Neurofibromatosis Type 1 Gene Research Articles

Muscular Impairment In Brazilian Adults With Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a genetic neurocutaneous disorder, autosomal dominant, with multisystemic manifestations, including a predisposition to tumor formation, bone dysplasias, neuromuscular and exercise capacity impairment and motor deficits, such as poor coordination, low muscle tone, and easy fatigability. Recent studies have illustrated a primary role for the NF1 gene product in muscle growth, strength and metabolism. PURPOSE: To evaluate body composition and muscle strength in Brazilian individuals with NF1. METHODS: 26 individuals with NF1 (14 male), aged 18-45 years, were compared to 26 controls, matched by sex, age, body mass index (BMI) and physical activity level. The following anthropometric parameters were measured: weight, height and waist circumference. Body composition was assessed by dual energy X-ray absorptiometry (DXA). The muscular strength was evaluated by the handgrip test using a dynamometer and presented as maximum muscle strength (Fmax) and per unit area (Farea). The physical activity level were evaluated by IPAQ short form. Statistical analyses used: Kolmogorov-Smirnov and T of Student paired. RESULTS: The mean age was 34.31 ± 6.05 and 32.92 ± 6.14 years old in the NF1 and control groups, respectively (p=0.316). Stature was lower in individuals with NF1 (1.61 ± 0.10 vs. 1.68 ± 0.08 meters, p=0.003). There were no differences in weight, BMI, waist circumference, fat mass, fat percentage and body fat index. Appendicular lean mass adjusted by BMI was lower in the NF1 group (0.743 ± 0.190 vs. 0.828 ± 0.161, p=0.048). Individuals with NF1 also presented reduction of Fmax (31.09 ± 12.20 vs. 37.47 ± 10.66 kg, p=0.035) and Farea (13.26 ± 4.17 vs. 15.62 ± 3.58 kg, p=0.028). CONCLUSION: The NF1 group in this study have lower lean mass adjusted for BMI and lower maximal muscle strength. It may indicate an early sarcopenia in this population, which requires further investigation about the mechanisms of these changes and the role of nutrition and exercise on these results. Supported by CAPES and FAPEMIG Grant (APQ-00928-11)

Pronounced maternal parent-of-origin bias for type-1 NF1 microdeletions.

Neurofibromatosis type 1 (NF1) is caused, in 4.7-11% of cases, by large deletions encompassing the NF1 gene and its flanking regions within 17q11.2. Different types of large NF1 deletion occur which are distinguishable by their breakpoint location and underlying mutational mechanism. Most common are the type-1 NF1 deletions of 1.4 Mb which exhibit recurrent breakpoints caused by nonallelic homologous recombination (NAHR), also termed unequal crossover. Here, we analyzed 37 unrelated families of patients with de novo type-1 NF1 deletions by means of short tandem repeat (STR) profiling to determine the parental origin of the deletions. We observed that 33 of the 37 type-1 deletions were of maternal origin (89.2% of cases; p < 0.0001). Analysis of the patients' siblings indicated that, in 14 informative cases, ten (71.4%) deletions resulted from interchromosomal unequal crossover during meiosis I. Our findings indicate a strong maternal parent-of-origin bias for type-1 NF1 deletions. A similarly pronounced maternal transmission bias has been reported for recurrent copy number variants (CNVs) within 16p11.2 associated with autism, but not so far for any other NAHR-mediated pathogenic CNVs. Region-specific genomic features are likely to be responsible for the maternal bias in the origin of both the 16p11.2 CNVs and type-1 NF1 deletions.

