Associations of clinical features in neurofibromatosis 1 (NF1)

Impact of neurofibromatosis type 1 on quality of life using the Skindex-29 questionnaire quality of life in NF1

BACKGROUND

Neurofibromatosis type 1 (NF1) is one of the most common RASopathies predisposing affected patients to melanic lesions and benign tumors. NF1 is associated with considerable esthetic and functional burden negatively affecting the patient's quality of life (QoL). This study aims to assess the clinical features of NF1 patients and evaluate their impact on QoL. We identified NF1 patients from a public health database of a region in Spain. All patients underwent clinical and ophthalmological evaluation for NF1 features. We measured QoL using the Spanish version of the Skindex-29.

RESULTS

Forty patients fulfilled the NF1 National Institute of Health criteria when we recruited patients. The median age was 42.00 years (IQR 26.5 -53.75). The median total Skindex-29 score was 12.3 (IQR 5.9-22.4); (emotion: 15.0, IQR 5.0-37.5; symptoms 8.9, IQR 0.0-17.9 and functioning 8.3; IQR 0.5-18.3). Women and NF1 patients with lower educational levels were associated with poorer QoL scores. We identified itching and sleep troubles to influence NF1 patients' QoL negatively.

CONCLUSION

NF1 considerably influences the psychological well-being of NF1 patients. We observed that female and low-educated patients scored higher on the emotional dimension of the Skindex-29 and could, therefore, be more at risk of depression. We also pointed out some "minor symptoms" that negatively impact NF1 patients' QoL such, as itching and sleep troubles which doctors could treat if sought by doctors.

Pediatric low-grade glioma and neurofibromatosis type 1: A single-institution experience

Background

Neurofibromatosis type 1 (NF1)-related gliomas appear to have a clinical behavior different from that of sporadic cases. The purpose of the study was to investigate the role of different factors in influencing the tumor response rate of children receiving chemotherapy for their symptomatic glioma.

Methods

Between 1995 and 2015, 60 patients with low-grade glioma (42 sporadic cases and 18 cases with NF1) were treated. Patients with brainstem gliomas were excluded. Thirty-nine patients underwent exclusive or postsurgical chemotherapy (vincristine/carboplatin-based regimen).

Results

Disease reduction was achieved in 12 of the 28 patients (42.8%) with sporadic low-grade glioma and in 9 of the 11 patients (81.8%) with NF1, with a significant difference between the 2 groups (P < 0.05). The response to chemotherapy in both the patient groups was not significantly influenced by sex, age, tumor site, and histopathology, although disease reduction occurred more frequently in children aged under 3 years.

Conclusions

Our study showed that pediatric patients with low-grade glioma and NF1 are more likely to respond to chemotherapy than those with non-NF1.

MR Imaging Characteristics and ADC Histogram Metrics for Differentiating Molecular Subgroups of Pediatric Low-Grade Gliomas

BACKGROUND AND PURPOSE

BRAF and type 1 neurofibromatosis status are distinctive features in pediatric low-grade gliomas with prognostic and therapeutic implications. We hypothesized that DWI metrics obtained through volumetric ADC histogram analyses of pediatric low-grade gliomas at baseline would enable early detection of BRAF and type 1 neurofibromatosis status.

MATERIALS AND METHODS

We retrospectively evaluated 40 pediatric patients with histologically proved pilocytic astrocytoma (n = 33), ganglioglioma (n = 4), pleomorphic xanthoastrocytoma (n = 2), and diffuse astrocytoma grade 2 (n = 1). Apart from 1 patient with type 1 neurofibromatosis who had a biopsy, 11 patients with type 1 neurofibromatosis underwent conventional MR imaging to diagnose a low-grade tumor without a biopsy. BRAF molecular analysis was performed for patients without type 1 neurofibromatosis. Eleven patients presented with BRAF V600E-mutant, 20 had BRAF-KIAA rearrangement, and 8 had BRAF wild-type tumors. Imaging studies were reviewed for location, margins, hemorrhage or calcifications, cystic components, and contrast enhancement. Histogram analysis of tumoral diffusivity was performed.

RESULTS

Diffusion histogram metrics (mean, median, and 10th and 90th percentiles) but not kurtosis or skewness were different among pediatric low-grade glioma subgroups (P < .05). Diffusivity was lowest in BRAF V600E-mutant tumors (the 10th percentile reached an area under the curve of 0.9 on receiver operating characteristic analysis). There were significant differences between evaluated pediatric low-grade glioma margins and cystic components (P = .03 and P = .001, respectively). Well-defined margins were characteristic of BRAF-KIAA or wild-type BRAF rather than BRAF V600E-mutant or type 1 neurofibromatosis tumors. None of the type 1 neurofibromatosis tumors showed a cystic component.

CONCLUSIONS

Imaging features of pediatric low-grade gliomas, including quantitative diffusion metrics, may assist in predicting BRAF and type 1 neurofibromatosis status, suggesting a radiologic-genetic correlation, and might enable early genetic signature characterization.

Case Report: Chemotherapy Indication in a Case of Neurofibromatosis Type 1 Presenting Optic Pathway Glioma: A One-Year Clinical Case Study Using Differential Tractography Approach

Neurofibromatosis type 1 (NF1) is associated with peripheral and central nervous system tumors. It is noteworthy that the regions in which these tumors frequently arise are the optic pathways (OPs) and the brainstem. Thus, we decided to trace the procedure of diffusion Magnetic Resonance Imaging (dMRI) alterations along with Short-Wavelength Automated Perimetry (SWAP) examinations of the OPs after surgery and chemotherapy over 1 year, which enabled us to evaluate chemotherapy's efficacy in an NF1 patient with an OP tumor. In this study, a 25-year-old woman with NF1 and left optic radiation (OR) glioma underwent surgery to remove the glioma. Immunohistochemistry (IHC) revealed a Pilocytic Astrocytoma (PA) WHO grade I. Post-operation chemotherapy done using nine treatment cycles of administering Temozolomide (TMZ) for 5 days every 4 weeks. Applying the region of interest (ROI) differential tractography method and SWAP four times every 3 months allowed us to follow the patient's visual acuity alterations longitudinally. The differential deterministic tractography method and statistical analyses enabled us to discover the white matter (WM) tracts anisotropy alterations over time. Furthermore, statistical analyses on the SWAP results along time illustrated possible alterations in visual acuity. Then, we could compare and associate the findings with the SWAP examinations and patient symptoms longitudinally. Statistical analyses of SWAP tests revealed a significant improvement in visual fields, and longitudinal differential tractography showed myelination and dense axonal packing in the left OR after 1 year of treatment. In this study, we examined an old hypothesis suggesting that chemotherapy is more effective than radiotherapy for NF1 patients with OP gliomas (OPGs) because of the radiation side effects on the visual field, cognition, and cerebrovascular complications. Our longitudinal clinical case study involving dMRI and SWAP on a single NF1-OPG patient showed that chemotherapy did not suppress the OP myelination over time. However, it should be noted that this is a clinical case study, and, therefore, the generalization of results is limited. Future investigations might focus on genetic-based imaging, particularly in more cases. Further, meta-analyses are recommended for giving a proper Field Of View (FOV) to researchers as a subtle clue regarding precision medicine.

