Neurofibromatosis Type 1 Mutations Research Articles

A cost savings approach to SPRED1 mutational analysis in individuals at risk for neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a clinically diagnosed autosomal dominant disorder requiring routine clinical management, particularly during the pediatric years. An overlapping disorder, Legius syndrome, at times is clinically indistinguishable from NF1 and results in a small percentage of individuals being mischaracterized. Distinguishing these two entities is increasingly important for prognosis, reproductive planning, and clinical management. The goal of our study was to evaluate the cost impact of genetic testing for patients with solely pigmentary findings. The costs of genetic testing in patients aged 1.5-18 years were modeled using a simulated population, assuming the clinical management approach of a single NF1 clinic. Two genetic testing algorithms (SPRED1 testing alone, and NF1 mutation analysis with reflex to SPRED1) were compared against a baseline of no genetic testing. The cost for SPRED1 mutation analysis for each individual meeting NF1 diagnostic criteria without neoplastic or boney manifestation, when compared to the no-testing approach with routine follow-up mutations between the ages of 10 and 14 years, was minimal (range of $4-$16). Based on the clinical practice of one NF1 clinic, we found that the cost difference to perform SPRED1 mutation analysis on individuals who meet diagnostic criteria for NF1 without neoplastic or boney manifestation were minimal. Therefore it is important that "when to test decisions" remain a physician/patient discussion, as individual benefits may be greatest at a different age than when it is most cost efficient.

Neurofibromatosis type 1 and pregnancy: Maternal complications and attitudes about prenatal diagnosis

Neurofibromatosis type 1 (NF1) is one of the most commoninherited genetic disorders with an incidence of 1/2,500 to 1/3,300 live births. The disease is caused by a mutation in NF1,atumorsuppressorgeneon17q11.2codingforneurofibromin,orbyamicrodeletioninvolvingtheNF1anditssurroundingregion.NF1is an autosomal dominant condition with complete penetranceafter childhood. Almost half the cases result from a de novomutation,whiletheothersinheritthealteredgenefromanaffectedparent.Thediseaseismarkedbypoorgenotype–phenotypecorre-lation and high inter- and intra-familial variability. Thereforegenetic counseling for affected individuals is hampered by thedifficulty in forecasting the clinical outcome for future offspring.Prenatal testing can be carried out if the parental mutation isknown, or if there are multiple affected family members, andlinkagehasbeenestablishedwithinthefamily;suchtestingisusefulfor establishing the presence of the parental mutation in the fetalDNA, but, as noted, cannot make any prediction about diseaseseverity [Origone et al., 2000; Terzi et al., 2009].Pregnancyhasalwaysbeenconsideredacriticaltimeforwomenwith NF1 because of reports of increased complications duringgestationarisingfrompre-eclampsia,pretermlabor,IUGR,hyper-tension, oligohydramnios, and spontaneous abortion and/or still-birth [Blickstein and Lancet, 1987; Sharma et al.,1991;Segalet al.,1999].Furthermore,casereportsdescribedtheassociationbetweenpregnancy and HELLP syndrome [Hagymasy et al., 1998; Agarwaletal.,2003],diagnosisofmalignantperipheralnervesheathtumor(MPNST)[Posmaaetal.,2003;KelloggandWatson,2010;Nelsonet al., 2010] and the occurrence of pheochromocytoma [Liu et al.,1996]. Although Dugoff and Sujansky [1996] presented a largestudy of pregnancy in 105 women, including data from 247gestations and noted a greater cesarean rate than in thegeneral population, they did not find an increased incidence ofany of these complications. However they did describe thegrowth of new neurofibromas and the enlargement ofexistingneurofibromasinmorethanthehalf.Althoughthemajor-ity of NF1 pregnant women did not report complications, someinvestigators proposed special monitoring in specific situations[Chetty et al., 2011].Here we describe our experience in the management of preg-nancies in women with NF1, and their attitude towards prenataldiagnosis. We included 43 women with a total of 79 pregnancies.Eightofthewomen(18.6%)werereferredforcareduringtheentiregestationalperiod,whiletheother35womenhadtheirpregnanciesdetected before joining our program; for them we obtained datafrom a review of their medical records and through personalinterviews. Among these 79 pregnancies, 65 were carried to termwhile the other 14 resulted in five first trimester spontaneousabortions, seven elective terminations (not related to concernsaboutNF1),andtwotherapeuticabortionsafterprenataldiagnosisthrough chorionic villus sampling (CVS). Two of the 65 full termpregnancies were twins, for a total of 67 live births.Forwomenvisitingourcenterbeforeandduringtheirpregnan-cies, we set up a model based on a set of preconceptional multi-specializedevaluationsthatwefeltwereaprerequisiteforaproperpersonalized management of pregnancy in women with NF1. The

