1
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Letelier A, Ljung R, Olsson A, Andersson NG. Silent variant in F8:c.222G>T (p.Thr74Thr) causes a partial exon skipping in a patient with mild hemophilia A. Mol Genet Genomic Med 2021; 10:e1856. [PMID: 34962362 PMCID: PMC8801133 DOI: 10.1002/mgg3.1856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Revised: 11/04/2021] [Accepted: 12/14/2021] [Indexed: 11/30/2022] Open
Abstract
One of the challenges of genetic testing in patients with hemophilia A is the interpretation of sequence variants. Here we report a silent variant found in exon 2 in the F8 gene in a 47‐year‐old patient with a previous von Willebrand disease (VWD) type 1 diagnosis. Clinically he had mild bleeding symptoms restricted to prolonged bleeding from minor wounds. Sanger sequencing of F8 gene using genomic DNA showed a hemizygous silent variant in exon 2: c.222G>T, p.Thr74Thr. When applying ACMG criteria, the variant was predicted to be “likely benign” in the analyzing software or VUS after curating. Sanger sequencing of the patient's cDNA after nested polymerase chain reaction showed that the patient had both a normal transcript containing exons 1–4 and a defect transcript lacking exon 2. These findings explain the patient's low FVIII:C level and led to the diagnosis of mild hemophilia A instead of VWD type 1. This case illustrates that mRNA work‐up may be needed to clarify a patient's phenotype–genotype.
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Affiliation(s)
- Anna Letelier
- Department of Clinical Sciences Lund (IKVL)-Pediatrics, Lund University, Lund, Sweden.,Department for Molecular Diagnostics, Clinical Genetics Hemophilia Laboratory, Region Skåne, Skåne University Hospital, Lund, Sweden
| | - Rolf Ljung
- Department of Clinical Sciences Lund (IKVL)-Pediatrics, Lund University, Lund, Sweden
| | - Anna Olsson
- Department of Medicine, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Nadine G Andersson
- Department of Clinical Sciences Lund (IKVL)-Pediatrics, Lund University, Lund, Sweden.,Department of Pediatric Hematology and Oncology, Region Skåne, Skåne University Hospital, Lund, Sweden
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2
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Lombardi S, Leo G, Merlin S, Follenzi A, McVey JH, Maestri I, Bernardi F, Pinotti M, Balestra D. Dissection of pleiotropic effects of variants in and adjacent to F8 exon 19 and rescue of mRNA splicing and protein function. Am J Hum Genet 2021; 108:1512-1525. [PMID: 34242570 DOI: 10.1016/j.ajhg.2021.06.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 06/14/2021] [Indexed: 12/11/2022] Open
Abstract
The pathogenic significance of nucleotide variants commonly relies on nucleotide position within the gene, with exonic changes generally attributed to quantitative or qualitative alteration of protein biosynthesis, secretion, activity, or clearance. However, these changes may exert pleiotropic effects on both protein biology and mRNA splicing due to the overlapping of the amino acid and splicing codes, thus shaping the disease phenotypes. Here, we focused on hemophilia A, in which the definition of F8 variants' causative role and association to bleeding phenotypes is crucial for proper classification, genetic counseling, and management of affected individuals. We extensively characterized a large panel of hemophilia A-causing variants (n = 30) within F8 exon 19 by combining and comparing in silico and recombinant expression analyses. We identified exonic variants with pleiotropic effects and dissected the altered protein features of all missense changes. Importantly, results from multiple prediction algorithms provided qualitative results, while recombinant assays allowed us to correctly infer the likely phenotype severity for 90% of variants. Molecular characterization of pathogenic variants was also instrumental for the development of tailored correction approaches to rescue splicing affecting variants or missense changes impairing protein folding. A single engineered U1snRNA rescued mRNA splicing of nine different variants and the use of a chaperone-like drug resulted in improved factor VIII protein secretion for four missense variants. Overall, dissection of the molecular mechanisms of a large panel of HA variants allowed precise classification of HA-affected individuals and favored the development of personalized therapeutic approaches.
