Background RASopathies are a group of disorders that result from mutations in genes coding for proteins involved in regulating the Ras-MAPK signaling pathway, and have an increased incidence of autism spectrum disorder (ASD). Legius syndrome is a rare RASopathy caused by loss-of-function mutations in the SPRED1 gene. The patient phenotype is similar to, but milder than, Neurofibromatosis type 1-another RASopathy caused by loss-of-function mutations in the NF1 gene. RASopathies exhibit increased activation of Ras-MAPK signaling and commonly manifest with cognitive impairments and ASD. Here, we investigated if a Spred1-/- mouse model for Legius syndrome recapitulates ASD-like symptoms, and whether targeting the Ras-MAPK pathway has therapeutic potential in this RASopathy mouse model. Methods We investigated social and communicative behaviors in Spred1-/- mice and probed therapeutic mechanisms underlying the observed behavioral phenotypes by pharmacological targeting of the Ras-MAPK pathway with the MEK inhibitor PD325901. Results Spred1-/- mice have robust increases in social dominance in the automated tube test and reduced adult ultrasonic vocalizations during social communication. Neonatal ultrasonic vocalization was also altered, with significant differences in spectral properties. Spred1-/- mice also exhibit impaired nesting behavior. Acute MEK inhibitor treatment in adulthood with PD325901 reversed the enhanced social dominance in Spred1-/- mice to normal levels, and improved nesting behavior in adult Spred1-/- mice. Limitations This study used an acute treatment protocol to administer the drug. It is not known what the effects of longer-term treatment would be on behavior. Further studies titrating the lowest dose of this drug that is required to alter Spred1-/- social behavior are still required. Finally, our findings are in a homozygous mouse model, whereas patients carry heterozygous mutations. These factors should be considered before any translational conclusions are drawn. Conclusions These results demonstrate for the first time that social behavior phenotypes in a mouse model for RASopathies (Spred1-/-) can be acutely reversed. This highlights a key role for Ras-MAPK dysregulation in mediating social behavior phenotypes in mouse models for ASD, suggesting that proper regulation of Ras-MAPK signaling is important for social behavior.

Purpose Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder associated with cognitive deficits. The NF1 cognitive phenotype is generally considered to be highly variable, possibly due to the observed T2-weighted hyperintensities, loss of heterozygosity, NF1-specific genetic modifiers, or allelic imbalance. Methods We investigated cognitive variability and assessed the contribution of genetic factors by performing a retrospective cohort study and a monozygotic twin case series. We included data of 497 children with genetically confirmed NF1 and an IQ assessment, including 12 monozygotic twin and 17 sibling sets. Results Individuals carrying an NF1 chromosomal microdeletion showed significant lower full-scale IQ (FSIQ) scores than individuals carrying intragenic pathogenic NF1 variants. For the intragenic subgroup, the variability in cognitive ability and the correlation of IQ between monozygotic NF1 twin pairs or between NF1 siblings is similar to the general population. Conclusions The variance and heritability of IQ in individuals with NF1 are similar to that of the general population, and hence mostly driven by genetic background differences. The only factor that significantly attenuates IQ in NF1 individuals is the NF1 chromosomal microdeletion genotype. Implications for clinical management are that individuals with intragenic NF1 variants that score <1.5–2 SD below the mean of the NF1 population should be screened for additional causes of cognitive disability.