Neurofibromatosis type 2 in the elderly population: Clinical and molecular features

Neurofibromatosis type 2 (NF2) is rare genetic disorder characterized by the development of multiple benign tumors of the nervous system. The majority of people with NF2 are diagnosed in the second or third decade of life with bilateral vestibular schwannomas. Among NF2 patients followed up in our NF2 clinic, seven patients have been diagnosed with NF2 after the age of 70 years. Bilateral vestibular schwannomas were present in 4/7 patients. No NF2 mutation was identified by blood screening, suggesting a high prevalence of NF2 somatic mosaicism. During a mean follow-up of 96 months, 8/11 vestibular schwannomas demonstrated no tumor growth, and only one patient required treatment. Other tumors, including meningiomas and other schwannomas, remained stable. One patient required shunting for secondary normal-pressure hydrocephalus. Thus, NF2 can occasionally be diagnosed in people aged 70 and older, and is characterized by a high prevalence of atypical forms and a low growth potential of tumors, arguing in favor of a wait-and-scan policy as initial management.

Abstract P3-08-09: Clinical and Pathological Characteristics of Breast Cancer in Women with Neurofibromatosis Type 1

Abstract Background: Neurofibromatosis type 1(NF1) is an autosomal dominant genetic disorder affecting 1 in 3,000 individuals worldwide. Risk of cancer, including breast cancer, is increased, as NF1 is a tumour suppressor gene. There is limited data on the characteristics of breast cancer in individuals with NF1. Objectives: To study the clinical and pathological characteristics of breast cancer in women with NF1. Methodology: Patients with both NF1 and breast cancer were identified retrospectively from hospital records as well as prospectively when seen at National Cancer Centre Singapore (NCCS) and Singapore General Hospital (SGH). All women had histologically proven breast cancer and fulfilled at least 2 of the 7 criteria developed by the NIH Consensus Conference for clinical diagnosis of NF1. Germline NF1 mutation sequencing is being performed on patients with blood specimens available. Details on patient demographics, tumour grade, stage, receptor status and clinical outcome were evaluated. The pathological characteristics of NF1-associated breast cancer were then compared to sporadic breast cancers in our 2001–2004 cohort, with a focus on grade and HER2 positivity rate. Results: We identified 13 women with NF1 and breast cancer seen at our institutions from 2001 to present date. Average age of breast cancer diagnosis for women testing positive was 48 years (range 30–64). All 13 patients had invasive ductal carcinoma; of which 5 were stage 3 or 4 at diagnosis. To date, 4 out of 12 patients with stage 1–3 breast cancer have relapsed. Grade, estrogen, progesterone and HER2 receptor status were fully available for 12 patients. Ten out of 12 tumours (83%) were grade 3, compared to 45% (705/1578) among our sporadic breast cancers (p = 0.007). Eight out of 12(67%) NF1-associated breast cancers were HER2 positive (IHC 3+ or FISH positive), compared to 27% (367/1367) in sporadic cancers (p = 0.002). Two other NF1-associated tumours were triple negative, and two were hormone receptor positive and HER2 negative. Six out of 12 (50%) NF1-associated cancers were estrogen receptor (ER) positive, compared to 67% (1124/1689) in sporadic cancers (p = 0.2). Conclusion: Our findings suggest that NF1-associated breast cancer tends to be more aggressive, with a higher frequency of grade 3 and HER2 positive tumours compared to sporadic breast cancer. Further genomic profiling of these tumours (in progress) may elucidate the role of NF1 in breast cancer. This may also have implications for sporadic tumours with somatic NF1 mutations in individuals without NF1. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-08-09.