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Affiliation(s)
- Silvia Lombardi
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara 44121, Italy
| | - Gabriele Leo
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara 44121, Italy
| | - Simone Merlin
- Department of Health Sciences, University of Piemonte Orientale, Novara 28100, Italy
| | - Antonia Follenzi
- Department of Health Sciences, University of Piemonte Orientale, Novara 28100, Italy
| | - John H McVey
- School of Bioscience and Medicine, University of Surrey, Guildford GU2 7XH, UK
| | - Iva Maestri
- Department of Experimental and Diagnostic Medicine, University of Ferrara, Ferrara 44123, Italy
| | - Francesco Bernardi
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara 44121, Italy
| | - Mirko Pinotti
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara 44121, Italy.
| | - Dario Balestra
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara 44121, Italy.
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3
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Lassalle F, Jourdy Y, Jouan L, Swystun L, Gauthier J, Zawadzki C, Goudemand J, Susen S, Rivard GE, Lillicrap D. The challenge of genetically unresolved haemophilia A patients: Interest of the combination of whole F8 gene sequencing and functional assays. Haemophilia 2020; 26:1056-1063. [PMID: 33094873 DOI: 10.1111/hae.14179] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/17/2020] [Accepted: 09/22/2020] [Indexed: 12/29/2022]
Abstract
BACKGROUND The causative variant remains unidentified in 2%-5% of haemophilia A (HA) patients despite an exhaustive sequencing of the full F8 coding sequence, splice consensus sequences, 5'/3' untranslated regions and copy number variant (CNV) analysis. Next-generation sequencing (NGS) has provided significant improvements for a complete F8 analysis. AIM The aim of this study was to identify and characterize pathogenic non-coding variants in F8 of 15 French and Canadian HA patients genetically unresolved, through the use of NGS, mRNA sequencing and functional confirmation of aberrant splicing. METHODS We sequenced the entire F8 gene using an NGS capture method. We analysed F8 mRNA in order to detect aberrant transcripts. The pathogenic effect of candidate intronic variants was further confirmed using a minigene assay. RESULTS After bioinformatic analysis, 11 deep intronic variants were identified in 13 patients (8 new variants and 3 previously reported). Three variants were confirmed to be likely pathogenic with the presence of an aberrant transcript during mRNA analysis and minigene assay. We also found a small intronic deletion in 6 patients, recently described as causing mild HA. CONCLUSION With this comprehensive work combining NGS and functional assays, we report new deep intronic variants that cause HA through splicing alteration mechanism. Functional analyses are critical to confirm the pathogenic effect of these variants and will be invaluable in the future to study the large number of variants of uncertain significance that may affect splicing that will be found in the human genome.
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Affiliation(s)
- Fanny Lassalle
- CHU Lille, Institut d'Hématologie - Transfusion, Pôle de Biologie Pathologie Génétique, Lille, France.,Univ Lille, Inserm, U1011 - EGID, Institut Pasteur de Lille, Lille, France
| | - Yohann Jourdy
- Service d'hématologie biologique, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, France.,EA 4609 Hémostase et Cancer, Université Claude Bernard Lyon 1, Lyon, France
| | - Loubna Jouan
- Integrated Centre for Pediatric Clinical Genomics, CHU Sainte Justine, Montreal, Canada
| | - Laura Swystun
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Canada
| | - Julie Gauthier
- Molecular Diagnostic Laboratory and Division of Medical Genetics, Department of Pediatrics, CHU Sainte Justine, Montreal, Canada
| | - Christophe Zawadzki
- CHU Lille, Institut d'Hématologie - Transfusion, Pôle de Biologie Pathologie Génétique, Lille, France
| | - Jenny Goudemand
- CHU Lille, Institut d'Hématologie - Transfusion, Pôle de Biologie Pathologie Génétique, Lille, France
| | - Sophie Susen
- CHU Lille, Institut d'Hématologie - Transfusion, Pôle de Biologie Pathologie Génétique, Lille, France.,Univ Lille, Inserm, U1011 - EGID, Institut Pasteur de Lille, Lille, France
| | | | - David Lillicrap
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Canada
