Neurofibromatosis type 1: New insights into neurocognitive issues

Contemporary Approach to Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheath Tumors

Most malignant peripheral nerve sheath tumors (MPNSTs) are clinically aggressive high-grade sarcomas, arising in individuals with neurofibromatosis type 1 (NF1) at a significantly elevated estimated lifetime frequency of 8%-13%. In the setting of NF1, MPNSTs arise from malignant transformation of benign plexiform neurofibroma and borderline atypical neurofibromas. Composed of neoplastic cells from the Schwannian lineage, these cancers recur in approximately 50% of individuals, and most patients die within five years of diagnosis, despite surgical resection, radiation, and chemotherapy. Treatment for metastatic disease is limited to cytotoxic chemotherapy and investigational clinical trials. In this article, we review the pathophysiology of this aggressive cancer and current approaches to surveillance and treatment.

Electroacupuncture Inhibits Neuroinflammation Induced by Astrocytic Necroptosis Through RIP1/MLKL/TLR4 Pathway in a Mouse Model of Spinal Cord Injury

Astrocytic necroptosis plays an essential role in the progression and regression of neurological disorders, which contributes to the neuroinflammation and disrupts neuronal regeneration and remyelination of severed axons. Electroacupuncture (EA), an effective therapeutic efficacy against spinal cord injury (SCI), has been proved to reduce neuronal cell apoptosis, inhibit inflammation, and prompt neural stem cell proliferation and differentiations. However, there have been few reports on whether EA regulate astrocytic necroptosis in SCI model. To investigate the effects of EA on astrocytic necroptosis and the mechanisms involved in the inhibition of astrocytic necroptosis after SCI in mice by EA, 8-week-old female C57BL/6 mice were subjected to SCI surgery and randomly divided into EA and SCI groups. Mice receiving sham surgery were included as sham group. "Jiaji" was selected as points for EA treatment, 10 min/day for 14 days. The in vitro data revealed that EA treatment significantly improved the nervous function and pathological changes after SCI. EA also reduced the number of GFAP/P-MLKL, GFAP/MLKL, GFAP/HMGB1, and Iba1/HMGB1 co-positive cells and inhibited the expressions of IL-6, IL-1β, and IL-33. The results indicate a significant reduction in inflammatory reaction and astrocytic necroptosis in mice with SCI by EA. Additionally, the expressions of RIP1, MLKL, and TLR4, which are associated with necroptosis, were found to be downregulated by EA. In this study, we confirmed that EA can inhibit neuroinflammation by reducing astrocytic necroptosis through downregulation of RIP1/MLKL/TLR4 pathway in mice with SCI.

Quality of life in individuals with neurofibromatosis type 1 associated cutaneous neurofibromas: validation of the Dutch cNF-Skindex

BACKGROUND

Almost all patients with Neurofibromatosis type 1 (NF1) develop cutaneous neurofibroma (cNF), benign dermal tumours that have a large impact on the patient's Quality of Life (QoL). The French cNF-Skindex is the first questionnaire to specifically assess cNF-related QoL in patients with NF1. We aimed to adapt and validate a Dutch version of the cNF-Skindex.

METHODS

The questionnaire was translated using forward and backwards translation, and subsequently administered to a sample of 59 patients on two separate occasions. Feasibility was evaluated by the presence of floor/ceiling effects. Reliability was assessed by evaluating internal consistency and test-retest reliability, by calculating Cronbach's alpha and Spearman's rank correlation coefficients. The EQ-5D-5L and SF-36 were used to evaluate convergent validity, using Spearman's rank correlation coefficients. An exploratory factor analysis was performed to study the data's internal structure. Multivariable linear regression was used to model the relationship between patient characteristics and the cNF-Skindex.

RESULTS

The Dutch cNF-Skindex demonstrated excellent feasibility and reliability (Cronbach's alpha 0.96, test-retest correlation coefficient 0.88). Convergent validity was confirmed for the EQ-5D-5L and relevant SF-36 scales. All items and subdomains from the original questionnaire were confirmed following exploratory factor analysis. The patient characteristics included in the multivariable linear regression were not significantly associated with the cNF-Skindex score.

CONCLUSIONS

The Dutch cNF-Skindex displayed excellent psychometric properties, enabling use in the Netherlands.

Inhibition of Anaplastic Lymphoma Kinase (Alk) as Therapeutic Target to Improve Brain Function in Neurofibromatosis Type 1 (Nf1)

Neurofibromatosis type 1 (Nf1) is a neurodevelopmental disorder and tumor syndrome caused by loss of function mutations in the neurofibromin gene (Nf1) and is estimated to affect 100,000 people in the US. Behavioral alterations and cognitive deficits have been found in 50-70% of children with Nf1 and include specific problems with attention, visual perception, language, learning, attention, and executive function. These behavioral alterations and cognitive deficits are observed in the absence of tumors or macroscopic structural abnormalities in the central nervous system. No effective treatments for the behavioral and cognitive disabilities of Nf1 exist. Inhibition of the anaplastic lymphoma kinase (Alk), a kinase which is negatively regulated by neurofibromin, allows for testing the hypothesis that this inhibition may be therapeutically beneficial in Nf1. In this review, we discuss this area of research and directions for the development of alternative therapeutic strategies to inhibit Alk. Even if the incidence of adverse reactions of currently available Alk inhibitors was reduced to half the dose, we anticipate that a long-term treatment would pose challenges for efficacy, safety, and tolerability. Therefore, future efforts are warranted to investigate alternative, potentially less toxic and more specific strategies to inhibit Alk function.

ERN GENTURIS tumour surveillance guidelines for individuals with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a multisystem genetic disorder, predisposing development of benign and malignant tumours. Given the oncogenic potential, long-term surveillance is important in patients with NF1. Proposals for NF1 care and its specific manifestations have been developed, but lack integration within routine care. This guideline aims to assimilate available information on NF1 associated tumours (based on evidence and/or expert opinion) to assist healthcare professionals in undertaking tumour surveillance of NF1 individuals.

METHODS

By comprehensive literature review, performed March 18th 2020, guidelines were developed by a NF1 expert group and patient representatives, conversant with clinical care of the wide NF1 disease spectrum. We used a modified Delphi procedure to overcome issues of variability in recommendations for specific (national) health care settings, and to deal with recommendations based on indirect (scarce) evidence.

FINDINGS

We defined proposals for personalised and targeted tumour management in NF1, ensuring appropriate care for those in need, whilst reducing unnecessary intervention. We also incorporated the tumour-related psychosocial and quality of life impact of NF1.

INTERPRETATION

The guideline reflects the current care for NF1 in Europe. They are not meant to be prescriptive and may be adjusted to local available resources at the treating centre, both within and outside EU countries.

