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Fukunaga N, Hayashi T, Yamada Y, Mizobuchi K, Ohta A, Nakano T. A novel stop-gain NF1 variant in neurofibromatosis type 1 and bilateral optic atrophy without optic gliomas. Ophthalmic Genet 2024; 45:186-192. [PMID: 37599594 DOI: 10.1080/13816810.2023.2245464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 06/25/2023] [Accepted: 08/01/2023] [Indexed: 08/22/2023]
Abstract
BACKGROUND Neurofibromatosis type 1 (NF1) is a multisystem disorder that primarily affects the skin and peripheral nervous system and is caused by chromosomal abnormalities and mostly truncating variants in the NF1 gene. Ocular complications such as Lisch nodules and optic pathway gliomas (OPGs) can occur in NF1 patients. Herein, we report a novel NF1 variant in an NF1 patient with bilateral optic atrophy. METHODS Ophthalmological examinations and genetic analyses were performed using targeted next-generation sequencing (NGS). RESULTS A 14-year-old girl diagnosed with NF1 visited our hospital with decreased visual acuity (VA). The patient had no family history of NF1 or visual impairment. Brain and orbital magnetic resonance imaging revealed no remarkable findings. Ophthalmoscopy revealed temporal pallor of the optic discs, which was confirmed by optical coherence tomography findings of significant thinning of the circumpapillary retinal nerve fiber layer in both eyes. At 23 years of age, the decimal-corrected VA had deteriorated to 0.2 in the right eye and 0.1 in the left eye. Additionally, the targeted NGS panel revealed a novel heterozygous stop-gain variant (p.Tyr628Ter) in the NF1 gene; however, no pathogenic variants in OPA1 or the mitochondrial DNA were identified. CONCLUSIONS A patient with NF1 without OPGs developed bilateral optic atrophy and carried a novel de novo stop-gain variant of NF1. Although the relationship between NF1 variants and bilateral optic atrophy remains unclear, further investigations are required.
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Affiliation(s)
- Naoko Fukunaga
- Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, Tokyo, Japan
| | - Takaaki Hayashi
- Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, Tokyo, Japan
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Yuki Yamada
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Kei Mizobuchi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Arihito Ohta
- Department of Dermatology, The Jikei University School of Medicine, Tokyo, Japan
| | - Tadashi Nakano
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
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2
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Pacot L, Ye M, Nectoux J, Laurendeau I, Briand-Suleau A, Coustier A, Maillard T, Barbance C, Orhant L, Vaucouleur N, Blanché H, Parfait B, Wolkenstein P, Vidaud M, Vidaud D, Pasmant E. Droplet Digital PCR for Fast and Accurate Characterization of NF1 Locus Deletions: Confirmation of the Predominant Maternal Origin of Type-1 Deletions. J Mol Diagn 2024; 26:150-157. [PMID: 38008284 DOI: 10.1016/j.jmoldx.2023.11.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/09/2023] [Accepted: 11/07/2023] [Indexed: 11/28/2023] Open
Abstract
Neurofibromatosis type-1 is a genetic disorder caused by loss-of-function variants in the tumor-suppressor NF1. Approximately 4% to 11% of neurofibromatosis type-1 patients have a NF1 locus complete deletion resulting from nonallelic homologous recombination between low copy repeats. Codeleted genes probably account for the more severe phenotype observed in NF1-deleted patients. This genotype-phenotype correlation highlights the need for a detailed molecular description. A droplet digital PCR (ddPCR) set along the NF1 locus was designed to delimitate the three recurrent NF1 deletion breakpoints. The ddPCR was tested in 121 samples from nonrelated NF1-deleted patients. Classification based on ddPCR versus multiplex ligation-dependent probe amplification (MLPA) was compared. In addition, microsatellites were analyzed to identify parental origin of deletions. ddPCR identified 77 type-1 (64%), 20 type-2 (16%), 7 type-3 (6%), and 17 atypical deletions (14%). The results were comparable with MLPA, except for three atypical deletions misclassified as type-2 using MLPA, for which the SUZ12 gene was not deleted. A significant maternal bias (25 of 30) in the origin of deletions was identified. This study proposes a fast and efficient ddPCR quantification to allow fine NF1 deletion classification. It indicates that ddPCR can be implemented easily into routine diagnosis to complement the techniques dedicated to NF1 point variant identification. This new tool may help unravel the genetic basis conditioning phenotypic variability in NF1-deleted patients and offer tailored genetic counseling.
