G2Cdb::Human Disease report

Disease id
D00000298
Name
Neurofibromatosis type I
Nervous system disease
yes

Genes (1)

Gene Name/Description Mutations Found Literature Mutations Type Genetic association?
G00000036 NF1
neurofibromin 1
Y (7485153) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (7575561) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (7981679) Splice site mutation (SpS) Y
G00000036 NF1
neurofibromin 1
Y (7981679) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (7981679) Nonsense (No) Y
G00000036 NF1
neurofibromin 1
Y (7981679) Microinsertion (MI) Y
G00000036 NF1
neurofibromin 1
Y (8081387) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (8116612) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (8123014) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (8317503) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (9003501) Microinsertion (MI) Y
G00000036 NF1
neurofibromin 1
Y (9003501) Nonsense (No) Y
G00000036 NF1
neurofibromin 1
Y (9003501) Splice site mutation (SpS) Y
G00000036 NF1
neurofibromin 1
Y (9003501) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (9475595) Microinsertion (MI) Y
G00000036 NF1
neurofibromin 1
Y (9654211) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (9783703) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (9783703) Nonsense (No) Y
G00000036 NF1
neurofibromin 1
Y (9783703) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (9783703) Splice site mutation (SpS) Y
G00000036 NF1
neurofibromin 1
Y (10593996) Splice site mutation (SpS) Y
G00000036 NF1
neurofibromin 1
Y (10633134) Single nucleotide polymorphism (SNP) Y
G00000036 NF1
neurofibromin 1
Y (10633134) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (10677298) Repeat polymorphism (RP) Y
G00000036 NF1
neurofibromin 1
Y (10677298) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (10721668) Nonsense (No) Y
G00000036 NF1
neurofibromin 1
Y (10862084) Nonsense (No) Y
G00000036 NF1
neurofibromin 1
Y (10862084) Splice site mutation (SpS) Y
G00000036 NF1
neurofibromin 1
Y (10862084) Microinsertion (MI) Y
G00000036 NF1
neurofibromin 1
Y (10862084) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (10862084) Translocation (T) Y
G00000036 NF1
neurofibromin 1
Y (11068991) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (11068991) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (11292340) Single nucleotide polymorphism (SNP) Y
G00000036 NF1
neurofibromin 1
Y (11409870) Splice site mutation (SpS) Y
G00000036 NF1
neurofibromin 1
Y (11748857) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (12112660) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (12112660) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (12112660) Insertion/deletion (I/D) Y
G00000036 NF1
neurofibromin 1
Y (12112660) Single nucleotide polymorphism (SNP) Y
G00000036 NF1
neurofibromin 1
Y (12552569) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (12552569) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (12552569) Nonsense (No) Y
G00000036 NF1
neurofibromin 1
Y (12552569) Microinsertion (MI) Y
G00000036 NF1
neurofibromin 1
Y (12552569) Splice site mutation (SpS) Y
G00000036 NF1
neurofibromin 1
Y (14722917) Single nucleotide polymorphism (SNP) Y
G00000036 NF1
neurofibromin 1
Y (14722917) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (15146469) Nonsense (No) Y
G00000036 NF1
neurofibromin 1
Y (15146469) Deletion (D) Y
G00000036 NF1
neurofibromin 1
Y (15146469) Insertion (I) Y
G00000036 NF1
neurofibromin 1
Y (15146469) Duplication (Du) Y
G00000036 NF1
neurofibromin 1
Y (15146469) Translocation (T) Y
G00000036 NF1
neurofibromin 1
Y (17353900) Single nucleotide polymorphism (SNP) Y

References

  • Genome-wide single-nucleotide polymorphism analysis in juvenile myelomonocytic leukemia identifies uniparental disomy surrounding the NF1 locus in cases associated with neurofibromatosis but not in cases with mutant RAS or PTPN11.

    Flotho C, Steinemann D, Mullighan CG, Neale G, Mayer K, Kratz CP, Schlegelberger B, Downing JR and Niemeyer CM

    Division of Pediatric Hematology-Oncology, University of Freiburg, Freiburg, Germany. christian.flotho@uniklinik-freiburg.de

    Juvenile myelomonocytic leukemia (JMML) is a malignant hematopoietic disorder whose proliferative component is a result of RAS pathway deregulation caused by somatic mutation in the RAS or PTPN11 oncogenes or in patients with underlying neurofibromatosis type 1 (NF-1), by loss of NF1 gene function. To search for potential collaborating genetic abnormalities, we used oligonucleotide arrays to analyse over 116 000 single-nucleotide polymorphisms across the genome in 16 JMML samples with normal karyotype. Evaluation of the SNP genotypes identified large regions of homozygosity on chromosome 17q, including the NF1 locus, in four of the five samples from patients with JMML and NF-1. The homozygous region was at least 55 million base pairs in each case. The genomic copy number was normal within the homozygous region, indicating uniparental disomy (UPD). In contrast, the array data provided no evidence for 17q UPD in any of the 11 JMML cases without NF-1. We used array-based comparative genomic hybridization to confirm 17q disomy, and microsatellite analysis was performed to verify homozygosity. Mutational analysis demonstrated that the inactivating NF1 lesion was present on both alleles in each case. In summary, our data indicate that a mitotic recombination event in a JMML-initiating cell led to 17q UPD with homozygous loss of normal NF1, provide confirmatory evidence that the NF1 gene is crucial for the increased incidence of JMML in NF-1 patients, and corroborate the concept that RAS pathway deregulation is central to JMML pathogenesis.

    Oncogene 2007;26;39;5816-21

  • Novel and recurrent mutations in the NF1 gene in Italian patients with neurofibromatosis type 1.

    De Luca A, Schirinzi A, Buccino A, Bottillo I, Sinibaldi L, Torrente I, Ciavarella A, Dottorini T, Porciello R, Giustini S, Calvieri S and Dallapiccola B

    IRCCS-CSS, San Giovanni Rotondo and CSS-Mendel Institute, Rome, Italy. a.deluca@css-mendel.it

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders in humans, affecting 1 in 3500 individuals. NF1 is a fully penetrant exhibiting a mutation rate some 10-fold higher compared to 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 NF1 gene, the presence of pseudogenes and the great variety of lesions. In the present study we attempted to delineate the NF1 mutational spectrum in the Italian population reporting four-year experience with the direct analysis of the whole NF1 coding region in 110 unrelated subjects affected by NF1. For each patient, the whole coding sequence and all splice sites were studied for mutations, either by the protein truncation test (PTT), or, most often, by denaturing high performance liquid chromatography (DHPLC). Mutations were identified in 75 (68%) patients. Twenty-two mutations were found to be novel. The detection rate for the different methods was 7/18 (39%) for PTT, and 68/103 (66%) for DHPLC. The mutations were evenly distributed along the NF1 coding sequence. Thirty-two of the 75 unrelated NF1 patients in which germline mutations were identified (32/75, 43%) harbour 23 different recurrent mutations. Fifteen sequence variants likely to represent non-pathogenic polymorphisms were observed at the NF1 locus. Genotype-phenotype analysis was unable to detect any obvious correlation.

    Human mutation 2004;23;6;629

  • Characterization of the somatic mutational spectrum of the neurofibromatosis type 1 (NF1) gene in neurofibromatosis patients with benign and malignant tumors.

    Upadhyaya M, Han S, Consoli C, Majounie E, Horan M, Thomas NS, Potts C, Griffiths S, Ruggieri M, von Deimling A and Cooper DN

    Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK. upadhyaya@cardiff.ac.uk

    One of the main features of neurofibromatosis type 1 (NF1) is benign neurofibromas, 10-20% of which become transformed into malignant peripheral nerve sheath tumors (MPNSTs). The molecular basis of NF1 tumorigenesis is, however, still unclear. Ninety-one tumors from 31 NF1 patients were screened for gross changes in the NF1 gene using microsatellite/restriction fragment length polymorphism (RFLP) markers; loss of heterozygosity (LOH) was found in 17 out of 91 (19%) tumors (including two out of seven MPNSTs). Denaturing high performance liquid chromatography (DHPLC) was then used to screen 43 LOH-negative and 10 LOH-positive tumors for NF1 microlesions at both RNA and DNA levels. Thirteen germline and 12 somatic mutations were identified, of which three germline (IVS7-2A>G, 3731delT, 6117delG) and eight somatic (1888delG, 4374-4375delCC, R2129S, 2088delG, 2341del18, IVS27b-5C>T, 4083insT, Q519P) were novel. A mosaic mutation (R2429X) was also identified in a neurofibroma by DHPLC analysis and cloning/sequencing. The observed somatic and germline mutational spectra were similar in terms of mutation type, relative frequency of occurrence, and putative underlying mechanisms of mutagenesis. Tumors lacking mutations were screened for NF1 gene promoter hypermethylation but none were found. Microsatellite instability (MSI) analysis revealed MSI in five out of 11 MPNSTs as compared to none out of 70 neurofibromas (p=1.8 x 10(-5)). The screening of seven MPNSTs for subtle mutations in the CDKN2A and TP53 genes proved negative, although the screening of 11 MPNSTs detected LOH involving either the TP53 or the CDKN2A gene in a total of four tumors. These findings are consistent with the view that NF1 tumorigenesis is a complex multistep process involving a variety of different types of genetic defect at multiple loci.

    Human mutation 2004;23;2;134-46

  • NF1 gene analysis based on DHPLC.

    De Luca A, Buccino A, Gianni D, Mangino M, Giustini S, Richetta A, Divona L, Calvieri S, Mingarelli R and Dallapiccola B

    IRCCS-CSS, San Giovanni Rotondo and CSS-Mendel Institute, Rome, Italy.