FUNDING

This guideline has been supported by the European Reference Network on Genetic Tumour Risk Syndromes (ERN GENTURIS). ERN GENTURIS is funded by the European Union. DGE is supported by the Manchester NIHRBiomedical Research Centre (IS-BRC-1215-20007).

Quality of life in neurofibromatosis 1: development and validation of a tool dedicated to cutaneous neurofibromas in adults

BACKGROUND

Cutaneous neurofibromas (cNF), present in 95% of individuals with neurofibromatosis 1 (NF1), are considered as one of the greatest medical burden because of physical disfigurement. No specific score evaluates their impact on quality of life (QoL).

OBJECTIVE

To develop a specific score assessing cNF-related QoL.

METHODS

Through a multidisciplinary workshop including 10 patients, 3 expert-in-NF1 physicians, 3 health care workers (nurses and psychologist) and 1 methodologist, the French version of the Skindex-16 was modified by adding 3 items. The new cNF-Skindex was validated among patients with NF1 recruited in the ComPaRe online cohort, in France (N=284). Construct validity was assessed by comparing it with the EQ-5D-5L, its visual analog scale and the MYMOP2 and by assessing its association with patients' characteristics. Reliability was assessed by a test-retest. An English version of the tool was developed using a back forward translation.

RESULTS

A total of 228 individuals with NF1, with cNF answered the 19-item questionnaire. These items fitted into 3 domains: emotions, symptoms, functioning. One was dropped during analysis because >90% responders were not concerned. The cNF-Skindex significantly correlated with the EQ-5D-5L (N=193) and MYMOP2 (N=210) indicating good external validity: rs 0.38 (p<0.001), and 0.58 (p<0.001) respectively. Having >50 cNF was the only independent variable associated with the total score cNF-Skindex (β=15.88, 95%CI 6.96 - 24.81, p=0.001), and with the 3 sub-scores: "functioning" (β=2.65, 95%CI 0.71 - 4.59, p=0.008), "emotions" (β=17.03, 95%CI 4.11 - 29.96, p=0.010) and "symptoms" (β=3.90, 95%CI 1.95 - 5.85, p<0.001). Test-retest reliability (N=133) found an ICC at 0.96 demonstrating good reproducibility.

CONCLUSION

The cNF-Skindex demonstrated excellent psychometric properties. The global and sub-scores were increased with higher number of cNF arguing for its use in further trials aiming to reduce their number or prevent their development. Cross-cultural validation and evaluation of its responsiveness are the next steps.

Computerized Working Memory Training for Children With Neurofibromatosis Type 1 (NF1): A Pilot Study

INTRODUCTION

The present study aimed to evaluate the feasibility and efficacy of CogmedRM, a computerized, home-based working memory (WM) training program, in children with NF1.

METHOD

A pre-post design was used to evaluate changes in performance-based measures of attention and WM, and parent-completed ratings of executive functioning. Children meeting eligibility criteria completed CogmedRM over 9 weeks. Primary outcomes included compliance statistics and change in attention and WM scores.

RESULTS

Thirty-one children (52% male; M age = 10.97 ± 2.51), aged 8-15, were screened for participation; 27 children (87%) evidenced WM difficulties and participated in CogmedRM training. On average, participants completed 19.7 out of 25 prescribed sessions, with an adherence rate of 69%. Participants demonstrated improvements in short-term memory, attention, and executive functioning (all Ps < .05).

CONCLUSION

Results suggest that computerized, home-based WM training programs may be both feasible and efficacious for children with NF1 and cognitive deficits.

Effects of Age on White Matter Microstructure in Children With Neurofibromatosis Type 1

Children with neurofibromatosis type 1 (NF1) often report cognitive challenges, though the etiology of such remains an area of active investigation. With the advent of treatments that may affect white matter microstructure, understanding the effects of age on white matter aberrancies in NF1 becomes crucial in determining the timing of such therapeutic interventions. A cross-sectional study was performed with diffusion tensor imaging from 18 NF1 children and 26 age-matched controls. Fractional anisotropy was determined by region of interest analyses for both groups over the corpus callosum, cingulate, and bilateral frontal and temporal white matter regions. Two-way analyses of variance were done with both ages combined and age-stratified into early childhood, middle childhood, and adolescence. Significant differences in fractional anisotropy between NF1 and controls were seen in the corpus callosum and frontal white matter regions when ages were combined. When stratified by age, we found that this difference was largely driven by the early childhood (1-5.9 years) and middle childhood (6-11.9 years) age groups, whereas no significant differences were appreciable in the adolescence age group (12-18 years). This study demonstrates age-related effects on white matter microstructure disorganization in NF1, suggesting that the appropriate timing of therapeutic intervention may be in early childhood.

Role of the parental NF1 carrier in effects of pharmacological inhibition of anaplastic lymphoma kinase in Neurofibromatosis 1 mutant mice

Neurofibromatosis type 1 (NF1), a genetically determined neurodevelopmental disorder and tumor syndrome, is associated with cognitive impairments, including in executive function and sleep-related problems. Consistent with the human data, NF1 heterozygous (Het) mice show impaired spatial learning and memory in the water maze and extinction of contextual fear memory. It is not clear whether neurological phenotypes might depend on the parental carrier. In this study, we compared the behavioral and cognitive performance of NF1 Het and wild-type litter mates with either the father (PC) or the mother (MC) as the NF1 carrier on a F1 C57BL/66/129SvJ background. The behavioral and cognitive phenotypes and responsiveness to Alk inhibition in heterozygous NF1 offspring depended on whether the parental carrier was maternal or paternal. Alk inhibition (20 mg/kg) increased activity levels during the dark period in NF1 Het PC, but not MC, mice. In the water maze, NF1 Het PC, but not MC, mice showed reduced cognitive flexibility and impaired ability to locate the third hidden platform location, which was improved by Alk inhibition (3.6 mg/kg). Consistent with reduced cognitive flexibility, WT, but not NF1, mice showed better performance in the third than second water maze probe trial. Finally, Alk inhibition (10 mg/kg) increased baseline activity of NF1 MC, but not PC, mice during the fear conditioning test. Thus, the effective dose depends on the behavioral test and genotype but indicates that in NF1 patients cognitive flexibility might be particularly sensitive to Alk inhibition.

Importance of Thalamostriatal Pathway Associated With Neurocognitive Dysfunctions in Children With Neurofibromatosis Type 1: Diffusion Tensor Imaging Findings

OBJECTIVE

To determine whether there is a difference between healthy control group and children with neurofibromatosis type 1 (NF1) in terms of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values in different regions of the brain associated with neurocognitive functions and to investigate the correlation between diffusion tensor imaging parameters and neurocognitive dysfunctions.

METHODS

The study included 28 children with NF1 and 21 controls. Nine distinct areas related to cognitive functions were selected for the analysis. The ADC and FA values were compared.