Insights into optic pathway glioma vision loss from mouse models of neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a common cancer predisposition syndrome caused by mutations in the NF1 gene. The NF1-encoded protein (neurofibromin) is an inhibitor of the oncoprotein RAS and controls cell growth and survival. Individuals with NF1 are prone to developing low-grade tumors of the optic nerves, chiasm, tracts, and radiations, termed optic pathway gliomas (OPGs), which can cause vision loss. A paucity of surgical tumor specimens and of patient-derived xenografts for investigative studies has limited our understanding of human NF1-associated OPG (NF1-OPG). However, mice genetically engineered to harbor Nf1 gene mutations develop optic gliomas that share many features of their human counterparts. These genetically engineered mouse (GEM) strains have provided important insights into the cellular and molecular determinants that underlie mouse Nf1 optic glioma development, maintenance, and associated vision loss, with relevance by extension to human NF1-OPG disease. Herein, we review our current understanding of NF1-OPG pathobiology and describe the mechanisms responsible for tumor initiation, growth, and associated vision loss in Nf1 GEM models. We also discuss how Nf1 GEM and other preclinical models can be deployed to identify and evaluate molecularly targeted therapies for OPG, particularly as they pertain to future strategies aimed at preventing or improving tumor-associated vision loss in children with NF1.

Clinical characteristics and NF1 gene mutation analysis of three successive generations in three different Indian families with neurofibromatosis type 1 and peripheral nerve sheath tumours

Neurofibromatosis type 1 (NF1) is a rare autosomal-dominant disorder caused by inactivation of NF1 tumour suppressor gene, which associates in the development of peripheral nerve tumours. NF1 is an important regulator of GAP and RAS proteins, mutations in NF1 results in the impairment in this function causing specific osseous lesions in any organ of the human body. In the present study, we investigated the clinical characteristics and NF1 gene mutation analysis of 3 unrelated Indian families with neurofibromatosis type 1. All the exons of NF1 gene was PCR amplified and sequenced. The structural and functional analysis was performed using molecular modelling tools. The sequence analysis of NF1 gene revealed; in family I five novel mutations p.R103K, p.D105N, p.M108I, p.L114M, p.E116X and p.A131S was observed in exon 4. In family II one missense p.A131S mutation and one silent p.L234L mutation was detected in exon 4. While, in family III one novel frame shift p.E225Rfs∗6 mutation was identified in exon 7 resulting in the truncated protein formation. Further, the structural analysis revealed all these mutations fall in the protein kinase C domain of NF1 gene causing loss of functional GRD and CSRD domains. In conclusion, novel mutations in the exon 4 and exon 7 of NF1 gene in these families correlating with genotype-phenotype characters explaining the neurofibromatosis type 1 and peripheral nerve sheath tumours condition in these patients.

Accurate Classification of NF1 Gene Variants in 84 Italian Patients with Neurofibromatosis Type 1.

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant genetic diseases. It is caused by mutations in the NF1 gene encoding for the large protein, neurofibromin. Genetic testing of NF1 is cumbersome because 50% of cases are sporadic, and there are no mutation hot spots. In addition, the most recognizable NF1 clinical features—café-au-lait (CALs) spots and axillary and/or inguinal freckling—appear early in childhood but are rather non-specific. Thus, the identification of causative variants is extremely important for early diagnosis, especially in paediatric patients. Here, we aimed to identify the underlying genetic defects in 72 index patients referred to our centre for NF1. Causative mutations were identified in 58 subjects, with 29 being novel changes. We evaluated missense and non-canonical splicing mutations with both protein and splicing prediction algorithms. The ratio of splicing mutations detected was higher than that reported in recent patients’ series and in the Human Gene Mutation Database (HGMD). After applying in silico predictive tools to 41 previously reported missense variants, we demonstrated that 46.3% of these putatively missense mutations were forecasted to alter splicing instead. Our data suggest that mutations affecting splicing can be frequently underscored if not analysed in depth. We confirm that hamartomas can be useful for diagnosing NF1 in children. Lisch nodules and cutaneous neurofibromas were more frequent in patients with frameshifting mutations. In conclusion, we demonstrated that comprehensive in silico analysis can be a highly specific method for predicting the nature of NF1 mutations and may help in assuring proper patient care.

