Neurofibromatosis Type 1 Phenotype Research Articles

Mutation analysis and clinical profile of South African patients with Neurofibromatosis type 1 (NF1) phenotype.

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic condition with complete age-dependent penetrance, variable expressivity and a global prevalence of ∼1/3,000. It is characteriszed by numerous café-au-lait macules, skin freckling in the inguinal or axillary regions, Lisch nodules of the iris, optic gliomas, neurofibromas, and tumour predisposition. The diagnostic testing strategy for NF1 includes testing for DNA single nucleotide variants (SNVs), copy number variants (CNVs) as well as RNA analysis for deep intronic and splice variants, which can cumulatively identify the causative variant in 95% of patients. In the present study, NF1 patients were screened using a next-generation sequencing (NGS) assay targeting NF1 exons and intron/exon boundaries for SNV and NF1 multiple ligation-dependent probe amplification (MLPA) analysis for CNV detection. Twenty-six unrelated Southern African patients clinically suspected of having NF1, based on the clinical diagnostic criteria developed by the National Institute of Health (NIH), were included in the current study. A detection rate of 58% (15/26) was obtained, with SNVs identified in 80% (12/15) using a targeted gene panel and NF1 gene deletion in 20% (3/15) identified using MLPA. Ten patients (38%) had no variants identified, although they met NF1 diagnostic criteria. One VUS was identified in this study in a patient that met NF1 diagnostic criteria, however there was no sufficient information to classify variant as pathogenic. The clinical features of Southern African patients with NF1 are similar to that of the known NF1 phenotype, with the exception of a lower frequency of plexiform neurofibromas and a higher frequency of developmental/intellectual disability compared to other cohorts. This is the first clinical and molecular characterisation of a Southern African ancestry NF1 cohort using both next-generation sequencing and MLPA analysis. A significant number of patients remained without a diagnosis following DNA-level testing. The current study offers a potential molecular testing strategy for our low resource environment that could benefit a significant proportion of patients who previously only received a clinical diagnosis without molecular confirmation.

Written language achievement in children and adolescents with neurofibromatosis type 1 and Plexiform Neurofibromas

ABSTRACT Neurofibromatosis type 1 (NF1) is associated with below average writing achievement. However, little is known about specific aspects of written language impacted by NF1, changes in writing over time, and associations between cognitive aspects of the NF1 phenotype and writing. At three timepoints over six years, children with NF1 and plexiform neurofibromas (PNs) completed Woodcock-Johnson tests of writing mechanics (Spelling, Punctuation & Capitalization, handwriting), written expression of ideas (Writing Samples), writing speed (Writing Fluency), and tests of general cognitive ability, executive function, memory, and attention. Children (N = 76, mean age = 12.8 ± 3.4 years) completed at least one baseline writing subtest. Overall writing scores were in the Average range (M = 93.4, SD = 17.4), but lower than population norms (p = 0.002). Scores were highest on Writing Samples (M = 95.2, SD = 17.3), and lowest for Punctuation & Capitalization (M = 87.9, SD = 18.8, p = 0.034). Writing scores were mostly stable over time. Nonverbal reasoning was related to some tests of writing mechanics and written expression of ideas. Short-term memory and inattention explained additional variance in Writing Samples and Spelling. Poor handwriting was associated with writing content beyond the impact of cognitive factors. Children with NF1 and PNs may benefit from early screening and writing support. Interventions should address the contribution of both cognitive and handwriting difficulties in written language.

Genotype-phenotype correlations of neurofibromatosis type 1: a cross-sectional study from a large Chinese cohort.

