RESUMO
Objective To explore the molecular pathogenesis of 3 Glanzmann's thrombasthenia pedigree by using bioinformatics software and provide evidence for in vitro experiments. Methods The genetic analysis of 3 pedigree diagnosed as Glanzmann's thrombasthenia was carried out. Clustalx-2.1 win software was used to analyze the conservatism of mutant sites in homologous sequences. Bioinformatics software such as PolyPhen-2, PROVEAN, SIFT and Mutationtaster was used to analyze the biological effect of mutation. SPDBV software constructed the molecular structure model of mutant protein and evaluated the influence of mutation on protein structure. Results The "new mutations" found in 3 Glanzmann's thrombasthenia pedigree were ITGA2B:c. 814G>C (p. Val272Leu), ITGA2B:c. 432G>A (p. Trp144Ter) and ACTN1:c. 2458A>G (p. Ile820Val). All three mutations were highly conserved among homologous species. Mutationtaster software showed that 3 new mutations were likely pathogenic. PolyPhen-2 and PROVEAN software showed ITGA2B p.Val272Leu and ACTN1 p.Ile820Val were benign and SIFT software showed that ITGA2B p. Val272Leu were likely pathogenic, while ACTN1 p. Ile820Val is benign. The result of SPDBV software showed that the Val272 of ITGA2B was transformed to Leu, neutralizing all the original hydrogen bond. The Trp144 of ITGA2B is transformed to Ter, resulting in the truncated proteins with only 113 amino acid residues. All these mutations affected the molecular structure of GPⅡb, resulting in a decrease ofGPⅡb/Ⅲa expression. When the Ile820 of ACTN1 is transformed to Val, onlyretained the hydrogen bond of Ile820 and Asp822, neutralized the rest hydrogen bond, whichaffected the molecular structure and protein function of ACTN1. Conclusion The mutations of ITGA2B:c.814G>C (p.VAL272LEU), ITGA2B:c.432G>A (p.Trp144Ter) and ACTN1:c.2458A>G (p.Ile820Val) are pathogenic.
RESUMO
Objective@#To investigate the molecular pathogenesis for a patient with Glanzmann thrombasthenia (GT). @*Methods@#The peripheral blood of a patient with Glanzmann′s thrombasthenia was collected, and the genetic mutations were detected by gene sequencing technology. The mutant plasmids were prepared by PCR site-directed mutagenesis and transfected into CHO-K1 cells of Chinese hamster ovary to construct in vitro eukaryotic expression system. The expressions of αⅡb and β3 protein subunits in CHO-K1 cells were detected by western blot. The expression levels of αⅡb and β3 in cellular membrane and cytoplasm of CHO-K1 cells were detected by flow cytometry. The expression and distribution of αⅡb and β3 in CHO-K1 cells were observed by immunofluorescent labeling under microscope. @*Results@#This patient was diagnosed with type Ⅱ GT. Gene sequencing revealed two mutations in ITGB3 gene which has not been reported in the literature. ITGB3 c.1495 T＞C missense mutation resulted in replacement of cysteine no.499 by arginine (p.C499R). ITGB3 c.1728 delC code shift mutation resulted in a change in the amino acid synthesis initiated by the β3 protein subunit serine no.577 and terminated by the 92nd amino acid following these changes. The results of western blotting showed that the synthesis and expression of primary structures of αⅡb and β3 were detectable in the lysates of mutant CHO-K1 cells. The results of flow cytometry showed that no expression of β3 on the surface and intracellular of mutant CHO-K1 cells was observed. Under fluorescence microscopy no distribution of β3 protein subunit was displayed in mutant CHO-K1 cells. @*Conclusion@#The mutation of ITGB3 c.1728 del C or ITGB3 c.1495 T＞C should be relevant to the cause of GT in this patient. The mutation of ITGB3 c.1728 del C and ITGB3 c.1495 T＞C seems not to affect the formation of the primary structure of β3 protein subunit, but did affect the formation of its high-level structure.