摘要
目的:对1例遗传性血小板无力症(GT)先证者及其家系成员进行表型和基因诊断,并探讨其分子发病机制。方法:通过血小板计数、血涂片观察血小板、出血时间测定、凝血象检查和血小板聚集试验进行表型诊断;流式细胞术检测血小板表面α_(Ⅱb)和β_3的含量;PCR法扩增先证者基因组DNAα_(Ⅱb)和β_3的所有外显子及其侧翼序列;PCR产物采用末端标记双脱氧法进行直接基因测序,对发现的突变位点采用AS-PCR法扩增先证者及其家系成员和正常人相对应的片段。结果:先证者血小板计数正常、血涂片血小板分散不聚集,出血时间明显延长,凝血象正常,对ADP、凝血酶、肾上腺素、胶原、花生四烯酸等多种诱聚剂反应低下,而对瑞斯托霉素的反应基本正常;先证者血小板表面未检测到α_(Ⅱb),β_3阳性血小板仅占8%,平均荧光强度明显减弱;先证者在α_(Ⅱb)基因外显子4存在C470A纯合突变,导致α_(Ⅱb)氨基酸序列Pro126His(P126H)替换。父母为近亲婚配,均为该位点的杂合突变。AS-PCR排除了该突变为基因多态性的可能。结论:整合素α_(Ⅱb)基因外显子4C470A(P126H)纯合错义突变是导致该患者GT的分子机制,是国际上首次报道的一种新的整合素α_(Ⅱb)基因错义突变。
Objective To identify the mutation of integrin αⅡb in a female proband with Glanzmann thrombasthenia. Methods A female patient was diagnosed as Glanzmann thrombasthenia through the platelet count, the platelet morphology and distribution on the blood film, the bleeding time assay, the coagulation profiles and the platelet aggregation test. The proband＇s platelets were analyzed by fluorescence-activated cell sorting （FACS）. All the exons and exon-intron boundaries of αⅡb and β3 gene were detected by PCR and direct DNA sequencing. The AS-PCR was used to exclude the possibility of the gene polymorphism. Results The proband had a normal platelet count and coagulation profiles, no clusters of normal platelets on the blood film, a prolonged bleeding time, and absent or minimal ex vivo platelet aggregation in response to ADP, thrombin, collagen, adrenaline and araehidonic acid, but had normal platelet aggregation in response to ristocetin. The FACS demonstrated trace amounts of β3 without αⅡb or αⅡbβ3 on the membrane. The DNA analysis revealed the proband homozygous for a C470→A substitution in her αⅡb gene, resulting in a Pro126→His substitution. The parents of the proband had a heterozygote C470A mutation. Conclusions αⅡb C470A（Pro126His） homozygous missense mutation causes Glanzmann thrombasthenia of the proband, and is a novel mutation in the integrin αⅡb that is identified for the first time in the world.
出处
《诊断学理论与实践》
2005年第6期451-454,461,共5页
Journal of Diagnostics Concepts & Practice