Epilepsy in NF1: a systematic review of the literature

Epilepsy is one of the possible neurological manifestations of the neurofibromatosis type 1 (NF1) that represents the most common neurocutaneous disorder. We performed a systematic review of the literature on epilepsy associated with NF1 since 1995 in order to better define prevalence and describe type and causes of seizures. Data on type, nature of studies, number of patients, gender, and inheritance of NF1 were recorded as well as data on causes, type, EEGs, brain imaging, intellectual disability (ID), surgical treatment, and outcome of epilepsy. We identified a total of 141 references through the literature search of Pubmed and Embase. After screening, 42 records were identified, including 11617 individuals with NF1 (53% of males). Overall prevalence was estimated at 5.4% lifelong with values that seemed to be slightly lower in children, 3.7% (p 0.0016). Neither gender differences nor correlation with NF1 inheritance was found. Focal with or without bilateral tonic-clonic seizures were the most common seizure type encountered (60.9%). Structural causes were identified in half of cases (114/226). Low-grade gliomas were the most frequent associated lesions followed by mesial temporal sclerosis, malformation of cortical development, dysembryoplastic neuroepithelial tumor, and cerebrovascular lesions. In these cases, the surgical approach improved the epileptic outcome. Prevalence of epilepsy is higher in subjects with NF1 respect of the general population, with values apparently significantly lower in pediatric age. Brain tumors and cytoarchitectural abnormalities are the most frequent causes of epilepsy in this population, although many other brain complications should be taken in account.

An Update on Neurofibromatosis Type 1-Associated Gliomas

Neurofibromatosis type 1 (NF1) is an autosomal dominant tumor predisposition syndrome that affects children and adults. Individuals with NF1 are at high risk for central nervous system neoplasms including gliomas. The purpose of this review is to discuss the spectrum of intracranial gliomas arising in individuals with NF1 with a focus on recent preclinical and clinical data. In this review, possible mechanisms of gliomagenesis are discussed, including the contribution of different signaling pathways and tumor microenvironment. Furthermore, we discuss the recent notable advances in the developing therapeutic landscape for NF1-associated gliomas including clinical trials and collaborative efforts.

NF1 Patients Receiving Breast Cancer Screening: Insights from The Ontario High Risk Breast Screening Program

Neurofibromatosis Type I (NF1) is caused by variants in neurofibromin (NF1). NF1 predisposes to a variety of benign and malignant tumor types, including breast cancer. Women with NF1 <50 years of age possess an up to five-fold increased risk of developing breast cancer compared with the general population. Impaired emotional functioning is reported as a comorbidity that may influence the participation of NF1 patients in regular clinical surveillance despite their increased risk of breast and other cancers. Despite emphasis on breast cancer surveillance in women with NF1, the uptake and feasibility of high-risk screening programs in this population remains unclear. A retrospective chart review between 2014–2018 of female NF1 patients seen at the Elizabeth Raab Neurofibromatosis Clinic (ERNC) in Ontario was conducted to examine the uptake of high-risk breast cancer screening, radiologic findings, and breast cancer characteristics. 61 women with pathogenic variants in NF1 enrolled in the high-risk Ontario breast screening program (HR-OBSP); 95% completed at least one high-risk breast screening modality, and four were diagnosed with invasive breast cancer. Our findings support the integration of a formal breast screening programs in clinical management of NF1 patients.

Pharmacoresistant seizures in neurofibromatosis type 1 related to hippocampal sclerosis: Three case presentation and review

Neurofibromatosis type 1 (NF1) is an autosomal dominantly inherited disorder, with an estimated prevalence of 1 in 3000-4000 people. Seizures occur 4-7% of individuals with NF1, mostly due to associated brain tumors or cortical malformations. Hippocampal sclerosis (HS) in the patients with NF1 has been reported very rarely and only 15 patients were found in review of English literature. We presented here 3 additional patients with NF1 and intractable seizures due to hippocampal sclerosis; in whom one of them underwent epilepsy surgery and he is seizure free for 5 years after right temporal lobectomy.

Determination of genetic aberrations and novel transcripts involved in the pathogenesis of oligodendroglioma using array comparative genomic hybridization and next generation sequencing

The aim of the present study was to determine the genetic aberrations and novel transcripts, particularly the fusion transcripts, involved in the pathogenesis of low-grade and anaplastic oligodendroglioma. In the present study, tissue samples were obtained from patients with oligodendroglioma and additionally from archived tissue samples from the Brain Tumor Tissue Bank of the Brain Tumor Foundation of Canada. Six samples were obtained, three of which were low-grade oligodendroglioma and the other three anaplastic oligodendroglioma. DNA and RNA were extracted from each tissue sample. The resulting genomic DNA was then hybridized using the Agilent CytoSure 4×180K oligonucleotide array. Human reference DNA and samples were labeled using Cy3 cytidine 5′-triphosphate (CTP) and Cy5 CTP, respectively, while human Cot-1 DNA was used to reduce non-specific binding. Microarray-based comparative genomic hybridization data was then analyzed for genetic aberrations using the Agilent Cytosure Interpret software v3.4.2. The total RNA isolated from each sample was mixed with oligo dT magnetic beads to enrich for poly(A) mRNA. cDNAs were then synthesized and subjected to end-repair, poly(A) addition and connected using sequencing adapters using the Illumina TruSeq RNA Sample Preparation kit. The fragments were then purified and selected as templates for polymerase chain reaction amplification. The final library was constructed with fragments between 350–450 base pairs and sequenced using deep transcriptome sequencing on an Illumina HiSeq 2500 sequencer. The array comparative genomic hybridization revealed numerous amplifications and deletions on several chromosomes in all samples. However, the most interesting result was from the next generation sequencing, where one anaplastic oligodendroglioma sample was demonstrated to have five novel fusion genes that may potentially serve a critical role in tumor pathogenesis and progression.

Cerebellar radiological abnormalities in children with neurofibromatosis type 1: part 1 - clinical and neuroimaging findings

Background

Many children with neurofibromatosis type 1 (NF1) have focal abnormal signal intensities (FASI) on brain MRI, whose full clinical impact and natural history have not been studied systematically. Our aims are to describe the clinical and neuroradiological features in children with NF1 and cerebellar FASI, and report on the natural history of FASI that display atypical features such as enhancement and mass effect.

Method

A retrospective review of the hospital charts and brain MRIs was performed on children from Manitoba diagnosed between 1999 and 2008 with NF1, who also had cerebellar FASI on MRI.

Results

Fifty patients (mean age: 16.1y, minimum-maximum: 6.4 - 30y, 27 M) were identified. Mean duration of follow up was 10.1y. Developmental delay, learning disabilities, tumors, and visual signs occurred commonly. Cerebellar signs were not reported. Mean age of the patients at baseline MRI was 7.8 (SD: 4.5) years. FASI occurred in several brain locations and were rarely confined to the cerebellum. FASI displayed mass effect and enhancement infrequently but were associated with malignancy only once. The number of FASI at baseline MRI was significantly less in patients with attention deficient hyperactivity disorder and more if a first degree relative had NF1 or if they had decreased visual acuity.

Discussion

Patients with NF1 and cerebellar FASI do not have motor or consistent non-motor (e.g. developmental delay or learning disabilities) cerebellar features. The number of FASI may correlate with some clinical features. FASI may display enhancement and mass effect but they rarely become malignant.

