Copy-number variations in adult patients with chronic immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease with heterogeneous background. FCGR2C mutations were defined in one third of the patients but genetic players have not been fully elucidated yet. Although childhood ITP present as benign, ITP in adulthood is chronic disease with treatment challenges. This study aimed to focus on adult ITP patients using a whole genome genotyping that is valuable approach to identify the responsible genomic regions for the disease. Herein 24 adult primary-refractory for ITP patients were evaluated using HumanCytoSNP12BeadChip,Illumina. Forty-six age and sex matched healthy individuals, and ptients awith nonhematological conditions were analyzed as controls. Identified CNV regions were verified by qRTPCR. T-cell receptor beta and delta (TCRB/TCRG) clonality were assessed by heteroduplex analysis in mosaic cases. Several CNV losses and gains were defined (losses:2q,7q,17q,19p, and gains: 1q,2p,3q,4q,7q,10q,12p,13q,14q,15q,17p,20q,21p,22q,Xp). Mosaic changes of different sizes (0.2-17.77Mb) were identified in five patients and three of them showed clonality. CNV regions that were unique to ITP patients were identified for the first time and among these genes, those related to immune regulation, and cellular trafficking were noteworthy. Conclusion: Identified CNV regions harbor several candidate genes, the functions of which might shed light on the pathogenesis of chronic ITP.

免疫性血小板减少症（immune thrombocytopenia, ITP）是一类背景异质性显著的自身免疫性疾病。已有研究证实，三分之一的患者存在FCGR2C基因突变，但该病的完整遗传致病机制仍未完全阐明。尽管儿童ITP通常呈良性病程，但成人ITP多为慢性疾病，临床治疗仍存在诸多难点。本研究聚焦成人ITP患者，采用全基因组基因分型技术这一有效手段，旨在明确该病的致病基因组区域。本研究纳入24例成人原发性难治性ITP患者，采用Illumina公司的HumanCytoSNP-12 BeadChip芯片进行基因分型检测；同时纳入46名年龄与性别相匹配的健康个体，以及非血液系统疾病患者作为对照。通过实时定量聚合酶链反应（qRT-PCR）对筛选出的拷贝数变异（copy number variation, CNV）区域进行验证。针对嵌合型病例，采用异源双链分析对T细胞受体β及δ链（TCRB/TCRG）克隆性进行检测评估。本研究共检测到多处CNV缺失与扩增区域：缺失区域包括2q、7q、17q、19p；扩增区域包括1q、2p、3q、4q、7q、10q、12p、13q、14q、15q、17p、20q、21p、22q、Xp。5例患者检测到不同长度（0.2~17.77 Mb）的嵌合型CNV变异，其中3例呈现克隆性特征。本研究首次鉴定出仅存在于ITP患者中的特异性CNV区域，其中与免疫调控及细胞转运相关的基因具有重要研究价值。结论：本研究鉴定出的CNV区域包含多个候选基因，其功能阐释可为慢性ITP的发病机制研究提供新的思路。