    The high mutation rate at the NF1 locus results in a wide range of molecular abnormalities. The majority of these mutations are private and rare, generating elevated allelic diversity with a restricted number of recurrent mutations. In this study, we have assessed the efficacy of denaturing high-performance liquid chromatography (DHPLC), for detecting mutation in the NF1 gene. DHPLC is a fast and highly sensitive technique based on the detection of heteroduplexes in PCR products by ion pair reverse-phase HPLC under partially denaturing conditions. We established theoretical conditions for DHPLC analysis of all coding exons and splice junctions of the NF1 gene using the WAVEmaker software version 4.1.40 and screened for mutations a panel of 40 unrelated NF1 patients (25 sporadic and 15 familial), genetically uncharacterized. Disruptive mutations were identified in 29 individuals with an overall mutation detection rate of 72.5%. The mutations included eight deletions (exons 4b, 7, 10a, 14, 26, and 31), one insertion (exon 8), nine nonsense mutation (exons 10a, 13, 23.1, 27a, 29, 31, and 36), six missense mutations (exons 15, 16, 17, 24, and 31), four splice errors (exons 11, 14, 36, and 40) and a complex rearrangement within exon 16. Eighteen (62%) of the identified disruptive mutations are novel. Seven unclassified and three previously reported polymorphisms were also detected. None of the missense mutations identified in this study were found after screening of 150 controls. Our results suggest that DHPLC provides an accurate method for the rapid identification of NF1 mutations.

    Human mutation 2003;21;2;171-2

  • Ten novel mutations in the human neurofibromatosis type 1 (NF1) gene in Italian patients.

    Origone P, De Luca A, Bellini C, Buccino A, Mingarelli R, Costabel S, La Rosa C, Garrè C, Coviello DA, Ajmar F, Dallapiccola B and Bonioli E

    Dipartimento di Oncologia, Biologia e Genetica, Università di Genova, Genova, Italy. origone@unige.it

    The entire NF1 coding region was analyzed for mutations in a panel of 108 unrelated Italian NF1 patients. Using PTT, SSCP, and DNA sequencing, we found 10 mutations which have never been reported before. Clinical diagnosis of NF1 was established according to the NIH consensus criteria in 100 individuals, while 8 were young children with only multiple cafè-au-lait spots. We detected 46 truncated fragments, and 24 of them were fully characterized by SSCP and direct sequencing. Of the 24, 14 were known mutations (R304X, R681X, Q682X, R1306X, R1362X, R1513X, R1748X, Q1794X, R1947X, Y2264X, R2237X, 2674delA, 6789delTTAC, 2027insC). The other 10 mutations represent novel changes that contribute to the germline mutational spectrum of the NF1 gene (K810X, Q2595X, 6772delT, 7190delCT, 7331delA, 1021insTT, 3921insT, 4106insTA, 7149insC, 2033insCG / 2034delA). PTT in a large number of Italian NF1 patients supports the usefulness of this method for characterization of mutations in disorders where the responsible gene is very large and the disease-causing mutations often create a stop codon. In agreement with previous reports, no mutational hotspots within the NF1 gene were detected.

    Human mutation 2002;20;1;74-5

  • Identification and characterization of four novel large deletions in the human neurofibromatosis type 1 (NF1) gene.

    Fang LJ, Vidaud D, Vidaud M and Thirion JP

    Département de Microbiologie et d'Infectiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.

    We studied 20 unrelated NF1 patients by Southern blots with seven cDNA probes and loss of heterozygosity (LOH) analysis with four intragenic microsatellites (IVS26-2.3, IVS27AC28.4, IVS27AC33.1, and IVS38GT53.0). Four novel large deletions (178, 184, 236, and 237) have been identified and characterized. The breakpoint of deletion 178 was located in between exons 23-2 and 27b and the sequences downstream of the breakpoint were deleted. For deletion 184, the breakpoint was in between exons 27b and 29, and the region upstream of the breakpoint was deleted. With deletion 236, the breakpoint was in between exons 14 and 18 and the region downstream of the breakpoint was deleted. The breakpoint of deletion 237 was in between exons 38 and 45 and the sequences upstream of the breakpoint were deleted. These deletions were distributed randomly across the NF1 gene and no deletion hot spot was found. Our study suggests that the combination of analyses of loss of heterozygosity, southern blotting and southern blot densitometry can be used as a powerful method to detect large deletions, especially when family record is not available or the patient is a sporadic case.

    Human mutation 2001;18;6;549-50

  • Somatic NF1 mutational spectrum in benign neurofibromas: mRNA splice defects are common among point mutations.

    Serra E, Ars E, Ravella A, Sánchez A, Puig S, Rosenbaum T, Estivill X and Lázaro C

    Centre de Genètica Mèdica i Molecular--IRO, Hospital Duran i Reynals, Barcelona, Spain.

    Neurofibromas, benign tumors that originate from the peripheral nerve sheath, are a hallmark of neurofibromatosis type 1 (NF1). Although loss of heterozygosity (LOH) is a common phenomenon in this neoplasia, it only accounts for part of the somatic NF1 mutations found. Somatic point mutations or the presence of "two hits" in the NF1 gene have only been reported for a few neurofibromas. The large size of the NF1 gene together with the multicellular composition of these tumors has greatly hampered their molecular characterization. Here, we present the somatic NF1 mutational analysis of the whole set of neurofibromas studied by our group and consisting in 126 tumors derived from 32 NF1 patients. We report the identification of 45 independent somatic NF1 mutations, 20 of which are reported for the first time. Different types of point mutations together with LOH affecting the NF1 gene and its surrounding region or extending along the 17q arm have been found. Among point mutations, those affecting the correct splicing of the NF1 gene are common, coinciding with results reported on germline NF1 mutations. In most cases, we have been able to confirm that both copies of the NF1 gene are inactivated. We have also found that both somatic and germline mutations can be expressed at the RNA level in the neoplastic cells. Furthermore, we have observed that the study of more than one tumor derived from the same patient is useful for the identification of the germline mutation. Finally, we have noticed that the culture of neurofibromas and their fibroblast clearance facilitates LOH detection in cases in which it is difficult to determine.

    Human genetics 2001;108;5;416-29

  • A novel mutation in the neurofibromatosis type 1 (NF1) gene promotes skipping of two exons by preventing exon definition.

    Fang LJ, Simard MJ, Vidaud D, Assouline B, Lemieux B, Vidaud M, Chabot B and Thirion JP

    Département de microbiologie et d'infectiologie, Universite Paris V 4 av. de l'Observatoire 75006, Paris, France.

    Using a protein truncation assay, we have identified a new mutation in the neurofibromatosis type 1 (NF1) gene that causes a severe defect in NF1 pre-mRNA splicing. The mutation, which consists of a G to A transition at position +1 of the 5' splice site of exon 12a, is associated with the loss of both exons 11 and 12a in the NF1 mRNA. Through the use of in vivo and in vitro splicing assays, we show that the mutation inactivates the 5' splice site of exon 12a, and prevents the definition of exon 12a, a process that is normally required to stimulate the weak 3' splice site of exon 12a. Because the 5' splice site mutation weakens the interaction of splicing factors with the 3' splice site of exon 12a, we propose that exon 11/exon 12a splicing is also compromised, leading to the exclusion of both exons 11 and 12a. Our results provide in vivo support for the importance of the exon definition model during NF1 splicing, and suggest that the NF1 region containing exons 11 and 12a plays an important role in the activity of neurofibromin.

    Journal of molecular biology 2001;307;5;1261-70

  • Identification of two novel frame shift mutations of the NF1 gene in Korean patients with neurofibromatosis type 1.

    Park KC, Choi HO, Han WS, Hwang JH, Park KH, Kim KH, Chung JH and Eun HC

    Department of Dermatology, Seoul National University, College of Medicine, Korea.

    Neurofibromatos is type 1 (NF1) is one of the most common inherited disorders and is characterized by abnormalities in multiple tissues derived from the neural crest. The NF-1 gene has been cloned and mapped to human chromosome 17q11.2. The NF-1 gene has an open reading frame that predicts a protein consisting of 2,818 amino acids, known as neurofibromin. Here, we report two kinds of novel frame shift mutations of the NF1 gene from 2 out of 56 unrelated Korean NF1 patients. These mutations were detected using polymerase chain reaction and single strand conformational polymorphism analysis. Sequencing analysis revealed four base pair insertion at codon 1270 of exon 22, and a base pair deletion at codon 1398 of exon 24. These mutations resulted in premature termination of the mutant alleles and may encode truncated forms of neurofibromin.

    Journal of Korean medical science 2000;15;5;542-4

  • Toward a survey of somatic mutation of the NF1 gene in benign neurofibromas of patients with neurofibromatosis type 1.

    Eisenbarth I, Beyer K, Krone W and Assum G

    Abteilung Humangenetik, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany. ingrid.eisenbarth@medizin.uni-ulm.de

    Neurofibromatosis type 1 (NF1), a common autosomal dominant disorder caused by mutations of the NF1 gene, is characterized by multiple neurofibromas, pigmentation anomalies, and a variety of other possible complications, including an increased risk of malignant neoplasias. Tumorigenesis in NF1 is believed to follow the two-hit hypothesis postulated for tumor-suppressor genes. Loss of heterozygosity (LOH) has been shown to occur in NF1-associated malignancies and in benign neurofibromas, but only few of the latter yielded a positive result. Here we describe a systematic approach of searching for somatic inactivation of the NF1 gene in neurofibromas. In the course of these studies, two new intragenic polymorphisms of the NF1 gene, a tetranucleotide repeat and a 21-bp duplication, could be identified. Three tumor-specific point mutations and two LOH events were detected among seven neurofibromas from four different NF1 patients. Our results suggest that small subtle mutations occur with similar frequency to that of LOH in benign neurofibromas and that somatic inactivation of the NF1 gene is a general event in these tumors. The spectrum of somatic mutations occurring in various tumors from individual NF1 patients may contribute to the understanding of variable expressivity of the NF1 phenotype.