RESULTS

There was a significant difference between NF1 and healthy control in terms of ADC values obtained from all areas. The ADC values at obtained from thalamus and striatum were positively correlated with the full-scale intelligence quotient (IQ), verbal IQ, and performance IQ.

CONCLUSIONS

We are speculated that the development of microstructural damage in the thalamostriatal pathway may lead to neurocognitive dysfunction.

Risk Factors for Bullying Victimization in Children with Neurofibromatosis Type 1 (NF1)

Neurofibromatosis type 1 (NF1) is an autosomal disorder associated with numerous physical stigmata. Children with NF1 are at known risk for attention-deficit/hyperactivity disorder (ADHD), academic struggles, and significant social difficulties and adverse social outcomes, including bullying victimization. The primary aim of this study was to identify risk factors associated with bullying victimization in children with NF1 to better inform clinicians regarding targets for prevention and clinical intervention. Children and a parent completed questionnaires assessing the bully victim status, and parents completed a measure of ADHD symptoms. Analyses were completed separately for parent-reported victimization of the child and the child’s self-report of victimization. According to the parent report, results suggest ADHD symptoms are a significant risk factor for these children being a target of bullying. Findings for academic disability were not conclusive, nor were findings related to having a parent with NF1. Findings indicate the need for further research into possible risk factors for social victimization in children with NF1. Results provide preliminary evidence that may guide clinicians working with children with NF1 and their parents in identifying higher-risk profiles that may warrant earlier and more intensive intervention to mitigate later risk for bullying victimization.

A 17-Year-Old Male with Large Retropharyngeal Neurofibroma as the Only Symptom of Neurofibromatosis Type 1 (NF1): A Case Report and Review of Literature

Retropharyngeal neurofibromas are rarely described in the literature and are commonly associated with severe airway-related symptoms. We report a unique case of a large retropharyngeal plexiform neurofibroma in an asymptomatic 17-year-old male patient. This patient was asymptomatic and presented for lower lip edema secondary to an insect bite. Head and neck imaging demonstrated an extensive retropharyngeal neurofibroma measuring 5.7 cm × 2.2 cm × 6.8 cm. Because of extensive involvement of cervical vasculature, the lesion was not resected in our institution and his care was referred to a large neurofibromatosis type I center.

Attention and Executive Disorders in Neurofibromatosis 1: Comparison Between NF1 With ADHD Symptomatology (NF1 + ADHD) and ADHD Per Se

Objective: To compare children with Neurofibromatosis type 1 and associated ADHD symptomatology (NF1 + ADHD) with children having received a diagnosis of ADHD without NF1. The idea was that performance differences in tasks of attention between these two groups would be attributable not to the ADHD symptomatology, but to NF1 alone. Method: One group of children with NF1 + ADHD (N = 32), one group of children with ADHD (N = 31), and one group of healthy controls (N = 40) participated in a set of computerized tasks assessing intensive, selective, and executive aspects of attention. Results: Differences were found between the two groups of patients in respect of several aspects of attention. Children with NF1 + ADHD did not always perform worse than children with ADHD. Several double dissociations can be established between the two groups of patients. Conclusion: ADHD symptomatology in NF1 does not contribute to all attention deficits, and ADHD cannot account for all attention impairments in NF1.

Sporadic and Familial Variants in NF1: An Explanation of the Wide Variability in Neurocognitive Phenotype?

Background: Cognitive impairment is the most common neurological manifestation in NF1 and occurs in 30–70% of NF1 cases. The onset and severity of each specific cognitive deficit varies greatly from child to child, with no apparent external causes. The wide variability of phenotype is the most complex aspect in terms of management and care. Despite multiple research, the mechanism underlying the high heterogeneity in NF1 has not yet been elucidated. While many studies have focused on the effects of specific and precise genetic mutations on the NF1 phenotype, little has been done on the impact of NF1 transmission (sporadic vs. familial cases). We used a complete neuropsychological evaluation designed to assess five large cognitive areas: general cognitive functions (WISC-IV and EVIP); reading skills (“L'Alouette,” ODEDYS-2 and Lobrot French reading tests); phonological process (ODEDYS-2 test); visual perceptual skills (JLO, Thurstone and Corsi block tests) and attention (CPT-II), as well as psychosocial adjustments (CBCL) to explore the impact of NF1 transmission on cognitive disease manifestation in 96 children affected by NF1 [55 sporadic cases (29♀, 26♂); 41 familial cases (24♀, 17♂)].

Results: Familial and Sporadic form of NF1 only differ in IQ expression. The families' socioeconomic status (SES) impacts IQ performance but not differently between sporadic and familial variants. However, SES is lower in familial variants than in the sporadic variant of NF1. No other cognitive differences emerge between sporadic and familial NF1.

Conclusions: Inheritance in NF1 failed to explain the phenotype variability in its entirety. IQ differences between groups seems in part linked to the environment where the child grows up. Children with NF1, and especially those that have early diagnoses (most often in inherited cases), must obtain careful monitoring from their early childhood, at home to strengthen investment in education and in school to early detect emerging academic problems and to quickly place them into care.

Trial Registration: IDRCB, IDRCB2008-A01444-51. Registered 19 January 2009.

Neurofibromatosis 1 French national guidelines based on an extensive literature review since 1966

Neurofibromatosis type 1 is a relatively common genetic disease, with a prevalence ranging between 1/3000 and 1/6000 people worldwide. The disease affects multiple systems with cutaneous, neurologic, and orthopedic as major manifestations which lead to significant morbidity or mortality. Indeed, NF1 patients are at an increased risk of malignancy and have a life expectancy about 10-15 years shorter than the general population. The mainstay of management of NF1 is a patient-centered longitudinal care with age-specific monitoring of clinical manifestations, aiming at the early recognition and symptomatic treatment of complications as they occur. Protocole national de diagnostic et de soins (PNDS) are mandatory French clinical practice guidelines for rare diseases required by the French national plan for rare diseases. Their purpose is to provide health care professionals with guidance regarding the optimal diagnostic and therapeutic management of patients affected with a rare disease; and thus, harmonizing their management nationwide. PNDS are usually developed through a critical literature review and a multidisciplinary expert consensus. The purpose of this article is to present the French guidelines on NF1, making them even more available to the international medical community. We further dwelled on the emerging new evidence that might have therapeutic potential or a strong impact on NF1 management in the coming feature. Given the complexity of the disease, the management of children and adults with NF1 entails the full complement healthcare providers and communication among the various specialties.

Guanfacine treatment improves ADHD phenotypes of impulsivity and hyperactivity in a neurofibromatosis type 1 mouse model

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a mutation in one copy of the neurofibromin gene (NF1^+/−). Even though approximately 40–60% of children with NF1 meet the criteria for attention deficit hyperactivity disorder (ADHD), very few preclinical studies, if any, have investigated alterations in impulsivity and risk-taking behavior. Mice with deletion of a single NF1 gene (Nf1^+/−) recapitulate many of the phenotypes of NF1 patients.