Tranilast inhibits the expression of genes related to epithelial-mesenchymal transition and angiogenesis in neurofibromin-deficient cells

Neurofibromatosis type 1 (NF1) is caused by germline mutations in the NF1 gene and is characterized by café au lait spots and benign tumours known as neurofibromas. NF1 encodes the tumour suppressor protein neurofibromin, which negatively regulates the small GTPase Ras, with the constitutive activation of Ras signalling resulting from NF1 mutations being thought to underlie neurofibroma development. We previously showed that knockdown of neurofibromin triggers epithelial-mesenchymal transition (EMT) signalling and that such signalling is activated in NF1-associated neurofibromas. With the use of a cell-based drug screening assay, we have now identified the antiallergy drug tranilast (N-(3,4-dimethoxycinnamoyl) anthranilic acid) as an inhibitor of EMT and found that it attenuated the expression of mesenchymal markers and angiogenesis-related genes in NF1-mutated sNF96.2 cells and in neurofibroma cells from NF1 patients. Tranilast also suppressed the proliferation of neurofibromin-deficient cells in vitro more effectively than it did that of intact cells. In addition, tranilast inhibited sNF96.2 cell migration and proliferation in vivo. Knockdown of type III collagen (COL3A1) also suppressed the proliferation of neurofibroma cells, whereas expression of COL3A1 and SOX2 was increased in tranilast-resistant cells, suggesting that COL3A1 and the transcription factor SOX2 might contribute to the development of tranilast resistance.

Neurofibromin (NF1) genetic variant structure-function analyses using a full-length mouse cDNA.

Neurofibromatosis type 1 (NF1) is caused by pathogenic variants or mutations in the NF1 gene that encodes neurofibromin. We describe here a new approach to determining the functional consequences of NF1 genetic variants. We established a heterologous cell culture expression system using a full-length mouse Nf1 cDNA (mNf1) and human cell lines. We demonstrate that the full-length murine cDNA produces a>250kDa neurofibromin protein that is capable of modulating Ras signaling. We created mutant cDNAs representing NF1 patient variants with different clinically relevant phenotypes, and assessed their ability to produce mature neurofibromin and restore Nf1 activity in NF1-/- cells. These cDNAs represent variants in multiple protein domains and various types of clinically relevant predicted variants. This approach will help advance research on neurofibromin structure and function, determine pathogenicity for missense variants, and allow for the development of activity assays and variant-directed therapeutics.

Clinical and molecular characterization of 112 single-center patients with Neurofibromatosis type 1

BackgroundThe aim of this retrospective study was to define clinical and molecular characteristics of a large sample of neurofibromatosis type 1 (NF1) patients, as well as to evaluate mutational spectrum and genotype-phenotype correlation. NF1 is a relatively common neurogenetic disorder (1:2500–1:3000 individuals). It is caused by mutations of the NF1 gene on chromosome 17ql1.2, with autosomal dominant pattern of inheritance and wide phenotypical variability. Café-au-lait spots (CALs), cutaneous and/or subcutaneous neurofibromas (CNFs/SCNFs), skinfold freckling, skeletal abnormalities, Lisch nodules of the iris and increased risk of learning and intellectual disabilities, as well as tumors of the nervous system and other organs are its main clinical features.MethodsThe preliminary group collected 168 subjects with clinical suspicion of NF1. They were evaluated following the National Institutes of Health (NIH) criteria for NF1, revised by Gutmann et al. 1997, integrated for 67 of them by molecular testing. According to these references, 112 of 168 patients were diagnosed as NF1. The sample was characterized by an equal sex ratio (57 males, 55 females) and age distribution ranging from 10 days to 60 years of age (mean age, 13 years).ResultsA wide spectrum of clinical features has been observed in our patients. Mutational analysis resulted positive in 51 cases (76%). Twenty-four mutations detected in our cohort have not been reported to date.ConclusionsThis study may contribute to a better definition of genotypic and phenotypic features of NF1 patients, with respect to further insights into the clinical characterization of the disease. In addition, an amplification of the spectrum of mutations in the NF1 gene has been documented.

Analysis of YAP1 and TAZ expression by immunohistochemical staining in malignant mesothelioma and reactive mesothelial cells.