An elderly patient presenting with a primary spinal multifocal intradural extramedullary pilocytic astrocytoma: a case report and review of the literature

BACKGROUND

Pilocytic astrocytoma is a low-grade central nervous system tumor most commonly seen in children. Dissemination from a primary intracranial tumor along the neuroaxis has been described at both presentation and disease progression. However, the development of an intradural extramedullary pilocytic astrocytoma independent of a primary intraparenchymal tumor in an adult patient with no history of pilocytic astrocytoma has rarely been reported.

CASE PRESENTATION

A 69-year-old woman presented with progressive myelopathic symptoms and thoracic radicular pain. MRI imaging of the whole spine showed an enhancing intradural extramedullary lesion extending from the cervical cord to T11 causing cord compression. Laminectomies were performed for surgical decompression and histopathology was consistent with pilocytic astrocytoma. Complete staging was done that included imaging of the brain and cerebrospinal fluid cytology. No other tumor was found by these methods. Postoperatively the patient was treated with large field spinal radiation and concurrent chemotherapy followed by adjuvant chemotherapy. She has thus far been clinically and radiographically stable.

CONCLUSION

This is a rare case of an adult with multiple spinal pilocytic astrocytomas in an intradural extramedullary location, typically the result of cerebrospinal fluid dissemination of neoplastic cells from a primary intracranial tumor site (i.e. drop metastasis). No conventional primary tumor was identified in this patient, suggesting these tumors may arise from heterotopic gliomas.

Racial/ethnic disparities and incidence of malignant peripheral nerve sheath tumors: results from the Surveillance, Epidemiology, and End Results Program, 2000-2014

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) are rare tumors, generally high-grade, and comprise ~ 5-10% of soft tissue sarcomas. Over two-thirds of MPNSTs metastasize, and upwards of 40% clinically recur. Etiologic risk factors for MPNSTs are historically understudied. There is evidence to suggest MPNST incidence differs across racial/ethnic groups in pediatric populations. Therefore, we sought to estimate differences in MPNST incidence by race/ethnicity among all ages in the United States.

METHODS

Incidence data were obtained from the Surveillance, Epidemiology, and End Results (SEER-18) Program, 2000-2014. Race/ethnicity was categorized as: White; Black; Asian; Other; and Latino/a ("Spanish-Hispanic-Latino"). Latino/a included all races, while all other categories excluded those identified as Latino/a. Age-adjusted incidence rate ratios (IRR) and 95% confidence intervals (CIs) were generated in SEER-STAT (v8.3.4). We estimated incidence rates among all ages, and among those diagnosed < 25 and ≥ 25 years.

RESULTS

MPNST cases were abstracted from SEER-18 (n = 1047). Among all age groups, Blacks experienced an elevated incidence of MPNSTs compared to Whites (IRR_Blacks = 1.26, 95% CI 1.04-1.50). Asian and Latinos/as experienced lower incidences compared to Whites (IRR_Asians = 0.78, 95% CI 0.61-0.99; IRR_Latinos/as = 0.84, 95% CI 0.69-1.02). In subgroup analyses, no statistically significant associations with MPNSTs were identified among cases diagnosed < 25 years of age, whereas the associations observed among all age groups were prominent among those diagnosed ≥ 25 years of age.

CONCLUSIONS

Incidence rates of MPNSTs were highest in Blacks compared to Whites and other minority groups. This study suggests specific patterns exist in terms of race/ethnicity and age at diagnosis of MPNSTs.

Ophthalmic manifestations in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a relatively common multisystemic inherited disease and has been extensively studied by multiple disciplines. Although genetic testing and confirmation are available, NF1 remains a clinical diagnosis. Many manifestations of NF1 involve the eye and orbit, and the ophthalmologist, therefore, plays a significant role in the diagnosis and treatment of NF1 patients. Improvements in diagnostic and imaging instruments have provided new insight to study the ophthalmic manifestations of the disease. We provide a comprehensive and up-to-date overview of the ocular and orbital manifestations of NF1.

Characterization of early communicative behavior in mouse models of neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a monogenic neurodevelopmental disease caused by germline loss-of-function mutations in the NF1 tumor suppressor gene. Cognitive impairments are observed in approximately 80% of children with this disease, with 45-60% exhibiting autism spectrum disorder (ASD) symptomatology. In light of the high comorbidity rate between ASD and NF1, we assessed early communicative behavior by maternal-separation induced pup ultrasonic vocalizations (USV) and developmental milestones in two distinct Nf1 genetically engineered models, one modeling clinical germline heterozygous loss of Nf1 function (Nf1^+/- mice), and a second with somatic biallelic Nf1 inactivation in neuroglial progenitor cells (Nf1^GFAP CKO mice). We observed altered USV production in both models: Nf1^+/- mice exhibited both increased USVs across development and alterations in aspects of pitch, while Nf1^GFAP CKO mice demonstrated a decrease in USVs. Developmental milestones, such as weight, pinnae detachment, and eye opening, were not disrupted in either model, indicating the USV deficits were not due to gross developmental delay, and likely reflected more specific alterations in USV circuitry. In this respect, increased whole-brain serotonin was observed in Nf1^+/- mice, but whole-brain levels of dopamine and its metabolites were unchanged at the age of peak USV disruption, and USV alterations did not correlate with overall level of neurofibromin loss. The early communicative phenotypes reported herein should motivate further studies into the risks mediated by haploinsufficiency and biallelic deletion of Nf1 across a full battery of ASD-relevant behavioral phenotypes, and a targeted analysis of underlying circuitry disruptions. Autism Res 2018, 11: 44-58. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

Neurofibromatosis type 1 (NF1) is a common neurogenetic disorder caused by mutation of the NF1 gene, in which 80% of affected children exhibit cognitive and behavioral issues. Based on emerging evidence that NF1 may be an autism predisposition gene, we examined autism spectrum disorder (ASD)-relevant early communicative behavior in Nf1 mouse models and observed alterations in both models. The changes in early communicative behavior in Nf1 mutant mice should motivate further studies into the causative factors and potential treatments for ASD arising in the context of NF1.

Optic Gliomas in Neurofibromatosis Type 1

PURPOSE

To examine the incidence, presentation, and outcome of optic gliomas in children with neurofibromatosis type 1 (NF1) in Southern California Kaiser Permanente.

METHODS

The authors queried the Southern California Kaiser Permanente electronic medical record database to find patients diagnosed as having NF1. Genetics, ophthalmology, and imaging medical records of patients with optic glioma were reviewed.

RESULTS

A total of 708 patients younger than 21 years had a diagnosis of NF1 in Southern California Kaiser Permanente and 30 (4.2%) had a diagnosis of optic glioma. The average age of diagnosis was 5 years, with a range of 18 months to 12 years. Half (15 of 30) of the patients diagnosed as having optic glioma presented with symptoms (eg, vision loss, proptosis, and precocious puberty). Eight of 15 of the symptomatic patients were treated with surgery and/or chemotherapy. Symptomatic children were diagnosed later than those diagnosed through routine screening (5.7 vs 3.9 years old). The oldest child presented with symptoms at age 12 years. One asymptomatic patient had prophylactic chemotherapy. Sixty-three percent (19 of 30) of the gliomas were bilateral, 23% (7 of 30) were right-sided, and 13% (4 of 30) were left-sided. Fifty-three percent (17 of 30) of the gliomas involved the optic chiasm.