Methods

We compared wild-type (WT) and Nf1^+/− mouse strains to investigate differences in impulsivity and hyperactivity using the delay discounting task (DDT), cliff avoidance reaction (CAR) test, and open field. We also investigated whether treatment with the clinically effective alpha-2A adrenergic receptor agonist, guanfacine (0.3 mg/kg, i.p.), would reverse deficits observed in behavioral inhibition.

Results

Nf1^+/− mice chose a higher percentage of smaller rewards when both 10- and 20-s delays were administered compared to WT mice, suggesting Nf1^+/− mice are more impulsive. When treated with guanfacine (0.3 mg/kg, i.p.), Nf1^+/− mice exhibited decreased impulsive choice by waiting for the larger, delayed reward. Nf1^+/− mice also exhibited deficits in behavioral inhibition compared to WT mice in the CAR test by repetitively entering the outer edge of the platform where they risk falling. Treatment with guanfacine ameliorated these deficits. In addition, Nf1^+/− mice exhibited hyperactivity as increased distance was traveled compared to WT controls in the open field. This hyperactivity in Nf1^+/− mice was reduced with guanfacine pre-treatment.

Conclusions

Overall, our study confirms that Nf1^+/− mice exhibit deficits in behavioral inhibition in multiple contexts, a key feature of ADHD, and can be used as a model system to identify alterations in neural circuitry associated with symptoms of ADHD in children with NF1.

Measurement considerations in pediatric research on autism spectrum disorders

Studying Autism Spectrum Disorders (ASD) in genetic syndromes has gained interest in the scientific community as a way to elucidate mechanisms and symptom profiles to understand ASD more broadly. Appropriate and adequate measurement of constructs, symptomatology, and outcomes in clinical research is of vital importance in establishing the prevalence of such symptoms and measuring change in symptoms in the context of clinical trials. As such, we provide an overview of the prevalence of ASD, present current diagnostic guidelines, discuss important comorbidities to consider, describe current assessment strategies in assessing ASD, and discuss these within the context of a specific genetic condition to highlight how ASD can be best evaluated.

RASopathies are associated with a distinct personality profile

Personality is a complex, yet partially heritable, trait. Although some Mendelian diseases like Williams-Beuren syndrome are associated with a particular personality profile, studies have failed to assign the personality features to a single gene or pathway. As a family of monogenic disorders caused by mutations in the Ras/MAPK pathway known to influence social behavior, RASopathies are likely to provide insight into the genetic basis of personality. Eighty subjects diagnosed with cardiofaciocutaneous syndrome, Costello syndrome, neurofibromatosis type 1, and Noonan syndrome were assessed using a parent-report BFQ-C (Big Five Questionnaire for Children) evaluating agreeableness, extraversion, conscientiousness, intellect/openness, and neuroticism, along with 55 unaffected sibling controls. A short questionnaire was added to assess sense of humor. RASopathy subjects and sibling controls were compared for individual components of personality, multidimensional personality profiles, and individual questions using Student tests, analysis of variance, and principal component analysis. RASopathy subjects were given lower scores on average compared to sibling controls in agreeableness, extraversion, conscientiousness, openness, and sense of humor, and similar scores in neuroticism. When comparing the multidimensional personality profile between groups, RASopathies showed a distinct profile from unaffected siblings, but no difference in this global profile was found within RASopathies, revealing a common profile for the Ras/MAPK-related disorders. In addition, several syndrome-specific strengths or weaknesses were observed in individual domains. We describe for the first time an association between a single pathway and a specific personality profile, providing a better understanding of the genetics underlying personality, and new tools for tailoring educational and behavioral approaches for individuals with RASopathies.

Emerging therapeutic targets for neurofibromatosis type 1

INTRODUCTION

Neurofibromatosis type 1 (NF1) is an autosomal dominantly inherited tumor predisposition syndrome with an incidence of one in 3000-4000 individuals with no currently effective therapies. The NF1 gene encodes neurofibromin, which functions as a negative regulator of RAS. NF1 is a chronic multisystem disorder affecting many different tissues. Due to cell-specific complexities of RAS signaling, therapeutic approaches for NF1 will likely have to focus on a particular tissue and manifestation of the disease. Areas covered: We discuss the multisystem nature of NF1 and the signaling pathways affected due to neurofibromin deficiency. We explore the cell-/tissue-specific molecular and cellular consequences of aberrant RAS signaling in NF1 and speculate on their potential as therapeutic targets for the disease. We discuss recent genomic, transcriptomic, and proteomic studies combined with molecular, cellular, and biochemical analyses which have identified several targets for specific NF1 manifestations. We also consider the possibility of patient-specific gene therapy approaches for NF1. Expert opinion: The emergence of NF1 genotype-phenotype correlations, characterization of cell-specific signaling pathways affected in NF1, identification of novel biomarkers, and the development of sophisticated animal models accurately reflecting human pathology will continue to provide opportunities to develop therapeutic approaches to combat this multisystem disorder.

Executive Function Deficits in Seriously Ill Children-Emerging Challenges and Possibilities for Clinical Care

The past years have seen an incredible increase in the quality and success rates of treatments in pediatric medicine. One of the resulting major challenges refers to the management of primary or secondary residual executive function deficits in affected children. These deficits lead to problems in the ability to acquire, understand, and apply abstract and complex knowledge and to plan, direct, and control actions. Executive functions deficits are important to consider because they are highly predictive of functioning in social and academic aspects of daily life. We argue that current clinical practice does not sufficiently account for the complex cognitive processes in this population. This is because widely applied pharmacological interventions only rarely account for the complexity of the underlying neuronal mechanisms and do not fit well into possibly powerful "individualized medicine" approaches. Novel treatment approaches targeting deficits in executive functions in seriously ill children could focus on neuronal oscillations, as these have some specific relations to different aspects of executive function. Importantly, such treatment approaches can be individually tailored to the individuals' deficits and can be transferred into home-treatment or e-health solutions. These approaches are easy-to-use, can be easily integrated into daily life, and are becoming increasingly cost-effective.