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4
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Deep intronic F8 c.5999-27A>G variant causes exon 19 skipping and leads to moderate hemophilia A. Blood Coagul Fibrinolysis 2020; 31:476-480. [PMID: 32833809 DOI: 10.1097/mbc.0000000000000950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
: Hemophilia A, an X-linked recessive bleeding disorder, is caused by mutations of F8 gene. In about 2% hemophilia A patients, no exonic mutation of F8 gene was found. We aimed to identify deep intronic mutations of F8 gene. We reanalyzed the next-generation sequencing data of six hemophilia A patients with negative F8 variant in either coding region or splice site. Deep intronic F8 c.5999-27A>G variant (NM_000132.3) was found in two unrelated moderate hemophilia A patients from different region, and one patient's mother was mild hemophilia A patient. Splice site prediction algorithms showed no impact of this variant on F8 mRNA splicing of exon 19, including Human Splicing Finder 3.1, NNSPLICE 0.9, NetGene2, and Transcript-inferred Pathogenicity score. Exonic splicing enhancer was predicted by ESEfinder, and no difference was found between the wild type and mutant sequence. The branch point predicted by SVM-BPfinder suggested that F8 c.5999-27A>G variant may disrupt the branch point in intron 18 and affect the acceptor site splicing of F8 exon 19. Sanger sequencing of F8 cDNA from peripheral blood mononuclear cells confirmed that F8 c.5999-27A>G variant caused F8 exon 19 skipping in proband and his mother. Skewed X chromosome inactivation was found in another X chromosome of this mother, combined with F8 c.5999-27A>G variant in trans. In conclusion, our study suggests that deep intronic F8 c.5999-27A>G variant may be responsible for F8 exon 19 skipping and lead to moderate hemophilia A. Systematic reanalysis of next-generation sequencing data could promote the diagnostic yields.
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5
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Famà R, Borroni E, Zanolini D, Merlin S, Bruscaggin V, Walker GE, Olgasi C, Babu D, Agnelli Giacchello J, Valeri F, Giordano M, Borchiellini A, Follenzi A. Identification and functional characterization of a novel splicing variant in the F8 coagulation gene causing severe hemophilia A. J Thromb Haemost 2020; 18:1050-1064. [PMID: 32078252 DOI: 10.1111/jth.14779] [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: 06/25/2019] [Revised: 01/30/2020] [Accepted: 02/10/2020] [Indexed: 11/27/2022]
Abstract
BACKGROUND We have identified a synonymous F8 variation in a severe hemophilia A (HA) patient who developed inhibitors following factor VIII (FVIII) prophylaxis. The unreported c.6273 G > A variant targets the consensus splicing site of exon 21. OBJECTIVES To determine the impact of c.6273 G > A nucleotide substitution on F8 splicing and its translated protein. METHODS Patient peripheral blood mononuclear cells were isolated and differentiated into monocyte-derived macrophages (MDMs). FVIII distribution in cell compartments was evaluated by immunofluorescence. The splicing of mutated exon 21 was assessed by exon trapping. Identified FVIII splicing variants were generated by site-directed mutagenesis, inserted into a lentiviral vector (LV) to transduce Chinese hamster ovary (CHO) cells, and inject into B6/129 HA-mice. FVIII activity was assessed by activated partial thromboplastin time, whereas anti-FVIII antibodies and FVIII antigen, by ELISA. RESULTS HA-MDMs demonstrated a predominant retention of FVIII around the endoplasmic reticulum. Exon trapping revealed the production of two isoforms: one retaining part of intron 21 and the other skipping exon 21. These variants, predicted to truncate FVIII in the C1 domain, were detected in the patient. CHO cells transduced with the two FVIII transcripts confirmed protein retention and absence of the C2 domain. HA mice injected with LV carrying FVIII mutants, partially recovered FVIII activity without the appearance of anti-FVIII antibodies. CONCLUSIONS Herein, we demonstrate the aberrant impact of a FVIII synonymous mutation on its transcription, activity, and pathological outcomes. Our data underline the importance of increasing the knowledge regarding the functional consequences of F8 mutations and their link to inhibitor development and an effective replacement therapy.
