Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
J Thromb Haemost. 2023 Dec;21(12):3597-3607. doi: 10.1016/j.jtha.2023.08.012. Epub 2023 Aug 20.
Glanzmann thrombasthenia (GT) is an autosomal recessive platelet aggregation disorder caused by mutations in ITGA2B or ITGB3.
We aimed to assess the phenotype and investigate the genetic etiology of a GT pedigree.
A patient with bleeding manifestations and mild mental retardation was enrolled. Complete blood count, coagulation, and platelet aggregation tests were performed. Causal mutations were identified via whole exome and genome sequencing and subsequently confirmed through polymerase chain reaction and Sanger sequencing. The transcription of ITGB3 was characterized using RNA sequencing and reverse transcription polymerase chain reaction. The αⅡb and β3 biosynthesis was investigated via whole blood flow cytometry and in vitro studies.
GT was diagnosed in a patient with defective platelet aggregation. Novel compound heterozygous ITGB3 variants were identified, with a maternal nonsense mutation (c.2222G>A, p.Trp741∗) and a paternal SINE-VNTR-Alu (SVA) retrotransposon insertion. The 5' truncated SVA element was inserted in a sense orientation in intron 11 of ITGB3, resulting in aberrant splicing of ITGB3 and significantly reducing β3 protein content. Meanwhile, both the expression and transportation of β3 were damaged by the ITGB3 c.2222G>A. Almost no αⅡb and β3 expressions were detected on the patient's platelets surface.
Novel compound heterozygous ITGB3 mutations were identified in the GT pedigree, resulting in defects of αⅡbβ3 biosynthesis. This is the first report of SVA retrotransposon insertion in the genetic pathogenesis of GT. Our study highlights the importance of combining multiple high-throughput sequencing technologies for the molecular diagnosis of genetic disorders.
Glanzmann 血小板无力症（GT）是一种常染色体隐性血小板聚集障碍，由 ITGA2B 或 ITGB3 基因突变引起。
评估 GT 家系的表型并探讨其遗传病因。
纳入一名有出血表现和轻度智力障碍的患者。进行全血细胞计数、凝血和血小板聚集试验。通过全外显子和基因组测序鉴定致病突变，随后通过聚合酶链反应和 Sanger 测序进行确认。使用 RNA 测序和逆转录聚合酶链反应来表征 ITGB3 的转录。通过全血流式细胞术和体外研究来研究 αⅡb 和 β3 的生物合成。
诊断出一名血小板聚集功能缺陷的 GT 患者。发现了新的复合杂合 ITGB3 变体，包括一个母系无义突变（c.2222G>A，p.Trp741∗）和一个父系 SINE-VNTR-Alu（SVA）反转录转座子插入。5'截断的 SVA 元件以顺式方向插入 ITGB3 的内含子 11 中，导致 ITGB3 的异常剪接，显著降低 β3 蛋白含量。同时，ITGB3 c.2222G>A 也损害了 β3 的表达和转运。患者血小板表面几乎检测不到 αⅡb 和 β3 的表达。
在 GT 家系中发现了新的复合杂合 ITGB3 突变，导致 αⅡbβ3 生物合成缺陷。这是 SVA 反转录转座子插入 GT 遗传发病机制的首次报道。我们的研究强调了结合多种高通量测序技术对遗传疾病进行分子诊断的重要性。
