Multimodal mechanisms of pathogenic variants in the signal peptide of FIX leading to hemophilia B.

Guomin Shen, Jian-Ke Tie, Weikai Li, Meng Gao, Qing Cao, Jinlong Yang, Yan Shen, Long Chen, Hongli Liu, Lei Zhang, Haiping Yang, Shixia Dong, Zihan Cui, Yanyan Dong, Zhenyu Hao

Journal: Blood advances 2024;8(15):3893-3905

PMID: 38820490

Free Full Text on Elsevier Science View on PubMed

Abstract

Signal peptide (SP) is essential for protein secretion, and pathogenic variants in the SP of factor IX (FIX) have been identified in hemophilia B (HB). However, the underlying mechanism for the genotype-phenotype correlation of these variants has not been well studied. Here, we systematically examined the effects of 13 pathogenic point variants in the SP of FIX using different approaches. Our results showed that these point variants lead to HB by missense variants and/or aberrant premessenger RNA (pre-mRNA) splicing. The missense variants in a hydrophobic core (h-region) mainly affected the cotranslational translocation function of the SP, and those in C-terminal containing cleavage site (c-region) caused FIX deficiency mainly by disturbing the cotranslational translocation and/or cleavage of the SP. Almost absolute aberrant pre-mRNA splicing was only observed in variants of c.82T>G, but a slight change of splicing patterns was found in variants of c.53G>T, c.77C>A, c.82T>C, and c.83G>A, indicating that these variants might have different degrees of impact on pre-mRNA splicing. Although two 6-nt deletion aberrant pre-mRNA splicing products caused FIX deficiency by disturbing the SP cleavage, they could produce some functional mature FIX, and vitamin K could increase the secretion of functional FIX. Taken together, our data indicated that pathogenic variants in the SP of FIX caused HB through diverse molecular mechanisms or even a mixture of several mechanisms, and vitamin K availability could be partially attributed to varying bleeding tendencies in patients carrying the same variant in the SP.

© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.

Address: Henan International Joint Laboratory of Thrombosis and Hemostasis, College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, People's Republic of China.; Department of Cell Biology, Harbin Medical University, Harbin, People's Republic of China.; Henan International Joint Laboratory of Thrombosis and Hemostasis, College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, People's Republic of China.; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO.; Henan International Joint Laboratory of Thrombosis and Hemostasis, College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, People's Republic of China.; Department of Cell Biology, Harbin Medical University, Harbin, People's Republic of China.; Henan International Joint Laboratory of Thrombosis and Hemostasis, College of Basic Medicine and Forensic Medicine, Henan University of Science and Technology, Luoyang, People's Republic of China.; First Affiliated Hospital of Henan University of Science and Technology, Luoyang, People's Republic of China.; College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, People's Republic of China.; State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, People's Republic of China.; Tianjin Key Laboratory of Gene Therapy for Blood Diseases, CAMS Key Laboratory of Gene Therapy for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, People's Republic of China.; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO.; Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC.

DOI: 10.1182/bloodadvances.2023012432

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MeSH Terms: Hemophilia B, Factor IX, Humans, RNA Splicing, Protein Sorting Signals, Mutation, Missense