CONCLUSIONS

Screening practices for optic glioma are inconsistent. Most children with NF1 at risk for optic glioma do not have even one visit with an ophthalmologist. Children with NF1 can develop asymptomatic optic glioma as early as age 1 year. Annual ophthalmologic examination and screening for precocious puberty in children with NF1 is important for early diagnosis of optic gliomas and may reduce morbidity. [J Pediatr Ophthalmol Strabismus. 2016;53(6):334-338.].

Neurofibromatosis type 1 associated low grade gliomas: A comparison with sporadic low grade gliomas

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder, associated with a variable clinical phenotype including café-au-lait spots, intertriginous freckling, Lisch nodules, neurofibromas, optic pathway gliomas and distinctive bony lesions. NF1 is caused by a mutation in the NF1 gene, which codes for neurofibromin, a large protein involved in the MAPK- and the mTOR-pathway through RAS-RAF signalling. NF1 is a known tumour predisposition syndrome, associated with different tumours of the nervous system including low grade gliomas (LGGs) in the paediatric population. The focus of this review is on grade I pilocytic astrocytomas (PAs), the most commonly observed histologic subtype of low grade gliomas in NF1. Clinically, these PAs have a better prognosis and show different localisation patterns than their sporadic counterparts, which are most commonly associated with a KIAA1549:BRAF fusion. In this review, possible mechanisms of tumourigenesis in LGGs with and without NF1 will be discussed, including the contribution of different signalling pathways and tumour microenvironment. Furthermore we will discuss how increased understanding of tumourigenesis may lead to new potential targets for treatment.

Neurofibromatosis: part 2 – clinical management

Part 1 of this guideline addressed the differential diagnosis of the neurofibromatoses (NF): neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2) and schwannomatosis (SCH). NF shares some features such as the genetic origin of the neural tumors and cutaneous manifestations, and affects nearly 80 thousand Brazilians. Increasing scientific knowledge on NF has allowed better clinical management and reduced rate of complications and morbidity, resulting in higher quality of life for NF patients. Most medical doctors are able to perform NF diagnosis, but the wide range of clinical manifestations and the inability to predict the onset or severity of new features, consequences, or complications make NF management a real clinical challenge, requiring the support of different specialists for proper treatment and genetic counseling, especially in NF2 and SCH. The present text suggests guidelines for the clinical management of NF, with emphasis on NF1.

Hyperactive RAS/PI3-K/MAPK Signaling Cascade in Migration and Adhesion of Nf1 Haploinsufficient Mesenchymal Stem/Progenitor Cells

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease caused by mutations in the NF1 tumor suppressor gene, which affect approximately 1 out of 3000 individuals. Patients with NF1 suffer from a range of malignant and nonmalignant manifestations such as plexiform neurofibromas and skeletal abnormalities. We previously demonstrated that Nf1 haploinsufficiency in mesenchymal stem/progenitor cells (MSPCs) results in impaired osteoblastic differentiation, which may be associated with the skeletal manifestations in NF1 patients. Here we sought to further ascertain the role of Nf1 in modulating the migration and adhesion of MSPCs of the Nf1 haploinsufficient (Nf1^+/−) mice. Nf1^+/− MSPCs demonstrated increased nuclear-cytoplasmic ratio, increased migration, and increased actin polymerization as compared to wild-type (WT) MSPCs. Additionally, Nf1^+/− MSPCs were noted to have significantly enhanced cell adhesion to fibronectin with selective affinity for CH271 with an overexpression of its complimentary receptor, CD49e. Nf1^+/− MSPCs also showed hyperactivation of phosphoinositide 3-kinase (PI3-K) and mitogen activated protein kinase (MAPK) signaling pathways when compared to WT MSPCs, which were both significantly reduced in the presence of their pharmacologic inhibitors, LY294002 and PD0325901, respectively. Collectively, our study suggests that both PI3-K and MAPK signaling pathways play a significant role in enhanced migration and adhesion of Nf1 haploinsufficient MSPCs.

Cognitive and behavioral problems in children with neurofibromatosis type 1: challenges and future directions

Cognitive and behavioral disorders affect nearly 80% of all children with the neurofibromatosis type 1 inherited cancer syndrome, and are among the most significant clinical manifestations for patients and their families. One of the barriers to successful therapeutic intervention is the wide spectrum of clinical phenotypic expression, ranging from visuospatial learning problems to social perceptual deficits (autism). Leveraging numerous small-animal models of neurofibromatosis type 1, several promising targets have been identified to treat the learning, attention, and autism spectrum phenotypes in this at-risk population. In this review, we provide an up-to-date summary of our current understanding of these disorders in NF1, and propose future research directions aimed at designing more effective therapeutic approaches and clinical trials.

CXCR4/CXCL12 mediate autocrine cell- cycle progression in NF1-associated malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas that arise in connective tissue surrounding peripheral nerves. They occur sporadically in a subset of patients with neurofibromatosis type 1 (NF1). MPNSTs are highly aggressive, therapeutically resistant, and typically fatal. Using comparative transcriptome analysis, we identified CXCR4, a G-protein-coupled receptor, as highly expressed in mouse models of NF1-deficient MPNSTs, but not in nontransformed precursor cells. The chemokine receptor CXCR4 and its ligand, CXCL12, promote MPNST growth by stimulating cyclin D1 expression and cell-cycle progression through PI3-kinase (PI3K) and β-catenin signaling. Suppression of CXCR4 activity either by shRNA or pharmacological inhibition decreases MPNST cell growth in culture and inhibits tumorigenesis in allografts and in spontaneous genetic mouse models of MPNST. We further demonstrate conservation of these activated molecular pathways in human MPNSTs. Our findings indicate a role for CXCR4 in NF1-associated MPNST development and identify a therapeutic target.

Skewed allele-specific expression of the NF1 gene in normal subjects: a possible mechanism for phenotypic variability in neurofibromatosis type 1

Neurofibromatosis type 1 is an autosomal dominant disorder characterized by neurocutaneous abnormalities, learning disabilities, and attention-deficit disorder. Neurofibromatosis type 1 symptom severity can be highly variable even within families where all affected members carry the same mutation. We hypothesized that variation in the expression of the normal NF1 allele may be a mechanism that participates in producing variable phenotypes. We performed allelic expression imbalance assays on healthy control individuals to estimate the prevalence of skewed allelic expression of the NF1 gene. Approximately 30% of individuals in our sample population showed significant skewing of allelic expression away from the expected 50:50 ratio, indicating that differential regulation of the NF1 alleles occurs in a high proportion of individuals. Differences of up to 25% in allele-specific expression of the NF1 alleles were identified. In individuals with Neurofibromatosis type 1, who carry a mutant allele (haploinsufficient), this degree of expression skewing may be sufficient to modulate the phenotype.

