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NF1
neurofibromin 1
The NF1 gene encodes neurofibromin, a tumour suppressor protein that controls cell growth by regulating signalling pathways critical for preventing uncontrolled cell division. Located on chromosome 17, NF1 produces neurofibromin, a large protein that acts as a molecular brake on cell proliferation.
NF1 is located on the long (q) arm of chromosome 17, at band 17q11.2. Arm ratio per GRCh38 - banding schematic.
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Overview
The NF1 gene encodes a protein known as neurofibromin, which appears in diverse tissue types throughout the body, including cells of the nervous system and the myelin-producing oligodendrocytes and Schwann cells that wrap around nerve fibres. Functioning as a tumour suppressor, neurofibromin is essential for keeping cellular division in check and preventing unregulated proliferation. This gene occupies a substantial stretch of chromosome 17 and ranks among the most frequently altered genes in heritable human disorders.
Pathogenic changes in NF1 follow an autosomal dominant inheritance pattern, meaning a single altered copy is sufficient to cause disease in most cases. The gene is particularly important in clinical genetics because variants are associated with neurofibromatosis type 1, a relatively common inherited condition. Beyond this primary disorder, NF1 variants also contribute to cancer predisposition, making the gene a focus of both diagnostic testing and ongoing research into targeted therapies.
What the gene does
Neurofibromin functions primarily as a negative regulator of the Ras signalling pathway, a critical cellular communication system that controls cell growth, differentiation, and survival. By deactivating Ras - a protein that promotes cellular proliferation when in its active state - neurofibromin prevents cells from receiving continuous growth signals that would otherwise drive uncontrolled division [PMID:31570380]. This regulatory activity places neurofibromin firmly in the category of tumour suppressors, proteins whose normal role is to halt excessive cell expansion.
This suppressive function proves especially vital in cells that produce myelin, the fatty insulating material that wraps around nerve fibres to enable proper electrical signal transmission. When neurofibromin activity is compromised, Ras signalling becomes hyperactive, leading to excessive cell division and tumour formation. Research suggests that neurofibromin also participates in other cellular processes beyond Ras regulation, including pathways involving cyclic AMP signalling and cytoskeletal organisation, though these functions are less well characterised [PMID:28481329].
The protein is expressed throughout development and in adult tissues, with particularly high levels in the nervous system. Evidence indicates that neurofibromin plays roles in learning and memory, as loss of function can affect synaptic plasticity and neuronal signalling. The broad tissue distribution and multiple biochemical activities of neurofibromin explain why NF1 variants produce such varied clinical manifestations across different organ systems [PMID:29644219].
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Chromosome location
The NF1 gene is located on the long arm of chromosome 17 at position 17q11.2, a region spanning approximately 350 kilobases of genomic DNA. This makes NF1 one of the largest human genes, containing 60 exons that encode the 2,839-amino-acid neurofibromin protein. The gene's substantial size contributes to its high mutation rate, as there are more opportunities for DNA replication errors or environmental damage to introduce pathogenic changes.
The chromosomal region surrounding NF1 includes several other genes and repetitive DNA sequences that can complicate genetic analysis. Approximately 5-10% of individuals with neurofibromatosis type 1 have deletions that remove not only NF1 but also neighbouring genes, often resulting in more severe clinical presentations. The gene's location in a genomically complex region means that specialised testing methods are sometimes required to detect large structural rearrangements that standard sequencing might miss.
Protein structure
Neurofibromin is a large, multidomain protein of 2,839 amino acids with several functionally distinct regions. The central Ras-GAP domain, spanning amino acids 1251-1482, is the best-characterised structural element and mediates the protein's key tumour suppressor function by accelerating GTP hydrolysis on Ras proteins. This domain shares structural similarity with other GAP proteins but has unique features that determine its specificity for particular Ras family members.
The CRAL-TRIO domain, located at amino acids 1580-1738, sits within a broader lipid-binding region extending from residue 1580 to 1837. This portion of neurofibromin is thought to interact with cellular membranes and lipid molecules, potentially regulating where the protein localises within cells and how it accesses Ras proteins embedded in membrane structures. A bipartite nuclear localisation signal at amino acids 2555-2571 enables neurofibromin to shuttle between the cytoplasm and nucleus, suggesting roles in both compartments.
The carboxy-terminal region includes a disordered segment from amino acids 2787-2839, which lacks stable three-dimensional structure and may serve as a flexible linker or interaction surface for binding partners. The presence of extensive regions outside the defined domains indicates that much of neurofibromin's structure remains incompletely understood, with ongoing research aimed at mapping additional functional elements and post-translational modifications that regulate protein activity.
Key variants
Over 1,000 different pathogenic variants in NF1 have been documented, making it one of the most polymorphic disease-associated genes in the human genome. The spectrum includes nonsense variants that introduce premature stop codons, frameshift variants caused by small insertions or deletions, splice-site changes that disrupt normal mRNA processing, and missense variants that alter critical amino acids within functional domains. Many of these changes result in production of severely truncated or unstable neurofibromin that cannot perform its normal regulatory functions.
