1
|
Liang Q, Zhang Z, Ding B, Shao Y, Ding Q, Dai J, Hu X, Wu W, Wang X. A noncanonical splicing variant c.875-5 T > G in von Willebrand factor causes in-frame exon skipping and type 2A von Willebrand disease. Thromb Res 2024; 236:51-60. [PMID: 38387303 DOI: 10.1016/j.thromres.2024.02.002] [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: 11/24/2023] [Revised: 01/16/2024] [Accepted: 02/01/2024] [Indexed: 02/24/2024]
Abstract
INTRODUCTION A novel variant involving noncanonical splicing acceptor site (c.875-5 T > G) in propeptide coding region of von Willebrand factor (VWF) was identified in a patient with type 2A von Willebrand disease (VWD), who co-inherited with a null variant (p.Tyr271*) and presented characteristic discrepancy of plasma level of VWF antigen and activity, and a selective reduction of both intermediate-molecular-weight (IMWMs) and high-molecular-weight VWF multimers (HMWMs). MATERIALS AND METHODS VWF mRNA transcripts obtained from peripheral leukocytes and platelets of the patients were investigated to analyze the consequence of c.875-5 T > G on splicing. The impact of the variant on expression and multimer assembly was further analyzed by in vitro expression studies in AtT-20 cells. The intracellular processing of VWF mutant and the Weibel-Palade bodies (WPBs) formation was evaluated by immunofluorescence staining and electron microscopy. RESULTS The mRNA transcript analysis revealed that c.875-5 T > G variant led to exon 8 skipping and an in-frame deletion of 41 amino acids in the D1 domain of VWF (p.Ser292_Glu333delinsLys), yielding a truncated propeptide. Consistent with the patient's laboratory manifestations, the AtT-20 cells transfected with mutant secreted less VWF, with the VWF antigen level in conditioned medium 47 % of wild-type. A slight retention in the endoplasmic reticulum was observed for the mutant. Almost complete loss of IMWMs and HMWMs in the medium and impaired WPBs formation in the cell, indicating truncated VWF propeptide lost its chaperon-like function for VWF multimerization and tubular storage. CONCLUSIONS The VWF splicing site variant (c.875-5 T > G) causes propeptide truncation, severely compromising VWF multimer assembly and tubular storage.
Collapse
Affiliation(s)
- Qian Liang
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Ziqi Zhang
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; Department of Molecular Biology, Shanghai Center for Clinical Laboratory, Shanghai, China
| | - Biying Ding
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Yanyan Shao
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Qiulan Ding
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; Collaborative Innovation Center of Hematology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Jing Dai
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Xiaobo Hu
- Department of Molecular Biology, Shanghai Center for Clinical Laboratory, Shanghai, China.
| | - Wenman Wu
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; Collaborative Innovation Center of Hematology, Shanghai Jiaotong University School of Medicine, Shanghai, China.
| | - Xuefeng Wang
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; Collaborative Innovation Center of Hematology, Shanghai Jiaotong University School of Medicine, Shanghai, China.
| |
Collapse
|
2
|
Yadegari H, Jamil MA, Marquardt N, Oldenburg J. A Homozygous Deep Intronic Variant Causes Von Willebrand Factor Deficiency and Lack of Endothelial-Specific Secretory Organelles, Weibel-Palade Bodies. Int J Mol Sci 2022; 23:ijms23063095. [PMID: 35328514 PMCID: PMC8950443 DOI: 10.3390/ijms23063095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 02/26/2022] [Accepted: 03/01/2022] [Indexed: 11/16/2022] Open
Abstract
A type 3 von Willebrand disease (VWD) index patient (IP) remains mutation-negative after completion of the conventional diagnostic analysis, including multiplex ligation-dependent probe amplification and sequencing of the promoter, exons, and flanking intronic regions of the VWF gene (VWF). In this study, we intended to elucidate causative mutation through next-generation sequencing (NGS) of the whole VWF (including complete intronic region), mRNA analysis, and study of the patient-derived endothelial colony-forming cells (ECFCs). The NGS revealed a variant in the intronic region of VWF (997 + 118 T > G in intron 8), for the first time. The bioinformatics assessments (e.g., SpliceAl) predicted this variant creates a new donor splice site (ss), which could outcompete the consensus 5′ donor ss at exon/intron 8. This would lead to an aberrant mRNA that contains a premature stop codon, targeting it to nonsense-mediated mRNA decay. The subsequent quantitative real-time PCR confirmed the virtual absence of VWF mRNA in IP ECFCs. Additionally, the IP ECFCs demonstrated a considerable reduction in VWF secretion (~6% of healthy donors), and they were devoid of endothelial-specific secretory organelles, Weibel−Palade bodies. Our findings underline the potential of NGS in conjunction with RNA analysis and patient-derived cell studies for genetic diagnosis of mutation-negative type 3 VWD patients.
Collapse
Affiliation(s)
- Hamideh Yadegari
- Correspondence: (H.Y.); (J.O.); Tel.: +49-228-287-10532 (H.Y.); +49-228-287-15175 (J.O.)
| | | | | | - Johannes Oldenburg
- Correspondence: (H.Y.); (J.O.); Tel.: +49-228-287-10532 (H.Y.); +49-228-287-15175 (J.O.)
| |
Collapse
|