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Lu YT, Rejiepu B, Zhang D, Cai DC, Yang KQ, Tian T, Zhou XL, Fan P. Childhood-Onset Refractory Hypertension Results from Neurofibromatosis Type 1 Caused by a Splicing NF1 Mutation. Kidney Blood Press Res 2023; 48:568-577. [PMID: 37562365 PMCID: PMC10614435 DOI: 10.1159/000533144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 07/19/2023] [Indexed: 08/12/2023] Open
Abstract
INTRODUCTION Neurofibromatosis type 1 (NF-1) is caused by mutations in the NF1 gene that encodes neurofibromin, a negative regulator of RAS proto-oncogene. Approximately one-third of the reported pathogenic mutations in NF1 are splicing mutations, but most consequences are unclear. The objective of this study was to identify the pathogenicity of splicing mutation in a Chinese family with NF-1 and determine the effects of the pre-mRNA splicing mutation by in vitro functional analysis. METHODS Next-generation sequencing was used to screen candidate mutations. We performed a minigene splicing assay to determine the effect of the splicing mutation on NF1 expression, and three-dimensional structure models of neurofibromin were generated using SWISS-MODEL and PROCHECK methods, respectively. RESULTS A pathogenic splicing mutation c.479+1G>C in NF1 was found in the proband characterized by childhood-onset refractory hypertension. In vitro analysis demonstrated that c.479+1G>C mutation caused the skipping of exon 4, leading to a glutamine-to-valine substitution at position 97 in neurofibromin and an open reading frame shift terminating at codon 108. Protein modeling showed that several major domains were missing in the truncated neurofibromin protein. CONCLUSION The splicing mutation c.479+1G>C identified in a Chinese patient with NF-1 and childhood-onset refractory hypertension caused the skipping of exon 4 and a truncated protein. Our findings offer new evidence for the molecular diagnosis of NF-1.
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Affiliation(s)
- Yi-Ting Lu
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Buweimairemu Rejiepu
- Department of Cardiac Surgery, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, China
| | - Di Zhang
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Dong-Cheng Cai
- Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Kun-Qi Yang
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Tao Tian
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xian-Liang Zhou
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Peng Fan
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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Alesi V, Genovese S, Lepri FR, Catino G, Loddo S, Orlando V, Di Tommaso S, Morgia A, Martucci L, Di Donato M, Digilio MC, Dallapiccola B, Novelli A, Capolino R. Deep Intronic LINE-1 Insertions in NF1: Expanding the Spectrum of Neurofibromatosis Type 1-Associated Rearrangements. Biomolecules 2023; 13:biom13050725. [PMID: 37238595 DOI: 10.3390/biom13050725] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/20/2023] [Accepted: 04/21/2023] [Indexed: 05/28/2023] Open
Abstract
Neurofibromatosis type 1 is an autosomal-dominant condition caused by NF1 gene inactivation. Clinical diagnosis is corroborated by genetic tests on gDNA and cDNA, which are inconclusive in approximately 3-5% of cases. Genomic DNA approaches may overlook splicing-affecting intronic variants and structural rearrangements, especially in regions enriched in repetitive sequences. On the other hand, while cDNA-based methods provide direct information about the effect of a variant on gene transcription, they are hampered by non-sense-mediated mRNA decay and skewed or monoallelic expression. Moreover, analyses on gene transcripts in some patients do not allow tracing back to the causative event, which is crucial for addressing genetic counselling, prenatal monitoring, and developing targeted therapies. We report on a familial NF1, caused by an insertion of a partial LINE-1 element inside intron 15, leading to exon 15 skipping. Only a few cases of LINE-1 insertion have been reported so far, hampering gDNA studies because of their size. Often, they result in exon skipping, and their recognition of cDNA may be difficult. A combined approach, based on Optical Genome Mapping, WGS, and cDNA studies, enabled us to detect the LINE-1 insertion and test its effects. Our results improve knowledge of the NF1 mutational spectrum and highlight the importance of custom-built approaches in undiagnosed patients.