Health literacy assessment in adults with neurofibromatosis: electronic and short-form measurement using FCCHL and Health LiTT

Determining health literacy level is an important prerequisite for effective patient education. We assessed multiple dimensions of health literacy and sociodemographic predictors of health literacy in patients with neurofibromatosis. In 86 individuals with a confirmed diagnosis of neurofibromatosis 1 (NF1), neurofibromatosis 2 (NF2), or schwannomatosis, we assessed health literacy status using two HL tools-the adapted functional, communicative, and critical health literacy scale (adapted FCCHL) and health literacy assessment using talking touchscreen technology (Health LiTT). Factor analyses of the adapted FCCHL in NF patients showed factor structure and psychometric properties similar to pilot work in other patient populations. As a group, patients with NF had moderate scores on the Health LiTT and moderate to high scores on the adapted FCCHL, with the highest score on the functional health literacy subscale. Patients with NF1, those with lower education and those with learning disabilities had lower scores on Health LiTT; in multivariate analysis, learning disability and education remained significant predictors of HealthLiTT scores. Only lower education was associated with lower adapted FCCHL scores. Results suggest utilizing health literacy tools in NF patients is feasible and could provide physicians with valuable information to tailor health communication to subpopulations with lower health literacy levels.

Numerical activities of daily living in adults with neurofibromatosis type 1

BACKGROUND

This study aimed to identify the mathematical domains affected in adults with neurofibromatosis 1 (NF1) and the impact of the numerical difficulties on the patients' activities of daily living.

METHODS

We assessed 28 adult patients with NF1 and 28 healthy control participants. All participants completed the standardised battery of numerical activities of daily living along with clinical batteries of cognitive (Mini-Mental State Examination) and daily functioning (instrumental activities of daily living). The group comparisons of the performance on numerical activities of daily living were carried out using t-test correcting for multiple comparisons.

RESULTS

The results showed that the NF1 group performed worse than controls in written subtractions, written multiplication, multiplication principles and digit comprehension (dot counting) tasks. Importantly, no significant differences in numerical ecological tasks were found between patients and controls, suggesting a possible use of compensatory strategies in daily living abilities in spite of calculation deficits.

CONCLUSION

The findings indicate that NF1 affects calculation but not the basic comprehension or representation of numbers in adult patients. These data have important implications for designing cognitive interventions tailored to the cognitive profile of individuals with NF1.

Computerized cognitive training for children with neurofibromatosis type 1: A pilot resting-state fMRI study

In this pilot study, we examined training effects of a computerized working memory program on resting state functional magnetic resonance imaging (fMRI) measures in children with neurofibromatosis type 1 (NF1). We contrasted pre- with post-training resting state fMRI and cognitive measures from 16 participants (nine males; 11.1 ± 2.3 years) with NF1 and documented working memory difficulties. Using non-parametric permutation test inference, we found significant regionally specific differences (family-wise error corrected) in two of four voxel-wise resting state measures: fractional amplitude of low frequency fluctuations (indexing peak-to-trough intensity of spontaneous oscillations) and regional homogeneity (indexing local intrinsic synchrony). Some cognitive task improvement was observed as well. These preliminary findings suggest that regionally specific changes in resting state fMRI indices may be associated with treatment-related cognitive amelioration in NF1. Nevertheless, current results must be interpreted with caution pending independent controlled replication.

Glial cells as key elements in the pathophysiology and treatment of bipolar disorder

OBJECTIVE

The exact pathophysiology of bipolar disorder (BD) is not yet fully understood, and there are many questions in this area which should be answered. This review aims to discuss the roles of glial cells in the pathophysiology of BD and their contribution to the mechanism of action of mood-stabilising drugs.

METHODS

We critically reviewed the most recent advances regarding glial cell roles in the pathophysiology and treatment of BD and the neuroprotective and neurotrophic effects of these cells.

RESULTS

Postmortem studies revealed a decrease in the glial cell number or density in the specific layers of prefrontal and anterior cingulate cortex in the patients with BD, whereas there was no difference in other brain regions, such as entorhinal cortex, amygdala and hippocampus. Astrocytes and oligodendrocytes were the most important glial types that were responsible for the glial reduction, but microglia activation rather than loss may be implicated in BD. The decreased number or density of glial cells may contribute to the pathological changes observed in neurons in the patients with BD. Alteration of specific neurotrophic factors such as glial cell line-derived neurotrophic factor and S100B may be an important feature of BD. Glial cells mediate the therapeutic effects of mood-stabilising agents in the treatment of BD.

CONCLUSION

Recent studies provide important evidence on the impairment of glial cells in the pathophysiology and treatment of BD. However, future controlled studies are necessary to elucidate different aspects of glial cells contribution to BD, and the mechanism of action of mood-stabilising drugs.

Oligodendrocyte Nf1 Controls Aberrant Notch Activation and Regulates Myelin Structure and Behavior

The RASopathy neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant genetic disorders. In NF1 patients, neurological issues may result from damaged myelin, and mice with a neurofibromin gene (Nf1) mutation show white matter (WM) defects including myelin decompaction. Using mouse genetics, we find that altered Nf1 gene-dose in mature oligodendrocytes results in progressive myelin defects and behavioral abnormalities mediated by aberrant Notch activation. Blocking Notch, upstream mitogen-activated protein kinase (MAPK), or nitric oxide signaling rescues myelin defects in hemizygous Nf1 mutants, and pharmacological gamma secretase inhibition rescues aberrant behavior with no effects in wild-type (WT) mice. Concomitant pathway inhibition rescues myelin abnormalities in homozygous mutants. Notch activation is also observed in Nf1^+/− mouse brains, and cells containing active Notch are increased in NF1 patient WM. We thus identify Notch as an Nf1 effector regulating myelin structure and behavior in a RASopathy and suggest that inhibition of Notch signaling may be a therapeutic strategy for NF1.

Neurocognitive outcomes in neurofibromatosis clinical trials: Recommendations for the domain of attention

Neurofibromatosis type 1 (NF1) is associated with neurocognitive deficits that can impact everyday functioning of children, adolescents, and adults with this disease. However, there is little agreement regarding measures to use as cognitive endpoints in clinical trials. This article describes the work of the Neurocognitive Committee of the Response Evaluation in Neurofibromatosis and Schwannomatosis (REiNS) International Collaboration. The goal of this committee is to identify standardized and specific cognitive assessment tools for use in NF clinical trials. The committee first identified cognitive domains relevant to NF1 and prioritized attention as the first domain of focus given prior and current trends in NF1 cognitive clinical trials. Performance measures and behavioral rating questionnaires of attention were reviewed by the group using established criteria to assess patient characteristics, psychometric properties, and feasibility. The highest rated tests underwent side-by-side comparison. The Digit Span subtest from the Wechsler scales was given the highest ratings of the performance measures due to its good psychometrics, feasibility, utility across a wide age range, and extensive use in previous research. The Conners scales achieved the highest ratings of the behavioral questionnaires for similar reasons. Future articles will focus on other cognitive domains, with the ultimate goal of achieving agreement for cognitive endpoints that can be used across NF clinical trials.