In vitro antisense therapeutics for a deep intronic mutation causing Neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is an autosomal-dominant disorder affecting about 1:33 000 newborns, mainly characterized by the development of tumors of the nervous system and ocular abnormalities. Around 85% of germline NF2 mutations are point mutations. Among them, ∼25% affect splicing and are associated with a variable disease severity. In the context of our NF2 Multidisciplinary Clinics, we have identified a patient fulfilling clinical criteria for the disease and exhibiting a severe phenotype. The patient carries a deep intronic mutation (g. 74409T>A, NG_009057.1) that produces the insertion of a cryptic exon of 167pb in the mature mRNA between exons 13 and 14, resulting in a truncated merlin protein (p.Pro482Profs*39). A mutation-specific antisense phosphorodiamidate morpholino oligomer was designed and used in vitro to effectively restore normal NF2 splicing in patient-derived primary fibroblasts. In addition, merlin protein levels were greatly recovered after morpholino treatment, decreasing patient's fibroblasts in vitro proliferation capacity and restoring cytoeskeleton organization. To our knowledge, this is the first NF2 case caused by a deep intronic mutation in which an in vitro antisense therapeutic approximation has been tested. These results open the possibility of using this approach in vivo for this type of mutation causing NF2.

A new nonsense mutation in the NF1 gene with neurofibromatosis–Noonan syndrome phenotype

Neurofibromatosis-Noonan syndrome is a rare autosomal dominant disorder which combines neurofibromatosis type 1 (NF1) features with Noonan syndrome. NF1 gene mutations are reported in the majority of these patients. Sequence analysis of the established genes for Noonan syndrome revealed no mutation; a heterozygous NF1 point mutation c.7549C>T in exon 51, creating a premature stop codon (p.R2517X), had been demonstrated. Neurofibromatosis-Noonan syndrome recently has been considered a subtype of NF1 and caused by different NF1 mutations. We report the case of a 14-year-old boy with neurofibromatosis type 1 with Noonan-like features, who complained of headache with triventricular hydrocephaly and a heterozygous NF1 point mutation c.7549C>T in exon 51.

Genotype-phenotype associations in neurofibromatosis type 1 (NF1): an increased risk of tumor complications in patients with NF1splice-site mutations?

Neurofibromatosis type 1 (NF1) is a complex neurocutaneous disorder with an increased susceptibility to develop both benign and malignant tumors but with a wide spectrum of inter and intrafamilial clinical variability. The establishment of genotype-phenotype associations in NF1 is potentially useful for targeted therapeutic intervention but has generally been unsuccessful, apart from small subsets of molecularly defined patients. The objective of this study was to evaluate the clinical phenotype associated with the specific types of NF1 mutation in a retrospectively recorded clinical dataset comprising 149 NF1 mutation-known individuals from unrelated families. Each patient was assessed for ten NF1-related clinical features, including the number of café-au-lait spots, cutaneous and subcutaneous neurofibromas and the presence/absence of intertriginous skin freckling, Lisch nodules, plexiform and spinal neurofibromas, optic gliomas, other neoplasms (in particular CNS gliomas, malignant peripheral nerve sheath tumors (MPNSTs), juvenile myelomonocytic leukemia, rhabdomyosarcoma, phaechromocytoma, gastrointestinal stromal tumors, juvenile xanthogranuloma, and lipoma) and evidence of learning difficulties. Gender and age at examination were also recorded. Patients were subcategorized according to their associated NF1 germ line mutations: frame shift deletions (52), splice-site mutations (23), nonsense mutations (36), missense mutations (32) and other types of mutation (6). A significant association was apparent between possession of a splice-site mutation and the presence of brain gliomas and MPNSTs (p = 0.006). If confirmed, these findings are likely to be clinically important since up to a third of NF1 patients harbor splice-site mutations. A significant influence of gender was also observed on the number of subcutaneous neurofibromas (females, p = 0.009) and preschool learning difficulties (females, p = 0.022).

