Variations of the candidate SEZ6L2 gene on Chromosome 16p11.2 in patients with autism spectrum disorders and in human populations.

BACKGROUND: Autism spectrum disorders (ASD) are a group of severe childhood neurodevelopmental disorders with still unknown etiology. One of the most frequently reported associations is the presence of recurrent de novo or inherited microdeletions and microduplications on chromosome 16p11.2. The analysis of rare variations of 8 candidate genes among the 27 genes located in this region suggested SEZ6L2 as a compelling candidate. METHODOLOGY/PRINCIPAL FINDINGS: We further explored the role of SEZ6L2 variations by screening its coding part in a group of 452 individuals, including 170 patients with ASD and 282 individuals from different ethnic backgrounds of the Human Genome Diversity Panel (HGDP), complementing the previously reported screening. We detected 7 previously unidentified non-synonymous variations of SEZ6L2 in ASD patients. We also identified 6 non-synonymous variations present only in HGDP. When we merged our results with the previously published, no enrichment of non-synonymous variation in SEZ6L2 was observed in the ASD group compared with controls. CONCLUSIONS/SIGNIFICANCE: Our results provide an extensive ascertainment of the genetic variability of SEZ6L2 in human populations and do not support a major role for SEZ6L2 sequence variations in the susceptibility to ASD.

Identification of pathway-biased and deleterious melatonin receptor mutants in autism spectrum disorders and in the general population.

Melatonin is a powerful antioxidant and a synchronizer of many physiological processes. Alteration of the melatonin pathway has been reported in circadian disorders, diabetes and autism spectrum disorders (ASD). However, very little is known about the genetic variability of melatonin receptors in humans. Here, we sequenced the melatonin receptor MTNR1A and MTNR1B, genes coding for MT1 and MT2 receptors, respectively, in a large panel of 941 individuals including 295 patients with ASD, 362 controls and 284 individuals from different ethnic backgrounds. We also sequenced GPR50, coding for the orphan melatonin-related receptor GPR50 in patients and controls. We identified six non-synonymous mutations for MTNR1A and ten for MTNR1B. The majority of these variations altered receptor function. Particularly interesting mutants are MT1-I49N, which is devoid of any melatonin binding and cell surface expression, and MT1-G166E and MT1-I212T, which showed severely impaired cell surface expression. Of note, several mutants possessed pathway-selective signaling properties, some preferentially inhibiting the adenylyl cyclase pathway, others preferentially activating the MAPK pathway. The prevalence of these deleterious mutations in cases and controls indicates that they do not represent major risk factor for ASD (MTNR1A case 3.6% vs controls 4.4%; MTNR1B case 4.7% vs 3% controls). Concerning GPR50, we detected a significant association between ASD and two variations, Delta502-505 and T532A, in affected males, but it did not hold up after Bonferonni correction for multiple testing. Our results represent the first functional ascertainment of melatonin receptors in humans and constitute a basis for future structure-function studies and for interpreting genetic data on the melatonin pathway in patients.

An investigation of ribosomal protein L10 gene in autism spectrum disorders.

BACKGROUND: Autism spectrum disorders (ASD) are severe neurodevelopmental disorders with the male:female ratio of 4:1, implying the contribution of X chromosome genetic factors to the susceptibility of ASD. The ribosomal protein L10 (RPL10) gene, located on chromosome Xq28, codes for a key protein in assembling large ribosomal subunit and protein synthesis. Two non-synonymous mutations of RPL10, L206M and H213Q, were identified in four boys with ASD. Moreover, functional studies of mutant RPL10 in yeast exhibited aberrant ribosomal profiles. These results provided a novel aspect of disease mechanisms for autism--aberrant processes of ribosome biosynthesis and translation. To confirm these initial findings, we re-sequenced RPL10 exons and quantified mRNA transcript level of RPL10 in our samples. METHODS: 141 individuals with ASD were recruited in this study. All RPL10 exons and flanking junctions were sequenced. Furthermore, mRNA transcript level of RPL10 was quantified in B lymphoblastoid cell lines (BLCL) of 48 patients and 27 controls using the method of SYBR Green quantitative PCR. Two sets of primer pairs were used to quantify the mRNA expression level of RPL10: RPL10-A and RPL10-B. RESULTS: No non-synonymous mutations were detected in our cohort. Male controls showed similar transcript level of RPL10 compared with female controls (RPL10-A, U = 81, P = 0.7; RPL10-B, U = 61.5, P = 0.2). We did not observe any significant difference in RPL10 transcript levels between cases and controls (RPL10-A, U = 531, P = 0.2; RPL10-B, U = 607.5, P = 0.7). CONCLUSION: Our results suggest that RPL10 has no major effect on the susceptibility to ASD.