Neurofibromatosis type 1 (NF1) is a highly heterogeneous autosomal genetic disorder characterized by a broad spectrum of clinical and molecular manifestations. The correlations between genotype and phenotype in NF1 remain elusive. This study aimed to elucidate genotype-phenotype associations in a large Chinese cohort of NF1 patients. We included NF1 patients from our center who underwent genetic testing for NF1 variants and systemic examination. Genotype-phenotype correlation analyses were performed, focusing on variation types and involved neurofibromin domains. A total of 195 patients were enrolled, comprising 105 males and 90 females, with a median age of 18years. Truncating variants, single amino acid variations, and splicing variants accounted for 139/195 (71.3%), 23/195 (11.8%), and 33/195 (16.9%), respectively. Patients with splicing variants exhibited a significantly higher prevalence of spinal plexiform neurofibromas (spinal PNF) than those with truncating variants (76.4% vs. 51.8%; p = 0.022). Variations affecting the PKC domain were associated with higher rates of cutaneous neurofibromas (CNF) (100% vs. 64.9%, p < 0.001), Lisch nodules (100% vs. 61.2%, p < 0.001), plexiform neurofibromas (PNF) (100% vs. 95.7%, p = 0.009), and psychiatric disorders (11.8% vs. 1.6%, p = 0.042). Patients with mutations in the CSRD had an elevated risk of secondary primary malignancies (11.6% vs. 2.8%, p = 0.015). GRD involvement might enhance the risk of Lisch nodules (76.9% vs. 53.7%, p = 0.044). Variations in the Sec14-PH domain were correlated with a higher rate of CNF (76.8% vs. 58.6%, p = 0.014). Additionally, we found that the p.R1748* variants carry a high risk of malignancy. Our study suggested some novel genotype-phenotype correlations within a Chinese cohort, providing innovative insights into this complex field that may contribute to genetic counseling, risk stratification, and clinical management for the NF1 population.

Vitamin D and Bone Metabolism in Adult Patients with Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a genetic multisystemic autosomal dominant disorder determining reduced life expectancy due to higher risk of developing benign and malignant tumors. Low levels of vitamin D and reduced bone mineral density (BMD) have been reported in young patients with NF1. However, correlation between vitamin D and NF1 phenotype needs to be elucidated. Aim of this study was to assess vitamin D levels and bone metabolism in NF1 patients, analyzing potential correlations with clinical phenotype. A cross-sectional study was carried out in a monocentric series of NF1 patients, evaluating genotype, clinical phenotype, BMD, biochemical evaluation with focus on serum 25OH-vitamin D, parathyroid hormone (PTH), calcium and phosphate levels. Correlations between clinical manifestations, neurofibromas, and vitamin D status have been studied in comparison with healthy controls. 31 NF1 adult patients were matched for sex, age and body mass index with 31 healthy controls. A significantly difference in vitamin D level emerged in NF1 patients compared to controls. Interestingly low vitamin D levels correlated with a more aggressive phenotype and with a bigger size of neurofibromas. These data underline that vitamin D deficiency/insufficiency may play a role in clinical severity of neurofibromas in patients with NF1, suggesting the need to check bone status and replace vitamin D in these patients.

Loss of NF1 in Drosophila Larvae Causes Tactile Hypersensitivity and Impaired Synaptic Transmission at the Neuromuscular Junction.

Autism spectrum disorder (ASD) is a neurodevelopmental condition in which the mechanisms underlying its core symptomatology are largely unknown. Studying animal models of monogenic syndromes associated with ASD, such as neurofibromatosis type 1 (NF1), can offer insights into its etiology. Here, we show that loss of function of the Drosophila NF1 ortholog results in tactile hypersensitivity following brief mechanical stimulation in the larva (mixed sexes), paralleling the sensory abnormalities observed in individuals with ASD. Mutant larvae also exhibit synaptic transmission deficits at the glutamatergic neuromuscular junction (NMJ), with increased spontaneous but reduced evoked release. While the latter is homeostatically compensated for by a postsynaptic increase in input resistance, the former is consistent with neuronal hyperexcitability. Indeed, diminished expression of NF1 specifically within central cholinergic neurons induces both excessive neuronal firing and tactile hypersensitivity, suggesting the two may be linked. Furthermore, both impaired synaptic transmission and behavioral deficits are fully rescued via knock-down of Ras proteins. These findings validate NF1 -/- Drosophila as a tractable model of ASD with the potential to elucidate important pathophysiological mechanisms.SIGNIFICANCE STATEMENT Autism spectrum disorder (ASD) affects 1-2% of the overall population and can considerably impact an individual's quality of life. However, there are currently no treatments available for its core symptoms, largely because of a poor understanding of the underlying mechanisms involved. Examining how loss of function of the ASD-associated NF1 gene affects behavior and physiology in Drosophila may shed light on this. In this study, we identify a novel, ASD-relevant behavioral phenotype in NF1 -/- larvae, namely an enhanced response to mechanical stimulation, which is associated with Ras-dependent synaptic transmission deficits indicative of neuronal hyperexcitability. Such insights support the use of Drosophila neurofibromatosis type 1 (NF1) models in ASD research and may provide outputs for genetic or pharmacological screens in future studies.