    American journal of human genetics 2000;66;2;393-401

  • A search for evidence of somatic mutations in the NF1 gene.

    John AM, Ruggieri M, Ferner R and Upadhyaya M

    Institute of Medical Genetics, University College of Medicine of Wales, Heath Park, Cardiff CF4 4XN, UK.

    Neurofibromatosis type I (NF1) is an autosomal dominant disorder affecting 1 in 3000 people. The NF1 gene is located on chromosome 17q11.2, spans 350 kb of genomic DNA, and contains 60 exons. A major phenotypic feature of the disease is the widespread occurrence of benign dermal and plexiform neurofibromas. Genetic and biochemical data support the hypothesis that NF1 acts as a tumour suppressor gene. Molecular analysis of a number of NF1 specific tumours has shown the inactivation of both NF1 alleles during tumourigenesis, in accordance with Knudson's "two hit" hypothesis. We have studied 82 tumours from 45 NF1 patients. Two separate strategies were used in this study to search for the somatic changes involved in the formation of NF1 tumours. First, evidence of loss of heterozygosity (LOH) of the NF1 gene region was investigated, and, second, a screen for the presence of sequence alterations was conducted on a large panel of DNA derived from matched blood/tumour pairs. In this study, the largest of its kind to date, we found that 12% of the tumours (10/82) exhibited LOH; previous studies have detected LOH in 3-36% of the neurofibromas examined. In addition, an SSCP/HA mutation screen identified five novel NF1 germline and two somatic mutations. In a plexiform neurofibroma from an NF1 patient, mutations in both NF1 alleles have been characterised.

    Journal of medical genetics 2000;37;1;44-9

  • A nonsense mutation at Arg-1947 in the NF1 gene in a case of neurofibromatosis type 1 in a Korean patient.

    Park KC, Choi HO, Park KH, Kim KH and Eun HC

    Department of Dermatology, Seoul National University College of Medicine, Chongno-gu, Korea. kcpark@medicine.snu.ac.kr

    We report a case of neurofibromatosis (NF) 1 presenting as a C-to-T transition changing an Arg-1947 codon to a stop codon. Because this mutation has been described in multiple Caucasian and Japanese families, the codon CGA for Arg-1947 in the NF1 gene is considered to be a hotspot for mutation in neurofibromatosis type 1 in all ethnic groups.

    Journal of human genetics 2000;45;2;84-5

  • Exhaustive mutation analysis of the NF1 gene allows identification of 95% of mutations and reveals a high frequency of unusual splicing defects.

    Messiaen LM, Callens T, Mortier G, Beysen D, Vandenbroucke I, Van Roy N, Speleman F and Paepe AD

    Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium. Ludwine.Messiaen@rug.ac.be

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders and is caused by mutations in the NF1 gene. Mutation detection is complex due to the large size of the NF1 gene, the presence of pseudogenes and the great variety of possible lesions. Although there is no evidence for locus heterogeneity in NF1, mutation detection rates rarely exceed 50%. We studied 67 unrelated NF1 patients fulfilling the NIH diagnostic criteria, 29 familial and 38 sporadic cases, using a cascade of complementary techniques. We performed a protein truncation test starting from puromycin-treated EBV cell lines and, if no mutation was found, continued with heteroduplex, FISH, Southern blot and cytogenetic analysis. We identified the germline mutation in 64 of 67 patients and 32 of the mutations are novel. This is the highest mutation detection rate reported in a study of typical NF1 patients. All mutations were studied at the genomic and RNA level. The mutational spectrum consisted of 25 nonsense, 12 frameshift, 19 splice mutations, six missense and/or small in-frame deletions, one deletion of the entire NF1 gene, and a translocation t(14;17)(q32;q11.2). Our data suggest that exons 10a-10c and 37 are mutation-rich regions and that together with some recurrent mutations they may account for almost 30% of the mutations in classical NF1 patients. We found a high frequency of unusual splice mutations outside of the AG/GT 5 cent and 3 cent splice sites. As some of these mutations form stable transcripts, it remains possible that a truncated neurofibromin is formed.

    Human mutation 2000;15;6;541-55

  • Unusual clustering of brain tumours in a family with NF1 and variable expression of cutaneous features.

    Faravelli F, Upadhyaya M, Osborn M, Huson SM, Hayward R and Winter R

    Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.

    Neurofibromatosis type 1 (NF1) is one of the commonest autosomal dominant disorders in man. It is characterised by café au lait spots, peripheral neurofibromas, Lisch nodules, axillary freckling, skeletal dysplasia, and optic glioma. Symptomatic brain tumours occur in 1.5-2.2% of patients with NF1. We report here a family where seven members developed brain tumours. Of these, three have a clinical history strongly suggestive of NF1, while two do not fulfil diagnostic criteria for the disorder. A splice site mutation in exon 29 of the NF1 gene was found in these two subjects. This lesion is thought to be disease causative since it creates a frameshift and a premature termination of the neurofibromin protein. Different hypotheses to explain the unusual recurrence of brain tumours in this family, such as the nature of the mutation or cosegregation of other predisposing genes, are discussed.

    Journal of medical genetics 1999;36;12;893-6

  • Neurofibromatosis type 1 (NF1): a protein truncation assay yielding identification of mutations in 73% of patients.

    Park VM and Pivnick EK

    Department of Obstetrics and Gynecology, University of Tennessee, Memphis 38163, USA.

    Neurofibromatosis type 1 (NF1) is caused by mutations in a tumour suppressor gene located on chromosome 17 (17q11.2). Disease causing mutations are dispersed throughout the gene, which spans 350 kilobases and includes 59 exons. A common consequence of NF1 mutations is introduction of a premature stop codon, and the majority of mutant genes encode truncated forms of neurofibromin. We used a protein truncation assay to screen for mutations in 15 NF1 patients and obtained positive results in 11 of them (73%). Sequencing of cDNA and genomic DNA yielded identification of 10 different mutations, including four splicing errors, three small deletions, two nonsense mutations, and one small insertion. Nine mutations were predicted to cause premature termination of translation, while one mutation caused in frame deletion as a result ofexon skipping. In one other case involving abnormal splicing, five different aberrantly spliced transcripts were detected. One germline nonsense mutation (R1306X, 3916C>T) corresponded to the same base change that occurs by mRNA editing in normal subjects. The second nonsense mutation (R2496X) was the sole germline mutation that has been previously described. The subjects studied represented typically affected NF1 patients and no correlations between genotype and phenotype were apparent. A high incidence of ocular hypertelorism was observed.

    Journal of medical genetics 1998;35;10;813-20

  • Gross deletions of the neurofibromatosis type 1 (NF1) gene are predominantly of maternal origin and commonly associated with a learning disability, dysmorphic features and developmental delay.

    Upadhyaya M, Ruggieri M, Maynard J, Osborn M, Hartog C, Mudd S, Penttinen M, Cordeiro I, Ponder M, Ponder BA, Krawczak M and Cooper DN

    Institute of Medical Genetics, University of Wales College of Medicine, Heath Park, Cardiff, UK.

    Mutation screening in neurofibromatosis type 1 (NF1) families has long been hampered by the complexity of the NF1 gene. By using a novel multi-track screening strategy, 67 NF1 families (54 two-generation, 13 three-generation) with a de novo mutation in the germline of the first generation were studied with two extragenic and 11 intragenic markers. The pathological lesion was identified in 31 cases. Loss of heterozygosity (LOH) in the affected individual revealed a gross gene deletion in 15 of the two-generation families; in 12 (80%) of them, the deletion was maternally derived. Eleven patients with a gross deletion exhibited developmental delay, ten had dysmorphic features and six manifested a learning disability. No gross deletion was apparent in any of the 13 three-generation families, suggesting that such lesions are subject to more intense selection. In these families, the new mutation was of paternal origin in 11 kindreds and the underlying mutational event could be characterised in three of them.

    Human genetics 1998;102;5;591-7

  • Novel recurrent nonsense mutation causing neurofibromatosis type 1 (NF1) in a family segregating both NF1 and Noonan syndrome.

    Bahuau M, Houdayer C, Assouline B, Blanchet-Bardon C, Le Merrer M, Lyonnet S, Giraud S, Récan D, Lakhdar H, Vidaud M and Vidaud D

    Laboratoire de Génétique Moléculaire, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris V, France.

    Neurofibromatosis type 1 (NF1), a genetic disorder with neuroectodermal involvement, demonstrates phenotypic overlap in some patients with Noonan syndrome (NS), ultimately resulting in the so-called neurofibromatosis-Noonan syndrome (NF-NS). A strong association of the two phenotypic traits was recently illustrated by a four-generation family, although NF1 and NS were eventually demonstrated to segregate independently on the basis of polymorphic DNA markers [Bahuau et al., 1996: Am J Med Genet 66:347-355]. Identification of the causal NF1 mutation seemed a prerequisite to further dissecting this singular familial association. Using the protein truncation assay, a nonsense mutation (C2446T-->R816X) of the neurofibromin gene was evidenced. This mutation occurred on a CpG dinucleotide within exon 16 and 5' to the GAP domain-specifying region of the gene. R816X creates a recognition site for endonuclease HphI, absent in 2 individuals with NS only. Screening 184 unrelated NF1 patients, three novel occurrences of the mutation were found in individuals diagnosed with classical NF1. Based on the assumption of genotype-phenotype correlation in these individuals, clinical and molecular analyses of this four-generation family demonstrated that the NF-NS phenotype was additive, being the result of both classical NF1 and NS. This particular observation also suggests the presence of an NS locus on 17q, which might be of interest for further linkage studies.