Gene mutations are involved in the development of malignant mesothelioma. Important mutations have been identified in the genes for cyclin-dependent kinase inhibitor 2A (p16) alternative reading frame, breast cancer-associated protein 1 (BAP1) and neurofibromatosis type 2 (NF2). Previously, the utility of detecting the loss of BAP1 by immunohistochemistry (IHC) and p16-deletion by fluorescence in situ hybridization has been identified in several studies. However, NF2-associated examinations have not been performed. The present study aimed to evaluate the expression of yes-associated protein 1 (YAP1) and tafazzin (TAZ) protein, which are associated with NF2 gene mutations, in malignant mesothelioma (MM) and reactive mesothelial cells (RMCs). Formalin-fixed paraffin-embedded tissues from 31 MM and 33 RMC samples were analyzed. The expression of YAP1 and TAZ protein were examined by IHC. Positivity for YAP1 was identified 27/31 MM and 15/33 RMC samples. Positivity for TAZ was identified in 28/31 MM and 18/33 RMC samples. Using the optimal cutoff points determined by the receiver operating characteristic curve, a positive IHC result for YAP1 and TAZ was 74% sensitive and 94% specific for detecting MM. The results indicate that increased expression of YAP1 and TAZ may be associated with mesothelial tumorization, and aid in the diagnosis of MM.

Heightened CXCR4 and CXCL12 expression in NF1-associated neurofibromas.

Neurofibromatosis type 1 (NF1) is a common autosomal dominantly inherited disorder that affects both the skin and the nervous system. NF1 occurs due to the mutations in the NF1 gene. Neurofibromas are the most common Schwann cell-based tumors in NF1 patients, which are mainly categorized into dermal and plexiform neurofibromas. Studies on different tumor types demonstrate that CXCR4 expression increases in tumor tissues and is linked to metastasis and cancer progression. In the present study, we aimed to analyze the gene expression of CXCR4, and its ligand CXCL12, in human neurofibromas. Eight NF1 patients aged between 5 and 37 (2 males, 6 females) were selected. The patient group comprised 1 plexiform neurofibroma, 1 pheochromocytoma, and 6 dermal neurofibromas. Following pathological examination and diagnosis, tumors were co-stained with antibodies against Schwann cell marker S100 and target molecule CXCR4. CXCR4 expression in Schwann cell-based tumors was detected at the protein level. RNA isolated from the same tumors was used for RT-PCR-based studies to measure the quantitative expression of CXCR4 and CXCL12. CXCR4 gene expression increased 3- to 120-fold and CXCL12 gene expression increased 33- to 512-fold in all human Schwann cell-based tumors. In order to validate the role of CXCR4 and its relationship with CXCL12 in NF1, future studies should be performed with additional tumors and different tumor types.

Targeted next-generation sequencing for differential diagnosis of neurofibromatosis type 2, schwannomatosis, and meningiomatosis.

Clinical overlap between neurofibromatosis type 2 (NF2), schwannomatosis, and meningiomatosis can make clinical diagnosis difficult. Hence, molecular investigation of germline and tumor tissues may improve the diagnosis. We present the targeted next-generation sequencing (NGS) of NF2, SMARCB1, LZTR1, SMARCE1, and SUFU tumor suppressor genes, using an amplicon-based approach. We analyzed blood DNA from a cohort of 196 patients, including patients with NF2 (N = 79), schwannomatosis (N = 40), meningiomatosis (N = 12), and no clearly established diagnosis (N = 65). Matched tumor DNA was analyzed when available. Forty-seven NF2-/SMARCB1-negative schwannomatosis patients and 27 NF2-negative meningiomatosis patients were also evaluated. A NF2 variant was found in 41/79 (52%) NF2 patients. SMARCB1 or LZTR1 variants were identified in 5/40 (12.5%) and 13/40 (∼32%) patients in the schwannomatosis cohort. Potentially pathogenic variants were found in 12/65 (18.5%) patients with no clearly established diagnosis. A LZTR1 variant was identified in 16/47 (34%) NF2/SMARCB1-negative schwannomatosis patients. A SMARCE1 variant was found in 3/39 (∼8%) meningiomatosis patients. No SUFU variant was found in the cohort. NGS was an effective and sensitive method to detect mutant alleles in blood or tumor DNA of mosaic NF2 patients. Interestingly, we identified a 4-hit mechanism resulting in the complete NF2 loss-of-function combined with SMARCB1 and LZTR1 haploinsufficiency in two-thirds of tumors from NF2 patients. Simultaneous investigation of NF2, SMARCB1, LZTR1, and SMARCE1 is a key element in the differential diagnosis of NF2, schwannomatosis, and meningiomatosis. The targeted NGS strategy is suitable for the identification of NF2 mosaicism in blood and for the investigation of tumors from these patients.