Conflict processing in juvenile patients with neurofibromatosis type 1 (NF1) and healthy controls - Two pathways to success

Neurofibromatosis Type 1 (NF1) is a monogenetic autosomal-dominant disorder with a broad spectrum of clinical symptoms and is commonly associated with cognitive deficits. Patients with NF1 frequently exhibit cognitive impairments like attention problems, working memory deficits and dysfunctional inhibitory control. The latter is also relevant for the resolution of cognitive conflicts. However, it is unclear how conflict monitoring processes are modulated in NF1. To examine this question in more detail, we used a system neurophysiological approach combining high-density ERP recordings with source localisation analyses in juvenile patients with NF1 and controls during a flanker task. Behaviourally, patients with NF1 perform significantly slower than controls. Specifically on trials with incompatible flanker-target pairings, however, the patients with NF1 made significantly fewer errors than healthy controls. Yet, importantly, this overall successful conflict resolution was reached via two different routes in the two groups. The healthy controls seem to arrive at a successful conflict monitoring performance through a developing conflict recognition via the N2 accompanied by a selectively enhanced N450 activation in the case of perceived flanker-target conflicts. The presumed dopamine deficiency in the patients with NF1 seems to result in a reduced ability to process conflicts via the N2. However, NF1 patients show an increased N450 irrespective of cognitive conflict. Activation differences in the orbitofrontal cortex (BA11) and anterior cingulate cortex (BA24) underlie these modulations. Taken together, juvenile patients with NF1 and juvenile healthy controls seem to accomplish conflict monitoring via two different cognitive neurophysiological pathways.

Cognitive and Behavioral Disorders in Children with Neurofibromatosis Type 1

AIM

The last systematic review of research on the behavior of children with neurofibromatosis type 1 (NF1) was in 2012. Since then, several important findings have been published. Therefore, the study aim was to synthesize recent relevant work related to this issue.

METHOD

We conducted a systematic review of the literature. Relevant articles were identified using the electronic databases PubMed, PsycINFO, and Scopus and a manual search of references lists. Thirty of 156 articles identified met the inclusion criteria. A quality evaluation of the articles was performed and the information was synthesized using a narrative approach.

RESULTS

Compared with controls, children and adolescents with NF1 present significant alterations in language, reading, visuospatial skills, motor function, executive function, attention, behavior, emotion, and social skills. The prevalence of attention-deficit/hyperactivity disorder (ADHD) is important and can affect cognition and executive function variables. A high prevalence of autistic traits and autistic spectrum disorder were reported. The benefits of using statins to treat cognitive deficits are unclear. However, children with NF1 and ADHD seem to benefit from methylphenidate treatment. The presence of hyperintensities in brain magnetic resonance imaging data seem to be related to poor cognitive performance. Analysis of these lesions could help to predict cognitive alterations in children with NF1.

INTERPRETATION

There has been important progress to evaluate cognitive characteristics of children with NF1 and to determine the physiological mechanisms of the concomitant disorders. However, discrepancies in relation to intelligence, learning disabilities, attention deficits, and treatment remain. Further investigations on this topic are recommended.

Therapeutic advances for the tumors associated with neurofibromatosis type 1, type 2, and schwannomatosis

Neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis (SWN) are tumor-suppressor syndromes. Each syndrome is an orphan disease; however, the tumors that arise within them represent the most common tumors of the nervous system worldwide. Systematic investigation of the pathways impacted by the loss of function of neurofibromin (encoded byNF1) and merlin (encoded byNF2) have led to therapeutic advances for patients with NF1 and NF2. In the syndrome of SWN, the genetic landscape is more complex, with 2 known causative genes (SMARCB1andLZTR1) accounting for up to 50% of familial SWN patients. The understanding of the molecular underpinnings of these syndromes is developing rapidly and offers more therapeutic options for the patients. In addition, common sporadic cancers harbor somatic alterations inNF1(ie, glioblastoma, breast cancer, melanoma),NF2(ie, meningioma, mesothelioma) andSMARCB1(ie, atypical teratoid/rhabdoid tumors) such that advances in management of syndromic tumors may benefit patients both with and without germline mutations. In this review, we discuss the clinical and genetic features of NF1, NF2 and SWN, the therapeutic advances for the tumors that arise within these syndromes and the interaction between these rare tumor syndromes and the common tumors that share these mutations.

Neurofibromatosis as a gateway to better treatment for a variety of malignancies

The neurofibromatoses (NF) are a group of rare genetic disorders that can affect all races equally at an incidence from 1:3000 (NF1) to a log unit lower for NF2 and schwannomatosis. Since the research community is reporting an increasing number of malignant cancers that carry mutations in the NF genes, the general interest of both the research and pharma community is increasing and the authors saw an opportunity to present a novel, fresh approach to drug discovery in NF. The aim of the paper is to challenge the current drug discovery approach to NF, whereby existing targeted therapies that are either in the clinic or on the market for other disease indications are repurposed for NF. We offer a suggestion for an alternative drug discovery approach. In the new approach, selective and tolerable targeted therapies would be developed for NF and later expanded to patients with more complex diseases such as malignant cancer in which the NF downstream pathways are deregulated. The Children's Tumor Foundation, together with some other major NF funders, is playing a key role in funding critical initiatives that will accelerate the development of better targeted therapies for NF patients, while these novel, innovative treatments could potentially be beneficial to molecularly characterized cancer patients in which NF mutations have been identified.

mTOR, a Potential Target to Treat Autism Spectrum Disorder

Mammalian target of rapamycin (mTOR) is a key regulator in various cellular processes, including cell growth, gene expression, and synaptic functions. Autism spectrum disorder (ASD) is frequently accompanied by monogenic disorders, such as tuberous sclerosis complex, phosphatase and tensin homolog tumor hamartoma syndrome, neurofibromatosis 1, and fragile X syndrome, in which mTOR is hyperactive. Mutations in the genes involved in the mTOR-mediated signaling pathway have been identified in some cases of syndromic ASD. Evidences indicate a pathogenic role for hyperactive mTOR-mediated signaling in ASD associated with these monogenic disorders, and mTOR inhibitors are a potential pharmacotherapy for ASD. Abnormal synaptic transmission through metabotropic glutamate receptor 5 may underlie in a part of ASD associated with hyperactive mTOR-mediated signaling. In this review, the relationship between mTOR and ASD is discussed.

Neurofibromatosis type 1: a multidisciplinary approach to care

Neurofibromatosis type 1 is a relatively common inherited disorder. Patients have a high predisposition to develop both benign and malignant tumours. Although many manifestations of neurofibromatosis type 1 affect the nervous system, other organs and tissues can also be affected. Because of the varying features and clinical heterogeneity inherent to this disorder, patients can present to different medical and surgical specialists and, therefore, the association of clinical symptoms with neurofibromatosis type 1 might not be appreciated. Thus, for prompt diagnosis and to provide optimum care for patients with neurofibromatosis type 1, clinicians must be aware of the diverse clinical features of this disorder. We advocate a multidisciplinary approach to care, entailing a dedicated team of specialists throughout the lifetime of the patient. As our understanding of this disorder deepens through basic laboratory and clinical investigations, swift implementation of new effective treatments becomes feasible.