Contribution of whole genome sequencing in the molecular diagnosis of mosaic partial deletion of the NF1 gene in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease with complete penetrance but highly variable expressivity. In most patients, Next Generation Sequencing (NGS) technologies allow the identification of a loss-of-function pathogenic variant in the NF1 gene, a negative regulator of the RAS-MAPK pathway. We describe the 5-year diagnosis wandering of a patient with a clear NF1 clinical diagnosis, but no molecular diagnosis using standard molecular technologies. The patient presented with a typical NF1 phenotype but NF1 targeted NGS, NF1 transcript analysis, MLPA, and array comparative genomic hybridization failed to reveal a genetic aberration. After 5years of unsuccessful investigations, trio WGS finally identified a de novo mosaic (VAF ~ 14%) 24.6kb germline deletion encompassing the promoter and first exon of NF1. This case report illustrates the relevance of WGS to detect structural variants including copy number variants that would be missed by alternative approaches. The identification of the causal pathogenic variant allowed a tailored genetic counseling with a targeted non-invasive prenatal diagnosis by detecting the deletion in plasmatic cell-free DNA from the proband's pregnant partner. This report clearly highlights the need to make WGS a clinically accessible test, offering a tremendous opportunity to identify a molecular diagnosis for otherwise unsolved cases.

Intragenic inversions in NF1 gene as pathogenic mechanism in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1), an autosomal dominant disorder characterized by skin pigmentary lesions and multiple cutaneous neurofibromas, is caused by neurofibromin 1 (NF1) loss of function variants. Currently, a molecular diagnosis is frequently established using a multistep protocol based on cDNA and gDNA sequence analysis and/or Multiplex Ligation-dependent Probe Amplification (MLPA) assay on genomic DNA, providing an overall detection rate of about 95-97%. The small proportion of clinically diagnosed patients, which at present do not obtain a molecular confirmation likely are mosaic, as their pathogenic variant may remain undetected due to low sensitivity of low coverage NGS approaches, or they may carry a type of pathogenic variant refractory to currently used technologies. Here, we report two unrelated patients presenting with two different inversions that disrupt the NF1 coding sequence, resulting in an NF1 phenotype. In one subject, the inversion was associated with microdeletions spanning a few NF1 exons at both breakpoints, while in the other the rearrangement did not cause exon loss, thus testing negative by MLPA assay. Considering the high proportion of repeated regions within the NF1 sequence, we propose that intragenic structural rearrangements should be considered as possible pathogenic mechanisms in patients fulfilling the NIH diagnostic criteria of NF1 but lacking of molecular confirmation and in patients with NF1 intragenic microdeletions.

Genotype-Phenotype Correlations in Neurofibromatosis Type 1: Identification of Novel and Recurrent NF1 Gene Variants and Correlations with Neurocognitive Phenotype.