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Affiliation(s)
- Laurence Pacot
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France; Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Manuela Ye
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France
| | - Juliette Nectoux
- Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Ingrid Laurendeau
- Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Audrey Briand-Suleau
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France; Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Audrey Coustier
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France
| | - Théodora Maillard
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France
| | - Cécile Barbance
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France
| | - Lucie Orhant
- Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Nicolas Vaucouleur
- Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | | | - Béatrice Parfait
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France; Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Pierre Wolkenstein
- Department of Dermatology, Hôpital Henri Mondor, Assistance Publique-Hôpital Paris, Créteil, France; INSERM, Clinical Investigation Center 1430, Referral Center of Neurofibromatosis, Hôpital Henri Mondor, Assistance Publique-Hôpital Paris, Faculté de Santé Paris Est Créteil, Créteil, France
| | - Michel Vidaud
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France; Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Dominique Vidaud
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France; Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France
| | - Eric Pasmant
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, CARPEM, Paris, France; Fédération de Génétique et Médecine Génomique, DMU BioPhyGen, Assistance Publique-Hôpital Paris, Centre-Université Paris Cité, Hôpital Cochin, Paris, France.
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3
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Büki G, Bekő A, Bödör C, Urbán P, Németh K, Hadzsiev K, Fekete G, Kehrer-Sawatzki H, Bene J. Identification of an NF1 Microdeletion with Optical Genome Mapping. Int J Mol Sci 2023; 24:13580. [PMID: 37686382 PMCID: PMC10487413 DOI: 10.3390/ijms241713580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/18/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023] Open
Abstract
Neurofibromatosis type 1 (NF1) is a clinically heterogeneous neurocutaneous disorder inherited in autosomal dominant manner. Approximately 5-10% of the cases are caused by NF1 microdeletions involving the NF1 gene and its flanking regions. Microdeletions, which lead to more severe clinical manifestations, can be subclassified into four different types (type 1, 2, 3 and atypical) according to their size, the genomic location of the breakpoints and the number of genes included within the deletion. Besides the prominent hallmarks of NF1, patients with NF1 microdeletions frequently exhibit specific additional clinical manifestations like dysmorphic facial features, macrocephaly, overgrowth, global developmental delay, cognitive disability and an increased risk of malignancies. It is important to identify the genes co-deleted with NF1, because they are likely to have an effect on the clinical manifestation. Multiplex ligation-dependent probe amplification (MLPA) and microarray analysis are the primary techniques for the investigation of NF1 microdeletions. However, based on previous research, optical genome mapping (OGM) could also serve as an alternative method to identify copy number variations (CNVs). Here, we present a case with NF1 microdeletion identified by means of OGM and demonstrate that this novel technology is a suitable tool for the identification and classification of the NF1 microdeletions.
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Affiliation(s)
- Gergely Büki
- Department of Medical Genetics, Clinical Center, Medical School, University of Pécs, 7624 Pécs, Hungary; (G.B.); (K.H.)
| | - Anna Bekő
- HCEMM-SE Molecular Oncohematology Research Group, Department of Pathology and Experimental Cancer Research, Semmelweis University, 1085 Budapest, Hungary; (A.B.); (C.B.)
| | - Csaba Bödör
- HCEMM-SE Molecular Oncohematology Research Group, Department of Pathology and Experimental Cancer Research, Semmelweis University, 1085 Budapest, Hungary; (A.B.); (C.B.)
| | - Péter Urbán
- Bioinformatics Research Group, Genomics and Bioinformatics Core Facility, Szentágothai Research Centre, University of Pécs, 7624 Pécs, Hungary;
| | - Krisztina Németh
- Pediatric Center, Tűzoltó Street Department, Faculty of Medicine, Semmelweis University, 1094 Budapest, Hungary; (K.N.); (G.F.)