Is there a relationship between executive functions and academic success in children with neurofibromatosis type 1?

The present study aimed to compare the executive function (EF) of children with neurofibromatosis type 1 (NF1) to those of typically developing children and to investigate whether those abilities could predict the child's academic success in terms of academic skills and enablers. Twenty-nine children with NF1 and 27 age-and-gender-matched controls (aged 8-16 years) were examined with two tests to measure EF in an ecologically valid manner: the Behavioural Assessment of the Dysexecutive Syndrome in Children (BADS-C) and the parent questionnaire for the Behavior Rating Inventory of Executive Function (BRIEF). In order to evaluate academic success we used the Academic Competence Evaluation Scales (ACES). The performance of the NF1 group was significantly lower on the Water and Key search subtest of the BADS-C and on four scales of the BRIEF: initiate; working memory; plan/organise and organisation of materials. Significant correlations and predictive models via regression analysis were generated for: BADS-C, BRIEF and ACES scores. Based on these findings, children with NF1 have executive dysfunction that partially accounts for their difficulties in academic achievements.

Activated Ras as a Therapeutic Target: Constraints on Directly Targeting Ras Isoforms and Wild-Type versus Mutated Proteins

The ability to selectively and directly target activated Ras would provide immense utility for treatment of the numerous cancers that are driven by oncogenic Ras mutations. Patients with disorders driven by overactivated wild-type Ras proteins, such as type 1 neurofibromatosis, might also benefit from progress made in that context. Activated Ras is an extremely challenging direct drug target due to the inherent difficulties in disrupting the protein:protein interactions that underlie its activation and function. Major investments have been made to target Ras through indirect routes. Inhibition of farnesyl transferase to block Ras maturation has failed in large clinical trials. Likely reasons for this disappointing outcome include the significant and underappreciated differences in the isoforms of Ras. It is still plausible that inhibition of farnesyl transferase will prove effective for disease that is driven by activated H-Ras. The principal current focus of drugs entering clinic trial is inhibition of pathways downstream of activated Ras, for example, trametinib, a first-in-class MEK inhibitor. The complexity of signaling that is driven by activated Ras indicates that effective inhibition of oncogenic transduction through this approach will be difficult, with resistance being likely to emerge through switch to parallel pathways. Durable disease responses will probably require combinatorial block of several downstream targets.

Familial mental retardation: a review and practical classification

Mental retardation (MR) is a definition which comprises a series of conditions whose common feature is an intellectual handicap that develops before the age of 18, afflicting 2-3% of the world's population. The classification of MR into different categories is determined by the extent of the handicap instead of its cause, which often remains unrecognized. Sometimes, MR runs in a family, characterizing familial MR, and those cases permit an in-depth look into the genetic causes and consequences of the problem. However, almost no work is available on the prevalence of familial MR among the registered MR cases, possibly because familial MR is a term with no clear definition. The scope of this work is to review the topic and discuss the implications of different genetic and environmental factors, which characterize particular categories of familial cases, suggesting a practical classification of familial MR, which is important for epidemiologic studies and also for counseling in the clinic. Some of the aspects are discussed under the perspective of a newly-developed country like Brazil.

Behaviour in children with neurofibromatosis type 1: cognition, executive function, attention, emotion, and social competence

AIM

This systematic review aimed to pull together the findings from research into behavioural systems and attention in children with neurofibromatosis type 1 (NF1) and to identify areas that need further study.

METHOD

Relevant papers were identified through searches of electronic databases (MEDLINE, PsycINFO, EMBASE) and manual searches through reference lists. In total, 5746 articles were identified and 57 met the inclusion criteria. The data were synthesized using the narrative approach, as the studies varied considerably in terms of participants and measures.

RESULTS

The results of the review showed that intelligence, academic skills, visuospatial skills, social competence, and attention are impaired in children with NF1. Evidence of deficits in memory, motor functioning, language, and executive functions was less clear.

INTERPRETATION

Research has made marked progress in outlining the behavioural phenotype of NF1. However, although the general areas of impairment are becoming better known, the exact nature of the impairment is still not understood in many areas of behaviour. Care needs to be taken with the way in which behavioural constructs are defined and measured, and the variability of problems in NF1 is a particular challenge. Nevertheless, research is steadily moving towards comprehensive understanding of behaviour in children with NF1.

Symptomatology of autism spectrum disorder in a population with neurofibromatosis type 1

AIM

Difficulties in neurocognition and social interaction are the most prominent causes of morbidity and long-term disability in children with neurofibromatosis type 1 (NF1). Symptoms of attention-deficit-hyperactivity disorder (ADHD) have also been extensively recognized in NF1. However, systematic evaluation of symptoms of autism spectrum disorder (ASD) in children with NF1 has been limited.

METHOD

We present a retrospective, cross-sectional study of the prevalence of symptoms of ASD and ADHD and their relationship in a consecutive series of 66 patients from our NF1 clinic. The Social Responsiveness Scale and the Vanderbilt ADHD Diagnostic Parent Rating Scale were used to assess symptoms of ASD and ADHD.

RESULTS

Sixty-six participants (42 males, 24 females) were included in this study. Mean age at assessment was 10 years 11 months (SD 5 y 4 mo). Forty percent of our NF1 sample had raised symptom levels reaching clinical significance on the Social Responsiveness Scale (T ≥ 60), and 14% reached levels consistent with those seen in children with ASDs (T ≥ 75). These raised levels were not explained by NF1 disease severity or externalizing/internalizing behavioral disorders. There was a statistically significant relationship between symptoms of ADHD and ASD (χ(2) =9.11, df=1, p=0.003, φ=0.56). Particularly salient were the relationships between attention and hyperactivity deficits, with impairments in social awareness and social motivation.

INTERPRETATION

We found that symptoms of ASD in our NF1 population were raised, consistent with previous reports. Further characterization of the specific ASD symptoms and their impact on daily function is fundamental to the development and implementation of effective interventions in this population, which will probably include a combination of medical and behavioral approaches.

Modeling cognitive dysfunction in neurofibromatosis-1

Cognitive dysfunction, including significant impairments in learning, behavior, and attention, is found in over 10% of children in the general population. However, in the common inherited cancer predisposition syndrome, neurofibromatosis type 1 (NF1), the prevalence of these cognitive deficits approaches 70%. As a monogenic disorder, NF1 provides a unique genetic tool to identify and dissect mechanistically the molecular and cellular bases underlying cognitive dysfunction. In this review, we discuss Nf1 fly and mouse systems that mimic many of the cognitive abnormalities seen in children with NF1. Further, we describe discoveries from these models that have uncovered defects in the regulation of Ras activity, cAMP generation, and dopamine homeostasis as key mechanisms important for cognitive dysfunction in children with NF1.