Neurofibromatosis type 1 (NF1) is one of the most common genetic tumor predisposition syndrome, caused by mutations in the NF1. To date, few genotype-phenotype correlations have been discerned in NF1, due to a highly variable clinical presentation. We aimed to study the molecular spectrum of NF1 and genotype-phenotype correlations in a monocentric study cohort of 85 NF1 patients (20 relatives, 65 sporadic cases). Clinical data were collected at the time of the mutation analysis and reviewed for accuracy in this investigation. An internal phenotypic categorization was applied. The 94% of the patients enrolled showed a severe phenotype with at least one systemic complication and a wide range of associated malignancies. Spine deformities were the most common complications in this cohort. We also reported 66 different NF1 mutations, of which 7 are novel mutations. Correlation analysis identified a slight significant inverse correlation between age at diagnosis and delayed acquisition of psychomotor skills with residual multi-domain cognitive impairment. Odds ratio with 95% confidence interval showed a higher prevalence of learning disabilities in patients carrying frameshift mutations. Overall, our results aim to offer an interesting contribution to studies on the genotype–phenotype of NF1 and in genetic management and counselling.

Therapeutic Vulnerability to ATR Inhibition in Concurrent NF1 and ATRX-Deficient/ALT-Positive High-Grade Solid Tumors

Simple SummaryTumors of the brain and nerves develop frequently in patients with neurofibromatosis type 1. Many are benign growths, such as pilocytic astrocytomas in the brain and neurofibromas in the nerves. However, in some patients, the tumors become malignant and may cause local damage, disseminate to distant sites and result in death. We studied changes in the levels of chromatin proteins and changes in telomeres, in cells obtained from mouse gliomas that are deficient in neurofibromin as well as excess brain and nerve tumor tissue from patients with neurofibromatosis type 1 or sporadic tumors lacking neurofibromin expression. A decrease in the levels of these proteins in experimental cell lines resulted in susceptibility to a class of specific drugs knowns as ATR inhibitors, which may represent a specific vulnerability of these tumor subgroups. We expect our data to provide the required rationale for the development of more accurate animal models to study neurofibromatosis, as well as specific molecularly based drugs for treatment as alternatives to the current, often devastating approaches of surgery, radiation, and chemotherapy.Subsets of Neurofibromatosis Type 1 (NF1)-associated solid tumors have been shown to display high frequencies of ATRX mutations and the presence of alternative lengthening of telomeres (ALT). We studied the phenotype of combined NF1 and ATRX deficiency in malignant solid tumors. Cell lines derived from NF1-deficient sporadic glioblastomas (U251, SF188), an NF1-associated ATRX mutant glioblastoma cell line (JHH-NF1-GBM1), an NF1-derived sarcoma cell line (JHH-CRC65), and two NF1-deficient MPNST cell lines (ST88-14, NF90.8) were utilized. Cancer cells were treated with ATR inhibitors, with or without a MEK inhibitor or temozolomide. In contrast to the glioma cell line SF188, combined ATRX knockout (KO) and TERC KO led to ALT-like properties and sensitized U251 glioma cells to ATR inhibition in vitro and in vivo. In addition, ATR inhibitors sensitized U251 cells to temozolomide, but not MEK inhibition, irrespective of ATRX level manipulation; whereas, the JHH-NF1-GBM1 cell line demonstrated sensitivity to ATR inhibition, but not temozolomide. Similar effects were noted using the MPNST cell line NF90.8 after combined ATRX knockdown and TERC KO; however, not in ST88-14. Taken together, our study supports the feasibility of targeting the ATR pathway in subsets of NF1-deficient and associated tumors.