Event Abstract Back to Event Social deficits in mouse models of Neurofibromatosis type 1 and Legius syndrome Sarah C. Borrie1*, Ellen Plasschaert1, Ype Elgersma2, Steven A. Kushner2, Eric Legius1 and Hilde Brems1 1 KU Leuven, Department of Human Genetics, Belgium 2 Erasmus Medical Center, Netherlands Neurofibromatosis type 1 (NF1) and Legius syndrome are neuro-cardio-facial-cutaneous (NCFC) disorders stemming from mutations in the RAS – MAPK pathway, in the NF1 and SPRED1 genes respectively. NF1 is a RAS-GAP protein, negatively regulating activation of RAS, while SPRED1 acts further downstream in the RAS-MAPK pathway, negatively regulating the activation of RAF1 by RAS. Common to these disorders are neurological problems including cognitive deficits and behavioral problems. Patients with NF1 exhibit deficits in memory and executive functioning, and have a high incidence of autism sprectrum disorder (ASD). Legius syndrome patients present a milder cognitive phenotype compared to NF1 patients, and ADHD and attentional problems are also reported. A mouse model of NF1, Nf1+/-, exhibits spatial memory and attentional impairments consistent with the human disorder, and the Spred1-/- mouse model for Legius syndrome also demonstrates spatial learning deficits. However, it is not known whether these models also recapitulate ASD-like symptoms seen in NF1. To further study this phenomenon, we studied social behaviors in Nf1+/- mice and Spred1-/- and Spred1+/- mice, to ask if social deficits are observed in these models, and whether any observed deficits can be rescued. Spred1-/- and Spred1+/- mice displayed abnormal social behavior in the automated tube test. Both genotypes won more encounters against wildtype littermates than expected by chance, indicative of disrupted social behavior. Other social behaviors were also impaired in Spred1-/- mice, including nesting, an intrinsic social behavior. Social deficits in Spred1-/- could be reversed in adult mice by inhibiting the RAS-MAPK pathway, suggesting that RAS – MAPK pathway overactivation underlies altered social behavior in this model. Studies in Nf1+/- mice show that similar social deficits are observed in the automated tube test. Other social behaviors are also being tested, and the role of RAS –MAPK signaling in mediating this phenotype in Nf1+/- is being investigated with pharmacological studies. Collectively these findings suggest that deficits in social behaviors that are core symptoms of NCFC syndromes can be reliably modelled in mouse models of NF1 and Legius syndrome, and that disruptions in RAS-MAPK signaling are important for these behavior alterations. Keywords: RAS-MAPK, NF1, Legius syndrome, ASD, Social Behaviour Conference: 12th National Congress of the Belgian Society for Neuroscience, Gent, Belgium, 22 May - 22 May, 2017. Presentation Type: Poster Presentation Topic: Disorders of the Nervous System Citation: Borrie SC, Plasschaert E, Elgersma Y, Kushner SA, Legius E and Brems H (2019). Social deficits in mouse models of Neurofibromatosis type 1 and Legius syndrome. Front. Neurosci. Conference Abstract: 12th National Congress of the Belgian Society for Neuroscience. doi: 10.3389/conf.fnins.2017.94.00027 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 24 Apr 2017; Published Online: 25 Jan 2019. * Correspondence: Dr. Sarah C Borrie, KU Leuven, Department of Human Genetics, Leuven, Belgium, sarah.borrie@kuleuven.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sarah C Borrie Ellen Plasschaert Ype Elgersma Steven A Kushner Eric Legius Hilde Brems Google Sarah C Borrie Ellen Plasschaert Ype Elgersma Steven A Kushner Eric Legius Hilde Brems Google Scholar Sarah C Borrie Ellen Plasschaert Ype Elgersma Steven A Kushner Eric Legius Hilde Brems PubMed Sarah C Borrie Ellen Plasschaert Ype Elgersma Steven A Kushner Eric Legius Hilde Brems Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Impairments in visuoperceptual processing have long been considered a hallmark deficit of individuals with Neurofibromatosis type 1 (NF1). However, it is unclear which specific visuoperceptual subprocesses are impaired and whether impairments on these tasks really result from visuoperceptual impairments or rather from confounding factors like Executive Functioning (EF) impairments, lower intelligence (IQ) and/or co‐occurring symptoms of Autism Spectrum Disorder (ASD). To answer these questions, we administered four visuoperceptual tasks and two control tasks in 39 children with NF1, 52 typically developing children and 52 children with ASD (8–18 years), all matched for age and gender. Furthermore, EF, IQ, and symptoms of ASD were assessed. Children with NF1 displayed intact visual form discrimination and intact information integration along the dorsal visual pathway. Moreover, their reduced performance on a task requiring integration of information along the ventral visual stream and their more detail‐oriented processing style appeared to result from confounding EF impairments and not from visuoperceptual impairments per se. The co‐occurring ASD symptoms and lower IQ of the children with NF1 did not impact substantially upon their visuoperceptual performance. These findings point to the large impact of EF impairments on the performance of visuoperceptual task and suggest that individuals with NF1 show intact visual form discrimination, intact visual integration, and typical visual processing style when potential confounding factors are controlled for. This may have large repercussions for the interpretation of other findings on visuoperceptual processing in individuals with NF1. © 2017 Wiley Periodicals, Inc.

To assess emotional and behavioral problems in children and adolescents with neurofibromatosis type 1,parents of 183 individuals aged 10.8 ± 3.1 years (range 6-17) completed the Child Behavior Checklist (CBCL). Also, 173 teachers completed the Teacher's Report Form (TRF), and 88 adolescents (children from 11 to 17 years) completed the Youth Self-Report (YSR). According to parental ratings, 32% scored in the clinical range (above the 90th percentile). This percentage was much lower when rated by teachers or adolescents themselves. Scores from all informants on scales for Somatic complaints, Social problems, and Attention problems were significantly different from normative scores. Attentional problems were associated with lower verbal IQ, male gender, younger age, and ADHD-symptoms. Disease-related factors did not predict behavioral problems scores. Substantial emotional and behavioral problems were reported by parents, teachers, and to a lesser extent by adolescents with NF1 themselves. Possibly, a positive illusory bias affects the observation of behavioral problems by adolescents with NF1.