Skin-derived precursor cells as an in vitro modelling tool for the study of type 1 neurofibromatosis

The most characteristic feature of neurofibromatosis type 1 (NF1) is the development of neurofibromas. It has been suggested that these tumors are caused by somatic inactivation of the wild-type NF1 allele, but the cell that originally suffers this mutation remains controversial. Several lines of evidence support the clonal origin of these tumors, and it has been recently suggested that skin-derived precursor cells (SKPs) could be the cell of origin of dermal neurofibromas. Nullizygous (NF1(-/-)) SKPs do give rise to neurofibromas when transplanted to heterozygous mice. Moreover, a nullizygous population of cells that is S100β negative is present in human neurofibromas, and NF1(+/-) multipotent progenitor cells are seemingly recruited to the tumor. This evidence supports the neurofibroma stem cell hypothesis and a putative involvement of SKPs in the aetiopathogenesis of the disease, suggesting that SKPs could become a valuable tool for the in vitro study of NF1.

From neurodevelopment to neurodegeneration: the interaction of neurofibromin and valosin-containing protein/p97 in regulation of dendritic spine formation

Both Neurofibromatosis type I (NF1) and inclusion body myopathy with Paget's disease of bone and frontotemporal dementia (IBMPFD) are autosomal dominant genetic disorders. These two diseases are fully penetrant but with high heterogeneity in phenotypes, suggesting the involvement of genetic modifiers in modulating patients' phenotypes. Although NF1 is recognized as a developmental disorder and IBMPFD is associated with degeneration of multiple tissues, a recent study discovered the direct protein interaction between neurofibromin, the protein product of the NF1 gene, and VCP/p97, encoded by the causative gene of IBMPFD. Both NF1 and VCP/p97 are critical for dendritic spine formation, which provides the cellular mechanism explaining the cognitive deficits and dementia found in patients. Moreover, disruption of the interaction between neurofibromin and VCP impairs dendritic spinogenesis. Neurofibromin likely influences multiple downstream pathways to control dendritic spinogenesis. One is to activate the protein kinase A pathway to initiate dendritic spine formation; another is to regulate the synaptic distribution of VCP and control the activity of VCP in dendritic spinogenesis. Since neurofibromin and VCP/p97 also regulate cell growth and bone metabolism, the understanding of neurofibromin and VCP/p97 in neurons may be applied to study of cancer and bone. Statin treatment rescues the spine defects caused by VCP deficiency, suggesting the potential role of statin in clinical treatment for these two diseases.

Neoplasms associated with germline and somatic NF1 gene mutations

INTRODUCTION

Neurofibromatosis 1 is a tumor predisposition genetic syndrome with autosomal dominant inheritance and virtually 100% penetrance by the age of 5 years. NF1 results from a loss-of-function mutation in the NF1 gene, resulting in decreased levels of neurofibromin in the cell. Neurofibromin is a negative regulator of various intracellular signaling pathways involved in the cellular proliferation. Although the loss of heterozygosity in the NF1 gene may predispose NF1 patients to certain malignancies, additional genetic alterations are a prerequisite for their development. The precise nature of these additional genetic alterations is not well defined, and genetic testing of all malignancies in NF1 patients becomes an essential component of future research in this subset of patients. In addition to germline NF1 mutations, alteration of the somatic NF1 gene is associated with sporadic malignancies such as adenocarcinoma of the colon, myelodysplastic syndrome, and anaplastic astrocytoma.

MATERIALS AND METHODS

A comprehensive English and non-English language search for all articles pertinent to malignancies associated with NF1 was conducted using PubMed, a search engine provided by the U.S. National Library of Medicine and the National Institutes of Health. Key words searched included the following: "malignancies associated with NF1", "tumors associated with NF1", and "NF1 and malignancies". A comprehensive analysis in terms age and mode of presentation, investigation and therapeutic modalities, and outcome of the published data was performed and compared with similar information on the sporadic cases.

RESULTS

Malignancies in NF1 patients typically occur at an earlier age and, with an exception of optic pathway gliomas, certain types of malignancies carry a poor prognosis compared with their sporadic counterparts. Malignancies are the leading cause of death in NF1 patients, resulting in a 10- to 15-year decreased life expectancy compared with the general population.

CONCLUSIONS

The lack of well-defined screening tests for early detection and the nonspecific clinical presentation contributes to a poorer outcome in malignancies associated with NF1. Small study group size, mixed patient population, and a lack of uniformity in reporting research results make comparison of treatment outcome for this group difficult. An International Consensus Meeting to address and recommend best practices for screening, diagnosis, management, and follow-up of malignancies associated with NF1 is needed.

Soft tissue sarcomas and central nervous system tumors in children with neurofibromatosis type 1

OBJECTS

We aim to evaluate the characteristics of pediatric patients with neurofibromatosis type 1 (NF1) who developed soft tissue sarcomas (STSs) and central nervous system (CNS) tumors that have been followed up in our center.

MATERIALS AND METHODS

Medical records of children with NF1 were retrospectively analyzed.

RESULTS

There were 78 patients who met at least two diagnostic criteria for NF1. The median age of patients was 10 years (0.5-18), and M/F ratio was 1.3. The prevalance of the optic glioma was 11.5% (n = 9), and one patient with optic glioma also had cystic astrocytoma, one patient had brain stem tumor, and one patient had a CNS tumor (without histopathologic diagnosis). Seven of nine children were ≥ 7 years old at the time of the diagnosis of optic glioma. Visual impairment developed in four patients, and two of them were treated with radiotherapy solely on the basis of evidence of clinical and radiological progression of the tumors. Four patients developed STSs. Two of them had malignant peripheral nerve sheath tumors (MPNST), and the remaining two had bladder rhabdomyosarcoma. Three of the four patients with STSs died with progressive disease.

CONCLUSION

The clinical course of malignancy in NF1 is often different from that of similar tumor types in the general population. Careful follow-up in patients with NF1 is required to enable the early diagnosis of malignancies, and the developments of new targeted therapies are needed for improvement of the outcome for patients of this group, especially with MPNST.

Susceptible stages in Schwann cells for NF1-associated plexiform neurofibroma development

Stem cells are under strict regulation by both intrinsic factors and the microenvironment. There is increasing evidence that many cancers initiate through acquisition of genetic mutations (loss of intrinsic control) in stem cells or their progenitors, followed by alterations of the surrounding microenvironment (loss of extrinsic control). In neurofibromatosis type 1 (NF1), deregulation of Ras signaling results in development of multiple neurofibromas, complex tumors of the peripheral nerves. Neurofibromas arise from the Schwann cell lineage following loss of function at the NF1 locus, which initiates a cascade of interactions with other cell types in the microenvironment and additional cell autonomous modifications. In this study, we sought to identify whether a temporal "window of opportunity" exists during which cells of the Schwann cell lineage can give rise to neurofibromas following loss of NF1. We showed that acute loss of NF1 in both embryonic and adult Schwann cells can lead to neurofibroma formation. However, the embryonic period when Schwann cell precursors and immature Schwann cells are most abundant coincides with enhanced susceptibility to plexiform neurofibroma tumorigenesis. This model has important implications for understanding early cellular events that dictate neurofibroma development, as well as for the development of novel therapies targeting these tumors.