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Affiliation(s)
- Rosella Famà
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | - Ester Borroni
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | - Diego Zanolini
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | - Simone Merlin
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | | | - Gillian E Walker
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | - Cristina Olgasi
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | - Deepak Babu
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | | | - Federica Valeri
- Hemostasis and Thrombosis Unit, Città Della Salute e Della Scienza, Molinette, Turin, Italy
| | - Mara Giordano
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
| | | | - Antonia Follenzi
- Department of Health Sciences, Università del Piemonte Orientale, Novara, Italy
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6
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Martorell L, Cortina V, Parra R, Barquinero J, Vidal F. Variable readthrough responsiveness of nonsense mutations in hemophilia A. Haematologica 2020; 105:508-518. [PMID: 31197069 PMCID: PMC7012483 DOI: 10.3324/haematol.2018.212118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 06/11/2019] [Indexed: 12/26/2022] Open
Abstract
Readthrough therapy relies on the use of small molecules that enable premature termination codons in mRNA open reading frames to be misinterpreted by the translation machinery, thus allowing the generation of full-length, potentially functional proteins from mRNA carrying nonsense mutations. In patients with hemophilia A, nonsense mutations potentially sensitive to readthrough agents represent approximately 16% of the point mutations. The aim of this study was to measure the readthrough effect of different compounds and to analyze the influence of premature termination codon context in selected nonsense mutations causing hemophilia A. To this end, primary fibroblasts from three patients with hemophilia A caused by nonsense mutations (p.W1586X, p.Q1636X and p.R1960X) and Chinese hamster ovary (CHO) cells transfected with 12 different plasmids encoding mutated F8 (p.Q462X, p.Q1705X, p.Q1764X, p.W274X, p.W1726X, p.W2015X, p.W2131X, p.R1715X, p.R1822X, p.R1960X, p.R2071X and p.R2228X) were treated with gentamicin, geneticin, PTC124, RTC13 or RTC14. Responses were assessed by analyzing not only F8 mRNA expression and FVIII biosynthesis (FVIII antigen by ELISA, western blot and immunofluorescence) but also the FVIII activity (by chromogenic assay). In the patients' fibroblasts, readthrough agents neither stabilized F8 mRNA nor increased FVIII protein or activity to detectable levels. In CHO cells, only in five of the 12 F8 variants, readthrough treatment increased both FVIII antigen and activity levels, which was associated with a reduction in intracellular accumulation of truncated forms and an increase in full-length proteins. These results provide experimental evidence of genetic context dependence of nonsense suppression by readthrough agents and of factors predicting responsiveness.
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Affiliation(s)
- Lluis Martorell
- Gene and Cell Therapy Laboratory, Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona (UAB).,Congenital Coagulopathies Laboratory, Banc de Sang i Teixits (BST)
| | - Vicente Cortina
- Vall d'Hebron Core Laboratory (Section of Thrombosis and Haemostasis), Hospital Vall d'Hebron
| | | | - Jordi Barquinero
- Gene and Cell Therapy Laboratory, Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona (UAB)
| | - Francisco Vidal
- Congenital Coagulopathies Laboratory, Banc de Sang i Teixits (BST) .,Molecular Diagnosis and Therapy Unit, VHIR-UAB.,CIBER de Enfermedades Cardiovasculares (CIBERCV), Barcelona, Spain
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7
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Jourdy Y, Fretigny M, Nougier C, Négrier C, Bozon D, Vinciguerra C. Splicing analysis of 26 F8 nucleotide variations using a minigene assay. Haemophilia 2019; 25:306-315. [PMID: 30690819 DOI: 10.1111/hae.13687] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 12/05/2018] [Accepted: 01/08/2019] [Indexed: 12/11/2022]
Abstract
BACKGROUND Classically, the study of splicing impact of variation located near the splice site is performed by both in silico and mRNA analysis. However, RNA sample was rarely available. OBJECTIVE To characterize a panel of putative haemophilia A splicing variations. MATERIALS AND METHODS Twenty-six F8 variations identified from a cohort of 2075 haemophilia A families were studied using both bioinformatic tools and in vitro minigene assays in HeLa and Huh7 cells. RESULTS An aberrant splicing was demonstrated for 21/26 tested sequence variations. A good correlation between in silico and in vitro analysis was obtained for variations affecting donor splice site (12/14) and for the synonymous variations located inside an exon (6/6). Conversely, no concordant results were observed for the six variations affecting acceptor splice sites. The variations resulted more frequently in exon skipping (n = 13) than in activation of nearby cryptic splice sites (n = 5), in use of a de novo splice site (n = 2) or in insertion of large intronic sequences (n = 1). This study allowed to reclassify 5 synonymous substitutions c.1167A>G (p.Gln389Gln), c.1569G>T (p.Leu523Leu), c.1752G>A (p.Gln584Gln), c.5586G>A (p.Leu1862Leu) and c.6066C>T (p.Gly2022Gly) as splicing variations. The pathological significance of five variations remained unclear (c.222G>A [p.Thr74Thr], c.237C>T [p.Asn79Asn], c.240C>T [p.Ile80Ile], c.2113+5_2113+8del and c.2113+5G>A). DISCUSSION The minigene assay herein gave additional evidences for the clinical significance of 21/26 F8 putative splice site mutations. Such investigation should be performed for each F8 putative splice site variation for which no mRNA sample is available, notably to greatly improve the genetic counselling given to female carriers.