Surgical Management of Vestibular Schwannomas and Hearing Rehabilitation in Neurofibromatosis Type 2

To report our approach to the surgical management of vestibular schwannomas (VSs) and hearing rehabilitation in neurofibromatosis Type 2 (NF2). Retrospective cohort study. Tertiary referral NF2 unit. Between 1981 and 2011, seventy-five patients were managed in our NF2 unit, of which, 58 patients are under current review. Patients who underwent VS excision were evaluated for tumor size, surgical approach, and outcomes of hearing and facial nerve function. All current patients were evaluated for NF2 mutation, hearing, and auditory implantation outcomes. Forty-four patients underwent resection of 50 VS in our unit, of which, 14% had facial neuroma excision and reinnervation during the same operation. At 12 months after surgery, facial nerve outcomes were House-Brackmann (HB) 1 in 33%, HB2 in 21%, and HB3 in 30%. Total VS resection was achieved in 78% of patients using a translabyrinthine approach. Seventy-two percent of the current patients have American Association of Otolaryngology-Head and Neck Surgery class A to C hearing (maximum speech discrimination score over 50%) in the better hearing ear, and a further 14% are full-time users of cochlear implants or auditory brainstem implants. The remaining patients have been assessed for auditory implantation. By following a policy of treating VS in NF2 patients where tumor growth is observed, complete tumor resection can be achieved through a translabyrinthine approach while achieving comparable facial nerve outcomes to published series. We advocate proactive hearing rehabilitation in all patients with timely assessment for auditory implantation to maintain quality of life.

Sleepless flies - Clinical and molecular genetic characterization of sleep disturbances in neurofibromatosis

Aims: Neurofibromatosis type 1 (NF1) is caused by mutations of the NF1 gene (17q22.1) and is mainly characterized by hyperpigmented macules of the skin (café-au-lait spots) and tumors of the perpheral nervous system (neurofibromas). However, in childhood behavioral problems can dominate the clinical picture. Sleep disturbances can play a key role and become a heavy burden for affected families. In drosophila NF1 mutations result in abnormalities of circadian rhythms. Therefore, we propose that sleep disturbances in children with NF1 might be caused by mutations of the human NF1 gene and are part of the phenotypic spectrum of the disease.

Café‐au‐lait macules and intertriginous freckling in piebaldism: Clinical overlap with neurofibromatosis type 1 and Legius syndrome

Piebaldism is an autosomal dominant disorder characterized by congenital hypopigmented patches of skin and hair and has been found to be associated with mutations in the KIT or SLUG genes. Café-au-lait macules (CALM) may occasionally be seen in piebaldism. There are four reports describing six patients who were said to have both piebaldism and neurofibromatosis type 1 (NF1) due to the presence of multiple CALM and intertriginous freckling, but none of these patients had undergone comprehensive NF1 mutation analysis. We describe a large family with piebaldism in which two members meet diagnostic criteria for NF1 based on the presence of >5 CALM and intertriginous freckling. Interestingly, only these two family members are of mixed race, which could be of importance. A novel complex mutation in the KIT gene was identified in several family members affected with piebaldism; the proband meeting diagnostic criteria for NF1 also underwent comprehensive NF1 and SPRED1 testing with no mutations detected. These findings suggest that piebaldism may occasionally include CALM and intertriginous freckling, which may create diagnostic confusion especially in the absence of a family history of piebaldism. However, careful clinical evaluation and molecular testing if necessary should distinguish these two disorders.

Clinical presentation, immunohistochemistry and electron microscopy indicate neurofibromatosis type 2‐associated gliomas to be spinal ependymomas

Neurofibromatosis type 2 (NF2) is a hereditary tumor syndrome. The hallmark of NF2 is bilateral vestibular schwannoma. In addition, glioma is one of the diagnostic criteria of NF2. In this retrospective study the clinical presentation and histopathological features of 12 spinal gliomas from NF2 patients were assessed. Ten tumors were previously diagnosed as ependymomas and two as astrocytomas. However, upon re-evaluation both astrocytomas expressed epithelial membrane antigen in a dot-like fashion and in one case it was possible to perform electron microscopy revealing junctional complexes and cilia typical for ependymoma. The findings suggest that NF2-associated spinal gliomas are ependymomas. Based on the fact that NF2-associated gliomas are almost exclusively spinal and that no NF2 mutations have been found in sporadic cerebral gliomas, we suggest that "glioma" in the current diagnostic criteria for NF2 should be specified as "spinal ependymoma".