The investigation for potential modifier genes in patients with neurofibromatosis type 1 based on next-generation sequencing.

IntroductionNeurofibromatosis type 1 (NF1) is a common Mendelian multi-system disorder that is characterized by café-au-lait spots (CLS), axillary freckling, optic glioma and plexiform neurofibroma. Various mutations of the NF1 gene are widely accepted to be the main cause of this disease, while whether there are still certain other modifier genes that could influence the phenotypes of NF1 is our concern.Patients and MethodsOne proband and his father are involved, who are characterized by plexiform neurofibroma and cutaneous neurofibroma, respectively. Enhanced Computed tomography (CT) and Positron emission tomography-CT (PET-CT) were taken to collect the radiographic data, and the specimens of this neurofibroma as well as the blood samples from the father and son were sent for panel mutation screening of 295 tumor-related genes based on next-generation screening. Furthermore, the NF1 gene mutations were referred with Canis lupus familiaris, Rattus norvegicus, Gallus gallus, Danio rerio, and Drosophila melanogaster NF1 sequencing for evolutionary conservativeness and then analyzed in Condel databases for pathogenicity prediction.ResultsThe radiography indicated that the benign plexiform neurofibroma only occurred in the son. Also, TP53, FANCA, BCL6, PIK3C2G, RNF43, FGFR4, FLT3, ERBB2, PAK7, NSD1, MEN1 and TSC1 were uniquely found mutated in the son, which could be candidates as new modifier genes; besides, RNF43 was also mutated in public neurofibroma seuquencing data. By KEGG pathway annotation, phosphoinositide-3-kinase-Akt pathway was altered in both the public plexiform neurofibroma sample and in our proband patient.ConclusionThis study reexamined the background germline mutations and suggested their potential value as modifier genes that may influence the phenotype heterogenity.

Three Novel NF1 Gene Mutations in a Cohort of Bulgarian Neurofibromatoses Patients

Neurofibromatosis (NF) is a clinically heterogeneous autosomal dominant disorder. Three distinct forms have been identified: neurofibromatosis type 1 (NF1), type 2 (NF2) and schwannomatosis. In the present study, we report clinical and genetic findings in the NF1 and NF2 genes in a cohort of 27 Bulgarian patients, with 18 cases (67%) genetically verified. Both NF1 and NF2 genes were screened by Sanger sequencing on DNA samples. The Sanger negative samples were screened by Multiplex Ligation-dependent Probe Amplification (MLPA) for deletions and duplications. The results from genetic testing revealed three novel mutations and fifteen previously reported ones (13 in the NF1 gene and 2 in the NF2 gene). The novel variants in the NF1 gene are a splice site mutation c.4725-1G>A, a small deletion of five bases c.823delATCTT, p.Leu275ValfsTer14, and a single base duplication c.6547dupC, p.Arg2183ProfsTer11. The novel splice site mutation is manifested by multiple “cafe au lait” macules and neurofibromas. Both novel out of frame mutations were found in patients with multiple “cafe au lait” spots and focal epilepsy. A segmental neurofibromatosis (SNF1) is restricted to one or more body segments. Here we present a case with SNF1 caused by a somatic deletion of exons 1 to 12 of the NF1 gene which is manifested by multiple neurofibromas in the right hand. Two nonsense mutations are found in the NF2 gene. Our study adds three novel mutations to the NF1 mutation spectra and contributes to the clinical-genetic NF1-characterization. Here we report strikingly different phenotypic spectra caused by the same mutation in a single family. Our findings contribute to the genotype- phenotype correlations which are difficult to establish, due to the extremely complex NF phenotype being a combination of clinical features.

