A frequent nonsense mutation in exon 1 across certain HLA-A and -B alleles in leukocytes of patients with acquired aplastic anemia.
A frequent nonsense mutation in exon 1 across certain HLA-A and -B alleles in leukocytes of patients with acquired aplastic anemia.
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DOI：
10.3324/haematol.2020.247809
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发表时间：
2021-06-01
期刊：
影响因子：
10.1
通讯作者：
Nakao S
中科院分区：
文献类型：
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作者：
Mizumaki H;Hosomichi K;Hosokawa K;Yoroidaka T;Imi T;Zaimoku Y;Katagiri T;Anh Thi Nguyen M;Cao Tran D;Ibrahim Yousef Elbadry M;Chonabayashi K;Yoshida Y;Takamatsu H;Ozawa T;Azuma F;Kishi H;Fujii Y;Ogawa S;Tajima A;Nakao S
在接受免疫抑制治疗的获得性再生障碍性贫血（AA）患者中经常检测到缺乏HLA等位基因表达的白细胞，尽管HLA缺失和HLA等位基因库可能获得功能缺失突变的确切机制尚不清楚。我们在AA患者缺乏hla的粒细胞中发现了不同HLA-A和-B等位基因的外显子1 （Exon1mut）的密码子19 （c.19C>T, p.R7X）的共同无义突变。通过微滴数字聚合酶链式反应（pcr）检测总DNA中仅有0.07%的Exon1mut HLA等位基因，发现29% (101/353)AA患者存在该突变，中位等位基因频率为0.42%（范围0.071% ~ 21.3%）。Exon1mut仅出现在12个不同的HLA-A （n=4）和HLA-B （n=8）等位基因中，包括B*40:02 （n=31）和A*02:06 (n=15)，对应4个HLA I类超型（A02、A03、B07和B44）。353例AA患者中至少拥有这12个HLA等位基因中的一个的比例（92%，P<0.001）和83例AA患者中6p染色体拷贝数中性杂合性缺失的比例（100%，P<0.001）显著高于18604名日本健康人的比例（81%）。82%（37/45）携带Exon1mut的AA患者对免疫抑制治疗有反应。由于Exon1mut而缺乏特定HLA-A或B等位基因的少量白细胞在AA患者中很常见。利用微滴数字聚合酶链反应法检测Exon1mut而不需要HLA分型，可能成为诊断骨髓衰竭患者免疫病理生理的有力工具。
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 underlying the HLA loss and HLA allele repertoire likely to acquire loss-of-function 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 heterozygosity 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 pathophysiology of patients with bone marrow failure.