    American journal of medical genetics 1998;75;3;265-72

  • Mutational and functional analysis of the neurofibromatosis type 1 (NF1) gene.

    Upadhyaya M, Osborn MJ, Maynard J, Kim MR, Tamanoi F and Cooper DN

    Institute of Medical Genetics, Heath Park, Cardiff, UK.

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders. It is caused by mutations in the NF1 gene which comprises 60 exons and is located on chromosome 17q. The NF1 gene product, neurofibromin, displays partial homology to GTPase-activating protein (GAP). The GAP-related domain (GRD), encoded by exons 20-27a, is the only region of neurofibromin to which a biological function has been ascribed. A total of 320 unrelated NF1 patients were screened for mutations in the GRD-encoding region of the NF1 gene. Sixteen different lesions in the NF1 GRD region were identified in a total of 20 patients. Of these lesions, 14 are novel and together comprise three missense, two nonsense and three splice site mutations plus six deletions of between 1 and 4 bp. The effect of one of the missense mutations (R1391S) was studied by in vitro expression of a site-directed mutant and GAP activity assay. The mutant protein, R1391S, was found to be some 300-fold less active than wild-type NF1 GRD. The mutations reported in this study therefore provide further material for the functional analysis of neurofibromin as well as an insight into the mutational spectrum of the NF1 GRD.

    Human genetics 1997;99;1;88-92

  • Molecular characterization of the breakpoints of a 12-kb deletion in the NF1 gene in a family showing germ-line mosaicism.

    Lázaro C, Gaona A, Lynch M, Kruyer H, Ravella A and Estivill X

    Department de Genètica Molecular, Institut de Recerca Oncològica, Hospital Duran i Reynals, Spain.

    Neurofibromatosis type 1 (NF1) is caused by deletions, insertions, translocations, and point mutations in the NF1 gene, which spans 350 kb on the long arm of human chromosome 17. Although several point mutations have been described, large molecular abnormalities have rarely been characterized in detail. We describe here the molecular breakpoints of a 12-kb deletion of the NF1 gene, which is responsible for the NF1 phenotype in a kindred with two children affected because of germline mosaicism in the unaffected father, who has the mutation in 10% of his spermatozoa. The mutation spans introns 31-39, removing 12,021 nt and inserting 30 bp, of which 19 bp are a direct repetition of a sequence located in intron 31, just 4 bp before the 5' breakpoint. The 5' and 3' breakpoints contain the sequence TATTTTA, which could be involved in the generation of the deletion. The most plausible explanation for the mechanism involved in the generation of this 12-kb deletion is homologous/nonhomologous recombination. Since sperm of the father does not contain the corresponding insertion of the 12-kb deleted sequence, this deletion could have occurred within the NF1 chromosome through loop formation. RNA from lymphocytes of one of the NF1 patients showed similar levels of the mutated and normal transcripts, suggesting that the NF1-mRNA from mutations causing frame shifts of the reading frame or stop codons in this gene is not degraded during its processing. The mutation was not detected in fresh lymphocytes from the unaffected father by PCR analysis, supporting the case for true germ-line mosaicism.

    American journal of human genetics 1995;57;5;1044-9

  • Reduced neurofibromin content but normal GAP activity in a patient with neurofibromatosis type 1 caused by a five base pair duplication in exon 12b of the NF1 gene.

    Böddrich A, Griesser J, Horn D, Kaufmann D, Krone W and Nürnberg P

    Institut für Medizinische Genetik, Universitätsklinikum Charité, Berlin, Germany.

    We screened a total of 87 unrelated patients with neurofibromatosis type 1 (NF1) for mutations in exons 11, 12a, and 12b of the NF1 gene using temperature gradient gel electrophoresis (TGGE). A novel mutation (1998insCCTCT) was found in exon 12b. The 5-bp duplication comprising nucleotides 1994 to 1998 is predicted to lead to a truncated protein product lacking three quarters of its C-terminal sequence including the entire GTPase-activating protein-(GAP)-related domain. This mutation is associated with a reduction by 50% of the detectable amount of neurofibromin found in this patient. Despite the reduced level of neurofibromin cellular GAP activity was normal, which suggests that defects in other functions of the neurofibromin molecule may be important in the pathogenesis of NF1.

    Biochemical and biophysical research communications 1995;214;3;895-904

  • Characterisation of inherited and sporadic mutations in neurofibromatosis type-1.

    Purandare SM, Lanyon WG and Connor JM

    Duncan Guthrie Institute of Medical Genetics, University of Glasgow, Yorkhill, UK.

    Neurofibromatosis type-1 (NF-1) is an autosomal dominant disorder, caused by mutations in the NF-1 gene. Mutation analysis in the NF-1 gene is complicated by the large size of the gene, the high mutation rate, and the presence of pseudogenes. By means of the polymerase chain reaction, we have amplified 70% of the NF-1 coding sequence using reverse transcribed mRNA and genomic DNA from 25 unrelated Scottish Caucasian patients. We have used chemical mismatch cleavage analysis and direct sequencing of asymmetrically amplifed PCR products to characterise mutations within the NF-1 gene. Using the above strategy, we detected 10 novel mutations and an intragenic polymorphism with a heterozygosity of approximately 47% in the Scottish population. Of the 10 mutations, 7 are potentially disease causing. They include splice site errors responsible for exon skipping (1721 + 3A to G) and (5749 + 2T to G), small insertions (7485insGG) and (6519insG), a nonsense mutation (R2496X), and missense and silent mutations (G1166D, K1419R, G1404G, S1311S, N1776N). A correlation of the phenotype with the genotype is presented. Thus, in this study we have identified a heterogeneous group of germline mutations, the majority of which are predicted to cause disruption of the protein product, neurofibromin. This approach has therefore proved to be useful for the detection of mutations in the gene for neurofibromatosis type-1, and can be applied to detection of molecular pathologies in general.

    Human molecular genetics 1994;3;7;1109-15

  • Deletions spanning the neurofibromatosis 1 gene: identification and phenotype of five patients.

    Kayes LM, Burke W, Riccardi VM, Bennett R, Ehrlich P, Rubenstein A and Stephens K

    Division of Medical Genetics, University of Washington School of Medicine, Seattle.

    Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder characterized by marked variation in clinical severity. To investigate the contribution to variability by genes either contiguous to or contained within the NF1 gene, we screened six NF1 patients with mild facial dysmorphology, mental retardation, and/or learning disabilities, for DNA rearrangement of the NF1 region. Five of the six patients had NF1 gene deletions on the basis of quantitative densitometry, locus hemizygosity, and analysis of somatic cell hybrid lines. Analyses of hybrid lines carrying each of the patient's chromosomes 17, with 15 regional DNA markers, demonstrated that each of the five patients carried a deletion > 700 kb in size. Minimally, each of the deletions involved the entire 350-kb NF1 gene; the three genes--EVI2A, EVI2B, and OMG--that are contained within an NF1 intron; and considerable flanking DNA. For four of the patients, the deletions mapped to the same interval; the deletion in the fifth patient was larger, extending farther in both directions. The remaining NF1 allele presumably produced functional neurofibromin; no gene rearrangements were detected, and RNA-PCR demonstrated that it was transcribed. These data provide compelling evidence that the NF1 disorder results from haploid insufficiency of neurofibromin. Of the three documented de novo deletion cases, two involved the paternal NF1 allele and one the maternal allele. The parental origin of the single remaining expressed NF1 allele had no dramatic effect on patient phenotype. The deletion patients exhibited a variable number of physical anomalies that were not correlated with the extent of their deletion. All five patients with deletions were remarkable for exhibiting a large number of neurofibromas for their age, suggesting that deletion of an unknown gene in the NF1 region may affect tumor initiation or development.

    Funded by: NINDS NIH HHS: F32-NS09121

    American journal of human genetics 1994;54;3;424-36

  • Analysis of NF1 gene mutations in neurofibromatosis type 1 patients in Japan.

    Hatta N, Horiuchi T and Fujita S

    First Department of Internal Medicine, School of Medicine, Ehime University, Japan.

    Neurofibromatosis type 1 (NF1) is one of the most common inherited disorders and is characterized by abnormalities in multiple tissues derived from the neural crest. Here, we report two novel deletion mutations of the NF1 gene from two out of 25 unrelated Japanese NF1 patients. These mutations were detected using polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP) analysis. Sequencing analysis revealed a 4 base pair (bp) deletion at 5679 (5679delACTG) in exon 30 in one patient and a single bp deletion at 5949 (5949delA) in exon 32 in the other patient. Both of these mutations resulted in frameshifts, followed by premature terminations of the mutant allele. Because only a few large rearrangements of the NF1 gene have been reported in NF1 patients, it is likely that subtle mutations such as these are common.

    Biochemical and biophysical research communications 1994;199;1;207-12

  • Two NF1 mutations: frameshift in the GAP-related domain, and loss of two codons toward the 3' end of the gene.

    Abernathy CR, Colman SD, Kousseff BG and Wallace MR

    Department of Pediatrics, University of Florida, Gainesville 32610.

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders, and is due to mutations within the NF1 gene on chromosome 17q11.2. Only the middle 400 amino acids of the associated protein (neurofibromin) have a known function, comprising a GTPase-activating-protein (GAP) domain. The large gene size and the fact that approximately half of cases are due to new mutation render mutation analysis difficult. NF1 direct mutation characterization is important for development of DNA diagnostic procedures, analysis of phenotype/genotype correlations, and delineation of functions for specific domains of neurofibromin. We report two mutations detected using PCR amplification of individual exons followed by heteroduplex analysis. One is a single base deletion in exon 24 which is predicted to result in a protein truncated early in the GAP-related domain. The other is a 6-bp deletion in exon 39 which is predicted to result in loss of two amino acids in the mature protein near the carboxy-terminus. The exon 24 mutant allele was shown to be expressed by RNA PCR analysis. The exon 39 mutation suggests that those two amino acids are important in neurofibromin function, perhaps indicating a functional domain.