Decreased expression of neurofibromin contributes to epithelial-mesenchymal transition in neurofibromatosis type 1

Plexiform and/or dermal neurofibromas are nerve sheath tumors of the peripheral nervous system that are usually present in individuals with neurofibromatosis type 1 (NF1). Neurofibromas arise from Schwann cells with biallelic inactivation of NF1, the gene that encodes neurofibromin. This protein is responsible for regulation of the Ras-mediated pathway, which has been shown to play a crucial role in epithelial-to-mesenchymal transition (EMT). EMT is a biological process that occurs during embryogenesis and wound healing and is involved in pathological processes such as organ fibrosis and cancer metastasis. However, the relationship between neurofibromin and EMT has not been elucidated. We investigated whether the EMT-related signaling pathway was upregulated in NF1-associated neurofibromas and Schwann cells by assessing the expression levels of the EMT-related transcription factors Snail, Slug, Twist, ZEB1 and ZEB2. Immunohistochemical studies and quantitative reverse transcription polymerase chain reaction revealed an increase in the expression levels of EMT-related transcription factors in neurofibroma specimens and NF1-derived Schwann cells (sNF96.2). In addition, the silencing of NF1 by siRNA induced the expression of EMT-related transcription factors in normal human Schwann cells and in epithelial-like breast cancer cells. Our findings suggest that the loss of neurofibromin activated the EMT-related signaling pathway and that the excessive mesenchymal reaction may play a key role in the development of NF1-associated neurofibromas.

The role of angiogenesis in the transformation of plexiform neurofibroma into malignant peripheral nerve sheath tumors in children with neurofibromatosis type 1

PURPOSE

The role of angiogenesis in the transformation of peripheral neurofibroma (PNF) to malignant peripheral nerve sheath tumor (MPNST) in neurofibromatosis type 1 (NF1) remains elusive and forms the objective of this study.

EXPERIMENTAL DESIGN

Archival tissue from 5 children with NF1 and PNF, who developed MPNST between the ages of 8 and 15 years were analyzed for differences in microvasculature. The role of proangiogenic growth factors such as Vascular Endothelial Growth Factor (VEGF), and its receptors Flk-1 and Flt-1, and vessel maturity, defined as von Willebrand factor (vWf), α-smooth muscle actin+ (SMA+), were evaluated by immuno-histochemistry.

RESULTS

A qualitative evaluation of the vasculature showed predominantly α-SMA+/vWf+ more stable vessels in PNF, and an irregular meshwork of α-SMA-/vWf+ endothelial cells structures in MPNST. In NF and PNF tumor cells were VEGF-, in contrast to VEGF+ tumor cells in MPNST. If present, the VEGF stain was confined mainly to the perivascular spaces in PNF, unlike the mainly stromal VEGF stain in MPNST. VEGF receptors also manifested a tumor stage-specific pattern. Flk-1 and Flt-1 were restricted to the mature, well-formed vasculature in PNF, but exhibited a diffuse pattern in MPNST.

CONCLUSION

Our study provides a rare opportunity to document consistent and histologically detectable differences in the vascular organization of PNF and MPNST. It permits a pair-wise evaluation of the malignant conversion of benign PNF into its malignant counterpart, in the same patients. The phenotypic variations and characteristics of the vessels in these tumors are consistent with the idea that a strong proangiogenic drive contributes to the progressive growth in MPNST.

Monozygotic twins discordant for neurofibromatosis 1

We present monozygotic twins discordant for the autosomal dominant disorder neurofibromatosis type 1 (NF1). The affected twin was diagnosed with NF1 at age 12, based upon accepted clinical criteria for the disorder. Both twins were re-examined at ages 35 and 57, at which times the unaffected twin continued to show no clinical manifestations of NF1. Short tandem repeat marker (STR) genotyping at 10 loci on chromosome 17 and 10 additional loci dispersed across the genome revealed identical genotypes for the twins, confirming their monozygosity. The affected twin has three children, two of whom also have NF1, while the unaffected twin has two children, both unaffected. Using lymphoblastoid, fibroblast, and buccal cell samples collected from both twins and from other family members in three generations, we discovered a pathogenic nonsense mutation in exon 40 of the NF1 gene. This mutation was found in all cell samples from the affected twin and her affected daughter, and in lymphoblastoid and buccal cells but not fibroblasts from the unaffected twin. We also found a novel non-synonymous change in exon 16 of the NF1 gene that was transmitted from the unaffected mother to both twins and co-segregated with the pathogenic mutation in the ensuing generation. All cells from the twins were heterozygous for this apparent exon 16 polymorphism and for single nucleotide polymorphisms (SNPs) within 2.5 kb flanking the site of the exon 40 nonsense mutation. This suggests that the NF1 gene of the unaffected twin differed in the respective lymphoblastoid cells and fibroblasts only at the mutation site itself, making post-zygotic mutation leading to mosaicism the most likely mechanism of phenotypic discordance. Although the unaffected twin is a mosaic, the distribution of the mutant allele among different cells and tissues appears to be insufficient to cause overt clinical manifestations of NF1.

Cell of origin and microenvironment contribution for NF1-associated dermal neurofibromas

The tumor predisposition disorder neurofibromatosis type I (NF1) is one of the most common genetic disorders of the nervous system. It is caused by mutations in the Nf1 tumor-suppressor gene, which encodes a GTPase-activating protein (GAP) that negatively regulates p21-RAS. Development of malignant nerve tumors and neurofibromas occurs frequently in NF1. However, little is known about the molecular mechanisms mediating the initiation and progression of these complex tumors, or the identity of the specific cell type that gives rise to dermal or cutaneous neurofibromas. In this study, we identify a population of stem/progenitor cells residing in the dermis termed skin-derived precursors (SKPs) that, through loss of Nf1, form neurofibromas. We propose that SKPs, or their derivatives, are the cell of origin of dermal neurofibroma. We also provide evidence that additional signals from nonneoplastic cells in the tumor microenvironment play essential roles in neurofibromagenesis.

Genetics of human iris colour and patterns

The presence of melanin pigment within the iris is responsible for the visual impression of human eye colouration with complex patterns also evident in this tissue, including Fuchs' crypts, nevi, Wolfflin nodules and contraction furrows. The genetic basis underlying the determination and inheritance of these traits has been the subject of debate and research from the very beginning of quantitative trait studies in humans. Although segregation of blue-brown eye colour has been described using a simple Mendelian dominant-recessive gene model this is too simplistic, and a new molecular genetic perspective is needed to fully understand the biological complexities of this process as a polygenic trait. Nevertheless, it has been estimated that 74% of the variance in human eye colour can be explained by one interval on chromosome 15 that contains the OCA2 gene. Fine mapping of this region has identified a single base change rs12913832 T/C within intron 86 of the upstream HERC2 locus that explains almost all of this association with blue-brown eye colour. A model is presented whereby this SNP, serving as a target site for the SWI/SNF family member HLTF, acts as part of a highly evolutionary conserved regulatory element required for OCA2 gene activation through chromatin remodelling. Major candidate genes possibly effecting iris patterns are also discussed, including MITF and PAX6.

