordination difficulties. DCD interferes with academic performance and participation in physical activities and psychosocial functions, such as self-esteem, cognition, or emotion, from childhood through adolescence to adulthood. DCD is a common pediatric condition and its prevalence is estimated to be 6% worldwide. Although English questionnaires are available, there is no questionnaire to identify DCD in Japan, and therefore, no information on its prevalence is available. Recently, we developed the Japanese version of the Developmental Coordination Disorder Questionnaire (DCDQ-J). The purpose of this study was to describe the applicability of the DCDQ-J for use with a community-based population of children in Japan and to investigate the relationships between coordination and attention-deficit hyperactivity disorder (ADHD) tendencies or intelligence. The DCDQ-J was completed by 6330 parents or guardians of children and adolescents. We employed the ADHD-rating scale and determined the intelligence quotient (IQ) of the children. Two-way analysis of variance showed that the scores linearly increased as the childrens grades advanced in 2 subscales, namely, control during movement and fine motor. In contrast, non-linear changes were found in the scores of the general coordination subscale. The total scores of the DCDQ-J and ADHD-RS were significantly correlated, but no relationship between DCDQ-J scores and IQ was found. The DCDQ-J is expected to be a useful screening tool to identify and assess motor coordination difficulties of children in Japan and enable cross-cultural comparisons.

Genetic correlation between autistic traits and IQ in a population-based sample of twins with autism spectrum disorders (ASDs)

Although there is accumulating evidence that intelligence quotient (IQ) indexes some aspects of the autistic spectrum disorders (ASDs), the causal relationship between autistic traits and IQ remains controversial. We examined the sources of covariation between autistic traits and IQ. As males have a four times greater risk of ASDs than females, gender-specific effects were also explored. Autistic traits and IQ were assessed in 45 twin male–male, female–female and opposite-sex pairs ascertained by the regional screening system in Nagoya, Japan. Sex-limited Cholesky structural equation models were used to decompose the correlations between autistic traits and IQ into genetic and environmental components, including sex-specific factors. Genetic correlations between autistic traits and IQ were high and not significantly different between boys and girls (−0.94 and −0.95, respectively), but genetic factors underlying the autistic traits were not entirely shared with the IQ. The individual-specific environmental correlation between autistic traits and IQ was estimated at −0.29 for boys and −0.59 for girls. There is a substantial overlap between the genetic factors that influence individual variation in autistic traits and IQ, irrespective of gender. The individual life experiences that increase autistic traits, however, have a moderate overlap with those that contribute to individual IQs.

Serum levels of platelet-derived growth factor BB homodimers are increased in male children with autism.

BACKGROUND The neurobiological basis of autism remains poorly understood. To examine the role played by serum cytokines in brain development, we hypothesized that Platelet-Derived Growth Factor (PDGF) and Vascular Endothelial Growth Factor (VEGF) may be associated with pathophysiology of autism. In this study, we screened serum levels of these growth factors in young male subjects with autism. METHODS We measured serum levels of PDGF subtypes and VEGF in the 31 male children with autism (6-19 years old) and 31 healthy age- and gender-matched subjects. RESULTS The serum levels of PDGF-BB in male children with autism (N=31, 5624.5+/-1651.8 pg/mL [mean+/-SD]) were significantly higher (two-tailed Students t-test: p=0.0188) than those of normal control subjects (N=31, 4758.2+/-1521.5 pg/mL [mean+/-SD]). There was a significant and positive correlation (Pearsons r=0.5320, p=0.0010) between the serum levels of PDGF-BB and the Autism Diagnostic Interview-Revised (ADI-R) domain C scores, which represent stereotyped patterns of behavior in the children with autism. However, there were no marked or significant correlations between serum PDGF-BB levels and clinical variables, including the other ADI-R scores and Intellectual Quotient (IQ) scores by WAIS-R. There were no significant change and correlations with clinical variables in serum PDGF-AA, PDGF-AB, and VEGF levels in the children with autism. CONCLUSIONS Increased levels of serum PDGF-BB homodimers might be implicated in the pathophysiology of autism.

Replication study of Japanese cohorts supports the role of STX1A in autism susceptibility.

Autism is a pervasive developmental disorder diagnosed in early childhood. Abnormalities of serotonergic neurotransmission have been reported in autism. Serotonin transporter (5-HTT), which modulates serotonin levels, is a major therapeutic target in autism. Therefore, factors that regulate 5-HTT expression might be implicated in autism. One candidate 5-HTT-regulatory protein is the presynaptic protein, syntaxin 1A (STX1A). We examined the association of STX1A with autism in a trio association study using DNA samples from Japanese trios with autistic probands. In TDT analysis, rs69510130 (p=0.027) showed nominal associations with autism; modest haplotype association was also observed. We further compared STX1A mRNA expression between the autistic and control groups in the postmortem brain. In the anterior cingulate gyrus region, STX1A expression in the autism group was found to be significantly lower than that of the control group. Thus, we suggest a possible role of STX1A in the pathogenesis of autism.