Frédérique Bonnet-Brilhault

X-linked mental retardation and autism are associated with a mutation in the NLGN4 gene, a member of the Neuroligin family

A large French family including members affected by nonspecific X-linked mental retardation, with or without autism or pervasive developmental disorder in affected male patients, has been found to have a 2-base-pair deletion in the Neuroligin 4 gene (NLGN4) located at Xp22.33. This mutation leads to a premature stop codon in the middle of the sequence of the normal protein and is thought to suppress the transmembrane domain and sequences important for the dimerization of neuroligins that are required for proper cell-cell interaction through binding to beta-neurexins. As the neuroligins are mostly enriched at excitatory synapses, these results suggest that a defect in synaptogenesis may lead to deficits in cognitive development and communication processes. The fact that the deletion was present in both autistic and nonautistic mentally retarded males suggests that the NLGN4 gene is not only involved in autism, as previously described, but also in mental retardation, indicating that some types of autistic disorder and mental retardation may have common genetic origins.

Recurrent Rearrangements in Synaptic and Neurodevelopmental Genes and Shared Biologic Pathways in Schizophrenia, Autism, and Mental Retardation

CONTEXT Results of comparative genomic hybridization studies have suggested that rare copy number variations (CNVs) at numerous loci are involved in the cause of mental retardation, autism spectrum disorders, and schizophrenia. OBJECTIVES To provide an estimate of the collective frequency of a set of recurrent or overlapping CNVs in 3 different groups of cases compared with healthy control subjects and to assess whether each CNV is present in more than 1 clinical category. DESIGN Case-control study. SETTING Academic research. PARTICIPANTS We investigated 28 candidate loci previously identified by comparative genomic hybridization studies for gene dosage alteration in 247 cases with mental retardation, in 260 cases with autism spectrum disorders, in 236 cases with schizophrenia or schizoaffective disorder, and in 236 controls. MAIN OUTCOME MEASURES Collective and individual frequencies of the analyzed CNVs in cases compared with controls. RESULTS Recurrent or overlapping CNVs were found in cases at 39.3% of the selected loci. The collective frequency of CNVs at these loci is significantly increased in cases with autism, in cases with schizophrenia, and in cases with mental retardation compared with controls (P < .001, P = .01, and P = .001, respectively, Fisher exact test). Individual significance (P = .02 without correction for multiple testing) was reached for the association between autism and a 350-kilobase deletion located at 22q11 and spanning the PRODH and DGCR6 genes. CONCLUSIONS Weakly to moderately recurrent CNVs (transmitted or occurring de novo) seem to be causative or contributory factors for these diseases. Most of these CNVs (which contain genes involved in neurotransmission or in synapse formation and maintenance) are present in the 3 pathologic conditions (schizophrenia, autism, and mental retardation), supporting the existence of shared biologic pathways in these neurodevelopmental disorders.

Cortical auditory processing and communication in children with autism: electrophysiological/behavioral relations

The purpose of the present study was to investigate the relations between late auditory evoked potentials (AEPs) recorded at temporal sites (the N1c wave or Tb) and verbal and non-verbal abilities in children with autism. The study was performed in 26 mentally retarded children with autism (AUT) aged 4-8 years (mean age +/- S.E.M. = 71 +/- 2 months; mean verbal and non-verbal developmental quotient +/- S.E.M. = 36 +/- 4 and 48 +/- 3). The stimuli used were 750 Hz tone bursts of 200 ms duration delivered binaurally at different intensity levels (50, 60, 70, 80 dB SPL) with 3-5 s interstimulus intervals. Temporal AEPs were first compared to those of a group of 16 normal children (NOR) in the same age range (mean age +/- S.E.M. = 69 +/- 3 months). We then focused on the AUT group and considered relations between temporal AEPs and the severity of disorders of verbal and non-verbal communication assessed using a behavior rating scale. AEPs recorded on left and right temporal sites were of smaller amplitude in the AUT group than in the NOR group. Increasing intensity-related amplitude was observed on both sides in NOR and only on the right side in AUT. The lack of intensity effect on the left side resulted in a particular pattern of asymmetry at the highest level of intensity (80 dB SPL) with greater N1c amplitude on the right than on the left side (the reverse was found in the NOR group). Electro-clinical correlations indicated that the greater the amplitude of the right temporal N1c responses, the higher the verbal and non-verbal communication abilities. This suggests a developmental reorganization of left-right hemisphere functions in autism, with preferential activation of the right hemisphere for functions usually allocated to the left hemisphere, particularly those involving the secondary auditory areas situated on the lateral surface of the superior temporal gyrus where the N1c/Tb wave is generated.