Mechanisms in the pathogenesis of malignant tumours in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a familial tumour syndrome. Malignant tumours can arise in the nervous and non-nervous system in either childhood or adulthood, with malignant peripheral nerve sheath tumours being most common. Rhabdomyosarcoma and neuroblastoma are paediatric neoplasms that are more common in children with NF1 than in those without the syndrome. Gastrointestinal stromal tumours, somatostatinomas, breast cancer, and phaeochromocytomas are seen in adults with NF1. Several pathways are thought to be involved in the development of tumours associated with NF1: rat sarcoma viral oncogene homologue (RAS)-mitogen activated protein kinase (MAPK), mammalian target of rapamycin (mTOR), and P21 protein (Cdc42/Rac)-activated kinase 1 (PAK1). New insights into the pathogenesis of these tumours will lead to a better understanding of tumour origin and development and will hopefully allow the discovery of new and specific treatments.

Unravelling the genetic basis of variable clinical expression in neurofibromatosis 1

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder which displays considerable inter- and intra-familial variability in phenotypic expression. To evaluate the genetic component of variable expressivity in NF1, we examined the phenotypic correlations between affected relatives in 750 NF1 patients from 275 multiplex families collected through the NF-France Network. Twelve NF1-related clinical features, including five quantitative traits (number of café-au-lait spots of small size and of large size, and number of cutaneous, subcutaneous and plexiform neurofibromas) and seven binary ones, were scored. All clinical features studied, with the exception of neoplasms, showed significant familial aggregation after adjusting for age and sex. For most of them, patterns of familial correlations indicated a strong genetic component with no apparent influence of the constitutional NF1 mutation. Heritability estimates of the five quantitative traits ranged from 0.26 to 0.62. Moreover, we investigated for the first time the role of the normal NF1 allele in the variable expression of NF1 through a family-based association study. Nine tag SNPs in NF1 were genotyped in 1132 individuals from 313 NF1 families. No significant deviations of transmission of any of the NF1 variants to affected offspring was found for any of the 12 clinical features examined, based on single marker or haplotype analysis. Taken together, our results provided evidence that genetic modifiers, unlinked to the NF1 locus, contribute to the variable expressivity of the disease.

Splanchnic artery aneurysms: the diagnostic contribution of ultrasonography in correlation with other imaging methods

Splanchnic artery aneurysms are localized vascular dilatations having a progressive evolution and leading towards severe complications (depletive rupture, distal emboli, organ ischemia). Treatment can be efficient when the condition is detected in time. The imaging techniques are highly efficient when it comes to detecting and locating splanchnic aneurysms. Each method has its own features. By knowing them, there is a better chance to track down the disease at an early stage.

Impact of neurofibromatosis type 1 on school performance

School functioning of 86 Dutch neurofibromatosis type 1 children (7-17 years) using teacher questionnaires was analyzed to determine the impact of neurofibromatosis type 1 on school performance. In all, 75% of the neurofibromatosis type 1 children performed more than 1 standard deviation below grade peers in at least one of the domains of spelling, mathematics, technical reading or comprehensive reading. Furthermore, neurofibromatosis type 1 children had a 4-fold increased risk for attending special education and a 6-fold increased risk for receiving remedial teaching for learning, behavior, speech, or motor problems. Children without apparent learning disabilities still frequently displayed neuropsychological deficits. Only 10% of the children did not show any school-functioning problems. Finally, it was found that the clinical severity of neurofibromatosis type 1 correlated with the cognitive deficits. Taken together, it was shown that neurofibromatosis type 1 has profound impact on school performance. Awareness of these problems may facilitate timely recognition and appropriate support.

Tumor microenvironment and neurofibromatosis type I: connecting the GAPs

The human disease von Recklinghausen's neurofibromatosis (Nf1) is one of the most common genetic disorders. It is caused by mutations in the NF1 tumor suppressor gene, which encodes a GTPase activating protein (GAP) that negatively regulates p21-RAS signaling. Dermal and plexiform neurofibromas as well as malignant peripheral nerve sheath tumors and other malignant tumors, are significant complications in Nf1. Neurofibromas are complex tumors and composed mainly of abnormal local cells including Schwann cells, endothelial cells, fibroblasts and additionally a large number of infiltrating inflammatory mast cells. Recent work has indicated a role for the microenvironment in plexiform neurofibroma genesis. The emerging evidence points to mast cells as crucial contributors to neurofibroma tumorigenesis. Therefore, further understanding of the molecular interactions between Schwann cells and their environment will provide tools to develop new therapies aimed at delaying or preventing tumor formation in Nf1 patients.

Optic pathway gliomas in neurofibromatosis-1: controversies and recommendations

Optic pathway glioma (OPG), seen in 15% to 20% of individuals with neurofibromatosis type 1 (NF1), account for significant morbidity in young children with NF1. Overwhelmingly a tumor of children younger than 7 years, OPG may present in individuals with NF1 at any age. Although many OPG may remain indolent and never cause signs or symptoms, others lead to vision loss, proptosis, or precocious puberty. Because the natural history and treatment of NF1-associated OPG is different from that of sporadic OPG in individuals without NF1, a task force composed of basic scientists and clinical researchers was assembled in 1997 to propose a set of guidelines for the diagnosis and management of NF1-associated OPG. This new review highlights advances in our understanding of the pathophysiology and clinical behavior of these tumors made over the last 10 years. Controversies in both the diagnosis and management of these tumors are examined. Finally, specific evidence-based recommendations are proposed for clinicians caring for children with NF1.

Associations of osseous abnormalities in Neurofibromatosis 1

The characteristic sites of Neurofibromatosis 1-associated osseous manifestations are the long bones (usually the tibia and fibula), vertebrae and sphenoid wing. Although these focal bony lesions may cause profound clinical consequences, a minority of people with NF1 are affected. However, most people with NF1 are shorter than expected for their age, gender and family. The pathogenesis of NF1 focal osteopathy and its relationship, if any, to short stature are unknown. We examined associations between the occurrence of various osseous lesions in 3377 NF1 probands from the Children's Tumor Foundation NF International Database. Using logistic regression analysis among 260 NF1 probands who had undergone radiological examination of both the spine and skull, we found associations between the occurrence of sphenoid wing and long bone osteopathy (conditional odds ratio [OR] = 6.1; 95% confidence interval [CI] = 1.7-22.3; P = 0.006) and between sphenoid wing and vertebral osteopathy (OR = 16.9; 95% CI = 5.3-53.3; P < 0.001) after adjusting for age and gender. Similar findings were observed from all 3377 NF1 probands using a multivariate probit regression model. In a separate analysis, we found lower age- and gender-standardized height in patients who had characteristic vertebral or sphenoid wing lesions than in people who did not (P < 0.05). We found no relationship between height and tibial osteopathy. We conclude that some people with NF1 are more likely to develop osseous manifestations than others and speculate that there may be a common pathogenetic mechanism responsible for the development of osseous abnormalities and that of the vertebrae and long bones.