Polymorphisms of coding trinucleotide repeats of homeogenes in neurodevelopmental psychiatric disorders.

OBJECTIVES: Autism (MIM#209850) and schizophrenia (MIM#181500) are both neurodevelopmental psychiatric disorders characterized by a highly genetic component. Homeogenes and forkhead genes encode transcription factors, which have been involved in brain development and cell differentiation. Thus, they are relevant candidate genes for psychiatric disorders. Genetic studies have reported an association between autism and DLX2, HOXA1, EN2, ARX, and FOXP2 genes whereas only three studies of EN2, OTX2, and FOXP2 were performed on schizophrenia. Interestingly, most of these candidate genes contain trinucleotide repeats coding for polyamino acid stretch in which instability can be the cause of neurodevelopmental disorders. Our goal was to identify variations of coding trinucleotide repeats in schizophrenia, autism, and idiopathic mental retardation. METHODS: We screened the coding trinucleotide repeats of OTX1, EN1, DLX2, HOXA1, and FOXP2 genes in populations suffering from schizophrenia (247 patients), autism (98 patients), and idiopathic mental retardation (56 patients), and compared them with control populations (112 super controls and 202 healthy controls). RESULTS: Novel deletions and insertions of coding trinucleotide repeats were found in the DLX2, HOXA1, and FOXP2 genes. Most of these variations were detected in controls and no difference in their distribution was observed between patient and control groups. Two different polymorphisms in FOXP2 were, however, found only in autistic patients and the functional consequences of these variations of repeats have to be characterized and correlated to particular clinical features. CONCLUSION: This study did not identify specific disease risk variants of trinucleotide repeats in OTX1, EN1, DLX2, HOXA1, and FOXP2 candidate genes in neurodevelopmental psychiatric disorders.

Analysis of X chromosome inactivation in autism spectrum disorders.

Autism spectrum disorders (ASD) are complex genetic disorders more frequently observed in males. Skewed X chromosome inactivation (XCI) is observed in heterozygous females carrying gene mutations involved in several X-linked syndromes. In this study, we aimed to estimate the role of X-linked genes in ASD susceptibility by ascertaining the XCI pattern in a sample of 543 informative mothers of children with ASD and in a sample of 163 affected girls. The XCI pattern was also determined in two control groups (144 adult females and 40 young females) with a similar age distribution to the mothers sample and affected girls sample, respectively. We observed no significant excess of skewed XCI in families with ASD. Interestingly, two mothers and one girl carrying known mutations in X-linked genes (NLGN3, ATRX, MECP2) showed highly skewed XCI, suggesting that ascertainment of XCI could reveal families with X-linked mutations. Linkage analysis was carried out in the subgroup of multiplex families with skewed XCI (> or = 80:20) and a modest increased allele sharing was obtained in the Xq27-Xq28 region, with a peak Z-score of 1.75 close to rs719489. In summary, our results suggest that there is no major X-linked gene subject to XCI and expressed in blood cells conferring susceptibility to ASD. However, the possibility that rare mutations in X-linked genes could contribute to ASD cannot be excluded. We propose that the XCI profile could be a useful criteria to prioritize families for mutation screening of X-linked candidate genes.

Mutations in the gene encoding the synaptic scaffolding protein SHANK3 are associated with autism spectrum disorders.