Rationale for haploinsufficiency correction therapy in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a genetic disorder with a wide range of manifestations and severity. Currently, the few available NF1 treatments target specific manifestations, with no available therapies targeted to correct the underlying driver of all NF1 manifestations. Evidence supports that haploinsufficiency in NF1 caused by a decreased amount of wild-type (WT) neurofibromin in all Nf1+/- cells directly causes or facilitates a range of NF1 manifestations. Consequently, NF1 haploinsufficiency correction therapy (NF1-HCT) represents a potentially effective approach to treat some NF1 manifestations. NF1-HCT would normalize the level of WT neurofibromin in all NF1-haploinsufficient cells, including those integral to the NF1 phenotype such as Schwann cells (SCs), melanocytes, neurons, bone cells, and cells of the tumor microenvironment. This would correct altered cellular signaling pathways and, in turn, restore normal function to cells with a retained WT allele. NF1-HCT will not restore WT neurofibromin in NF1-/- cells; however, by restoring function in the surrounding Nf1+/- microenvironment cells, NF1-HCT is predicted to have a beneficial effect on NF1-/- cells. NF1-HCT is expected to have a clinical effect in some NF1 manifestations, as follows: (i) prevention, or delay of onset, of potential manifestations; and (ii) reversal, or halting/slowing progression, of established manifestations. This review describes the rationale for NF1-HCT, including specific NF1 considerations (e.g., NF1 clinical phenotype, neurofibromin function/regulation, NF1 mutational spectrum, genotype-phenotype correlation, and the impact of haploinsufficiency in NF1), HCT in other haploinsufficient diseases, potential NF1-HCT drug treatment strategies, and the potential advantages/challenges of NF1-HCT.

Analysis of patient-specific NF1 variants leads to functional insights for Ras signaling that can impact personalized medicine.

We have created a panel of 29 NF1 variant complementary DNAs (cDNAs) representing missense variants, many with clinically relevant phenotypes, in-frame deletions, splice variants, and nonsense variants. We have determined the functional consequences of the variants, assessing their ability to produce mature neurofibromin and restore Ras signaling activity in NF1 null (-/-) cells. cDNAs demonstrate variant-specific differences in neurofibromin protein levels, suggesting that some variants lead to neurofibromatosis type 1 (NF1) gene or protein instability or enhanced degradation. When expressed at high levels, some variant proteins are still able to repress Ras activity, indicating that the NF1 phenotype may be due to low protein abundance. In contrast, other variant proteins are incapable of repressing Ras activity, indicating that some do not functionally engage Ras and stimulate GTPase activity. We observed that effects on protein abundance and Ras activity can be mutually exclusive. These assays allow us to categorize variants by functional effects, may help to classify variants of unknown significance, and may have future implications for more directed therapeutics.

Genotype-phenotype correlation in neurofibromatosis type-1: NF1 whole gene deletions lead to high tumor-burden and increased tumor-growth.

Neurofibromatosis type-1 (NF1) patients suffer from cutaneous and subcutaneous neurofibromas (CNF) and large plexiform neurofibromas (PNF). Whole gene deletions of the NF1 gene can cause a more severe phenotype compared to smaller intragenic changes. Two distinct groups of NF1 whole gene deletions are type-1 deletions and atypical deletions. Our aim was to assess volumes and averaged annual growth-rates of CNF and PNF in patients with NF1 whole gene deletions and to compare these with NF1 patients without large deletions of the NF1 gene.We retrospectively evaluated 140 whole-body MR examinations of 38 patients with NF1 whole gene deletions (type-1 group: n = 27/atypical group n = 11) and an age- and sex matched collective of 38 NF1-patients. Age-dependent subgroups were created (0–18 vs >18 years). Sixty-four patients received follow-up MRI examinations (NF1whole gene deletion n = 32/control group n = 32). Whole-body tumor-volumes were semi-automatically assessed (MedX, V3.42). Tumor volumes and averaged annual growth-rates were compared.Median tumor-burden was significantly higher in the type-1 group (418ml; IQR 77 – 950ml, p = 0.012) but not in the atypical group (356ml;IQR 140–1190ml, p = 0.099) when compared to the controls (49ml; IQR 11–691ml). Averaged annual growth rates were significantly higher in both the type-1 group (14%/year; IQR 45–36%/year, p = 0.004) and atypical group (11%/year; IQR 5–23%/year, p = 0.014) compared to the controls (4%/year; IQR1–8%/year). Averaged annual growth rates were significantly higher in pediatric patients with type-1 deletions (21%/year) compared with adult patients (8%/year, p = 0.014) and also compared with pediatric patients without large deletions of the NF1 gene (3.3%/year, p = 0.0015).NF1 whole gene deletions cause a more severe phenotype of NF1 with higher tumor burden and higher growth-rates compared to NF1 patients without large deletions of the NF1 gene. In particular, pediatric patients with type-1 deletions display a pronounced tumor growth.