Comprehensive NF1 screening on cultured Schwann cells from neurofibromas

Neurofibromatosis type 1 (NF1) is mainly characterized by the occurrence of benign peripheral nerve sheath tumors or neurofibromas. Thorough investigation of the somatic mutation spectrum has thus far been hampered by the large size of the NF1 gene and the considerable proportion of NF1 heterozygous cells within the tumors. We developed an improved somatic mutation detection strategy on cultured Schwann cells derived from neurofibromas and investigated 38 tumors from nine NF1 patients. Twenty-nine somatic NF1 lesions were detected which represents the highest NF1 somatic mutation detection rate described so far (76%). Furthermore, our data strongly suggest that the acquired second hit underlies reduced NF1 expression in Schwann cell cultures. Together, these data clearly illustrate that two inactivating NF1 mutations, in a subpopulation of the Schwann cells, are required for neurofibroma formation in NF1 tumorigenesis. The observed somatic mutation spectrum shows that intragenic NF1 mutations (26/29) are most prevalent, particularly frameshift mutations (12/29, 41%). We hypothesize that this mutation signature might reflect slightly reduced DNA repair efficiency as a trigger for NF1 somatic inactivation preceding tumorigenesis. Joint analysis of the current and previously published NF1 mutation data revealed a significant difference in the somatic mutation spectrum in patients with a NF1 microdeletion vs. non-microdeletion patients with respect to the prevalence of loss of heterozygosity events (0/15 vs. 41/81). Differences in somatic inactivation mechanism might therefore exist between NF1 microdeletion patients and the general NF1 population.

Neurofibromin: a general outlook

Neurofibromin is a cytoplasmic protein that is predominantly expressed in neurons, Schwann cells, oligodendrocytes, astrocytes and leukocytes. It is encoded by the gene NF1, located on chromosome 17, at q11.2, and has different biochemical functions, including association to microtubules and participation in several signaling pathways. Alterations in this protein are responsible for a phacomatosis named neurofibromatosis type 1.

Is osseous dysplasia a primary feature of neurofibromatosis 1 (NF1)?

Characteristic skeletal lesions are a cardinal feature of the autosomal dominant condition, neurofibromatosis 1 (NF1). The most frequently involved skeletal sites are the sphenoid wing, vertebrae, and tibia. Osseous lesions may range in severity in NF1 but are often progressive. They may lead to serious clinical consequences and be resistant to treatment. The skeletal lesions of NF1 are usually considered to be 'dysplasias', i.e. primary defects of bone, although there is no direct evidence supporting this interpretation. Moreover, it is difficult to understand why a generalized dysplasia of bone would produce focal lesions that show such a striking predisposition to only a few bones. We review the clinical and pathological features of NF1 skeletal lesions and propose that they result from an abnormal response of NF1 halpoinsufficient bone to abnormal mechanical forces rather than from a primary osseous dysplasia.

Analysis of neurofibromatosis 1 (NF1) lesions by body segment

Café-au-lait spots and neurofibromas are defining features of neurofibromatosis 1 (NF1), but they vary greatly in number, size, and clinical importance from patient to patient. The cause of this variability is unknown. We tested the hypotheses that development of these lesions is influenced by local or familial factors. The presence or absence of café-au-lait spots, cutaneous neurofibromas, and diffuse plexiform neurofibromas was recorded for each of 10 divisions of the body surface in 547 NF1 patients, including 117 affected individuals in 52 families. We used stratified Mantel-Haenszel tests to look for local associations between the presence of diffuse plexiform neurofibromas, cutaneous neurofibromas, and café-au-lait spots in individual body segments of NF1 patients. We used a random effects model to obtain intrafamilial correlation coefficients for the age-adjusted number of body divisions affected with each of the three lesions. No significant association was observed between the occurrence of cutaneous and diffuse plexiform neurofibromas, between café-au-lait spots and cutaneous neurofibromas, or between café-au-lait spots and plexiform neurofibromas in the same body segment. The correlation among relatives in the number of body segments affected with café-au-lait spots was 0.45 (95% confidence interval [CI] = 0.18-0.71), with cutaneous neurofibromas, 0.37 (95% CI = 0.15-0.55), and with plexiform neurofibromas, 0.35 (95% CI = 0.15-0.57). We conclude that the development of café-au-lait spots, cutaneous neurofibromas, and plexiform neurofibromas are spatially independent in NF1 patients but that the development of all three lesions is influenced by familial factors.

Utility and limitations of genetic disease databases in clinical genetics research: A neurofibromatosis 1 database example

Databases that collect clinical information on patients with particular genetic diseases can be used to investigate the clinical history of a disorder, its genetics, and genotype-phenotype correlations. A database can also serve as a valuable source of patients for studies of disease pathogenesis, variability, or treatment. We review the strengths and limitations of genetic disease databases in the context of our experience with the National Neurofibromatosis Foundation International Database (NNFFID). Genetic disease databases have been developed by individual investigators, scientific consortia, patient support organizations, and commercial enterprises. Databases vary from simple lists of affected individuals to comprehensive collections of detailed clinical and genetic information. Data may be obtained from people who volunteer to be included, systematic assessments of patients seen at participating medical centers, or population-based registries. Access to information may be highly restricted or widely available. These variables all affect the possible uses and usefulness of the data for research. Technical aspects of data entry, organization, storage, and retrieval, as well as issues related to data quality, confidentiality, and security, help determine how well a system actually functions. We discuss examples of research that have been accomplished with genetic disease databases and make recommendations regarding the organization and operation of these resources.

Genetic counseling throughout the life cycle

As the definition of genetic counseling continues to evolve, so does the application of genetic counseling services in all areas of medicine and throughout the human life cycle. While governmental policy, economics, ethics, and religion continue to influence society's views regarding the necessity of testing germ cells for mutations to prevent the birth of an affected child or predicting whether healthy adults will develop future life-threatening illness, patient autonomy in the choice of whether to know, or not know, one's genetic make-up remains a core principle of genetic counseling.

Patterns of associations of clinical features in neurofibromatosis 1 (NF1)

Neurofibromatosis 1 (NF1) is a common, fully penetrant autosomal dominant disease. The clinical course is generally progressive but highly variable, and the pathogenesis is poorly understood. We studied statistical associations among 13 of the most common or important clinical features in data from four separate sets of NF1 patients: a "developmental sample" of 1,413 probands from the NNFF International Database, an independent "validation sample" of 1,384 probands from the same database, 511 affected relatives of these probands, and 441 patients from a population-based registry in northwest England. We developed logistic regressive models for each of the 13 features using the developmental sample and attempted to validate these models in the other three samples. Age and gender were included as covariates in all models. Models were successfully developed and validated for ten of the 13 features analysed. The results are consistent with grouping nine of the clinical features into three sets: (1) café-au-lait spots, intertriginous freckling and Lisch nodules; (2) cutaneous, subcutaneous and plexiform neurofibromas; (3) macrocephaly, optic glioma and other neoplasms. In addition, three-way interactions among café-au-lait spots, intertriginous freckling and subcutaneous neurofibromas indicate that the first two groups are not independent. Our studies show that some individuals with NF1 are more likely than others to develop certain clinical features of the disease. Some NF1 features appear to share pathogenic mechanisms that are not common to all features.

Neurofibromatosis 1: clinical manifestations and diagnostic criteria

Neurofibromatosis 1 occurs in 2 to 3 people per 10,000. The most frequent clinical features are café-au-lait macules, neurofibromas, intertriginous freckling, Lisch nodules, and learning disabilities, but optic and other gliomas, malignant peripheral nerve sheath tumors, and characteristic osseous lesions also can be present. Two striking aspects of neurofibromatosis 1 are its progressive nature and its extreme variability. This article reviews the natural history and some important clinical manifestations of neurofibromatosis 1, with emphasis on features that constitute the standard diagnostic criteria. The pathogenic implications of these clinical manifestations are also considered.