Oncogene Mutation Survey in MPNST Cell Lines Enhances the Dominant Role of Hyperactive Ras in NF1 Associated Pro-Survival and Malignancy

Malignant peripheral nerve sheath tumors (MPNST) are a type of soft tissue sarcoma that can be associated with germline mutations in Neurofibromatosis type 1 (NF1) or may occur sporadically. Although the etiology of MPNST is poorly understood, it is clear that a loss of function of the NF1 gene, encoding a Ras-GAP, is an important factor in the tumorigenesis of the inherited form of MPNST. Tumor latency in NF1 patients suggests that additional mutational events are probably required for malignancy. In order to define oncogene mutations associated with 5 MPNST cell lines, we assayed the 238 most frequent mutations in 19 commonly activated oncogenes using mass spectroscopy-based analysis. All 238 mutation sites in the assayed oncogenes were determined to harbor only wild-type sequences. These data suggest that hyperactive Ras resulting from the loss function of neurofibromin may be sufficient to set up the direction of malignant transformation of Schwann cells to MPNST.

Mitotic recombination of chromosome arm 17q as a cause of loss of heterozygosity of NF1 in neurofibromatosis type 1-associated glomus tumors.

Neurofibromatosis type 1 (NF1) is a common, autosomal dominant, tumor-predisposition syndrome that arises secondary to mutations in NF1. Glomus tumors are painful benign tumors that originate from the glomus body in the fingers and toes due to biallelic inactivation of NF1. We karyotyped cultures from four previously reported and one new glomus tumor and hybridized tumor (and matching germline) DNA on Illumina HumanOmni1-Quad SNP arrays (≈ 1 × 10(6) SNPs). Two tumors displayed evidence of copy-neutral loss of heterozygosity of chromosome arm 17q not observed in the germline sample, consistent with a mitotic recombination event. One of these two tumors, NF1-G12, featured extreme polyploidy (near-tetraploidy, near-hexaploidy, or near-septaploidy) across all chromosomes. In the remaining four tumors, there were few cytogenetic abnormalities observed, and copy-number analysis was consistent with diploidy in all chromosomes. This is the first study of glomus tumors cytogenetics, to our knowledge, and the first to report biallelic inactivation of NF1 secondary to mitotic recombination of chromosome arm 17q in multiple NF1-associated glomus tumors. We have observed mitotic recombination in 22% of molecularly characterized NF1-associated glomus tumors, suggesting that it is a not uncommon mechanism in the reduction to homozygosity of the NF1 germline mutation in these tumors. In tumor NF1-G12, we hypothesize that mitotic recombination also "unmasked" (reduced to homozygosity) a hypomorphic germline allele in a gene on chromosome arm 17q associated with chromosomal instability, resulting in the extreme polyploidy.

Concomitant Occurrence of Segmental Neurofibromatosis and Lung Adenocarcinoma

Neurofibromatosis type 1 (NF1) caused by a loss-of functional mutation in NF1 encoding neurofibromin is an autosomal dominant disorder characterized by café-au-lait spots, neurofibromas, intertriginous freckles, and Lisch nodules. Segmental neurofibromatosis (SN) represents a postzygotic mutation and loss of heterozygosity in neurofibromin. SN occurring in the elder persons may be associated with internal malignant tumors. Here, we reported a case of 58-year-old woman with concomitant occurrence of SN and lung adenocarcinoma. The onset of SN in aged persons would be a sign of concomitant occurrence of internal malignant tumors.

Dissecting genetic pathways in schwannomatosis and malignant rhabdoid tumour

Schwannomatosis is a form of Neurofibromatosis type 2 (NF2) characterized by multiple schwannomas without vestibular involvement, affecting the cranium, spine and periphery. Several recent genetic studies have implicated the SMARCB1/INI1 tumour suppressor gene in familial schwannomatosis. SMARCB1 is located centromeric to NF2 on 22q and loss of function of SMARCB1 is also a hallmark of malignant rhabdoid tumour (MRT), a highly aggressive tumour of infancy. Both familial and sporadic schwannoma tumours show a mosaic pattern of SMARCB1 protein expression, suggestive of tumour cells either haploinsufficient, or null for SMARCB1 protein. Familial schwannomas linked to constitutional SMARCB1 mutation can also have somatic mutation of NF2, and conversely, schwannoma tumours associated with constitutional NF2 mutation show mosaic loss of SMARCB1, suggesting the involvement of a four-hit mechanism. Molecular analysis for evidence of constitutional SMARCB1 mutation is important in both familial and sporadically occurring schwannomatosis because of the transmission risk for a mutation predisposing to the incurable MRT, in early childhood. However as for NF2, recent evidence suggests that constitutional SMARCB1 mutations have variable penetrance and exhibit mosaicism, highlighting the importance of examining multiple tumour tissue samples as well as blood in affected individuals to ascertain germline predisposition and to provide accurate counseling for transmission risk. Further studies are needed to define the SMARCB1 mutation spectrum in schwannomatosis and to dissect the strikingly different biology between schwannoma and MRT.