Exploring associations between constipation, severity of neurofibromatosis type 1 and NF1 mutational spectrum

Neurofibromatosis type 1 (NF1) is inherited in an autosomal dominant manner and is a rather common rare disease. Until recently, studies on gastrointestinal symptoms in patients with NF1 have been few and mostly described as case reports. In three previously published studies, the frequency of constipation in patients with NF1 has been found to be as high as 30%. In this study, associations between the frequency of constipation and NF1 disease severity and NF1 mutational spectrum were investigated. Among 277 patients with NF1, 49 had constipation. The highest rate of constipation was found among patients with a high perception of NF1 illness burden, and patients with constipation had a significantly higher NF1 illness burden when comparing the “not bothered” and the “very bothered” (p = 0.013). We found no significant association between constipation and the remaining measures on severity of NF1, nor between constipation and genetic variants. When observing the NF1 mutational spectrum, one variant (c.1013A>G (p.Asp338Gly/p.?) was identified in three patients with constipation of which two patients were related. The variant c.2970_2972delAAT (p.Met992del) associated with a mild NF1 phenotype was identified in two related patients with constipation. This study is the first to explore the association between symptoms of constipation, NF1 severity, and NF1 mutational spectrum. The results suggest an association between constipation and a high degree of illness burden. Awareness of this association among physicians could lead to more patients with NF1 being diagnosed with constipation. Constipation impacts on quality of life, hence a timely diagnosis and treatment will improve quality of life.

Novel Mutation C.7348C&gt;T in NF1 Gene Identified by Whole-Exome Sequencing in Patient with Overlapping Clinical Symptoms of Neurofibromatosis Type 1 and Bannayan–Riley–Ruvalcaba Syndrome

Neurofibromatosis type 1 (NF-1) is an autosomal dominant disorder provoking benign cutaneous and nerve sheath tumors. The cutaneous tumors termed as plexiform neurofibromas, which some of them are extremely visible, and can influence the quality of life. They can also develop into invasive forms of carcinomas and infiltrate into multiple tissues, thus endangering the patient’s life. The loss-of-function mutations in NF1 gene are responsible for NF-1 type. Due to the large size of NF1 gene (~350 kb and 60 exons), exist some pseudogenes on another locus, and lack mutation hotspot the molecular characterizing of patients is complex. In this study, we reported a patient showed symptoms of both NF-1 and Bannayan–Riley–Ruvalcaba syndrome (BRRS), then performed a whole-exome sequencing (WES) and a data analysis for molecular characterization. These results showed a single heterozygous nucleotide variant (c.7348C>T) in NF1 gene, which results in a premature stop codon (p.Arg2450Ter) and a truncated protein, causing clinical symptoms of the patient. According to the results, WES is a quick and cost-effective approach for molecular diagnosis of the mixed phenotype of NF-1.