| | - Kinga Hadzsiev
- Department of Medical Genetics, Clinical Center, Medical School, University of Pécs, 7624 Pécs, Hungary; (G.B.); (K.H.)
| | - György Fekete
- Pediatric Center, Tűzoltó Street Department, Faculty of Medicine, Semmelweis University, 1094 Budapest, Hungary; (K.N.); (G.F.)
| | | | - Judit Bene
- Department of Medical Genetics, Clinical Center, Medical School, University of Pécs, 7624 Pécs, Hungary; (G.B.); (K.H.)
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4
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Neurofibromatosis Type 1: Pediatric Aspects and Review of Genotype-Phenotype Correlations. Cancers (Basel) 2023; 15:cancers15041217. [PMID: 36831560 PMCID: PMC9954221 DOI: 10.3390/cancers15041217] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/12/2023] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
Neurofibromatosis type 1 (NF1) is an autosomal dominant condition, with a birth incidence of approximately 1:2000-3000, caused by germline pathogenic variants in NF1, a tumor suppressor gene encoding neurofibromin, a negative regulator of the RAS/MAPK pathway. This explains why NF1 is included in the group of RASopathies and shares several clinical features with Noonan syndrome. Here, we describe the main clinical characteristics and complications associated with NF1, particularly those occurring in pediatric age. NF1 has complete penetrance and shows wide inter- and intrafamilial phenotypic variability and age-dependent appearance of manifestations. Clinical presentation and history of NF1 are multisystemic and highly unpredictable, especially in the first years of life when penetrance is still incomplete. In this scenario of extreme phenotypic variability, some genotype-phenotype associations need to be taken into consideration, as they strongly impact on genetic counseling and prognostication of the disease. We provide a synthetic review, based on the most recent literature data, of all known genotype-phenotype correlations from a genetic and clinical perspective. Molecular diagnosis is fundamental for the confirmation of doubtful clinical diagnoses, especially in the light of recently revised diagnostic criteria, and for the early identification of genotypes, albeit few, that correlate with specific phenotypes.
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5
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Chen JL, Miller DT, Schmidt LS, Malkin D, Korf BR, Eng C, Kwiatkowski DJ, Giannikou K. Mosaicism in Tumor Suppressor Gene Syndromes: Prevalence, Diagnostic Strategies, and Transmission Risk. Annu Rev Genomics Hum Genet 2022; 23:331-361. [PMID: 36044908 DOI: 10.1146/annurev-genom-120121-105450] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A mosaic state arises when pathogenic variants are acquired in certain cell lineages during postzygotic development, and mosaic individuals may present with a generalized or localized phenotype. Here, we review the current state of knowledge regarding mosaicism for eight common tumor suppressor genes-NF1, NF2, TSC1, TSC2, PTEN, VHL, RB1, and TP53-and their related genetic syndromes/entities. We compare and discuss approaches for comprehensive diagnostic genetic testing, the spectrum of variant allele frequency, and disease severity. We also review affected individuals who have no mutation identified after conventional genetic analysis, as well as genotype-phenotype correlations and transmission risk for each tumor suppressor gene in full heterozygous and mosaic patients. This review provides new insight into similarities as well as marked differences regarding the appreciation of mosaicism in these tumor suppressor syndromes.