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Affiliation(s)
- Yohann Jourdy
- Service d'Hématologie Biologique, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France.,EA 4609 Hémostase et Cancer, Université Claude Bernard Lyon 1, University Lyon, Lyon, France
| | - Mathilde Fretigny
- Service d'Hématologie Biologique, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France
| | - Christophe Nougier
- Service d'Hématologie Biologique, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France
| | - Claude Négrier
- Service d'Hématologie Biologique, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France.,EA 4609 Hémostase et Cancer, Université Claude Bernard Lyon 1, University Lyon, Lyon, France
| | - Dominique Bozon
- Laboratoire de Cardiogénétique Moléculaire, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France
| | - Christine Vinciguerra
- Service d'Hématologie Biologique, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, France.,EA 4609 Hémostase et Cancer, Université Claude Bernard Lyon 1, University Lyon, Lyon, France
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8
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Spena S, Garagiola I, Cannavò A, Mortarino M, Mannucci PM, Rosendaal FR, Peyvandi F. Prediction of factor VIII inhibitor development in the SIPPET cohort by mutational analysis and factor VIII antigen measurement. J Thromb Haemost 2018; 16:778-790. [PMID: 29399993 DOI: 10.1111/jth.13961] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Indexed: 01/28/2023]
Abstract
Essentials A residual factor VIII synthesis is likely to be protective towards inhibitor (INH) development. Mutation type-inhibitor risk association was explored in 231 patients with severe hemophilia A. A 2-fold increase in INH development for in silico null vs. non-null mutations was found. A 3.5-fold increase in INH risk for antigen negative vs. antigen positive mutations was found. SUMMARY Background The type of F8 mutation is the main predictor of inhibitor development in patients with severe hemophilia A. Mutations expected to allow residual synthesis of factor VIII are likely to play a protective role against alloantibody development by inducing immune tolerance. According to the expected full or partial impairment of FVIII synthesis, F8 variants are commonly classified as null and non-null. Objectives To explore the mutation type-inhibitor risk association in a cohort of 231 patients with severe hemophilia A enrolled in the Survey of Inhibitors in Plasma-Product Exposed Toddlers (SIPPET) randomized trial. Methods The genetic defects in these patients, consisting of inversions of intron 22 (n = 110) and intron 1 (n = 6), large deletions (n = 16), and nonsense (n = 38), frameshift (n = 28), missense (n = 19) and splicing (n = 14) variants, of which 34 have been previously unreported, were reclassified according to two additional criteria: the functional effects of missense and splicing alterations as predicted by multiple in silico analyses, and the levels of FVIII antigen in patient plasma. Results A two-fold increase in inhibitor development for in silico null mutations as compared with in silico non-null mutations (hazard ratio [HR] 2.08, 95% confidence interval [CI] 0.84-5.17) and a 3.5-fold increase in inhibitor development for antigen-negative mutations as compared with antigen-positive mutations (HR 3.61, 95% CI 0.89-14.74] were found. Conclusions Our findings confirm an association between the synthesis of minute amounts of FVIII and inhibitor protection, and underline the importance of investigating the residual FVIII antigen levels associated with causative variants in order to understand their clinical relevance.