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Affiliation(s)
- Viola Alesi
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Silvia Genovese
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Francesca Romana Lepri
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Giorgia Catino
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Sara Loddo
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Valeria Orlando
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Silvia Di Tommaso
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Alessandra Morgia
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Licia Martucci
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Maddalena Di Donato
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Maria Cristina Digilio
- Medical Genetics Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
- Genetics and Rare Disease Research Division, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Bruno Dallapiccola
- Genetics and Rare Disease Research Division, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Antonio Novelli
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
| | - Rossella Capolino
- Medical Genetics Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
- Genetics and Rare Disease Research Division, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy
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Douben H, Hoogeveen-westerveld M, Nellist M, Louwen J, Haan MK, Punt M, van Ommeren B, van Unen L, Elfferich P, Kasteleijn E, van Bever Y, van Vliet M, Oostenbrink R, Saris JJ, Wagner A, van Ierland Y, van Ham T, van Minkelen R. Functional Assays Combined with Pre-mRNA-Splicing Analysis Improve Variant Classification and Diagnostics for Individuals with Neurofibromatosis Type 1 and Legius Syndrome. Hum Mutat 2023; 2023:1-14. [DOI: 10.1155/2023/9628049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Neurofibromatosis type 1 (NF1) and Legius syndrome (LS) are caused by inactivating variants in NF1 and SPRED1. NF1 encodes neurofibromin (NF), a GTPase-activating protein (GAP) for RAS that interacts with the SPRED1 product, Sprouty-related protein with an EVH (Ena/Vasp homology) domain 1 (SPRED1). Obtaining a clinical and molecular diagnosis of NF1 or LS can be challenging due to the phenotypic diversity, the size and complexity of the NF1 and SPRED1 loci, and uncertainty over the effects of some NF1 and SPRED1 variants on pre-mRNA splicing and/or protein expression and function. To improve NF1 and SPRED1 variant classification and establish pathogenicity for NF1 and SPRED1 variants identified in individuals with NF1 or LS, we analyzed patient RNA by RT-PCR and performed in vitro exon trap experiments and estimated NF and SPRED1 protein expression, RAS GAP activity, and interaction. We obtained evidence to support pathogenicity according to American College of Medical Genetics guidelines for 73/114 variants tested, demonstrating the utility of functional approaches for NF1 and SPRED1 variant classification and NF and LS diagnostics.
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Dekker J, Schot R, Bongaerts M, de Valk WG, van Veghel-Plandsoen MM, Monfils K, Douben H, Elfferich P, Kasteleijn E, van Unen LMA, Geeven G, Saris JJ, van Ierland Y, Verheijen FW, van der Sterre MLT, Sadeghi Niaraki F, Smits DJ, Huidekoper HH, Williams M, Wilke M, Verhoeven VJM, Joosten M, Kievit AJA, van de Laar IMBH, Hoefsloot LH, Hoogeveen-Westerveld M, Nellist M, Mancini GMS, van Ham TJ. Web-accessible application for identifying pathogenic transcripts with RNA-seq: Increased sensitivity in diagnosis of neurodevelopmental disorders. Am J Hum Genet 2023; 110:251-72. [PMID: 36669495 DOI: 10.1016/j.ajhg.2022.12.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 12/21/2022] [Indexed: 01/20/2023] Open
Abstract
For neurodevelopmental disorders (NDDs), a molecular diagnosis is key for management, predicting outcome, and counseling. Often, routine DNA-based tests fail to establish a genetic diagnosis in NDDs. Transcriptome analysis (RNA sequencing [RNA-seq]) promises to improve the diagnostic yield but has not been applied to NDDs in routine diagnostics. Here, we explored the diagnostic potential of RNA-seq in 96 individuals including 67 undiagnosed subjects with NDDs. We performed RNA-seq on single individuals' cultured skin fibroblasts, with and without cycloheximide treatment, and used modified OUTRIDER Z scores to detect gene expression outliers and mis-splicing by exonic and intronic outliers. Analysis was performed by a user-friendly web application, and candidate pathogenic transcriptional events were confirmed by secondary assays. We identified intragenic deletions, monoallelic expression, and pseudoexonic insertions but also synonymous and non-synonymous variants with deleterious effects on transcription, increasing the diagnostic yield for NDDs by 13%. We found that cycloheximide treatment and exonic/intronic Z score analysis increased detection and resolution of aberrant splicing. Importantly, in one individual mis-splicing was found in a candidate gene nearly matching the individual's specific phenotype. However, pathogenic splicing occurred in another neuronal-expressed gene and provided a molecular diagnosis, stressing the need to customize RNA-seq. Lastly, our web browser application allowed custom analysis settings that facilitate diagnostic application and ranked pathogenic transcripts as top candidates. Our results demonstrate that RNA-seq is a complementary method in the genomic diagnosis of NDDs and, by providing accessible analysis with improved sensitivity, our transcriptome analysis approach facilitates wider implementation of RNA-seq in routine genome diagnostics.
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