Large deletions encompassing the entire NF1 gene or multiple exons account for 5-10% of pathogenic variants and are typically associated with more severe clinical presentations. Mosaic variants, present in only a subset of an individual's cells, can cause segmental or milder forms of neurofibromatosis type 1. The high spontaneous mutation rate means that approximately half of affected individuals have de novo variants not inherited from either parent, reflecting new mutational events during germ cell formation or early embryonic development.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.206_207delGA | - | Pathogenic | ★★☆☆ | Neurofibromatosis, type 1 |
c.2252delG | - | Pathogenic/Likely pathogenic | ★★☆☆ | Neurofibromatosis, type 1 |
c.4111delG | - | Pathogenic | ★★☆☆ | Neurofibromatosis, type 1 |
c.4516del | - | Pathogenic | ★★☆☆ | Neurofibromatosis, type 1 |
c.5206delG | - | Pathogenic | ★★☆☆ | not provided |
c.6085del | - | Pathogenic | ★★☆☆ | Neurofibromatosis, type 1 |
c.1007G>A | p.Trp336Ter | Pathogenic | ★★☆☆ | Neurofibromatosis, type 1 |
c.1008G>A | p.Trp336Ter | Pathogenic | ★★☆☆ | not provided |
c.1013A>G | p.Asp338Gly | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.2378del | p.Asn793fs | Pathogenic/Likely pathogenic | ★★☆☆ | Neurofibromatosis, type 1 |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants in NF1 cause neurofibromatosis type 1, an autosomal dominant condition characterised by café-au-lait spots, freckling in skin folds, benign nerve sheath tumours called neurofibromas, and distinctive bone changes. The condition shows complete penetrance but highly variable expressivity, meaning that whilst nearly all carriers develop some features, the severity and specific manifestations vary considerably even within families sharing the same variant.
Individuals with neurofibromatosis type 1 face increased risks of both benign and malignant tumours. Plexiform neurofibromas, which involve multiple nerve fascicles, can transform into malignant peripheral nerve sheath tumours in some cases. Other associated cancers include juvenile myelomonocytic leukaemia in early childhood, gliomas of the optic pathway and brain, gastrointestinal stromal tumours, and phaeochromocytomas. The condition also affects learning and cognition in many individuals, with attention difficulties and specific learning disabilities being common even in the absence of structural brain abnormalities.
Inheritance pattern
Conditions caused by pathogenic NF1 variants typically follow autosomal dominant inheritance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
UK clinical status
Within the NHS Genomic Medicine Service, NF1 holds green (high-evidence) status across numerous clinical panels, reflecting its well-established role in multiple disease areas. The gene appears on the Neurofibromatosis Type 1 (GMS) panel (R222), which supports diagnostic testing for individuals with suspected neurofibromatosis, and the Segmental or atypical neurofibromatosis type 1 testing panel (R376) for mosaic or localised presentations.
NF1's cancer predisposition properties are recognised through inclusion on multiple oncology panels, including Adult solid tumours cancer susceptibility, Childhood solid tumours cancer susceptibility, Sarcoma susceptibility, and Inherited phaeochromocytoma and paraganglioma panels. The gene also features on developmental disorder panels such as DDG2P, Intellectual disability (R29), and Skeletal dysplasia (R104), acknowledging the broader phenotypic spectrum beyond tumour formation. Green ratings on the RASopathies panel and Paediatric or syndromic cardiomyopathy panel (R135) reflect overlapping features with related genetic conditions affecting Ras pathway signalling.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
Research into lifestyle factors for individuals with neurofibromatosis type 1 suggests that general health maintenance may support overall wellbeing, though no specific dietary interventions have been shown to prevent tumour formation or modify disease progression. Maintaining a balanced diet, regular physical activity appropriate to individual capabilities, and routine health monitoring are recommended for the general population and may help manage some associated features such as cardiovascular risk factors that can occur in this condition.
Sun protection is often discussed in the context of neurofibromatosis type 1, given that café-au-lait spots may become more prominent with ultraviolet exposure, though evidence does not suggest that sun exposure influences internal tumour development. Some observational studies have explored whether environmental factors or specific nutrients influence disease severity, but findings remain inconclusive and no particular lifestyle modification has demonstrated clear benefit in preventing complications specific to NF1 variants.
Supplement considerations
No dietary supplements have been proven to prevent the development of neurofibromas or reduce cancer risk in individuals with NF1 variants. Whilst various compounds have been investigated in laboratory models for potential effects on Ras pathway signalling or tumour growth, these have not translated into evidence-based supplement recommendations for clinical use.
Individuals with neurofibromatosis type 1 should discuss any planned supplement use with their healthcare team, as some products might interact with medications or monitoring tests. Standard nutritional recommendations for bone health, including adequate vitamin D and calcium intake, may be relevant given that bone abnormalities can occur in this condition, but supplementation decisions should be guided by individual nutritional assessment and clinical need rather than the genetic diagnosis alone.
Frequently asked questions
What is the difference between neurofibromatosis type 1 and type 2?