    Human mutation 1994;3;4;347-52

  • Tandem duplication within a neurofibromatosis type 1 (NF1) gene exon in a family with features of Watson syndrome and Noonan syndrome.

    Tassabehji M, Strachan T, Sharland M, Colley A, Donnai D, Harris R and Thakker N

    University Department of Medical Genetics, St. Mary's Hospital, Manchester, United Kingdom.

    Type 1 neurofibromatosis (NF1), Watson syndrome (WS), and Noonan syndrome (NS) show some overlap in clinical manifestations. In addition, WS has been shown to be linked to markers flanking the NF1 locus and a deletion at the NF1 locus demonstrated in a WS patient. This suggests either that WS and NF1 are allelic or that phenotypes arise from mutations in very closely linked genes. Here we provide evidence for the former by demonstrating a mutation in the NF1 gene in a family with features of both WS and NS. The mutation is an almost perfect in-frame tandem duplication of 42 bases in exon 28 of the NF1 gene. Unlike the mutations previously described in classical NF1, which show a preponderance of null alleles, the mutation in this family would be expected to result in a mutant neurofibromin product.

    Funded by: Wellcome Trust

    American journal of human genetics 1993;53;1;90-5

Literature (25)

Pubmed - human_disease

  • Genome-wide single-nucleotide polymorphism analysis in juvenile myelomonocytic leukemia identifies uniparental disomy surrounding the NF1 locus in cases associated with neurofibromatosis but not in cases with mutant RAS or PTPN11.

    Flotho C, Steinemann D, Mullighan CG, Neale G, Mayer K, Kratz CP, Schlegelberger B, Downing JR and Niemeyer CM

    Division of Pediatric Hematology-Oncology, University of Freiburg, Freiburg, Germany. christian.flotho@uniklinik-freiburg.de

    Juvenile myelomonocytic leukemia (JMML) is a malignant hematopoietic disorder whose proliferative component is a result of RAS pathway deregulation caused by somatic mutation in the RAS or PTPN11 oncogenes or in patients with underlying neurofibromatosis type 1 (NF-1), by loss of NF1 gene function. To search for potential collaborating genetic abnormalities, we used oligonucleotide arrays to analyse over 116 000 single-nucleotide polymorphisms across the genome in 16 JMML samples with normal karyotype. Evaluation of the SNP genotypes identified large regions of homozygosity on chromosome 17q, including the NF1 locus, in four of the five samples from patients with JMML and NF-1. The homozygous region was at least 55 million base pairs in each case. The genomic copy number was normal within the homozygous region, indicating uniparental disomy (UPD). In contrast, the array data provided no evidence for 17q UPD in any of the 11 JMML cases without NF-1. We used array-based comparative genomic hybridization to confirm 17q disomy, and microsatellite analysis was performed to verify homozygosity. Mutational analysis demonstrated that the inactivating NF1 lesion was present on both alleles in each case. In summary, our data indicate that a mitotic recombination event in a JMML-initiating cell led to 17q UPD with homozygous loss of normal NF1, provide confirmatory evidence that the NF1 gene is crucial for the increased incidence of JMML in NF-1 patients, and corroborate the concept that RAS pathway deregulation is central to JMML pathogenesis.

    Oncogene 2007;26;39;5816-21

  • Characterization of the somatic mutational spectrum of the neurofibromatosis type 1 (NF1) gene in neurofibromatosis patients with benign and malignant tumors.

    Upadhyaya M, Han S, Consoli C, Majounie E, Horan M, Thomas NS, Potts C, Griffiths S, Ruggieri M, von Deimling A and Cooper DN

    Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK. upadhyaya@cardiff.ac.uk

    One of the main features of neurofibromatosis type 1 (NF1) is benign neurofibromas, 10-20% of which become transformed into malignant peripheral nerve sheath tumors (MPNSTs). The molecular basis of NF1 tumorigenesis is, however, still unclear. Ninety-one tumors from 31 NF1 patients were screened for gross changes in the NF1 gene using microsatellite/restriction fragment length polymorphism (RFLP) markers; loss of heterozygosity (LOH) was found in 17 out of 91 (19%) tumors (including two out of seven MPNSTs). Denaturing high performance liquid chromatography (DHPLC) was then used to screen 43 LOH-negative and 10 LOH-positive tumors for NF1 microlesions at both RNA and DNA levels. Thirteen germline and 12 somatic mutations were identified, of which three germline (IVS7-2A>G, 3731delT, 6117delG) and eight somatic (1888delG, 4374-4375delCC, R2129S, 2088delG, 2341del18, IVS27b-5C>T, 4083insT, Q519P) were novel. A mosaic mutation (R2429X) was also identified in a neurofibroma by DHPLC analysis and cloning/sequencing. The observed somatic and germline mutational spectra were similar in terms of mutation type, relative frequency of occurrence, and putative underlying mechanisms of mutagenesis. Tumors lacking mutations were screened for NF1 gene promoter hypermethylation but none were found. Microsatellite instability (MSI) analysis revealed MSI in five out of 11 MPNSTs as compared to none out of 70 neurofibromas (p=1.8 x 10(-5)). The screening of seven MPNSTs for subtle mutations in the CDKN2A and TP53 genes proved negative, although the screening of 11 MPNSTs detected LOH involving either the TP53 or the CDKN2A gene in a total of four tumors. These findings are consistent with the view that NF1 tumorigenesis is a complex multistep process involving a variety of different types of genetic defect at multiple loci.

    Human mutation 2004;23;2;134-46

  • Ten novel mutations in the human neurofibromatosis type 1 (NF1) gene in Italian patients.

    Origone P, De Luca A, Bellini C, Buccino A, Mingarelli R, Costabel S, La Rosa C, Garrè C, Coviello DA, Ajmar F, Dallapiccola B and Bonioli E

    Dipartimento di Oncologia, Biologia e Genetica, Università di Genova, Genova, Italy. origone@unige.it

    The entire NF1 coding region was analyzed for mutations in a panel of 108 unrelated Italian NF1 patients. Using PTT, SSCP, and DNA sequencing, we found 10 mutations which have never been reported before. Clinical diagnosis of NF1 was established according to the NIH consensus criteria in 100 individuals, while 8 were young children with only multiple cafè-au-lait spots. We detected 46 truncated fragments, and 24 of them were fully characterized by SSCP and direct sequencing. Of the 24, 14 were known mutations (R304X, R681X, Q682X, R1306X, R1362X, R1513X, R1748X, Q1794X, R1947X, Y2264X, R2237X, 2674delA, 6789delTTAC, 2027insC). The other 10 mutations represent novel changes that contribute to the germline mutational spectrum of the NF1 gene (K810X, Q2595X, 6772delT, 7190delCT, 7331delA, 1021insTT, 3921insT, 4106insTA, 7149insC, 2033insCG / 2034delA). PTT in a large number of Italian NF1 patients supports the usefulness of this method for characterization of mutations in disorders where the responsible gene is very large and the disease-causing mutations often create a stop codon. In agreement with previous reports, no mutational hotspots within the NF1 gene were detected.

    Human mutation 2002;20;1;74-5

  • Somatic NF1 mutational spectrum in benign neurofibromas: mRNA splice defects are common among point mutations.

    Serra E, Ars E, Ravella A, Sánchez A, Puig S, Rosenbaum T, Estivill X and Lázaro C

    Centre de Genètica Mèdica i Molecular--IRO, Hospital Duran i Reynals, Barcelona, Spain.

    Neurofibromas, benign tumors that originate from the peripheral nerve sheath, are a hallmark of neurofibromatosis type 1 (NF1). Although loss of heterozygosity (LOH) is a common phenomenon in this neoplasia, it only accounts for part of the somatic NF1 mutations found. Somatic point mutations or the presence of "two hits" in the NF1 gene have only been reported for a few neurofibromas. The large size of the NF1 gene together with the multicellular composition of these tumors has greatly hampered their molecular characterization. Here, we present the somatic NF1 mutational analysis of the whole set of neurofibromas studied by our group and consisting in 126 tumors derived from 32 NF1 patients. We report the identification of 45 independent somatic NF1 mutations, 20 of which are reported for the first time. Different types of point mutations together with LOH affecting the NF1 gene and its surrounding region or extending along the 17q arm have been found. Among point mutations, those affecting the correct splicing of the NF1 gene are common, coinciding with results reported on germline NF1 mutations. In most cases, we have been able to confirm that both copies of the NF1 gene are inactivated. We have also found that both somatic and germline mutations can be expressed at the RNA level in the neoplastic cells. Furthermore, we have observed that the study of more than one tumor derived from the same patient is useful for the identification of the germline mutation. Finally, we have noticed that the culture of neurofibromas and their fibroblast clearance facilitates LOH detection in cases in which it is difficult to determine.

    Human genetics 2001;108;5;416-29

  • A novel mutation in the neurofibromatosis type 1 (NF1) gene promotes skipping of two exons by preventing exon definition.

    Fang LJ, Simard MJ, Vidaud D, Assouline B, Lemieux B, Vidaud M, Chabot B and Thirion JP

    Département de microbiologie et d'infectiologie, Universite Paris V 4 av. de l'Observatoire 75006, Paris, France.

