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Dericquebourg A, Fretigny M, Leuci A, Zawadzki C, Huguenin Y, Castet SM, Dargaud Y, Vinciguerra C, Jourdy Y. Whole F8 gene sequencing combined with splicing functional analyses led to a substantial increase of the molecular diagnosis yield for non-severe haemophilia A. Haemophilia 2023; 29:1320-1333. [PMID: 37410802 DOI: 10.1111/hae.14824] [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: 04/26/2023] [Revised: 06/02/2023] [Accepted: 06/24/2023] [Indexed: 07/08/2023]
Abstract
INTRODUCTION Conventional genetic investigation fails to identify the F8 causal variant in 2.5%-10% of haemophilia A (HA) patients with non-severe phenotypes. In these cases, F8 deep intronic variants could be causal. AIM To identify pathogenic F8 deep intronic variants in genetically unresolved families with non-severe HA analysed in the haematology laboratory of the Hospices Civils de Lyon. METHODS The whole F8 was analysed by next generation sequencing. The pathogenic impact of candidate variants identified was assessed using both in silico analysis (MaxEntScan and spliceAI) and functional analysis (RNA or minigene assay). RESULTS Sequencing was performed in 49/55 families included for which a DNA sample from a male propositus was available. In total, 33 candidate variants from 43 propositi were identified. These variants corresponded to 31 single nucleotide substitutions, one 173-bp deletion, and an 869-bp tandem triplication. No candidate variant was found in six propositi. The most frequent variants found were the association of [c.2113+1154G>C and c.5374-304C>T], identified in five propositi, and the c.2114-6529C>G identified in nine propositi. Four variants had been previously described as HA-causing. Splicing functional assay found a deleterious impact for 11 substitutions (c.671-94G>A, c.788-312A>G, c.2113+1154G>C, c.2114-6529C>G, c.5999-820A>T, c.5999-786C>A, c.5999-669G>T, c.5999-669G>A, c.5999-669G>C, c.6900+4104A>C, and c.6901-2992A>G). The HA-causing variant was identified in 33/49 (67%) cases. In total, F8 deep intronic variants caused 8.8% of the non-severe HA among the 1643 families analysed in our laboratory. CONCLUSION The results emphasise the value of whole F8 gene sequencing combined with splicing functional analyses to improve the diagnosis yield for non-severe HA.
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Affiliation(s)
- Amy Dericquebourg
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service d'hématologie biologique, Bron, France
- Université Claude Bernard Lyon 1, UR4609 Hémostase et thrombose, Lyon, France
| | - Mathilde Fretigny
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service d'hématologie biologique, Bron, France
| | - Alexandre Leuci
- Université Claude Bernard Lyon 1, UR4609 Hémostase et thrombose, Lyon, France
| | - Christophe Zawadzki
- Pôle de Biologie Pathologie Génétique, Institut d'Hématologie - Transfusion, CHU Lille, Lille, France
| | - Yoann Huguenin
- Centre de Ressources et de Compétence des Maladies Hémorragiques Constitutionnelles, Hôpital Pellegrin, CHU de Bordeaux, Bordeaux, France
| | - Sabine-Marie Castet
- Centre de Ressources et de Compétence des Maladies Hémorragiques Constitutionnelles, Hôpital Pellegrin, CHU de Bordeaux, Bordeaux, France
| | - Yesim Dargaud
- Université Claude Bernard Lyon 1, UR4609 Hémostase et thrombose, Lyon, France
- Unité d'Hémostase Clinique, Centre National de Reference de l'Hémophilie, Hôpital Cardiologique Louis Pradel, Université Lyon, Lyon, France
| | - Christine Vinciguerra
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service d'hématologie biologique, Bron, France
- Université Claude Bernard Lyon 1, UR4609 Hémostase et thrombose, Lyon, France
| | - Yohann Jourdy
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service d'hématologie biologique, Bron, France
- Université Claude Bernard Lyon 1, UR4609 Hémostase et thrombose, Lyon, France
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Dardik R, Janczar S, Lalezari S, Avishai E, Levy-Mendelovich S, Barg AA, Martinowitz U, Babol-Pokora K, Mlynarski W, Kenet G. Four Decades of Carrier Detection and Prenatal Diagnosis in Hemophilia A: Historical Overview, State of the Art and Future Directions. Int J Mol Sci 2023; 24:11846. [PMID: 37511607 PMCID: PMC10380558 DOI: 10.3390/ijms241411846] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 07/09/2023] [Accepted: 07/21/2023] [Indexed: 07/30/2023] Open
Abstract