Possible Implication of RNF135 in High Type 1 Neurofibromatosis Tumoral Risk

Background: Recurrent type 1 and 2 microdeletions of NF1 (neurofibromatosis, type 1) gene leads to a more severe phenotype than heterozygous point mutations. The associated deletion of RNF135 (Ring Finger protein 135), a flanking NF1 gene, is known to be responsible for the childhood overgrowth syndrome but its implication in tumoral severity has never been proven.Methods and Results: A Single Nucleotide Polymorphisms array (715K) was performed in a patient with a very severe form of type 1 neurofibromatosis, as revealed by massive cervico-mediastinal plexiform neurofibromas. It showed a small 126kb atypical deletion encompassing only RNF135 and the first exon of NF1.Conclusion: This observation highlights the possible role of RNF135 in tumoral severity in type 1 neurofibromatosis caused by recurrent type 1 and type 2 microdeletions.

Whole-exome sequencing of duodenal neuroendocrine tumors in patients with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a hereditary cancer predisposition syndrome characterized by frequent cutaneous and nervous system abnormalities. Patients with NF1 also have an increased prevalence of multiple gastrointestinal and peripancreatic neoplasms—neuroendocrine tumors of the ampulla that express somatostatin are particularly characteristic of NF1. In this study, we characterize the genetic alterations of a clinically well-characterized cohort of six NF1-associated duodenal neuroendocrine tumors using whole-exome sequencing. We identified inactivating somatic mutations in the NF1 gene in three of six tumors; the only other gene altered in more than one tumor was IFNB1. Copy number analysis revealed deletion/loss of heterozygosity of chromosome 22 in three of six patients. Analysis of germline variants revealed germline deleterious NF1 variants in four of six patients, as well as deleterious variants in other tumor suppressor genes in two of four patients with deleterious NF1 variants. Taken together, these data confirm the importance of somatic inactivation of the wild-type NF1 allele in the formation of NF1-associated duodenal neuroendocrine tumors and suggest that loss of chromosome 22 is important in at least a subset of cases. However, we did not identify any genes altered in the majority of NF1-associated duodenal neuroendocrine tumors that uniquely characterize the genomic landscape of this tumor. Still, the genetic alterations in these tumors are distinct from sporadic neuroendocrine tumors occurring at these sites, highlighting that unique genetic alterations drive syndromic tumors.

Neurofibromatosis type 1 as a model system to study molecular mechanisms of autism spectrum disorder symptoms.

Neurofibromatosis type 1 (NF1) is monogenic neurodevelopmental disorder caused by mutation of NF1 gene, which leads to increased susceptibility to various tumors formations. Additionally, majority of patients with NF1 are experience high incidence of cognitive deficits. Particularly, we review the growing number of reports demonstrated a higher incidence of autism spectrum disorder (ASD) in individuals with NF1. In this review we also discuss face validity of preclinical Nf1 mouse models. Then we describe discoveries from these animal models that have uncovered the deficiencies in the regulation of Ras and other intracellular pathways as critical mechanisms underlying the Nf1 cognitive problems. We also summarize and interpret recent preclinical and clinical studies that point toward potential pharmacological therapies for NF1 patients.

Optic Pathway Gliomas in Neurofibromatosis Type 1.

Neurofibromatosis type 1 (NF1) is one of the most common brain tumor predisposition syndromes, in which affected children are prone to the development of low-grade gliomas. While NF1-associated gliomas can be found in several brain regions, the majority arise in the optic nerves, chiasm, tracts, and radiations (optic pathway gliomas; OPGs). Owing to their location, 35-50% of affected children present with reduced visual acuity. Unfortunately, despite tumor stabilization following chemotherapy, vision does not improve in most children. For this reasons, more effective therapies are being sought that reflect a deeper understanding of the NF1 gene and the use of authenticated Nf1 genetically-engineered mouse strains. The implementation of these models for drug discovery and validation has galvanized molecularly-targeted clinical trials in children with NF1-OPG. Future research focused on defining the cellular and molecular factors that underlie optic glioma development and progression also has the potential to provide personalized risk assessment strategies for this pediatric population.