Attention skills in children with neurofibromatosis type 1

Children with neurofibromatosis type 1 are at increased risk for the development of attention problems relative to their unaffected peers. Previous studies have reported deficits in sustained auditory attention, but other aspects of attention, including sustained visual attention, divided attention, response inhibition, and selective attention, have not been consistently documented. In the present study, we specifically investigated attention skills in children with neurofibromatosis type 1 using measures of visual and sustained auditory attention, divided attention, selective attention, and response inhibition. Consistent with previous reports, we confirmed the presence of deficits in sustained visual and auditory attention in children with neurofibromatosis type 1 but also identified deficits in divided attention and response inhibition. Based on the high frequency and wide spectrum of attention system impairments in this at-risk population, we advocate screening children with neurofibromatosis type 1 for attention problems and providing appropriate interventions that address all aspects of their executive functioning.

New models for considering the role of medication in the treatment and elucidation of the etiology of autism

Autism spectrum disorder (ASD) is a lifelong neurodevelopmental disorder. Over the past decades, much research has been conducted to elucidate a single etiological factor and effective pharmacotherapuetics to address the core symptom domains of ASD with limited success. Research has changed focus from behavioral observations of ASD to translating findings from animal models, genomic manipulation studies and basic science studies to pharmacological agents with the aim to lessen or reverse core symptoms of ASD. This paper evaluates potential models for translating information from the biology of ASD to pharmacological treatments.

The Learning Disabilities Network (LeaDNet): using neurofibromatosis type 1 (NF1) as a paradigm for translational research

Learning disabilities and other cognitive disorders represent one of the most important unmet medical needs and a significant source of lifelong disability. To accelerate progress in this area, an international consortium of researchers and clinicians, the Learning Disabilities Network (LeaDNet), was established in 2006. Initially, LeaDNet focused on neurofibromatosis type 1 (NF1), a common single gene disorder with a frequency of 1:3,000. Although NF1 is best recognized as an inherited tumor predisposition syndrome, learning, cognitive, and neurobehavioral deficits account for significant morbidity in this condition and can have a profound impact on the quality of life of affected individuals. Recently, there have been groundbreaking advances in our understanding of the molecular, cellular, and neural systems underpinnings of NF1-associated learning deficits in animal models, which precipitated clinical trials using a molecularly targeted treatment for these deficits. However, much remains to be learned about the spectrum of cognitive, neurological, and psychiatric phenotypes associated with the NF1 clinical syndrome. In addition, there is a pressing need to accelerate the identification of specific clinical targets and treatments for these phenotypes. The successes with NF1 have allowed LeaDNet investigators to broaden their initial focus to other genetic disorders characterized by learning disabilities and cognitive deficits including other RASopathies (caused by changes in the Ras signaling pathway). The ultimate mission of LeaDNet is to leverage an international translational consortium of clinicians and neuroscientists to integrate bench-to-bedside knowledge across a broad range of cognitive genetic disorders, with the goal of accelerating the development of rational and biologically based treatments.

Cognitive profiles of neurofibromatosis type 1 patients with minor brain malformations

Neurofibromatosis type 1 is a genetic condition associated with increased risk of abnormal brain development. The relationship between a specific type of brain malformation and a distinct cognitive sign/deficiency remains unknown. This study investigated the frequency of brain malformations in children with neurofibromatosis type 1, and the impact of those brain malformations on cognitive performance. A retrospective examination was performed of cranial magnetic resonance imaging and clinical records in 604 neurofibromatosis type 1 patients. Eighteen patients with brain malformations and intellectual evaluations were available and compared to a subset of neurofibromatosis type 1 patients (n = 20) without brain malformations. The most common brain malformations included hypothalamic hamartomas and Chiari I malformation. More complex migration disorders were also observed. Comparisons of cognitive profiles between groups revealed differences in patients with hamartomas compared with those manifesting Chiari I malformations or control subjects. As a group, those with hamartomas demonstrated below-average global intellect, whereas patients with Chiari I or no malformations performed in the average range. Disorders in cell organization, expressed as brain malformations (hamartomas or more complex defects), may comprise part of the expression of organizational and developmental defects in patients with neurofibromatosis type 1 and possibly other rat sarcoma gene-mitogen activated protein kinase pathway disorders.

Lovastatin regulates brain spontaneous low-frequency brain activity in neurofibromatosis type 1

In the neurofibromatosis type 1 (NF1) mouse model, lovastatin, used clinically for hypercholesterolemia, improves cognitive dysfunction. While such impairment has been studied in NF1, the neural substrates remain unclear. The aim of this imaging add-on to a Phase 1 open-label trial was to examine the effect of lovastatin on Default Network (DN) resting state functional connectivity (RSFC). Seven children with NF1 (aged 11.9 ± 2.2; 1 female) were treated with lovastatin once daily for 12 weeks. A 7-min 3-T echo-planar-imaging scan was collected one day before beginning treatment (off-drug) and the last day of treatment (on-drug) while performing a flanker task. After regressing-out task-associated variance, we used the residual time series as "continuous resting-state data" for RSFC analyses using 11 DN regions of interest. For qualitative comparisons, we included a group of 19 typically developing children (TDC) collected elsewhere. In the on-drug condition, lovastatin increased long-range positive RSFC within DN core regions (i.e., anterior medial prefrontal cortex and posterior cingulate cortex, PCC). In addition, lovastatin produced less diffuse local RSFC in the dorsomedial prefrontal cortex and PCC. The pattern of RSFC observed in the NF1 participants when on-drug closely resembled the RSFC patterns exhibited by the TDC. Lovastatin administration in this open trial regulated anterior-posterior long-range and local RSFC within the DN. These preliminary results are consistent with a role for lovastatin in normalization of developmental processes and with apparent benefits in a mouse NF1 model.

Inhibition and Termination of Physiological Responses by GTPase Activating Proteins

Physiological processes are strictly organized in space and time. However, in cell physiology research, more attention is given to the question of space rather than to time. To function as a signal, environmental changes must be restricted in time; they need not only be initiated but also terminated. In this review, we concentrate on the role of one specific protein family involved in biological signal termination. GTPase activating proteins (GAPs) accelerate the endogenously low GTP hydrolysis rate of monomeric guanine nucleotide-binding proteins (GNBPs), limiting thereby their prevalence in the active, GTP-bound form. We discuss cases where defective or excessive GAP activity of specific proteins causes significant alteration in the function of the nervous, endocrine, and hemopoietic systems, or contributes to development of infections and tumors. Biochemical and genetic data as well as observations from human pathology support the notion that GAPs represent vital elements in the spatiotemporal fine tuning of physiological processes.