Hemophilia A (HA), a rare recessive X-linked bleeding disorder, is caused by either deficiency or dysfunction of coagulation factor VIII (FVIII) resulting from deleterious mutations in the F8 gene encoding FVIII. Over the last 4 decades, the methods aimed at determining the HA carrier status in female relatives of HA patients have evolved from phenotypic studies based on coagulation tests providing merely probabilistic results, via genetic linkage studies based on polymorphic markers providing more accurate results, to next generation sequencing studies enabling highly precise identification of the causative F8 mutation. In parallel, the options for prenatal diagnosis of HA have progressed from examination of FVIII levels in fetal blood samples at weeks 20-22 of pregnancy to genetic analysis of fetal DNA extracted from chorionic villus tissue at weeks 11-14 of pregnancy. In some countries, in vitro fertilization (IVF) combined with preimplantation genetic diagnosis (PGD) has gradually become the procedure of choice for HA carriers who wish to prevent further transmission of HA without the need to undergo termination of pregnancies diagnosed with affected fetuses. In rare cases, genetic analysis of a HA carrier might be complicated by skewed X chromosome inactivation (XCI) of her non-hemophilic X chromosome, thus leading to the phenotypic manifestation of moderate to severe HA. Such skewed XCI may be associated with deleterious mutations in X-linked genes located on the non-hemophilic X chromosome, which should be considered in the process of genetic counseling and PGD planning for the symptomatic HA carrier. Therefore, whole exome sequencing, combined with X-chromosome targeted bioinformatic analysis, is highly recommended for symptomatic HA carriers diagnosed with skewed XCI in order to identify additional deleterious mutations potentially involved in XCI skewing. Identification of such mutations, which may profoundly impact the reproductive choices of HA carriers with skewed XCI, is extremely important.
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Affiliation(s)
- Rima Dardik
- National Hemophilia Center, Sheba Medical Center, Ramat Gan 52621, Israel
- Amalia Biron Research Institute of Thrombosis and Hemostasis, Sackler School of Medicine, Tel Aviv University, Tel Aviv 52621, Israel
| | - Szymon Janczar
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 90-419 Lodz, Poland
| | - Shadan Lalezari
- National Hemophilia Center, Sheba Medical Center, Ramat Gan 52621, Israel
- Amalia Biron Research Institute of Thrombosis and Hemostasis, Sackler School of Medicine, Tel Aviv University, Tel Aviv 52621, Israel
| | - Einat Avishai
- National Hemophilia Center, Sheba Medical Center, Ramat Gan 52621, Israel
- Amalia Biron Research Institute of Thrombosis and Hemostasis, Sackler School of Medicine, Tel Aviv University, Tel Aviv 52621, Israel
| | - Sarina Levy-Mendelovich
- National Hemophilia Center, Sheba Medical Center, Ramat Gan 52621, Israel
- Amalia Biron Research Institute of Thrombosis and Hemostasis, Sackler School of Medicine, Tel Aviv University, Tel Aviv 52621, Israel
| | - Assaf Arie Barg
- National Hemophilia Center, Sheba Medical Center, Ramat Gan 52621, Israel
- Amalia Biron Research Institute of Thrombosis and Hemostasis, Sackler School of Medicine, Tel Aviv University, Tel Aviv 52621, Israel
| | - Uri Martinowitz
- National Hemophilia Center, Sheba Medical Center, Ramat Gan 52621, Israel
| | - Katarzyna Babol-Pokora
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 90-419 Lodz, Poland
| | - Wojciech Mlynarski
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 90-419 Lodz, Poland
| | - Gili Kenet
- National Hemophilia Center, Sheba Medical Center, Ramat Gan 52621, Israel
- Amalia Biron Research Institute of Thrombosis and Hemostasis, Sackler School of Medicine, Tel Aviv University, Tel Aviv 52621, Israel
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Keegan NP, Wilton SD, Fletcher S. Analysis of Pathogenic Pseudoexons Reveals Novel Mechanisms Driving Cryptic Splicing. Front Genet 2022; 12:806946. [PMID: 35140743 PMCID: PMC8819188 DOI: 10.3389/fgene.2021.806946] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 12/09/2021] [Indexed: 12/16/2022] Open
Abstract
Understanding pre-mRNA splicing is crucial to accurately diagnosing and treating genetic diseases. However, mutations that alter splicing can exert highly diverse effects. Of all the known types of splicing mutations, perhaps the rarest and most difficult to predict are those that activate pseudoexons, sometimes also called cryptic exons. Unlike other splicing mutations that either destroy or redirect existing splice events, pseudoexon mutations appear to create entirely new exons within introns. Since exon definition in vertebrates requires coordinated arrangements of numerous RNA motifs, one might expect that pseudoexons would only arise when rearrangements of intronic DNA create novel exons by chance. Surprisingly, although such mutations do occur, a far more common cause of pseudoexons is deep-intronic single nucleotide variants, raising the question of why these