Neurofibromatosis type 1 and type 2 are distinct genetic conditions caused by variants in different genes. Type 1, caused by NF1 variants, primarily affects peripheral nerves and skin, producing neurofibromas and café-au-lait spots. Type 2, caused by variants in the NF2 gene, predominantly affects the central nervous system with characteristic bilateral vestibular schwannomas (tumours on hearing nerves). Despite similar names, they have different clinical features, inheritance patterns, and management approaches.
Can NF1 variants skip generations?
NF1 variants follow autosomal dominant inheritance with very high penetrance, meaning they typically do not skip generations in the traditional sense. However, mild or mosaic cases in a parent might go unrecognised, creating the appearance of skipped generations. Additionally, approximately half of cases result from new (de novo) variants occurring for the first time in an affected individual, with no prior family history.
How does neurofibromin regulate cell growth?
Neurofibromin acts as a GTPase-activating protein (GAP) that turns off Ras proteins, which are molecular switches controlling cell growth and division. When Ras is bound to GTP, it signals cells to grow and divide; neurofibromin accelerates the conversion of GTP to GDP, thereby inactivating Ras and preventing excessive cellular proliferation. Loss of neurofibromin function leads to persistent Ras activation and uncontrolled cell growth.
What types of cancers are associated with NF1 variants?
Individuals with pathogenic NF1 variants have elevated risks for several cancer types, including malignant peripheral nerve sheath tumours (which can arise from plexiform neurofibromas), gliomas of the optic pathway and brain, juvenile myelomonocytic leukaemia in young children, gastrointestinal stromal tumours, phaeochromocytomas, and breast cancer. The lifetime cancer risk is substantially higher than in the general population, though most carriers will not develop malignancy.
Why is the NF1 gene so large compared to other genes?
NF1 spans approximately 350 kilobases of genomic DNA with 60 exons, making it one of the largest known human genes. This extensive size likely reflects the need to encode a very large, multifunctional protein with diverse regulatory roles across many cell types. The gene's size contributes to its high mutation rate, as larger genes present more opportunities for errors during DNA replication and are more susceptible to deletions and rearrangements.
References
- Lauchle JO, Braun BS, Loh ML. Inherited predispositions and hyperactive Ras in myeloid leukemogenesis. Pediatric blood & cancer. 2006. PMID: 16261595
- Trovó-Marqui AB, Tajara EH. Neurofibromin: a general outlook. Clinical genetics. 2006. PMID: 16813595
- Yohay KH. The genetic and molecular pathogenesis of NF1 and NF2. Seminars in pediatric neurology. 2006. PMID: 16818172
- Carroll SL, Stonecypher MS. Tumor suppressor mutations and growth factor signaling in the pathogenesis of NF1-associated peripheral nerve sheath tumors: II. The role of dysregulated growth factor signaling. Journal of neuropathology and experimental neurology. 2005. PMID: 15715079
- Ward BA, Gutmann DH. Neurofibromatosis 1: from lab bench to clinic. Pediatric neurology. 2005. PMID: 15797177
- Arun D, Gutmann DH. Recent advances in neurofibromatosis type 1. Current opinion in neurology. 2004. PMID: 15021234
- Carroll SL, Stonecypher MS. Tumor suppressor mutations and growth factor signaling in the pathogenesis of NF1-associated peripheral nerve sheath tumors. I. The role of tumor suppressor mutations. Journal of neuropathology and experimental neurology. 2004. PMID: 15581179
- Dasgupta B, Gutmann DH. Neurofibromatosis 1: closing the GAP between mice and men. Current opinion in genetics & development. 2003. PMID: 12573431
- Viskochil DH. It takes two to tango: mast cell and Schwann cell interactions in neurofibromas. The Journal of clinical investigation. 2003. PMID: 14679174
- Yang FC, Ingram DA, Chen S. Neurofibromin-deficient Schwann cells secrete a potent migratory stimulus for Nf1+/- mast cells. The Journal of clinical investigation. 2003. PMID: 14679180
- Kluwe L, Friedrich RE, Korf B. NF1 mutations in neurofibromatosis 1 patients with plexiform neurofibromas. Human mutation. 2002. PMID: 11857752
- Packer RJ, Gutmann DH, Rubenstein A. Plexiform neurofibromas in NF1: toward biologic-based therapy. Neurology. 2002. PMID: 12041525
- Korf BR. Clinical features and pathobiology of neurofibromatosis 1. Journal of child neurology. 2002. PMID: 12403555
- Gutmann DH. Neurofibromin in the brain. Journal of child neurology. 2002. PMID: 12403558
- Reed N, Gutmann DH. Tumorigenesis in neurofibromatosis: new insights and potential therapies. Trends in molecular medicine. 2001. PMID: 11286939
- Cooper LJ, Shannon KM, Loken MR. Evidence that juvenile myelomonocytic leukemia can arise from a pluripotential stem cell. Blood. 2000. PMID: 10979983
- Korf BR. Malignancy in neurofibromatosis type 1. The oncologist. 2000. PMID: 11110599
- Gutzmer R, Herbst RA, Mommert S. Allelic loss at the neurofibromatosis type 1 (NF1) gene locus is frequent in desmoplastic neurotropic melanoma. Human genetics. 2000. PMID: 11129335