The aim of this study was to provide a broad picture of Executive Functioning (EF) in NF1 children, while taking into account their lower average IQ and increased Autism Spectrum Disorder (ASD) symptoms. This was done by administering an extended battery of tasks and questionnaires, designed to reduce task impurity, that measures five EF domains (inhibition, cognitive flexibility, working memory, generativity and planning) in a laboratory setting and in daily life. Data are presented for 42 age‐ and gender‐matched NF1, 52 typically developing, and 52 ASD children (8–18 years). Our results indicated that although EF is highly influenced by IQ and severity of ASD symptoms, EF deficits seem to be a core feature of NF1 and not merely a secondary effect of a lower IQ and/or increased ASD symptoms. However, additional research is needed to confirm these findings. © 2016 Wiley Periodicals, Inc.

The best known café-au-lait syndrome is neurofibromatosis type 1 (NF1). Legius syndrome (LS) is another, rarer syndrome with café-au-lait macules (CALMs). In young patients their clinical picture is often indistinguishable. We investigated the presence of choroidal abnormalities in syndromes with CALMs as a candidate tool for a more efficient diagnosis. Thirty-four patients with NF1 (14 with a truncating mutation, 14 with a non-truncating mutation and 6 with unknown mutation) and 11 patients with LS. All patients underwent an ophthalmological examination. Infrared images were performed. Choroidal nodules were diagnosed in 65% of the NF1 group. About 71% of NF1 patients with a truncating mutation and 50% of patients with a non-truncating mutation were found to have nodules. Choroidal nodules were seen in 18% of the LS patients, never more than one nodule/eye was detected in this group. Choroidal nodules are more abundantly present in NF1 genotypes with truncating mutations. In contrast, the number of choroidal nodules in LS is comparable with their presence in healthy individuals. Especially at an early age, when the clinical picture is incomplete, the detection of choroidal nodules is of diagnostic value, and helps in an appropriate genetic counselling and follow-up. These results support the suggestion to include choroidal nodules to the diagnostic criteria for NF1.

ImportanceRecent reports have demonstrated a higher incidence of autism spectrum disorder (ASD) and substantially elevated autistic trait burden in individuals with neurofibromatosis type 1 (NF1). However, important discrepancies regarding the distribution of autistic traits, sex predominance, and association between ASD symptoms and attentional problems have emerged, and critical features of the ASD phenotype within NF1 have never been adequately explored. Establishing NF1 as a monogenic cause for ASD has important implications for affected patients and for future research focused on establishing convergent pathogenic mechanisms relevant to the potential treatment targets for ASD.ObjectiveTo characterize the quantitative autistic trait (QAT) burden in a pooled NF1 data set.Design, Setting, and ParticipantsAnonymized, individual-level primary data were accumulated from 6 tertiary referral centers in the United States, Belgium, United Kingdom, and Australia. A total of 531 individuals recruited from NF1 clinical centers were included in the study.Main Outcomes and MeasuresDistribution of ASD traits (Social Responsiveness Scale, second edition [SRS-2], with T scores of ≥75 associated with a categorical ASD diagnosis); attention-deficit/hyperactivity disorder (ADHD) traits (4 versions of Conners Rating Scale, with T scores of ≥65 indicating clinically significant ADHD symptoms); ASD symptom structure, latent structure, base rate derived from mixture modeling; and familiality.ResultsOf the 531 patients included in the analysis, 247 were male (46.5%); median age was 11 years (range, 2.5-83.9 years). QAT scores were continuously distributed and pathologically shifted; 13.2% (95% CI, 10.3%-16.1%) of individuals scored within the most severe range (ie, above the first percentile of the general population distribution) in which the male to female ratio was markedly attenuated (1.6:1) relative to idiopathic ASD. Autistic symptoms in this NF1 cohort demonstrated a robust unitary factor structure, with the first principal component explaining 30.9% of the variance in SRS-2 scores, and a strong association with ADHD symptoms (r = 0.61). Within-family correlation for QAT burden (intraclass correlation coefficient, 0.73 in NF1-affected first-degree relatives) exceeded that observed in the general population and ASD family samples.Conclusions and RelevanceThis study provides confirmation that the diversity of mutations that give rise to NF1 function as quantitative trait loci for ASD. Moreover, the within-family correlation implicates a high degree of mutational specificity for this associated phenotype. Clinicians should be alerted to the increased frequency of this disabling comorbidity, and the scientific community should be aware of the potential for this monogenic disorder to help elucidate the biological features of idiopathic autism.

