Experimental Study On Gene Mutations Of Glanzmann Thrombasthenia

Objective To identify the mutation of integrinαⅡbβ3 in four probands with Glanzmann thrombasthenia through phenotype and gene diagnosis and investigate molecular pathogenesis of GT . Methods⑴four patients were 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 with turbidimetry.⑵The probands'platelets were analyzed by fluorescence—activated cell sorting(FACS) to determine thrombasthenia type.⑶All the exons and exon-intron boundaries ofαⅡb andβ3 gene were detected by PCR and direct DNA sequencing.⑷Search the mutable site through direct gene sequencing the PCR amplified product.Results⑴T he probands had normal platelet counts and coagulation profiles.no c1usters of norm al platelets on the blood film,a prolonged bleeding time.and absent or minimal ex vivo platelet aggregation in response to ADP,but had normal platelet aggregation in response to ristocetin.⑵GPⅡb mean fluorescence intensity on the membrane were obviously decreased in 3 probands compared with control platelets, GPⅢa mean fluorescence intensity was decreased in a proband.⑶T here are threeαⅡb gene mutations in four probands, oneβ3 gene mutation. The first patient was homozygous for a R551Q missense mutation in herⅡb gene17exon; The third patient for a X892 nonsense mutation in hisⅡb gene 26 exon; The second patient was heterozygous for a L965P frame-shift mutation and a S957L missense mutation in herⅡb gene 28 exon, his mother was heterozygous for a L965P frame-shift mutation,his father was heterozygous for a S957L missense mutation in hisⅡb gene 28 exon .The forth patient was homozygous for a C400Y missense mutation in herⅢa gene 9 exon, her father was homozygous for a C400Y missense mutation and her mother was heterozygous for a C400Y missense mutation inⅢa gene 9 exon.⑷Exclude possibility of the gene polymorphism.Conclusions Gene mutations ofαⅡb orβ3 subunit cause Glanzmann thrombasthenia. Our studies of four probands prove that S957L and L965P inαⅡb 28 exon are novel missense mutations ,X892 inαⅡb 26 exon is a novel homozygous nonsense mutation.