Novel mutations of integrin alpha IIb and beta 3 genes in Turkish children with Glanzmann's thrombasthenia

Abstract

Glanzmann's thrombasthenia (GT) is an inherited disorder of platelet aggregation, characterized by qualitative and quantitative defect on platelet alpha IIb beta 3 integrin (GpIIb/IIIa), resulting in lifelong bleeding tendency due to defective platelet plug formation. The alpha IIb gene (ITGA2B) and beta 3 gene (ITGB3) are closely located at chromosome 17q21.31-32. ITGA2B consist of 30 exons and encoding alpha chain, whereas ITGB3 has 15 exons and encoding beta chain. Until now, according to the Human Gene Mutation Database (HGMD), 138 mutations at ITGA2B gene and 101 mutations at ITGB3 gene have been identified. We aimed to determine whether there was any mutation in the ITGA2B and ITGB3 genes, and a correlation between clinical phenotype and genotype in Turkish GT patients. We examined 20 patients with GT followed at the Department of Pediatric Hematology, Meram Faculty of Medicine, for Clinical and Laboratory Findings and Molecular Genetic Analysis. Peripheral blood was collected from patients, and a written informed consent for genetic analysis was obtained from parents. DNA was isolated from by proteinase K and phenol/chloroform extraction. ITGA2B and ITGB3 genes were screened by polymerase chain reaction. There were 12 females and 8 males with a median age of 15.25 years. Major clinical presentations of these patients were mucocutaneous bleedings. The most common bleeding type was epistaxis (85%). Life-threatening bleedings were seen in five patients. Seven (35%) patients showed various mutations in the ITGA2B or ITGB3 genes. We detected four novel mutations in three different regions and two mutations defined previously within the ITGA2B gene. These changes are at exon 4; c.570 T4G alteration, at exon 13 c.1277 T4A, c. 1291 T4G alterations, at exon 19 c.1921A4G alterations. And from the start point of exon 14, behind 107 bases, we detected a heterozygous alteration at Thymine to Guanine. According to PolyPhen Database Program and NCBI Multiple Alignment Tool Database, four transitions are conserved at evolutionary process, so we can say that these transitions are novel mutations. c. 468T4G alteration at exon 4 and c. 1378 T4A alteration at exon 13 were reported to HGMD previously. Screening the exons of the ITGB3 gene from the same patient groups, we reported a novel missense mutation at exon 5, at nucleotide 680. No correlation was found between clinical phenotype and genotype. These mutations were described for the first time in Turkish population, and all novel mutations are not defined previously. Furthermore, collaborative studies are needed for the population point of view.