SHANK3 (also known as ProSAP2) regulates the structural organization of dendritic spines and is a binding partner of neuroligins; genes encoding neuroligins are mutated in autism and Asperger syndrome. Here, we report that a mutation of a single copy of SHANK3 on chromosome 22q13 can result in language and/or social communication disorders. These mutations concern only a small number of individuals, but they shed light on one gene dosage-sensitive synaptic pathway that is involved in autism spectrum disorders.

Shared executive dysfunctions in unaffected relatives of patients with autism and obsessive-compulsive disorder.

BACKGROUND: Executive dysfunctions have been studied as a potential endophenotype associated with the genetic basis of autism. Given that recent findings from clinical and molecular genetic studies suggest that autism and obsessive-compulsive disorder (OCD) could share a common pattern of heritability, we assessed executive functions as a possible common cognitive endophenotype in unaffected family members of individuals with either autism or OCD. METHODS: Five tests assessing executive functions (Tower of London, verbal fluency, design fluency, trail making and association fluency) were proposed to 58 unaffected first-degree relatives (parents and siblings) of probands with autism and 64 unaffected first-degree relatives of OCD patients. Results were compared with those of 47 healthy controls matched for age, sex, and level of education. RESULTS: In the Tower of London test, both groups of unaffected relatives showed significantly lower scores and longer response times compared with controls. No differences were observed between autism and OCD relatives and healthy controls in the four other tasks (verbal fluency, design fluency, trail making test and association fluency). CONCLUSIONS: Our findings show the existence of executive dysfunction in the unaffected first-degree relatives of probands with OCD, similar to those observed in the relatives of patients with autism. These results support and extend previous cognitive studies on probands indicating executive dysfunctions in autism and OCD. Planning and working memory processes could thus represent a common cognitive endophenotype in autism and OCD that could help in the identification of genes conferring vulnerability to these disorders.

Exploratory analysis of obsessive compulsive symptom dimensions in children and adolescents: a prospective follow-up study.

BACKGROUND: Recent statistical approaches based on factor analysis of obsessive compulsive (OC) symptoms in adult patients have identified dimensions that seem more effective in symptom-based taxonomies and appear to be more stable over time. Although a phenotypic continuum from childhood to adulthood has been hypothesized, no factor analytic studies have been performed in juvenile patients, and the stability of OC dimensions in children and adolescents has not been assessed. METHODS: This study was designed to perform an exploratory factor analysis of OC symptoms in a sample of children and adolescents with OC disorder (OCD) and to investigate the course of factors over time (mean follow-up period: four years). RESULTS: We report for the first time that four symptom dimensions, remarkably similar to those previously described in adults, underlined the heterogeneity of OC symptoms in children and adolescents. Moreover, after follow-up, the symptom dimensions identified remained essentially unmodified. The changes observed concerned the intensity of dimensions rather than shifts from one dimension to another. CONCLUSION: These findings reinforce the hypothesis of a phenotypic continuum of OC symptoms from childhood to adulthood. They also strengthen the interest for investigating the clinical, neurobiological and genetic heterogeneity of OCD using a dimension-based approach.

Platelet serotonergic markers as endophenotypes for obsessive-compulsive disorder.

Although compelling evidence has shown that obsessive-compulsive disorder (OCD) has a strong genetic component, its genetic basis remains to be elucidated. Identifying biological abnormalities in nonaffected relatives is one of the strategies advocated to isolate genetic vulnerability factors in complex disorders. Since peripheral serotonergic disturbances are frequently observed in OCD patients, the aim of this study was to investigate if they could represent endophenotypes, by searching for similar abnormalities in the unaffected parents of OCD patients. We assessed whole blood serotonin (5-HT) concentration, platelet 5-HT transporter (5-HTT) and 5-HT2A receptor-binding characteristics, and platelet inositol trisphosphate (IP3) content in a sample of OCD probands (n = 48) and their unaffected parents (n = 65), and compared them with sex- and age-matched controls (n = 113). Lower whole blood 5-HT concentration, fewer platelet 5-HTT-binding sites, and higher platelet IP3 content were found in OCD probands and their unaffected parents compared to controls. Whole blood 5-HT concentration showed a strong correlation within families (p < 0.001). The only parameter that appeared to discriminate affected and unaffected subjects was 5-HT2A receptor-binding characteristics, with increased receptor number and affinity in parents and no change in OCD probands. The presence of peripheral serotonergic abnormalities in OCD patients and their unaffected parents supports a familial origin of these disturbances. These alterations may serve as endophenotypic markers in OCD, and could contribute to the study of the biological mechanisms and genetic underpinnings of the disorder.