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Affiliation(s)
- Jillian L Chen
- Cancer Genetics Laboratory, Division of Pulmonary and Critical Care Medicine and Division of Genetics, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA; .,Boston University School of Medicine, Boston, Massachusetts, USA
| | - David T Miller
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Laura S Schmidt
- Urologic Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.,Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - David Malkin
- Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada
| | - Bruce R Korf
- Department of Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Charis Eng
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.,Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio, USA.,Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.,Germline High Risk Cancer Focus Group, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio, USA
| | - David J Kwiatkowski
- Cancer Genetics Laboratory, Division of Pulmonary and Critical Care Medicine and Division of Genetics, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA;
| | - Krinio Giannikou
- Cancer Genetics Laboratory, Division of Pulmonary and Critical Care Medicine and Division of Genetics, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA; .,Division of Hematology and Oncology, Cancer and Blood Disease Institute, Children's Hospital Los Angeles, Los Angeles, California, USA;
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6
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He Q, Jiang J, Yang J, Zeng J, Zhang H, Zhang Z. A novel mutation of the NF1 gene in a Chinese family with neurofibromatosis type 1. Am J Transl Res 2022; 14:5139-5145. [PMID: 35958499 PMCID: PMC9360891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND Mutations in the neurofibromin 1 (NF1) gene are associated with clinical manifestations of neurofibromatosis type 1 (NF1). OBJECTIVE To clarify the relationship between NF1 variants and disease phenotype. METHODS Peripheral blood samples were collected from a patient and her relatives and genomic DNA was extracted for next-generation sequencing (NGS) to detect potential variants; the results were validated by Sanger sequencing. RESULTS A novel frameshift variant c.4508_c.4509delAT (p.Asn1503fsTer26) was detected in exon 34 of the NF1 gene in the patient and her daughter, but not in any other (healthy) family member. This c.4508_c.4509delAT (p.Asn1503fsTer26) frameshift variant of NF1 may underlie NF1 in this family. CONCLUSIONS This finding expands the spectrum of pathogenic mutations of the NF1 gene, which could aid genetic counseling and prenatal diagnosis.
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Affiliation(s)
- Qi He
- Department of Dermatology, Affiliated Hospital of North Sichuan Medical CollegeNanchong 637000, Sichuan, China
| | - Jingjing Jiang
- Department of Dermatology, Affiliated Hospital of North Sichuan Medical CollegeNanchong 637000, Sichuan, China
| | - Jiao Yang
- Department of Dermatology, Affiliated Hospital of North Sichuan Medical CollegeNanchong 637000, Sichuan, China
| | - Junjie Zeng
- Department of Dermatology, Taikang Sichuan Southwest Hospital Company LimitedChengdu 610000, Sichuan, China
| | - Huan Zhang
- Department of Dermatology, Affiliated Hospital of North Sichuan Medical CollegeNanchong 637000, Sichuan, China
| | - Zhengzhong Zhang
- Department of Dermatology, Affiliated Hospital of North Sichuan Medical CollegeNanchong 637000, Sichuan, China
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7
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Ho SK, Luk HM, Ng SY, Yu KP, Cheng SS, Ng PP, Mok MT, Hau EW, Lo IF. Old and new perspectives on Neurofibromatosis type 1: Clinical and molecular characterization of 832 patients from a single centre over 16 years. Eur J Med Genet 2022; 65:104474. [PMID: 35240321 DOI: 10.1016/j.ejmg.2022.104474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 01/17/2022] [Accepted: 02/25/2022] [Indexed: 11/03/2022]
Abstract
Neurofibromatosis type 1 (NF1; OMIM #162200) is the commonest multi-systemic neurocutaneous tumour-predisposition disorder. It has an age-related complete penetrance but a highly variable inter- and intra-familial expressivity. This article summarizes the clinical features and molecular characteristics of 832 clinically or molecularly confirmed NF1 patients from 697 unrelated families recruited from a single centre in Hong Kong diagnosed during the 16 years period from Jan 2005 to Jan 2021. In this study, we have estimated the incidences of clinical features, reported on the molecular findings and explored new genotype-phenotype correlations.
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Affiliation(s)
- Stephanie Kl Ho
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Ho-Ming Luk
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Samuel Yl Ng
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Kris Pt Yu
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Shirley Sw Cheng
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Phoebe Py Ng
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Myth Ts Mok
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Edgar Wl Hau
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China
| | - Ivan Fm Lo
- Clinical Genetic Service, Department of Health, Hong Kong SAR, China.