Neurofibromatosis Type 1 (NF1) is a common autosomal dominant single-gene disorder, in which the co-occurrence of autism spectrum disorder (ASD) has attracted considerable research interest recently with prevalence estimates of 21-40%. However, detailed characterization of the ASD behavioral phenotype in NF1 is still lacking. This study characterized the phenotypic profile of ASD symptomatology presenting in 4-16 year old children with NF1 (n = 36) using evidence from parent-rated Social Responsiveness Scale and researcher autism diagnostic observation Scale-2. Compared to IQ-matched reference groups of children with autism and ASD, the NF1 profile shows overall similarity but improved eye contact, less repetitive behaviors and better language skills.

Neurofibromatosis type 1 (NF1) is one of the most common single-gene disorders affecting fine and visual-motor skills. This case-control study investigated motor timing as a possible related performance deficit in children with NF1. A visual-motor reaction time (VRT) test was administered in 20 NF1 children (mean age 9 years 7 months) and 20 age- and gender-matched typically developing (TD) children. Copying and tracing performance were evaluated using the Beery-Buktenica Developmental Test of Visual-Motor Integration (Beery VMI). Children with NF1 responded with an increased reaction time (RT) to temporally predictive stimuli compared to TD children, whereas RT at unpredictive stimuli did not differ between groups. Motor timing indexed by the RT decrease at predictive stimuli significantly associated with the Beery VMI copy and tracing outcomes. Deficient motor timing as an actual symptom may add to further research on the pathogenesis of NF1-associated motor impairment and the development of more effective treatment.

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic condition. While considerable work has focused on cognitive functioning, several research groups also observed difficulties in social functioning as a prominent feature of NF1. These problems and the possible link between NF1 and Autism Spectrum Disorder (ASD) have become increasingly important in recent NF1 literature. The aim of the current study was to assess ASD characteristics in a hospital-based NF1 pediatric population (n = 82) using the standardized Children Social Behavior Questionnaire (CSBQ) and Social Responsiveness Scale (SRS) to account for the prevalence, severity, and nature of social problems. In a parallel study, comprehensive ASD assessment was performed in a subgroup of NF1 children with a strong suspicion of ASD (n = 31). Results indicate that NF1 children have more social problems than typical controls, more frequently reported above 8 years. The SRS shows that 63% is at risk of ASD symptoms. According to item analyses, most problems were observed on items measuring orientation in, understanding of and being tuned onto a social situation (CSBQ) and social cognition and communication (SRS). In the parallel study, 27 NF1 children were diagnosed with ASD. These children have a distinct phenotype compared to a heterogeneous ASD group, with pronounced social-communicative impairments and fewer restrictive/repetitive behaviors. This study provides a better understanding of social problems in NF1 and the phenotypical overlap with ASD symptomatology. Despite their willingness to engage with others, NF1 children with or without ASD encounter various difficulties in their social-communicative life.

IMPROVED MICROSTRUCTURAL CHARACTERISATION OF T2-HYPERINTENSE LESIONS BY COMBINING MULTI-SHELL DIFFUSION MRI AND MYELIN WATER IMAGING Thibo Billiet, Sabine Deprez, Burkhard Maedler, Felice D'Arco, Ellen Plasschaert, Ronald Peeters, Hui Zhang, Alexander Leemans, Bea Van den Bergh, Mathieu Vandenbulcke, Eric Legius, Stefan Sunaert, and Louise Emsell Translational MRI, Imaging & Pathology, KU Leuven & Radiology, University Hospitals Leuven, Leuven, Belgium, Medical Imaging Research Center, Leuven, Belgium, Stereotaxis and MR-based Intervention, Department of Neurosurgery, Bonn University Hospital, Bonn, Germany, Diagnostic Imaging and Radiotherapy, University Federico II of Naples, Salerno, Italy, Human Genetics, KU Leuven & University Hospitals Leuven, Leuven, Belgium, Computer Science, University College London, London, United Kingdom, University Medical Center, Utrecht, Netherlands, Developmental Psychology, Tilburg University, Tilburg, Netherlands, Psychiatry, KU Leuven & University Hospitals Leuven, Leuven, Belgium