NF1 microdeletion syndrome: case report of two new patients

Background17q11.2 microdeletions, which include the neurofibromatosis type 1 (NF1) gene region, are responsible for the NF1 microdeletion syndrome, observed in 4.2% of all NF1 patients. Large deletions of the NF1 gene and its flanking regions are associated with a more severe NF1 phenotype than the NF1 general population.Case presentationWe hereby describe the clinical and molecular features of two girls (aged 2 and 4 years, respectively), with non-mosaic atypical deletions. Patient 1 showed fifteen café-au-lait spots and axillary freckling, as well as a Lisch nodule in the left eye, strabismus, high-arched palate, malocclusion, severe kyphoscoliosis, bilateral calcaneovalgus foot, mild generalized hypotonia, hyperactivity and deficits of speech-related abilities. NF1 genomic rearrangements through multiplex ligation-dependent probe amplification (MLPA) detected an heterozygous deletion of the whole NF1 gene. Array comparative genomic hybridization (a-CGH) analysis defined a 17q11.2 deletion of about 1 Mb (breakpoints at positions 29,124,299 and 30,151,654), which involved different genes (partially CRLF3, ATAD5, TEFM, ADAP2, RNF135, OMG, EVI2B, EVI2A, RAB11FIP4), including NF1. Patient 2 showed growth and developmental delay, supravalvular pulmonary stenosis, twenty-five café-au-lait spots, axillary freckling, craniofacial dysmorphic features, short neck with pterygium, limb abnormalities and foci of neural dysplasia on brain magnetic resonance imaging (MRI). MLPA detected an heterozygous deletion of NF1, which was detailed by a-CGH indicating the positions 29,124,299 and 30,326,958 as its breakpoints, and which included aside from the genes deleted in Patient 1 also COPRS, UTP6 and partially SUZ12. Fluorescent in situ hybridization (FISH) analysis of the parents documented a de novo origin of the deletions in both cases.ConclusionsThe present report will likely provide further insights and a better characterization of NF1 microdeletion syndrome.

Non-Coding RNA and Tumor Development in Neurofibromatosis Type 1: ANRIL Rs2151280 Is Associated with Optic Glioma Development and a Mild Phenotype in Neurofibromatosis Type 1 Patients.

Non-coding RNAs (ncRNAs) are known to regulate gene expression at the transcriptional and post-transcriptional levels, chromatin remodeling, and signal transduction. The identification of different species of ncRNAs, microRNAs (miRNAs), circular RNAs (circRNAs), and long ncRNAs (lncRNAs)—and in some cases, their combined regulatory function on specific target genes—may help to elucidate their role in biological processes. NcRNAs’ deregulation has an impact on the impairment of physiological programs, driving cells in cancer development. We here carried out a review of literature concerning the implication of ncRNAs on tumor development in neurofibromatosis type 1 (NF1), an inherited tumor predisposition syndrome. A number of miRNAs and a lncRNA has been implicated in NF1-associated tumors, such as malignant peripheral nerve sheath tumors (MPNSTs) and astrocytoma, as well as in the pathognomonic neurofibromas. Some authors reported that the lncRNA ANRIL was deregulated in the blood of NF1 patients with plexiform neurofibromas (PNFs), even if its role should be further elucidated. We here provided original data concerning the association of a specific genotype about ANRIL rs2151280 with the presence of optic gliomas and a mild expression of the NF1 phenotype. We also detected the LOH of ANRIL in different tumors from NF1 patients, supporting the involvement of ANRIL in some NF1-associated tumors. Our results suggest that ANRIL rs2151280 may be a potential diagnostic and prognostic marker, addressing early diagnosis of optic glioma and predicting the phenotype severity in NF1 patients.

The Role of Co-Deleted Genes in Neurofibromatosis Type 1 Microdeletions: An Evolutive Approach.

Neurofibromatosis type 1 (NF1) is a cancer predisposition syndrome that results from dominant loss-of-function mutations mainly in the NF1 gene. Large rearrangements are present in 5–10% of affected patients, generally encompass NF1 neighboring genes, and are correlated with a more severe NF1 phenotype. Evident genotype–phenotype correlations and the importance of the co-deleted genes are difficult to establish. In our study we employed an evolutionary approach to provide further insights into the understanding of the fundamental function of genes that are co-deleted in subjects with NF1 microdeletions. Our goal was to access the ortholog and paralog relationship of these genes in primates and verify if purifying or positive selection are acting on these genes. Fourteen genes were analyzed in twelve mammalian species. Of these, four and ten genes showed positive selection and purifying selection, respectively. The protein, RNF135, showed three sites under positive selection at the RING finger domain, which may have been selected to increase efficiency in ubiquitination routes in primates. The phylogenetic analysis suggests distinct evolutionary constraint between the analyzed genes. With these analyses, we hope to help clarify the correlation of the co-deletion of these genes and the more severe phenotype of NF1.

