Page 79 - 2021_06-Haematologica-web
P. 79
Bone Marrow Failure
A frequent nonsense mutation in exon 1 across certain HLA-A and HLA-B alleles in leukocytes of patients with acquired aplastic anemia
Ferrata Storti Foundation
Haematologica 2021 Volume 106(6):1581-1590
Hiroki Mizumaki,1 Kazuyoshi Hosomichi,2 Kohei Hosokawa,1 Takeshi Yoroidaka,1 Tatsuya Imi,1 Yoshitaka Zaimoku,1 Takamasa Katagiri,3 Mai Anh Thi Nguyen,1 Dung Cao Tran,1 Mahmoud Ibrahim Yousef Elbadry,1,4 Kazuhisa Chonabayashi,5 Yoshinori Yoshida,5 Hiroyuki Takamatsu,1 Tatsuhiko Ozawa,6 Fumihiro Azuma,7 Hiroyuki Kishi,6 Yoichi Fujii,8 Seishi Ogawa,8,9 Atsushi Tajima2 and Shinji Nakao1
1Department of Hematology, Kanazawa University, Kanazawa, Japan; 2Department of Bioinformatics and Genomics, Graduate School of Advanced Preventive Medical Sciences, Kanazawa University, Kanazawa, Japan; 3Clinical Laboratory Sciences, Kanazawa University Graduate School, Kanazawa, Japan; 4Department of Internal Medicine, Division of Hematology, Faculty of Medicine, Sohag University, Sohag, Egypt; 5Center for iPS Cell Research and Application, Kyoto University, Kyoto, Japan; 6Department of Immunology, University of Toyama, Toyama, Japan; 7HLA Laboratory, Japanese Red Cross Kanto-Koshinetsu Block Blood Center, Kotoku, Japan; 8Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Kyoto, Japan and 9Department of Medicine, Center for Hematology and Regenerative Medicine (HERM), Karolinska Institute, Stockholm, Sweden
ABSTRACT
Leukocytes that lack expression of HLA alleles are frequently detected in patients with acquired aplastic anemia (AA) who respond to immunosuppressive therapy, although the exact mechanisms under- lying the HLA loss and HLA allele repertoire likely to acquire loss-of-func- tion mutations are unknown. We identified a common nonsense mutation at codon 19 (c.19C>T, p.R7X) in exon 1 (Exon1mut) of different HLA-A and -B alleles in HLA-lacking granulocytes from AA patients. A droplet digital polymerase chain reaction assay capable of detecting as few as 0.07% Exon1mut HLA alleles in total DNA revealed that the mutation was present in 29% (101/353) of AA patients, with a median allele frequency of 0.42% (range, 0.071% to 21.3%). Exon1mut occurred in only 12 different HLA-A (n=4) and HLA-B (n=8) alleles, including B*40:02 (n=31) and A*02:06 (n=15), which correspond to four HLA class I supertypes (A02, A03, B07, and B44). The percentages of patients who possessed at least one of these 12 HLA alleles were significantly higher in the 353 AA patients (92%, P<0.001) and in 83 AA patients with copy number neutral loss of heterozy- gosity in chromosome 6p (100%, P<0.001) than the percentage (81%) in 18,604 Japanese healthy individuals. Eighty-two percent (37/45) of AA patients with Exon1mut responded to immunosuppressive therapy. Small populations of leukocytes that lack particular HLA-A or B alleles due to Exon1mut are common in AA patients. The detection of Exon1mut using a droplet digital polymerase chain reaction assay without the need for HLA typing may serve as a powerful tool for diagnosing the immune patho- physiology of patients with bone marrow failure.
Introduction
Acquired aplastic anemia (AA) is a rare condition characterized by pancytopenia and bone marrow hypoplasia resulting from immune-mediated suppression of hematopoietic stem progenitor cells (HSPC).1 Among several different immune mechanisms, cytotoxic T lymphocytes that recognize auto-antigens presented by HSPC are thought to play a critical role in the development of AA,2-7 based on the finding that leukocytes that lack particular HLA-A or HLA-B alleles (HLA-allele-
Correspondence:
SHINJI NAKAO
snakao8205@staff.kanazawa-u.ac.jp
Received: February 16, 2020. Accepted: May 14, 2020. Pre-published: May 21, 2020.
https://doi.org/10.3324/haematol.2020.247809
©2021 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
haematologica | 2021; 106(6)
1581
ARTICLE
