Phenotype and genotype of FXIII deficiency in two unrelated probands: identification of a novel F13A1 large deletion mediated by complex rearrangement
Phenotype and genotype of FXIII deficiency in two unrelated probands: identification of a novel F13A1 large deletion mediated by complex rearrangement
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两个无关先证者 FXIII 缺陷的表型和基因型 复杂重排介导的异常 F13A1 大缺失的鉴定
DOI：
10.1186/s13023-019-1144-z
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发表时间：
2019-07-24
影响因子：
3.7
通讯作者：
Ding, Qiulan
中科院分区：
文献类型：
--
作者：
Ma, Siyu;Chen, Changming;Ding, Qiulan
背景遗传性凝血因子XIII缺乏症(FXIIID)是一种严重且未得到充分诊断的罕见出血性疾病。目前仅有5个涉及F13A1一个或多个外显子的大片段缺失的报道，缺乏多重连接依赖的探针扩增(MLPA)分析可能低估了F13A1和F13B的拷贝数变异(CNV)。我们对两个无关的重度FXIIID先证者的临床表现进行了特征描述，并探讨了发病机制。结果两个先证者在确诊前都经历了几次致命性出血和伤口愈合延迟。用氨释法测定FXIII活性，用ELISA法测定FXIII-A和FXIII-B抗原。对F13A1和F13B的所有外显子，包括外显子-内含子边界和启动子区域进行扩增和直接测序。用CNVplex(R)方法检测F13A1和F13B的拷贝数变异(CNV)。结合长程聚合酶链式反应(LR-PCR)策略确定F13A1大片段缺失的断裂点。先证者1被发现有一个新的小缺失(c.1147 del)和一个错义突变p.Arg383Ser的复合杂合突变。先证者2是F13A1中新的大片段缺失(g.[77815_112815del；112837_116628del])和错义突变p.Arg716Gly的复合杂合体。对大的缺失断裂点的生物信息学分析预测，具有TCT和C两个同源性的两个分叉停滞和模板切换和/或微同源介导的断裂诱导复制(FoSTeS/MMBIR)事件可能是导致复杂重排的原因。结论首次检测出两个I型FXIIID家系，并首次采用CNVplex(R)方法检测F13A1和F13B的CNV。F13A1中的g.[77815_112815del；112837_116628del]在两个FoSTeS/MMBIR事件的介导下发生了大量杂合性缺失。
BackgroundInherited Factor XIII deficiency (FXIIID) is one of the most severe and under-diagnosed rare bleeding disorders. Only 5 large deletions involving one or more exons in F13A1 have been reported, and lacking of multiplex ligation-dependent probe amplification (MLPA) assay might underestimate the copy number variations (CNVs) in F13A1 and F13B. We had characterized the clinical presentation of two unrelated severe FXIIID probands and explored the pathogenic mechanisms.ResultsBoth probands experienced several episodes of fatal bleeding and delayed wound healings prior to diagnosis. FXIII activity was measured by the ammonia release assay, and FXIII-A and FXIII-B antigens were determined by ELISA. All the exons including exon-intron boundaries and promoter regions of F13A1 and F13B were amplified and directly sequenced. Copy number variations (CNVs) of F13A1 and F13B were detected by the CNVplex (R) method. Breakpoints of the F13A1 large deletion were identified by quantitative primer walking combined long-range PCR (LR-PCR) strategies. Proband 1 was found to have compound heterozygous mutations of a novel small deletion (c.1147del) and a missense mutation p.Arg383Ser. Proband 2 was compound heterozygous for a novel large deletion (g.[77815_112815del;112837_116628del]) and a missense mutation p.Arg716Gly in F13A1. Bioinformatics analysis of the large deletion breakpoints predicted that two fork stalling and template switching and/or microhomology-mediated break-induced replication (FoSTeS/MMBIR) events with two homologies of TCT and C might be responsible for the complex rearrangement. Prophylactic replacement therapy was immediately administered for the two probands upon establishment of the diagnosis.ConclusionsWe detected two type I FXIIID pedigrees and adopted CNVplex (R) method to detect CNVs of F13A1 and F13B for the first time. A large heterozygous deletion of g.[77815_112815del;112837_116628del] in F13A1, mediated by two FoSTeS/MMBIR events, was identified.