Exploring the somatic NF1 mutational spectrum associated with NF1 cutaneous neurofibromas

Neurofibromatosis type-1 (NF1), caused by heterozygous inactivation of the NF1 tumour suppressor gene, is associated with the development of benign and malignant peripheral nerve sheath tumours (MPNSTs). Although numerous germline NF1 mutations have been identified, relatively few somatic NF1 mutations have been described in neurofibromas. Here we have screened 109 cutaneous neurofibromas, excised from 46 unrelated NF1 patients, for somatic NF1 mutations. NF1 mutation screening (involving loss-of-heterozygosity (LOH) analysis, multiplex ligation-dependent probe amplification and DNA sequencing) identified 77 somatic NF1 point mutations, of which 53 were novel. LOH spanning the NF1 gene region was evident in 25 neurofibromas, but in contrast to previous data from MPNSTs, it was absent at the TP53, CDKN2A and RB1 gene loci. Analysis of DNA/RNA from neurofibroma-derived Schwann cell cultures revealed NF1 mutations in four tumours whose presence had been overlooked in the tumour DNA. Bioinformatics analysis suggested that four of seven novel somatic NF1 missense mutations (p.A330T, p.Q519P, p.A776T, p.S1463F) could be of functional/clinical significance. Functional analysis confirmed this prediction for p.S1463F, located within the GTPase-activating protein-related domain, as this mutation resulted in a 150-fold increase in activated GTP-bound Ras. Comparison of the relative frequencies of the different types of somatic NF1 mutation observed with those of their previously reported germline counterparts revealed significant (P=0.001) differences. Although non-identical somatic mutations involving either the same or adjacent nucleotides were identified in three pairs of tumours from the same patients (P<0.0002), no association was noted between the type of germline and somatic NF1 lesion within the same individual.

Objective assessment of nasality in flemish adults with neurofibromatosis type 1

When characterizing the speech of a patient with neurofibromatosis type 1 (NF1), hypernasality is often mentioned. As few studies applied technically assisted evaluations of nasality in NF1 patients, the aim of the present study was to document the nasal resonance of adults with NF1 using nasometry. The nasometric data obtained from the NF1 patients were compared with the nasalance scores of a healthy control group and with normative data. The final study group consisted of 24 adult NF1 patients and 16 controls, all living in the East Flemish part of Belgium. Nasalance scores were obtained while the participants sustained three vowels (/a:/, /i./, and /u./) and one consonant (/m/) and read three standard nasalance passages. Despite the inter- and intra-subject variability, we observed that NF1 patients as a group exhibited higher mean nasalance scores than controls. This finding was especially clear in males. Potential genotype-phenotype correlations between NF1 mutation type and hypernasality were examined but could not be demonstrated. Conversely, comparison of the nasometric data obtained from the NF1 patients with magnetic resonance imaging findings showed some degree of interesting correlation. We conclude that, notwithstanding the small sample size for some analyses, nasality is an area of interest in the NF1 population. As altered nasality influences speech intelligibility, nasality requires attention during follow-up visits, particularly when it concerns a male NF1 patient.