Autism and Nonsyndromic Mental Retardation Associated with a De Novo Mutation in the NLGN4X Gene Promoter Causing an Increased Expression Level

BACKGROUND Pathogenic mutations in the X-linked Neuroligin 4 gene (NLGN4X) in autism spectrum disorders (ASDs) and/or mental retardation (MR) are rare. However, nothing is known regarding a possible altered expression level of NLGN4X that would be caused by mutations in regulatory sequences. We investigated this issue by analyzing these regions in patients with ASDs and no mutation in the NLGN4X coding sequence. METHODS We studied 96 patients who met all DSM-IV criteria for autism. The entire coding sequence and the regulatory sequences of the NLGN4X gene were analyzed by polymerase chain reaction and direct sequencing. RESULTS We identified a de novo 1 base pair (-335G>A) substitution located in the promoter region in a patient with autism and nonsyndromic profound MR. Interestingly, this variation is associated with an increased level of the NLGN4X transcript in the patient compared with male control subjects as well as his father. Further in vitro luciferase reporter and electrophoretic mobility shift assays confirmed, respectively, that this mutation increases gene expression and is probably caused by altered binding of transcription factors in the mutated promoter sequence. CONCLUSIONS This result brings further insight about the phenotypic spectrum of NLGN4X mutations and suggests that the analysis of the expression level of NLGN4X might detect new cases.

Quality of life of adolescents with autism spectrum disorders: comparison to adolescents with diabetes

Relationships are of great importance during adolescence. Because of their social, communication and behavioral impairments, adolescents with Asperger’s syndrome (AS) or high functioning autism (HFA) probably suffer from considerable impairment of their quality of life when facing their peers in school. Nevertheless, only one recent study has been published on this subject, indicating a lower health-related quality of life in children and adolescents with autism spectrum disorders (ASD) than in healthy controls. The goals of our study were to clarify the consequences of autistic disorder without mental retardation on such adolescents’ daily lives, and to consider them in comparison with the impact of a chronic somatic disease (diabetes) and with the period of adolescence itself, using the VSP-A questionnaire. Adolescents with diabetes were chosen as a comparison group because of the encumbrance of having a constant need for insulin supplementation, to be assimilated to the constant need for communicative adjustments in teenagers with ASD, and the consequences in daily life. The effects of social skill training and social support on quality of life and the appropriateness of using the VSP-A in this population were also studied. Twenty-six adolescents with AS and HFA, 44 diabetic adolescents, and 250 controls completed a self-administered and validated questionnaire on quality of life, the VSP-A. Scores for adolescents with ASD were significantly lower than those of the control and the diabetic adolescents, especially for friendships, leisure time, and affective and sexual relationships. On the other hand, better scores were obtained for the relationships with parents and teachers and for self-image. Social parameters affected the quality of life of subjects with ASD, such as having friends, regularly participating in a sport, and having the support of a school carer. For subjects with autistic spectrum disorders and without mental retardation, impairment of quality of life is significant in adolescence and young adulthood. Such adolescents are dissatisfied with their relationships, although they often have real motivation to succeed with them. Relevance of VSP-A questionnaire in these special individuals is discussed.

Can pupil size and pupil responses during visual scanning contribute to the diagnosis of autism spectrum disorder in children

The purpose of this study was to determine whether baseline pupil size and pupil responses during visual scanning with eye-tracking technology could discriminate children with autism spectrum disorder (ASD) from mental age-matched and chronological age-matched controls. To this end, we used stimuli consisting in still color photographs presented centrally to the participants midline on a stimulus monitor. Each child was presented with a series of neutral faces, virtual faces (avatars) and different objects, separated by black slides. We recorded the mean pupil size and pupil size changes over time in each of the three categories of stimuli and during exposure to the black slides. Fifty-seven children participated in study (19 ASD, mean age 118 months; 19 mental age-matched controls, mean age 87 months; and 19 chronological age-matched controls, mean age 118 months). We compared the baseline pupil size and pupil responses during visual scanning among the three diagnostic groups. During the presentation of slides, the mean pupil size in the ASD group was clearly smaller than in the MA-matched and CA-matched groups. Discriminate analysis of pupil size during the presentation of black slides and slides with visual stimuli successfully predicted group membership in 72% of the participants. Group membership was correctly classified in 89% of the participants in the ASD group, in 63% in the MA-matched group and in 63% in the CA-matched group. These potential biomarkers may contribute to our understanding of the differences in neurological development in the brain in autism and could prove useful as indicators of ASD.