    Using a protein truncation assay, we have identified a new mutation in the neurofibromatosis type 1 (NF1) gene that causes a severe defect in NF1 pre-mRNA splicing. The mutation, which consists of a G to A transition at position +1 of the 5' splice site of exon 12a, is associated with the loss of both exons 11 and 12a in the NF1 mRNA. Through the use of in vivo and in vitro splicing assays, we show that the mutation inactivates the 5' splice site of exon 12a, and prevents the definition of exon 12a, a process that is normally required to stimulate the weak 3' splice site of exon 12a. Because the 5' splice site mutation weakens the interaction of splicing factors with the 3' splice site of exon 12a, we propose that exon 11/exon 12a splicing is also compromised, leading to the exclusion of both exons 11 and 12a. Our results provide in vivo support for the importance of the exon definition model during NF1 splicing, and suggest that the NF1 region containing exons 11 and 12a plays an important role in the activity of neurofibromin.

    Journal of molecular biology 2001;307;5;1261-70

  • Identification of two novel frame shift mutations of the NF1 gene in Korean patients with neurofibromatosis type 1.

    Park KC, Choi HO, Han WS, Hwang JH, Park KH, Kim KH, Chung JH and Eun HC

    Department of Dermatology, Seoul National University, College of Medicine, Korea.

    Neurofibromatos is type 1 (NF1) is one of the most common inherited disorders and is characterized by abnormalities in multiple tissues derived from the neural crest. The NF-1 gene has been cloned and mapped to human chromosome 17q11.2. The NF-1 gene has an open reading frame that predicts a protein consisting of 2,818 amino acids, known as neurofibromin. Here, we report two kinds of novel frame shift mutations of the NF1 gene from 2 out of 56 unrelated Korean NF1 patients. These mutations were detected using polymerase chain reaction and single strand conformational polymorphism analysis. Sequencing analysis revealed four base pair insertion at codon 1270 of exon 22, and a base pair deletion at codon 1398 of exon 24. These mutations resulted in premature termination of the mutant alleles and may encode truncated forms of neurofibromin.

    Journal of Korean medical science 2000;15;5;542-4

  • Toward a survey of somatic mutation of the NF1 gene in benign neurofibromas of patients with neurofibromatosis type 1.

    Eisenbarth I, Beyer K, Krone W and Assum G

    Abteilung Humangenetik, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany. ingrid.eisenbarth@medizin.uni-ulm.de

    Neurofibromatosis type 1 (NF1), a common autosomal dominant disorder caused by mutations of the NF1 gene, is characterized by multiple neurofibromas, pigmentation anomalies, and a variety of other possible complications, including an increased risk of malignant neoplasias. Tumorigenesis in NF1 is believed to follow the two-hit hypothesis postulated for tumor-suppressor genes. Loss of heterozygosity (LOH) has been shown to occur in NF1-associated malignancies and in benign neurofibromas, but only few of the latter yielded a positive result. Here we describe a systematic approach of searching for somatic inactivation of the NF1 gene in neurofibromas. In the course of these studies, two new intragenic polymorphisms of the NF1 gene, a tetranucleotide repeat and a 21-bp duplication, could be identified. Three tumor-specific point mutations and two LOH events were detected among seven neurofibromas from four different NF1 patients. Our results suggest that small subtle mutations occur with similar frequency to that of LOH in benign neurofibromas and that somatic inactivation of the NF1 gene is a general event in these tumors. The spectrum of somatic mutations occurring in various tumors from individual NF1 patients may contribute to the understanding of variable expressivity of the NF1 phenotype.

    American journal of human genetics 2000;66;2;393-401

  • A search for evidence of somatic mutations in the NF1 gene.

    John AM, Ruggieri M, Ferner R and Upadhyaya M

    Institute of Medical Genetics, University College of Medicine of Wales, Heath Park, Cardiff CF4 4XN, UK.

    Neurofibromatosis type I (NF1) is an autosomal dominant disorder affecting 1 in 3000 people. The NF1 gene is located on chromosome 17q11.2, spans 350 kb of genomic DNA, and contains 60 exons. A major phenotypic feature of the disease is the widespread occurrence of benign dermal and plexiform neurofibromas. Genetic and biochemical data support the hypothesis that NF1 acts as a tumour suppressor gene. Molecular analysis of a number of NF1 specific tumours has shown the inactivation of both NF1 alleles during tumourigenesis, in accordance with Knudson's "two hit" hypothesis. We have studied 82 tumours from 45 NF1 patients. Two separate strategies were used in this study to search for the somatic changes involved in the formation of NF1 tumours. First, evidence of loss of heterozygosity (LOH) of the NF1 gene region was investigated, and, second, a screen for the presence of sequence alterations was conducted on a large panel of DNA derived from matched blood/tumour pairs. In this study, the largest of its kind to date, we found that 12% of the tumours (10/82) exhibited LOH; previous studies have detected LOH in 3-36% of the neurofibromas examined. In addition, an SSCP/HA mutation screen identified five novel NF1 germline and two somatic mutations. In a plexiform neurofibroma from an NF1 patient, mutations in both NF1 alleles have been characterised.

    Journal of medical genetics 2000;37;1;44-9

  • Exhaustive mutation analysis of the NF1 gene allows identification of 95% of mutations and reveals a high frequency of unusual splicing defects.

    Messiaen LM, Callens T, Mortier G, Beysen D, Vandenbroucke I, Van Roy N, Speleman F and Paepe AD

    Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium. Ludwine.Messiaen@rug.ac.be

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders and is caused by mutations in the NF1 gene. Mutation detection is complex due to the large size of the NF1 gene, the presence of pseudogenes and the great variety of possible lesions. Although there is no evidence for locus heterogeneity in NF1, mutation detection rates rarely exceed 50%. We studied 67 unrelated NF1 patients fulfilling the NIH diagnostic criteria, 29 familial and 38 sporadic cases, using a cascade of complementary techniques. We performed a protein truncation test starting from puromycin-treated EBV cell lines and, if no mutation was found, continued with heteroduplex, FISH, Southern blot and cytogenetic analysis. We identified the germline mutation in 64 of 67 patients and 32 of the mutations are novel. This is the highest mutation detection rate reported in a study of typical NF1 patients. All mutations were studied at the genomic and RNA level. The mutational spectrum consisted of 25 nonsense, 12 frameshift, 19 splice mutations, six missense and/or small in-frame deletions, one deletion of the entire NF1 gene, and a translocation t(14;17)(q32;q11.2). Our data suggest that exons 10a-10c and 37 are mutation-rich regions and that together with some recurrent mutations they may account for almost 30% of the mutations in classical NF1 patients. We found a high frequency of unusual splice mutations outside of the AG/GT 5 cent and 3 cent splice sites. As some of these mutations form stable transcripts, it remains possible that a truncated neurofibromin is formed.

    Human mutation 2000;15;6;541-55

  • Unusual clustering of brain tumours in a family with NF1 and variable expression of cutaneous features.

    Faravelli F, Upadhyaya M, Osborn M, Huson SM, Hayward R and Winter R

    Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.

    Neurofibromatosis type 1 (NF1) is one of the commonest autosomal dominant disorders in man. It is characterised by café au lait spots, peripheral neurofibromas, Lisch nodules, axillary freckling, skeletal dysplasia, and optic glioma. Symptomatic brain tumours occur in 1.5-2.2% of patients with NF1. We report here a family where seven members developed brain tumours. Of these, three have a clinical history strongly suggestive of NF1, while two do not fulfil diagnostic criteria for the disorder. A splice site mutation in exon 29 of the NF1 gene was found in these two subjects. This lesion is thought to be disease causative since it creates a frameshift and a premature termination of the neurofibromin protein. Different hypotheses to explain the unusual recurrence of brain tumours in this family, such as the nature of the mutation or cosegregation of other predisposing genes, are discussed.

    Journal of medical genetics 1999;36;12;893-6

  • Neurofibromatosis type 1 (NF1): a protein truncation assay yielding identification of mutations in 73% of patients.

    Park VM and Pivnick EK

    Department of Obstetrics and Gynecology, University of Tennessee, Memphis 38163, USA.

    Neurofibromatosis type 1 (NF1) is caused by mutations in a tumour suppressor gene located on chromosome 17 (17q11.2). Disease causing mutations are dispersed throughout the gene, which spans 350 kilobases and includes 59 exons. A common consequence of NF1 mutations is introduction of a premature stop codon, and the majority of mutant genes encode truncated forms of neurofibromin. We used a protein truncation assay to screen for mutations in 15 NF1 patients and obtained positive results in 11 of them (73%). Sequencing of cDNA and genomic DNA yielded identification of 10 different mutations, including four splicing errors, three small deletions, two nonsense mutations, and one small insertion. Nine mutations were predicted to cause premature termination of translation, while one mutation caused in frame deletion as a result ofexon skipping. In one other case involving abnormal splicing, five different aberrantly spliced transcripts were detected. One germline nonsense mutation (R1306X, 3916C>T) corresponded to the same base change that occurs by mRNA editing in normal subjects. The second nonsense mutation (R2496X) was the sole germline mutation that has been previously described. The subjects studied represented typically affected NF1 patients and no correlations between genotype and phenotype were apparent. A high incidence of ocular hypertelorism was observed.

    Journal of medical genetics 1998;35;10;813-20

  • Gross deletions of the neurofibromatosis type 1 (NF1) gene are predominantly of maternal origin and commonly associated with a learning disability, dysmorphic features and developmental delay.

    Upadhyaya M, Ruggieri M, Maynard J, Osborn M, Hartog C, Mudd S, Penttinen M, Cordeiro I, Ponder M, Ponder BA, Krawczak M and Cooper DN

    Institute of Medical Genetics, University of Wales College of Medicine, Heath Park, Cardiff, UK.