Clinico-pathological and biomolecular findings in Italian patients with multiple cutaneous neurofibromas

BackgroundNeurofibroma occurs as isolated or multiple lesions frequently associated with neurofibromatosis type 1 (NF1), a common autosomal dominant disorder affecting 1 in 3500 individuals. It is caused by mutations in the NF1 gene, which comprises 60 exons and is located on chromosome 17q11.2. NF1 is a fully penetrant gene exhibiting a mutation rate some 10-fold higher compared with most other disease genes. As a consequence, a high number of cases (up to 50%) are sporadic. Mutation detection is complex due to the large size of the NF1 gene, the presence of pseudogenes and the great variety of lesions.Methods110 patients with at least two neurofibroma lesions recorded in the files of the Pathology Department of the University of Modena during the period 1999-2010, were included in this study. Through interviews and examination of clinical charts, pedigrees were drawn for all patients who were affected by at least two neurofibromas. We attempted to delineate the clinical features of NF1 and the mutational spectrum in the cohort of 11 NF1 families identified. For each proband, the whole coding sequence and all splice sites were studied for mutations, either by the protein truncation test (PTT), or, more frequently, by denaturing high performance liquid chromatography (DHPLC). Two GIST tumors of NF1 patients were tested for somatic NF1 mutations.ResultsNF1 germline mutations were identified in 7 (68%) patients. A novel mutation, c.3457_3460delCTCA in exon 20, was detected in two unrelated patients and was associated with different clinical features. No NF1 somatic mutations were detected in the GIST tumors. A wide phenotypic and genotypic variability was registered, both in the spectrum of skin lesions and visceral neoplasms, even among members of the same family who had different clinical manifestations. A proclivity to multiple tumors arising in the same subject, and a higher tumor burden per family were the most relevant findings observed in patients affected with the NF1 mutation.ConclusionsWe report a novel NF1 mutation and we contribute data for the refinement of the NF1 genotype-phenotype spectrum.

A Highly Sensitive Genetic Protocol to Detect NF1 Mutations

Neurofibromatosis type 1 (NF1) is a hereditary disorder caused by mutations in the NF1 gene. Detecting mutation in NF1 is hindered by the gene's large size, the lack of mutation hotspots, the presence of pseudogenes, and the wide variety of possible lesions. We developed a method for detecting germline mutations by combining an original RNA-based cDNA-PCR mutation detection method and denaturing high-performance liquid chromatography (DHPLC) with multiplex ligation-dependent probe amplification (MLPA). The protocol was validated in a cohort of 56 blood samples from NF1 patients who fulfilled NIH diagnostic criteria, identifying the germline mutation in 53 cases (95% sensitivity). The efficiency and reliability of this approach facilitated detection of different types of mutations, including single-base substitutions, deletions or insertions of one to several nucleotides, microdeletions, and changes in intragenic copy number. Because mutational screening for minor lesions was performed using cDNA and the characterization of mutated alleles was performed at both the RNA and genomic DNA level, the analysis provided insight into the nature of the different mutations and their effect on NF1 mRNA splicing. After validation, we implemented the protocol as a routine test. Here we present the overall unbiased spectrum of NF1 mutations identified in 93 patients in a cohort of 105. The results indicate that this protocol is a powerful new tool for the molecular diagnosis of NF1.

Preclincial testing of Sorafenib and RAD001 in the Nfflox/flox;DhhCre mouse model of plexiform neurofibroma using magnetic resonance imaging

Neurofibromatosis type 1 (NF1) is an inherited disease predisposing affected patients to variable numbers of benign neurofibromas. To date there are no effective chemotherapeutic drugs available for this slow growing tumor. Molecularly targeted agents that aim to slow neurofibroma growth are being tested in clinical trials. So preclinical models for testing potential therapies are urgently needed to prioritize drugs for clinical trials of neurofibromas. We used magnetic resonance imaging (MRI) to monitor neurofibroma development in the Nf1(flox/flox) ;DhhCre mouse model of GEM grade I neurofibroma. Based on studies implicating mTOR and Raf signaling in NF1 mutant cells, we tested the therapeutic effect of RAD001 and Sorafenib in this model. Mice were scanned to establish growth rate followed by 8 weeks of drug treatment, then re-imaged after the last dose of drug treatment. Tumor volumes were determined by volumetric measurement. We found that rate of tumor growth varied among mice, as it does in human patients. RAD001 inhibited its predicted target pS6K, yet there was no significant decrease in the tumor volume in RAD001 treated mice compared to the vehicle control group. Sorafenib inhibited cyclinD1 expression and cell proliferation in tumors, and volumetric measurements identified significant decreases in tumor volume in some mice. The data demonstrate that volumetric MRI analysis can be used to monitor the therapeutic effect in the preclinical neurofibroma drug screening, and suggest that Sorafenib might have clinical activity in some neurofibromas.