Clinical findings and mutation analysis of NF1 patients in Turkey

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease that is caused by mutations of the NF1 gene. NF1 is clinically characterized by neurofibromas, pigmentation anomalies, and an increased risk of malignant tumors. The mutation rate of NF1 is one of the highest known for human disorders: approximately 50% of all affected individuals are sporadic cases and carry de novo mutations Therefore mutation analysis of NF1 may be an important tool in early diagnosis and genetic counseling. This is the first large NF1 study performed in Turkey. The data collected in this study enabled us to overview the genetic and clinical aspects of NF1 molecular diagnostics. The patients, who were clinically diagnosed for NF1, were included in this study. These patients were clinically evaluated, and subgroup of them genotyped or DNA sequenced for mutations in NF1, either to confirm the clinical diagnosis or to identify pathogenic mutations. The mutation detection rate was 52%, based on analysis of only genomic DNA. We observed that frameshift mutations were the largest proportion of the identified mutations (38.5%). The frequency of microdeletions was 26.9% and the splice site and nonsense mutations were 11.5% in this cohort. Turkish NF1 patients have similar NF1 germline mutations compared to other populations. Considering that some of these detected mutations belonged to the patients who did not fulfill the NIH criteria for NF1 diagnosis, mutation analysis of NF1 is an important tool in early diagnosis and genetic counseling.

The effect of estradiol, testosterone, and human chorionic gonadotropin on the proliferation of Schwann cells with NF1 +/- or NF1 -/- genotype derived from human cutaneous neurofibromas.

Dermal neurofibromas are the hallmarks of neurofibromatosis type 1 (NF1). Neurofibromas harbor Schwann cells with two different genotypes: Schwann cells which carry the germline mutation and a healthy NF1 allele (NF1 +/-), and a subpopulation of Schwann cells which harbor the so-called second hit leading to inactivation of both NF1 alleles (NF1 -/-). The second hit in the NF1 gene of Schwann cells is considered to be the initial step in the development of neurofibromas. Dermal neurofibromas typically start to grow in puberty, and their number and size increase during pregnancy, indicating hormone responsiveness. This is the first study to address the effect of human chorionic gonadotropin (hCG) on the proliferation of human NF1 +/- and NF1 -/- Schwann cells in vitro. In addition, the effects of estradiol and testosterone were also investigated. The results showed that NF1 -/- Schwann cells were more sensitive to estradiol, testosterone, and human chorionic gonadotropin than NF1 +/- cells. Specifically, the proliferation of NF1 -/- Schwann cells was increased by up to 99, 110, and 170% compared to vehicle control when treated with estradiol, testosterone, and hCG, respectively. Interestingly, no effect of estradiol, testosterone, or hCG on the proliferation of the cells with NF1 +/- genotype was observed. To conclude, the somatic second hit in the NF1 gene sensitizes Schwann cells to sex hormones resulting in a highly increased proliferation. Our results highlight the significance of sex hormones in the regulation of neurofibroma growth.

The effect of parental age on NF1 patients in Turkey.

Neurofibromatosis type 1 (NF1) is the most common neurogenetic disorder worldwide, and its clinical presentations are highly variable. NF1 is caused by mutations in the NF1 gene, and 50% of NF1 cases are sporadic, which occur in the absence of a family history of the disease and usually result from a new mutation in the germline of a parent. Advanced paternal age may increase the risk for germinal NF1 mutations; however, some dominant conditions, including neurofibromatosis, have shown a lesser association with paternal age, although there are conflicting reports in the literature. We investigated the effects of paternal and maternal age in 241 NF1 patients (121 sporadic and 120 familial cases) who were seen in Hacettepe hospital, a reference center for genetic diseases in Turkey. For statistical analysis, Spearman's and Chi-square tests were used. In this study, we evaluated paternal and maternal age at birth in sporadic and familial cases of NF1. We also compared the effect of parental age on the appearance and coexistence of various NF1 symptoms. There were no significant statistical differences between paternal age and coexistence of the NF1 symptoms. However, a slightly negative correlation was observed between paternal age and the coexistence of NF1 symptoms in familial cases (p < 0.05). We did not find strong evidence for the effect of parental age on the clinical severity of NF1.