1H–13C NMR-based urine metabolic profiling in autism spectrum disorders

Autism Spectrum Disorders (ASD) are a group of developmental disorders caused by environmental and genetic factors. Diagnosis is based on behavioral and developmental signs detected before 3 years of age with no reliable biological marker. The purpose of this study was to evaluate the potential use of a 2D NMR-based approach to express the global biochemical signature of autistic individuals compared to normal controls. This technique has greater spectral resolution than to 1D (1)H NMR spectroscopy, which is limited by overlapping signals. The urinary metabolic profiles of 30 autistic and 28 matched healthy children were obtained using a (1)H-(13)C NMR-based approach. The data acquired were processed by multivariate orthogonal partial least-squares discriminant analysis (OPLS-DA). Some discriminating metabolites were identified: β-alanine, glycine, taurine and succinate concentrations were significatively higher, and creatine and 3-methylhistidine concentrations were lower in autistic children than in controls. We also noted differences in several other metabolites that were unidentified but characterized by a cross peak correlation in (1)H-(13)C HSQC. Statistical models of (1)H and (1)H-(13)C analyses were compared and only 2D spectra allowed the characterization of statistically relevant changes [R(2)Y(cum)=0.78 and Q(2)(cum)=0.60] in the low abundance metabolites. This method has the potential to contribute to the diagnosis of neurodevelopment disorders but needs to be validated on larger cohorts and on other developmental disorders to define its specificity.

Use of early intervention for young children with autism spectrum disorder across Europe

Little is known about use of early interventions for autism spectrum disorder in Europe. Parents of children with autism spectrum disorder aged 7 years or younger (N = 1680) were recruited through parent organisations in 18 European countries and completed an online survey about the interventions their child received. There was considerable variation in use of interventions, and in some countries more than 20% of children received no intervention at all. The most frequently reported interventions were speech and language therapy (64%) and behavioural, developmental and relationship-based interventions (55%). In some parts of Europe, use of behavioural, developmental and relationship-based interventions was associated with higher parental educational level and time passed since diagnosis, rather than with child characteristics. These findings highlight the need to monitor use of intervention for children with autism spectrum disorder in Europe in order to contrast inequalities.

Metabolomics Study of Urine in Autism Spectrum Disorders Using a Multiplatform Analytical Methodology

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with no clinical biomarker. The aims of this study were to characterize a metabolic signature of ASD and to evaluate multiplatform analytical methodologies in order to develop predictive tools for diagnosis and disease follow-up. Urine samples were analyzed using (1)H and (1)H-(13)C NMR-based approaches and LC-HRMS-based approaches (ESI+ and ESI- on HILIC and C18 chromatography columns). Data tables obtained from the six analytical modalities on a training set of 46 urine samples (22 autistic children and 24 controls) were processed by multivariate analysis (orthogonal partial least-squares discriminant analysis, OPLS-DA). The predictions from each of these OPLS-DA models were then evaluated using a prediction set of 16 samples (8 autistic children and 8 controls) and receiver operating characteristic curves. Thereafter, a data fusion block-scaling OPLS-DA model was generated from the 6 best models obtained for each modality. This fused OPLS-DA model showed an enhanced performance (R(2)Y(cum) = 0.88, Q(2)(cum) = 0.75) compared to each analytical modality model, as well as a better predictive capacity (AUC = 0.91, p-value = 0.006). Metabolites that are most significantly different between autistic and control children (p < 0.05) are indoxyl sulfate, N-α-acetyl-l-arginine, methyl guanidine, and phenylacetylglutamine. This multimodality approach has the potential to contribute to find robust biomarkers and characterize a metabolic phenotype of the ASD population.

An electrophysiological correlate of voice processing in 4- to 5-year-old children

Cortical auditory evoked potentials were studied in responses to voice and environmental sounds in 4- to 5-year-old children. A specific response to voice was dissociated from the response to environmental sounds. It appeared as a positive deflection recorded at right fronto-temporal sites and beginning within 60ms of stimulus onset. We termed this response Fronto-Temporal Positivity to Voice (FTPV).