Next Generation Sequencing Identified a Novel Multi Exon Deletion of the NF1 Gene in a Chinese Pedigree with Neurofibromatosis Type 1.

Neurofibromatosis type 1 (NF1) is a genetic disease involving neurocutaneous abnormalities. Neurofibromatosis type 1 is an autosomal dominant disorder characterized by the neurofibromas and café-au-lait spots. Mutation in the NF 1 gene causes NF1. The NF 1 gene encodes neurofibromin. In this study, we found a 31-year-old Chinese boy with NF1. He presented only with café-au-lait spots over the whole body. The proband’s mother had a severe phenotype with neurofibroma and café-au-lait macules over her whole body, mostly in the facial region. A novel multi exon deletion c.(4661+1_4662-1)_(5748+1_5749-1)del; [EX36_39DEL] on the NF 1 gene has been identified in the proband. Quantitative real-time polymerase chain reaction (qPCR) confirmed that this mutation is co-segregated well and was inherited from the proband’s mother. The mutation was absent in the proband’s father and normal individuals. The novel multi exon deletion results in the formation of a truncated NF1 protein that caused the NF1 phenotype in this family. Our present study also emphasized the significance of rapid, accurate and cost-effective screening for the patient with NF1 by next generation sequencing (NGS).

Social Function and Autism Spectrum Disorder in Children and Adults with Neurofibromatosis Type 1: a Systematic Review and Meta-Analysis.

In light of the proliferation of recent research into social function in neurofibromatosis type 1 (NF1), a systematic review and meta-analysis is required to synthesise data and place findings within the context of a theoretical framework. This paper reviews findings from research into social function and autism spectrum disorder (ASD) in children and adults with NF1 and integrates these findings with the Socio-Cognitive Integration Abilities Model (SOCIAL). It also critically appraises links between social outcomes, internal and external factors moderating social functioning, cognitive domains implicated in social functioning, and underlying neural pathology in NF1. A systematic literature search conducted in MedLine (Ovid), PsycINFO (Ovid), Embase (Ovid), and PubMed electronic databases yielded 35 papers that met inclusion criteria for the systematic review. Out of these papers, 22 papers provided sufficient data for meta-analysis. Findings from this review and meta-analysis provide evidence that children and adults with NF1 exhibit significantly higher prevalence and severity of social dysfunction and ASD symptomatology. To date, very few studies have examined social cognition in NF1 but results indicate the presence of both perceptual and higher-level impairments in this population. The results of this review also provide support for age, gender, and comorbid ADHD as moderating factors for social outcomes in NF1. Suggestions for future research are offered to further our understanding of the social phenotype in NF1 and to facilitate the development of targeted interventions.

Attention to faces in social context in children with neurofibromatosis type 1.

To examine visual attention to faces within social scenes in children with neurofibromatosis type 1 (NF1) and typically developing peers. Using eye-tracking technology we investigated the time taken to fixate on a face and the percentage of time spent attending to faces relative to the rest of the screen within social scenes in 24 children with NF1 (17 females, seven males; mean age 10y 4mo [SD 1y 9mo]). Results were compared with those of 24 age-matched typically developing controls (11 females, 13 males; mean age 10y 3mo [SD 2y]). There was no significant between-group differences in time taken to initially fixate on a face (p=0.617); however, children with NF1 spent less time attending to faces within scenes than controls (p=0.048). Decreased attention to faces was associated with elevated autism traits in children with NF1. Children with NF1 spend less time attending to faces than typically developing children when presented in social scenes. Our findings contribute to a growing body of literature suggesting that abnormal face processing is a key aspect of the social-cognitive phenotype of NF1 and appears to be related to autism spectrum disorder traits. Clinicians should consider the impact of reduced attention to faces when designing and implementing treatment programmes for social dysfunction in this population. Children with neurofibromatosis type 1 (NF1) demonstrated atypical gaze behaviour when attending to faces. NF1 gaze behaviour was characterized by normal initial fixation on faces but shorter face dwell time. Decreased attention to faces was associated with elevated autism traits in the sample with NF1.