一个类遗传性血小板无力症家系及其分子发病机制研究

The clinical characteristics and molecular pathogenesis of a variant Glanzmann＇ s thrombasthenia-like pedigree

目的报告一个遗传性血小板功能障碍家系并探索其分子发病机制。方法收集该家系临床资料，采用二代高通量测序法进行遗传性血液病和血小板功能相关近600种基因突变筛查。采用RT-PCR及一代测序法检测先证者及其父母RASGRP2基因部分转录本序列。结果该遗传性血小板功能障碍家系临床表现符合变异型血小板无力症，表现为反复皮肤黏膜严重出血，先证者血小板对多种不同浓度的生理性诱聚剂反应低下甚至缺如。先证者未检出整合素α IIbB3基因突变，而存在RASGRP2IVS3．1C〉G纯合突变，其父母均为该位点杂合突变。先证者在扩增区检测出2种转录本，功能型RASGRP2蛋白对应的正常转录本未检出，其父母同时存在正常转录本及异常转录本，但以正常转录本为主。结论RASGRP2基因IVS3-1C〉G纯合突变是导致该家系先证者发生血小板功能障碍陛出血的原因。RASGRP2基因IVS3．1C〉G突变导致RASGRP2异常剪接，发挥激活Rapl的RASGRP2蛋白缺失，进而导致血小板功能障碍。本研究为国内首次报道RASGRP2基因异常导致血小板功能障碍性出血，也是国际上首次报道该突变类型。

Objective To review the clinical characteristics of a pedigree with inherited hemorrhagic disease to explore its molecular pathogenesis. Methods The clinical data of the pedigree with inherited hemorrhagic disease were collected. After extracting DNA, next generation sequencing was utilized to detect the potential gene mutation. The changes of RASGRP2 transcript of this proband and his parents were detected using RT- PCR to compare with normal control. Results The phenotype of the proband in this pedigree with inherited platelet dysfunction and bleeding disorder was similar to variant Glanzmann＇ s thrombasthenia, the maximum aggregations of platelet in response to the physiological agonists including ADP, epinephrine and arachidonic acid were significantly lower, leading to severe spontaneous mucosal bleeding. Integrin ctIIb133 gene mutation was not detected, but another gene mutation RASGRP2 IVS3-1 stood out. The mutation was homozygous in the proband and heterozygosis in both of his parents. Two transcript types were detected in the proband, without transcripts coding functional RASGRP2 protein, however, his parents had functional transcripts and abnormal transcripts, with the normal transcripts in the majority. Conclusions The RASGRP2 IVS3-1 gene mutation was responsible for the inherited hemorrhagic disease. The RASGRP2 IVS3- 1 gene mutation led to abnormal alternative splicing, without formation of functional RASGRP2 protein. The RASGRP2 protein is at the nexus of calcium-dependent platelet activation and hemostasis after damage of blood vessels. Spontaneous mucosal bleeding was a result of the lack of the functional RASGRP2 protein. This was the first report of RASGRP2 gene mutation resulting in bleeding disorder in China, and also the first report of the mutation type of RASGRP2 IVS3-1.