    Mutation screening in neurofibromatosis type 1 (NF1) families has long been hampered by the complexity of the NF1 gene. By using a novel multi-track screening strategy, 67 NF1 families (54 two-generation, 13 three-generation) with a de novo mutation in the germline of the first generation were studied with two extragenic and 11 intragenic markers. The pathological lesion was identified in 31 cases. Loss of heterozygosity (LOH) in the affected individual revealed a gross gene deletion in 15 of the two-generation families; in 12 (80%) of them, the deletion was maternally derived. Eleven patients with a gross deletion exhibited developmental delay, ten had dysmorphic features and six manifested a learning disability. No gross deletion was apparent in any of the 13 three-generation families, suggesting that such lesions are subject to more intense selection. In these families, the new mutation was of paternal origin in 11 kindreds and the underlying mutational event could be characterised in three of them.

    Human genetics 1998;102;5;591-7

  • Novel recurrent nonsense mutation causing neurofibromatosis type 1 (NF1) in a family segregating both NF1 and Noonan syndrome.

    Bahuau M, Houdayer C, Assouline B, Blanchet-Bardon C, Le Merrer M, Lyonnet S, Giraud S, Récan D, Lakhdar H, Vidaud M and Vidaud D

    Laboratoire de Génétique Moléculaire, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris V, France.

    Neurofibromatosis type 1 (NF1), a genetic disorder with neuroectodermal involvement, demonstrates phenotypic overlap in some patients with Noonan syndrome (NS), ultimately resulting in the so-called neurofibromatosis-Noonan syndrome (NF-NS). A strong association of the two phenotypic traits was recently illustrated by a four-generation family, although NF1 and NS were eventually demonstrated to segregate independently on the basis of polymorphic DNA markers [Bahuau et al., 1996: Am J Med Genet 66:347-355]. Identification of the causal NF1 mutation seemed a prerequisite to further dissecting this singular familial association. Using the protein truncation assay, a nonsense mutation (C2446T-->R816X) of the neurofibromin gene was evidenced. This mutation occurred on a CpG dinucleotide within exon 16 and 5' to the GAP domain-specifying region of the gene. R816X creates a recognition site for endonuclease HphI, absent in 2 individuals with NS only. Screening 184 unrelated NF1 patients, three novel occurrences of the mutation were found in individuals diagnosed with classical NF1. Based on the assumption of genotype-phenotype correlation in these individuals, clinical and molecular analyses of this four-generation family demonstrated that the NF-NS phenotype was additive, being the result of both classical NF1 and NS. This particular observation also suggests the presence of an NS locus on 17q, which might be of interest for further linkage studies.

    American journal of medical genetics 1998;75;3;265-72

  • Molecular characterization of the breakpoints of a 12-kb deletion in the NF1 gene in a family showing germ-line mosaicism.

    Lázaro C, Gaona A, Lynch M, Kruyer H, Ravella A and Estivill X

    Department de Genètica Molecular, Institut de Recerca Oncològica, Hospital Duran i Reynals, Spain.

    Neurofibromatosis type 1 (NF1) is caused by deletions, insertions, translocations, and point mutations in the NF1 gene, which spans 350 kb on the long arm of human chromosome 17. Although several point mutations have been described, large molecular abnormalities have rarely been characterized in detail. We describe here the molecular breakpoints of a 12-kb deletion of the NF1 gene, which is responsible for the NF1 phenotype in a kindred with two children affected because of germline mosaicism in the unaffected father, who has the mutation in 10% of his spermatozoa. The mutation spans introns 31-39, removing 12,021 nt and inserting 30 bp, of which 19 bp are a direct repetition of a sequence located in intron 31, just 4 bp before the 5' breakpoint. The 5' and 3' breakpoints contain the sequence TATTTTA, which could be involved in the generation of the deletion. The most plausible explanation for the mechanism involved in the generation of this 12-kb deletion is homologous/nonhomologous recombination. Since sperm of the father does not contain the corresponding insertion of the 12-kb deleted sequence, this deletion could have occurred within the NF1 chromosome through loop formation. RNA from lymphocytes of one of the NF1 patients showed similar levels of the mutated and normal transcripts, suggesting that the NF1-mRNA from mutations causing frame shifts of the reading frame or stop codons in this gene is not degraded during its processing. The mutation was not detected in fresh lymphocytes from the unaffected father by PCR analysis, supporting the case for true germ-line mosaicism.

    American journal of human genetics 1995;57;5;1044-9

  • Reduced neurofibromin content but normal GAP activity in a patient with neurofibromatosis type 1 caused by a five base pair duplication in exon 12b of the NF1 gene.

    Böddrich A, Griesser J, Horn D, Kaufmann D, Krone W and Nürnberg P

    Institut für Medizinische Genetik, Universitätsklinikum Charité, Berlin, Germany.

    We screened a total of 87 unrelated patients with neurofibromatosis type 1 (NF1) for mutations in exons 11, 12a, and 12b of the NF1 gene using temperature gradient gel electrophoresis (TGGE). A novel mutation (1998insCCTCT) was found in exon 12b. The 5-bp duplication comprising nucleotides 1994 to 1998 is predicted to lead to a truncated protein product lacking three quarters of its C-terminal sequence including the entire GTPase-activating protein-(GAP)-related domain. This mutation is associated with a reduction by 50% of the detectable amount of neurofibromin found in this patient. Despite the reduced level of neurofibromin cellular GAP activity was normal, which suggests that defects in other functions of the neurofibromin molecule may be important in the pathogenesis of NF1.

    Biochemical and biophysical research communications 1995;214;3;895-904

  • Deletions spanning the neurofibromatosis 1 gene: identification and phenotype of five patients.

    Kayes LM, Burke W, Riccardi VM, Bennett R, Ehrlich P, Rubenstein A and Stephens K

    Division of Medical Genetics, University of Washington School of Medicine, Seattle.

    Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder characterized by marked variation in clinical severity. To investigate the contribution to variability by genes either contiguous to or contained within the NF1 gene, we screened six NF1 patients with mild facial dysmorphology, mental retardation, and/or learning disabilities, for DNA rearrangement of the NF1 region. Five of the six patients had NF1 gene deletions on the basis of quantitative densitometry, locus hemizygosity, and analysis of somatic cell hybrid lines. Analyses of hybrid lines carrying each of the patient's chromosomes 17, with 15 regional DNA markers, demonstrated that each of the five patients carried a deletion > 700 kb in size. Minimally, each of the deletions involved the entire 350-kb NF1 gene; the three genes--EVI2A, EVI2B, and OMG--that are contained within an NF1 intron; and considerable flanking DNA. For four of the patients, the deletions mapped to the same interval; the deletion in the fifth patient was larger, extending farther in both directions. The remaining NF1 allele presumably produced functional neurofibromin; no gene rearrangements were detected, and RNA-PCR demonstrated that it was transcribed. These data provide compelling evidence that the NF1 disorder results from haploid insufficiency of neurofibromin. Of the three documented de novo deletion cases, two involved the paternal NF1 allele and one the maternal allele. The parental origin of the single remaining expressed NF1 allele had no dramatic effect on patient phenotype. The deletion patients exhibited a variable number of physical anomalies that were not correlated with the extent of their deletion. All five patients with deletions were remarkable for exhibiting a large number of neurofibromas for their age, suggesting that deletion of an unknown gene in the NF1 region may affect tumor initiation or development.

    Funded by: NINDS NIH HHS: F32-NS09121

    American journal of human genetics 1994;54;3;424-36

  • Analysis of NF1 gene mutations in neurofibromatosis type 1 patients in Japan.

    Hatta N, Horiuchi T and Fujita S

    First Department of Internal Medicine, School of Medicine, Ehime University, Japan.

    Neurofibromatosis type 1 (NF1) is one of the most common inherited disorders and is characterized by abnormalities in multiple tissues derived from the neural crest. Here, we report two novel deletion mutations of the NF1 gene from two out of 25 unrelated Japanese NF1 patients. These mutations were detected using polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP) analysis. Sequencing analysis revealed a 4 base pair (bp) deletion at 5679 (5679delACTG) in exon 30 in one patient and a single bp deletion at 5949 (5949delA) in exon 32 in the other patient. Both of these mutations resulted in frameshifts, followed by premature terminations of the mutant allele. Because only a few large rearrangements of the NF1 gene have been reported in NF1 patients, it is likely that subtle mutations such as these are common.

    Biochemical and biophysical research communications 1994;199;1;207-12

Pubmed - other

  • Novel and recurrent mutations in the NF1 gene in Italian patients with neurofibromatosis type 1.

    De Luca A, Schirinzi A, Buccino A, Bottillo I, Sinibaldi L, Torrente I, Ciavarella A, Dottorini T, Porciello R, Giustini S, Calvieri S and Dallapiccola B

    IRCCS-CSS, San Giovanni Rotondo and CSS-Mendel Institute, Rome, Italy. a.deluca@css-mendel.it

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders in humans, affecting 1 in 3500 individuals. NF1 is a fully penetrant exhibiting a mutation rate some 10-fold higher compared to 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 NF1 gene, the presence of pseudogenes and the great variety of lesions. In the present study we attempted to delineate the NF1 mutational spectrum in the Italian population reporting four-year experience with the direct analysis of the whole NF1 coding region in 110 unrelated subjects affected by NF1. For each patient, the whole coding sequence and all splice sites were studied for mutations, either by the protein truncation test (PTT), or, most often, by denaturing high performance liquid chromatography (DHPLC). Mutations were identified in 75 (68%) patients. Twenty-two mutations were found to be novel. The detection rate for the different methods was 7/18 (39%) for PTT, and 68/103 (66%) for DHPLC. The mutations were evenly distributed along the NF1 coding sequence. Thirty-two of the 75 unrelated NF1 patients in which germline mutations were identified (32/75, 43%) harbour 23 different recurrent mutations. Fifteen sequence variants likely to represent non-pathogenic polymorphisms were observed at the NF1 locus. Genotype-phenotype analysis was unable to detect any obvious correlation.