Admixture analysis of age at onset in obsessive-compulsive disorder.

BACKGROUND: Age at onset (AAO) has been useful to explore the clinical, neurobiological and genetic heterogeneity of obsessive-compulsive disorder (OCD). However, none of the various thresholds of AAO used in previous studies have been validated, and it remains an unproven notion that AAO is a marker for different subtypes of OCD. If AAO is a clinical indicator of different biological subtypes, then subgroups based on distinct AAOs should have separate normal distributions as well as different clinical characteristics. METHOD: Admixture analysis was used to determine the best-fitting model for the observed AAO of 161 OCD patients. RESULTS: The observed distribution of AAO in OCD is a mixture of two Gaussian distributions with mean ages of 11.1 +/- 4.1 and 23.5 +/- 11.1 years. The first distribution, defined by early-onset OCD, had increased frequency of Tourette's syndrome and increased family history of OCD. The second distribution, defined by late-onset OCD, showed elevated prevalence of general anxiety disorder and major depressive disorder. CONCLUSIONS: These results, based on a statistically validated AAO cut-off and those of previous studies on AAO in OCD, suggest that AAO is a crucial phenotypic characteristic in understanding the genetic basis of this disorder.

Perception of complex sounds in autism: abnormal auditory cortical processing in children.

OBJECTIVE: The authors have previously described less activation of left speech-related temporal areas in adults with autism when listening to speech-like sounds than in normal adults. Here, they investigated whether this abnormal cortical processing was also present in children with primary autism. METHOD: Regional cerebral blood flow was measured with positron emission tomography after premedication in 11 autistic children and six nonautistic mentally retarded children during rest and while they were listening to speech-like sounds. RESULTS: As with autistic adults, direct comparison between the two groups revealed significantly less activation in the autistic group localized in left speech-related areas. CONCLUSIONS: For the first time to their knowledge, an activation study was performed in children with autism and has confirmed previous results obtained in adults. The abnormal cortical auditory processing observed in both children and adults with autism could be involved in inadequate behavioral responses to sounds and in language impairments characteristic of autism.

Discrimination of face identities and expressions in children with autism: same or different?

Autism is a pervasive developmental disorder (PDD) characterized by the association of communication and socialization impairments, and by repetitive stereotyped behaviours. The Minnesota Test of Affective Processing (MNTAP) was used to investigate the discrimination of face identities and face expressions by autistic children. Young children in the 6- to 10-year-old age range suffering from PDD were compared to paired normal children. When the expressions on faces remained neutral, autistic patients had more difficulty in distinguishing different faces than in matching the same facial identities in face pairs: they perceived different faces as being identical. However, recognition errors disappeared when expressions were changed together with face identity. When autistic children were asked to distinguish expressions, they discriminated better identity than difference, just as normal children do. Analysis of face and expression discrimination in terms of identity and difference is a novel approach for the understanding of the clinical features of autism. Autistic children seek sameness and use an atypical strategy to analyse human faces and expressions.

Mental disorders in obese children and adolescents.

OBJECTIVE: To evaluate the type and frequency of psychiatric disorders in obese children and adolescents; to assess the correlation between psychopathology and severity of obesity; to explore the relationship between psychiatric disorders in obese children and obesity and psychopathology in their parents. METHODS: One hundred fifty-five children referred and followed for obesity were evaluated (98 girls and 57 boys; age, 5 to 17 years). Psychiatric disorders were assessed through a standardized diagnostic interview schedule (K-SADS R) and self-report questionnaires completed by the child (STAIC Trait-anxiety and CDI for depression) or his (her) parents (CBCL or GHQ). These obese children were compared with insulin-dependent diabetic (IDDM) outpatient children (N = 171) on questionnaire data. RESULTS: Eighty-eight obese children obtained a DSM-IV diagnosis, most often an anxiety disorder (N = 63). Psychological disorders were particularly pronounced in those obese children whose parents were disturbed. There was no correlation between severity of obesity in the child or his (her) parents and frequency of psychiatric disorders. Compared with diabetic children, they displayed significantly higher internalized and externalized questionnaire scores and poorer social skills. CONCLUSION: These results highlight the importance of including a child psychiatric component in the treatment of obesity, which must engage the whole family.