latent exon-like tracts near the mutation sites have not already been purged from the genome by the evolutionary advantage of more efficient splicing. Possible answers may lie in deep intronic splicing processes such as recursive splicing or poison exon splicing. Because these processes utilize intronic motifs that benignly engage with the spliceosome, the regions involved may be more susceptible to exonization than other intronic regions would be. We speculated that a comprehensive study of reported pseudoexons might detect alignments with known deep intronic splice sites and could also permit the characterisation of novel pseudoexon categories. In this report, we present and analyse a catalogue of over 400 published pseudoexon splice events. In addition to confirming prior observations of the most common pseudoexon mutation types, the size of this catalogue also enabled us to suggest new categories for some of the rarer types of pseudoexon mutation. By comparing our catalogue against published datasets of non-canonical splice events, we also found that 15.7% of pseudoexons exhibit some splicing activity at one or both of their splice sites in non-mutant cells. Importantly, this included seven examples of experimentally confirmed recursive splice sites, confirming for the first time a long-suspected link between these two splicing phenomena. These findings have the potential to improve the fidelity of genetic diagnostics and reveal new targets for splice-modulating therapies.
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Affiliation(s)
- Niall P. Keegan
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
- *Correspondence: Niall P. Keegan,
| | - Steve D. Wilton
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
| | - Sue Fletcher
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
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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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Inaba H, Shinozawa K, Amano K, Fukutake K. Identification of deep intronic individual variants in patients with hemophilia A by next-generation sequencing of the whole factor VIII gene. Res Pract Thromb Haemost 2017; 1:264-274. [PMID: 30046696 PMCID: PMC6058261 DOI: 10.1002/rth2.12031] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 06/27/2017] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND No genetic defects are found in the coagulation factor VIII gene (F8) of approximately 2% of patients with hemophilia A. Recently, genomic variants causative of hemophilia A that were located deep within introns have been reported. OBJECTIVES We aimed to establish a comprehensive method of analysis of F8 using next-generation sequencing (NGS) and investigate the variants located deep within the introns of F8. PATIENTS/METHODS Forty-five male patients with hemophilia A, including 31 with previously identified causative mutations, were investigated. RESULTS Our NGS analysis allowed for the identification of genetic variants in roughly 99% of F8. We confirmed that our NGS analysis can detect the single nucleotide variants and small deletions with high accuracy. After filtering, a total of 27 rare and unique individual variants from 16 patients remained. Three of these variants, c.144-10810T>C, c.1010-365A>G, and c.5219+9065A>G, were predicted as deleterious with high expected accuracy by PredictSNP2 analysis. We also predicted the impact on splicing by in silico analysis using three different algorithms. Two patients with unknown causative mutations carried unique individual variants, c.144-10810T>C and c.6723+193G>A. We inferred that the c.144-10810T>C variant likely causes hemophilia, while the effect of the c.6723+193G>A variant remains unclear. Our analysis showed that the c.6429+14194T>C variant was significantly detected in patients carrying the intron 22 inversion. CONCLUSIONS Rare and unique individual variants located deep within the F8 introns in patients with hemophilia A are not uncommon. Future studies are necessary to determine the function and effect of these variants on F8 expression.
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Affiliation(s)
- Hiroshi Inaba
- Department of Laboratory MedicineTokyo Medical UniversityTokyoJapan
| | - Keiko Shinozawa
- Department of Molecular Genetics of Coagulation DisordersTokyo Medical UniversityTokyoJapan
| | - Kagehiro Amano
- Department of Laboratory MedicineTokyo Medical UniversityTokyoJapan
- Department of Molecular Genetics of Coagulation DisordersTokyo Medical UniversityTokyoJapan
| | - Katsuyuki Fukutake
- Department of Laboratory MedicineTokyo Medical UniversityTokyoJapan
- Department of Molecular Genetics of Coagulation DisordersTokyo Medical UniversityTokyoJapan
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