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Affiliation(s)
- S Spena
- Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy
| | - I Garagiola
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, and Luigi Villa Foudation, Milan, Italy
| | - A Cannavò
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, and Luigi Villa Foudation, Milan, Italy
- Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands
| | - M Mortarino
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, and Luigi Villa Foudation, Milan, Italy
| | - P M Mannucci
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, and Luigi Villa Foudation, Milan, Italy
| | - F R Rosendaal
- Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands
| | - F Peyvandi
- Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, and Luigi Villa Foudation, Milan, Italy
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9
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Jourdy Y, Janin A, Fretigny M, Lienhart A, Négrier C, Bozon D, Vinciguerra C. Reccurrent F8 Intronic Deletion Found in Mild Hemophilia A Causes Alu Exonization. Am J Hum Genet 2018; 102:199-206. [PMID: 29357978 DOI: 10.1016/j.ajhg.2017.12.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 12/12/2017] [Indexed: 01/12/2023] Open
Abstract
Incorporation of distant intronic sequences in mature mRNA is an underappreciated cause of genetic disease. Several disease-causing pseudoexons have been found to contain repetitive elements such as Alu elements. This study describes an original pathological mechanism by which a small intronic deletion leads to Alu exonization. We identified an intronic deletion, c.2113+461_2113+473del, in the F8 intron 13, in two individuals with mild hemophilia A. In vivo and in vitro transcript analysis found an aberrant transcript, with an insertion of a 122-bp intronic fragment (c.2113_2114ins2113+477_2113+598) at the exon 13-14 junction. This out-of-frame insertion is predicted to lead to truncated protein (p.Gly705Aspfs∗37). DNA sequencing analysis found that the pseudoexon corresponds to antisense AluY element and the deletion removed a part of the poly(T)-tail from the right arm of these AluY. The heterogenous nuclear riboprotein C1/C2 (hnRNP C) is an important antisense Alu-derived cryptic exon silencer and binds to poly(T)-tracts. Disruption of the hnRNP C binding site in AluY T-tract by mutagenesis or hnRNP C knockdown using siRNA in HeLa cells reproduced the effect of c.2113+461_2113+473del. The screening of 114 unrelated families with mild hemophilia A in whom no genetic event was previously identified found a deletion in the poly(T)-tail of AluY in intron 13 in 54% of case subjects (n = 61/114). In conclusion, this study describes a deletion leading to Alu exonization found in 6.1% of families with mild hemophila A in France.
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Affiliation(s)
- Yohann Jourdy
- Service d'hématologie biologique, Centre de Biologie et Pathologie Est, Bron (69500) Hospices Civils de Lyon, France; EA 4609 Hémostase et cancer, Lyon (69008), Université Claude Bernard Lyon 1, Univ Lyon, France.
| | - Alexandre Janin
- Laboratoire de Cardiogénétique Moléculaire, Centre de Biologie et Pathologie Est, Bron (69500), Hospices Civils de Lyon, France; Institut NeuroMyoGène, Université Claude Bernard Lyon 1, Univ Lyon, France, CNRS UMR 5510, Villeurbanne (69100), France; INSERM U1217, Villeurbanne, France
| | - Mathilde Fretigny
- Service d'hématologie biologique, Centre de Biologie et Pathologie Est, Bron (69500) Hospices Civils de Lyon, France
| | - Anne Lienhart
- Unité d'hémostase clinique, Hôpital Cardiologique Louis Pradel, Bron (69500), Hospices Civils de Lyon, France
| | - Claude Négrier
- Service d'hématologie biologique, Centre de Biologie et Pathologie Est, Bron (69500) Hospices Civils de Lyon, France; EA 4609 Hémostase et cancer, Lyon (69008), Université Claude Bernard Lyon 1, Univ Lyon, France; Unité d'hémostase clinique, Hôpital Cardiologique Louis Pradel, Bron (69500), Hospices Civils de Lyon, France
| | - Dominique Bozon
- Laboratoire de Cardiogénétique Moléculaire, Centre de Biologie et Pathologie Est, Bron (69500), Hospices Civils de Lyon, France
| | - Christine Vinciguerra
- Service d'hématologie biologique, Centre de Biologie et Pathologie Est, Bron (69500) Hospices Civils de Lyon, France; EA 4609 Hémostase et cancer, Lyon (69008), Université Claude Bernard Lyon 1, Univ Lyon, France
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