Frequency and transmission of glutamate receptors GRIK2 and GRIK3 polymorphisms in patients with obsessive compulsive disorder.

Several lines of evidence suggest that obsessive compulsive disorder (OCD) could be the consequence of glutamatergic dysfunction. We performed a case-control study in 156 patients and 141 controls and the transmission disequilibrium test in 124 parent-offspring trios to search for association between OCD and two kainate receptors, GRIK2 and GRIK3. Using three single nucleotide polymorphisms (SNP) in GRIK2 and one in GRIK3, we found no evidence for association in case-control or family-based analyses. Only the GRIK2 SNP I867, recently associated with autism, was less transmitted than expected (p < 0.03), supporting a functional role for this variant. These findings suggest the need for further investigation of the role of GRIK2 in OCD.

Platelet serotonergic predictors of clinical improvement in obsessive compulsive disorder.

OBJECTIVE: Serotonin reuptake inhibitors (SRIs) are the most efficient pharmacological treatment of obsessive-compulsive disorders (OCD). Previous studies have suggested that some peripheral serotonergic parameters can be used to predict the clinical outcome of the treatment of OCD patients with SRIs. We tried to identify further peripheral serotonergic parameters that could help predict the clinical outcome of SRI treatment in a sample of patients with OCD. METHODS: We compared 19 OCD patients before and after 8 weeks of SRI treatment with 19 sex-matched and age-matched controls. We assessed clinical improvement and whole-blood serotonin (5-HT) concentration, platelet 5-HT transporter (5-HTT) and 5-HT2A receptor binding characteristics and platelet IP3 content. RESULTS: Before treatment, OCD patients had higher platelet IP3 content and fewer 5-HTT binding sites than the controls. Treatment with SRIs further lowered the number of 5-HTT binding sites, normalized platelet IP3 contents, and lowered the number of platelet 5-HT2A binding sites and whole-blood 5-HT concentrations below control values. The patients who improved most following SRI treatment had higher whole-blood 5-HT concentrations before treatment. CONCLUSION: Our results confirm that whole-blood 5-HT concentration is a predictor for clinical improvement and indicate that abnormal intracellular mechanisms may be involved in OCD patients, in particular, the overstimulation of the phosphoinositide signaling system.

Perception of complex sounds: abnormal pattern of cortical activation in autism.

OBJECTIVE: Bilateral temporal hypoperfusion at rest was recently described in autism. In normal adults, these regions are activated by listening to speech-like sounds. To investigate auditory cortical processing in autism, the authors performed a positron emission tomography activation study. METHOD: Regional cerebral blood flow was measured in five autistic adults and eight comparison subjects during rest and while listening to speech-like sounds. RESULTS: Similar to the comparison subjects, autistic patients showed a bilateral activation of the superior temporal gyrus. However, an abnormal pattern of hemispheric activation was observed in the autistic group. The volume of activation was larger on the right side in the autistic patients, whereas the reverse pattern was found in the comparison group. The direct comparison between the two groups showed that the right middle frontal gyrus exhibited significantly greater activation in the autistic group. Conversely, the left temporal areas exhibited less activation in autistic patients. CONCLUSIONS: These findings suggest that abnormal auditory cortical processing is implicated in the language impairments and the inadequate response to sounds typically seen in autism.

Binge eating and psychopathology in severely obese adolescents.