    Human mutation 2004;23;6;629

  • NF1 gene analysis based on DHPLC.

    De Luca A, Buccino A, Gianni D, Mangino M, Giustini S, Richetta A, Divona L, Calvieri S, Mingarelli R and Dallapiccola B

    IRCCS-CSS, San Giovanni Rotondo and CSS-Mendel Institute, Rome, Italy.

    The high mutation rate at the NF1 locus results in a wide range of molecular abnormalities. The majority of these mutations are private and rare, generating elevated allelic diversity with a restricted number of recurrent mutations. In this study, we have assessed the efficacy of denaturing high-performance liquid chromatography (DHPLC), for detecting mutation in the NF1 gene. DHPLC is a fast and highly sensitive technique based on the detection of heteroduplexes in PCR products by ion pair reverse-phase HPLC under partially denaturing conditions. We established theoretical conditions for DHPLC analysis of all coding exons and splice junctions of the NF1 gene using the WAVEmaker software version 4.1.40 and screened for mutations a panel of 40 unrelated NF1 patients (25 sporadic and 15 familial), genetically uncharacterized. Disruptive mutations were identified in 29 individuals with an overall mutation detection rate of 72.5%. The mutations included eight deletions (exons 4b, 7, 10a, 14, 26, and 31), one insertion (exon 8), nine nonsense mutation (exons 10a, 13, 23.1, 27a, 29, 31, and 36), six missense mutations (exons 15, 16, 17, 24, and 31), four splice errors (exons 11, 14, 36, and 40) and a complex rearrangement within exon 16. Eighteen (62%) of the identified disruptive mutations are novel. Seven unclassified and three previously reported polymorphisms were also detected. None of the missense mutations identified in this study were found after screening of 150 controls. Our results suggest that DHPLC provides an accurate method for the rapid identification of NF1 mutations.

    Human mutation 2003;21;2;171-2

  • Identification and characterization of four novel large deletions in the human neurofibromatosis type 1 (NF1) gene.

    Fang LJ, Vidaud D, Vidaud M and Thirion JP

    Département de Microbiologie et d'Infectiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.

    We studied 20 unrelated NF1 patients by Southern blots with seven cDNA probes and loss of heterozygosity (LOH) analysis with four intragenic microsatellites (IVS26-2.3, IVS27AC28.4, IVS27AC33.1, and IVS38GT53.0). Four novel large deletions (178, 184, 236, and 237) have been identified and characterized. The breakpoint of deletion 178 was located in between exons 23-2 and 27b and the sequences downstream of the breakpoint were deleted. For deletion 184, the breakpoint was in between exons 27b and 29, and the region upstream of the breakpoint was deleted. With deletion 236, the breakpoint was in between exons 14 and 18 and the region downstream of the breakpoint was deleted. The breakpoint of deletion 237 was in between exons 38 and 45 and the sequences upstream of the breakpoint were deleted. These deletions were distributed randomly across the NF1 gene and no deletion hot spot was found. Our study suggests that the combination of analyses of loss of heterozygosity, southern blotting and southern blot densitometry can be used as a powerful method to detect large deletions, especially when family record is not available or the patient is a sporadic case.

    Human mutation 2001;18;6;549-50

  • A nonsense mutation at Arg-1947 in the NF1 gene in a case of neurofibromatosis type 1 in a Korean patient.

    Park KC, Choi HO, Park KH, Kim KH and Eun HC

    Department of Dermatology, Seoul National University College of Medicine, Chongno-gu, Korea. kcpark@medicine.snu.ac.kr

    We report a case of neurofibromatosis (NF) 1 presenting as a C-to-T transition changing an Arg-1947 codon to a stop codon. Because this mutation has been described in multiple Caucasian and Japanese families, the codon CGA for Arg-1947 in the NF1 gene is considered to be a hotspot for mutation in neurofibromatosis type 1 in all ethnic groups.

    Journal of human genetics 2000;45;2;84-5

  • Mutational and functional analysis of the neurofibromatosis type 1 (NF1) gene.

    Upadhyaya M, Osborn MJ, Maynard J, Kim MR, Tamanoi F and Cooper DN

    Institute of Medical Genetics, Heath Park, Cardiff, UK.

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders. It is caused by mutations in the NF1 gene which comprises 60 exons and is located on chromosome 17q. The NF1 gene product, neurofibromin, displays partial homology to GTPase-activating protein (GAP). The GAP-related domain (GRD), encoded by exons 20-27a, is the only region of neurofibromin to which a biological function has been ascribed. A total of 320 unrelated NF1 patients were screened for mutations in the GRD-encoding region of the NF1 gene. Sixteen different lesions in the NF1 GRD region were identified in a total of 20 patients. Of these lesions, 14 are novel and together comprise three missense, two nonsense and three splice site mutations plus six deletions of between 1 and 4 bp. The effect of one of the missense mutations (R1391S) was studied by in vitro expression of a site-directed mutant and GAP activity assay. The mutant protein, R1391S, was found to be some 300-fold less active than wild-type NF1 GRD. The mutations reported in this study therefore provide further material for the functional analysis of neurofibromin as well as an insight into the mutational spectrum of the NF1 GRD.

    Human genetics 1997;99;1;88-92

  • Characterisation of inherited and sporadic mutations in neurofibromatosis type-1.

    Purandare SM, Lanyon WG and Connor JM

    Duncan Guthrie Institute of Medical Genetics, University of Glasgow, Yorkhill, UK.

    Neurofibromatosis type-1 (NF-1) is an autosomal dominant disorder, caused by mutations in the NF-1 gene. Mutation analysis in the NF-1 gene is complicated by the large size of the gene, the high mutation rate, and the presence of pseudogenes. By means of the polymerase chain reaction, we have amplified 70% of the NF-1 coding sequence using reverse transcribed mRNA and genomic DNA from 25 unrelated Scottish Caucasian patients. We have used chemical mismatch cleavage analysis and direct sequencing of asymmetrically amplifed PCR products to characterise mutations within the NF-1 gene. Using the above strategy, we detected 10 novel mutations and an intragenic polymorphism with a heterozygosity of approximately 47% in the Scottish population. Of the 10 mutations, 7 are potentially disease causing. They include splice site errors responsible for exon skipping (1721 + 3A to G) and (5749 + 2T to G), small insertions (7485insGG) and (6519insG), a nonsense mutation (R2496X), and missense and silent mutations (G1166D, K1419R, G1404G, S1311S, N1776N). A correlation of the phenotype with the genotype is presented. Thus, in this study we have identified a heterogeneous group of germline mutations, the majority of which are predicted to cause disruption of the protein product, neurofibromin. This approach has therefore proved to be useful for the detection of mutations in the gene for neurofibromatosis type-1, and can be applied to detection of molecular pathologies in general.

    Human molecular genetics 1994;3;7;1109-15

  • Two NF1 mutations: frameshift in the GAP-related domain, and loss of two codons toward the 3' end of the gene.

    Abernathy CR, Colman SD, Kousseff BG and Wallace MR

    Department of Pediatrics, University of Florida, Gainesville 32610.

    Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders, and is due to mutations within the NF1 gene on chromosome 17q11.2. Only the middle 400 amino acids of the associated protein (neurofibromin) have a known function, comprising a GTPase-activating-protein (GAP) domain. The large gene size and the fact that approximately half of cases are due to new mutation render mutation analysis difficult. NF1 direct mutation characterization is important for development of DNA diagnostic procedures, analysis of phenotype/genotype correlations, and delineation of functions for specific domains of neurofibromin. We report two mutations detected using PCR amplification of individual exons followed by heteroduplex analysis. One is a single base deletion in exon 24 which is predicted to result in a protein truncated early in the GAP-related domain. The other is a 6-bp deletion in exon 39 which is predicted to result in loss of two amino acids in the mature protein near the carboxy-terminus. The exon 24 mutant allele was shown to be expressed by RNA PCR analysis. The exon 39 mutation suggests that those two amino acids are important in neurofibromin function, perhaps indicating a functional domain.

    Human mutation 1994;3;4;347-52

  • Tandem duplication within a neurofibromatosis type 1 (NF1) gene exon in a family with features of Watson syndrome and Noonan syndrome.

    Tassabehji M, Strachan T, Sharland M, Colley A, Donnai D, Harris R and Thakker N

    University Department of Medical Genetics, St. Mary's Hospital, Manchester, United Kingdom.

    Type 1 neurofibromatosis (NF1), Watson syndrome (WS), and Noonan syndrome (NS) show some overlap in clinical manifestations. In addition, WS has been shown to be linked to markers flanking the NF1 locus and a deletion at the NF1 locus demonstrated in a WS patient. This suggests either that WS and NF1 are allelic or that phenotypes arise from mutations in very closely linked genes. Here we provide evidence for the former by demonstrating a mutation in the NF1 gene in a family with features of both WS and NS. The mutation is an almost perfect in-frame tandem duplication of 42 bases in exon 28 of the NF1 gene. Unlike the mutations previously described in classical NF1, which show a preponderance of null alleles, the mutation in this family would be expected to result in a mutant neurofibromin product.

    Funded by: Wellcome Trust

    American journal of human genetics 1993;53;1;90-5

© G2C 2014. The Genes to Cognition Programme received funding from The Wellcome Trust and the EU FP7 Framework Programmes:
EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

Cookies Policy | Terms and Conditions. This site is hosted by Edinburgh University and the Genes to Cognition Programme.