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8
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Kehrer-Sawatzki H, Wahlländer U, Cooper DN, Mautner VF. Atypical NF1 Microdeletions: Challenges and Opportunities for Genotype/Phenotype Correlations in Patients with Large NF1 Deletions. Genes (Basel) 2021; 12:genes12101639. [PMID: 34681033 PMCID: PMC8535936 DOI: 10.3390/genes12101639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 09/30/2021] [Accepted: 10/14/2021] [Indexed: 11/16/2022] Open
Abstract
Patients with neurofibromatosis type 1 (NF1) and type 1 NF1 deletions often exhibit more severe clinical manifestations than patients with intragenic NF1 gene mutations, including facial dysmorphic features, overgrowth, severe global developmental delay, severe autistic symptoms and considerably reduced cognitive abilities, all of which are detectable from a very young age. Type 1 NF1 deletions encompass 1.4 Mb and are associated with the loss of 14 protein-coding genes, including NF1 and SUZ12. Atypical NF1 deletions, which do not encompass all 14 protein-coding genes located within the type 1 NF1 deletion region, have the potential to contribute to the delineation of the genotype/phenotype relationship in patients with NF1 microdeletions. Here, we review all atypical NF1 deletions reported to date as well as the clinical phenotype observed in the patients concerned. We compare these findings with those of a newly identified atypical NF1 deletion of 698 kb which, in addition to the NF1 gene, includes five genes located centromeric to NF1. The atypical NF1 deletion in this patient does not include the SUZ12 gene but does encompass CRLF3. Comparative analysis of such atypical NF1 deletions suggests that SUZ12 hemizygosity is likely to contribute significantly to the reduced cognitive abilities, severe global developmental delay and facial dysmorphisms observed in patients with type 1 NF1 deletions.
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Affiliation(s)
- Hildegard Kehrer-Sawatzki
- Institute of Human Genetics, University of Ulm, 89081 Ulm, Germany
- Correspondence: ; Tel.: +49-731-500-65421
| | - Ute Wahlländer
- Kliniken des Bezirks Oberbayern (KBO), Children Clinical Center Munich, 81377 Munich, Germany;
| | - David N. Cooper
- Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff CF14 4XN, UK;
| | - Victor-Felix Mautner
- Department of Neurology, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany;
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9
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Kehrer-Sawatzki H, Cooper DN. Classification of NF1 microdeletions and its importance for establishing genotype/phenotype correlations in patients with NF1 microdeletions. Hum Genet 2021; 140:1635-1649. [PMID: 34535841 PMCID: PMC8553723 DOI: 10.1007/s00439-021-02363-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 09/01/2021] [Indexed: 01/12/2023]
Abstract
An estimated 5–11% of patients with neurofibromatosis type-1 (NF1) harbour large deletions encompassing the NF1 gene and flanking regions. These NF1 microdeletions are subclassified into type 1, 2, 3 and atypical deletions which are distinguishable from each other by their extent and by the number of genes included within the deletion regions as well as the frequency of mosaicism with normal cells. Most common are type-1 NF1 deletions which encompass 1.4-Mb and 14 protein-coding genes. Type-1 deletions are frequently associated with overgrowth, global developmental delay, cognitive disability and dysmorphic facial features which are uncommon in patients with intragenic pathogenic NF1 gene variants. Further, patients with type-1 NF1 deletions frequently exhibit high numbers of neurofibromas and have an increased risk of malignant peripheral nerve sheath tumours. Genes located within the type-1 NF1 microdeletion interval and co-deleted with NF1 are likely to act as modifiers responsible for the severe disease phenotype in patients with NF1 microdeletions, thereby causing the NF1 microdeletion syndrome. Genotype/phenotype correlations in patients with NF1 microdeletions of different lengths are important to identify such modifier genes. However, these correlations are critically dependent upon the accurate characterization of the deletions in terms of their extent. In this review, we outline the utility as well as the shortcomings of multiplex ligation-dependent probe amplification (MLPA) to classify the different types of NF1 microdeletion and indicate the importance of high-resolution microarray analysis for correct classification, a necessary precondition to identify those genes responsible for the NF1 microdeletion syndrome.
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Affiliation(s)
| | - David N Cooper
- Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
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