OBJECTIVE: The authors describe binge eating and psychopathology in severely obese adolescents who are seeking treatment for obesity and search for specific psychological features that may be associated with binge eating. METHOD: Obese adolescents (n = 102) were assessed with the Binge Eating Scale (BES), the State-Trait Anxiety Inventory for Children (STAIC), the Beck Depression Inventory (BDI), Coopersmith's Self-Esteem Inventory (SEI), and the Body-Esteem subscale from the Piers-Harris Children's Self-Concept Scale (PHCSS). They were also evaluated with the Montgomery and Asberg Depression Rating Scale (MADRS) and the Brief Scale for Anxiety (BSA). Two subgroups (i.e., binge eaters and non-binge eaters) were then established according to the BES score. RESULTS: Binge eating symptoms were frequent in this population and the binge eating dimension was related to high levels of anxiety and depression, as well as to low levels of self-esteem and body-esteem. The dimensions of anxiety and depression were associated specifically with binge eaters. DISCUSSION: As observed in the obese adult population, binge eating symptoms were found frequently in severely obese adolescents seeking treatment and were related strongly to studied parameters. Obese adolescents who binge eat are a subgroup with high psychopathologic distress.

Psychopathology and quality of life for adolescents with asthma and their parents.

Asthma is known to have a direct impact on the quality of life of children with asthma and their families as a consequence of the attacks on day-to-day life. Psychopathological factors may be associated with poor quality of life by modulating the handicap and the patient's experience of it. The authors' objective was to evaluate the relationship between emotional and behavioral problems and quality of life, as assessed by the Pediatric Asthma Quality of Life Questionnaire and the Pediatric Asthma Caregiver's Quality of Life Questionnaire. The study group consisted of 100 adolescent outpatients with asthma who were undergoing regular checkups: 70 boys and 30 girls, ages 12 to 19. They were evaluated by means of self-administered questionnaires completed by their parents. Path analysis was used to propose a model of relationships between psychopathology and quality of life. The quality of life of the children with asthma and their parents was clearly associated with the presence or absence of psychological problems in the patients. Emotional problems were associated with the quality of life of both the patients and their parents; behavioral problems had a smaller effect on the quality of life of the parents only. The authors proposed a structural model of the quality of life of adolescents with asthma and their parents in which quality of life is dependent on psychological variables and is responsible for emotional problems. Multivariate analyses indicated that the quality of life of the children with asthma and their parents and the correlation between quality of life and psychopathology depended little on medical variables such as the duration of illness, its pretreatment severity, or hospitalizations in the past year. In contrast, the quality of life of the parents depended on that of the children and vice versa. This study showed that scores on the Pediatric Asthma Quality of Life Questionnaire and the Pediatric Asthma Caregiver's Quality of Life Questionnaire reflected not only the medical status of the patients but also psychological variables, which appeared to be a consequence of the functional handicap associated with asthma. Patients who assess the quality of their lives as poor would benefit from psychological evaluation and support.

Association between the dopamine receptor D4 (DRD4) gene and obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is a frequent and disabling anxiety disorder. Dopamine (DA) might be involved in its pathophysiology, therefore DA receptors are candidate genes in OCD. A 48-base pairs (bp) polymorphism located in the third exon of the dopamine receptor type 4 (DRD4) gene has been described. Previous case control studies, however, have reported inconclusive results in OCD. The aim of the study was to study this polymorphism in a family-based association study of 55 trios. Extended transmission-disequilibrium test (ETDT) for preferential allele transmission in this group showed an absence of transmission of the allele 2 for the 48 bp repeat polymorphism of the DRD4 gene (P = 0.005). Moreover, in a population-based association study, we found a significantly lower frequency of the allele 2 in patients suffering from OCD compared to ethnically-matched controls (P = 0.02). We found no association of DRD4 48 bp polymorphism with OCD in the subgroup of patients with comorbid tics. This study is the first to report on a significant association of variants of the DRD4 gene in OCD, found on both family- and population-based studies. The results suggest that the 2 allele or a nearby genetic variation could have a protective effect against OCD symptoms.

Fringe phenotypes in autism: a review of clinical, biochemical and cognitive studies.

Progress in identifying the genetic vulnerability factors in autism requires correct identification of the inherited phenotype(s). This can be achieved not only by the accurate description of the affected subject but also by the identification of vulnerability traits in non-affected relatives of autistic probands. This review will focus on this last strategy and principally on clinical, biochemical and cognitive traits.