Effect of c.1431C>T mutation, a causative mutation of Glanzmann's thrombasthenia, on ITGB3 splicing, gene and protein expression.

BACKGROUND: /aim: Recently, it was reported that the non-synonymous c.1431C>T (p. G477=) mutation of the integrin subunit β3 (ITGB3) gene is the cause of Glanzmann's thrombasthenia (GT). However, the functional consequences of this mutation on the ITGB3 gene and protein expression remain to be elucidated. Therefore, this study was conducted to cover this scientific shortage.

METHODS: Peripheral blood samples were collected from Chinese family members (parents and proband and his sister), and DNA was extracted and sequenced using whole-exome and Sanger sequencing. The effect of c.1431C>T mutation on the splicing of mRNA was verified by the in vitro minigene assay and the three variants that resulted from the mutation were cloned into a phage vector and pEGFP-C1 vector, and ITGB3 gene and protein expression was detected in the transfected 293T cells using qPCR and Western blotting.

RESULTS: Minigene splicing assay showed that c.1431C>T mutation causes three kinds of alternative splicing;(1) a 95bp deletion in the middle of exon10, (2) a 155bp deletion (95bp deletion in the middle of exon10 plus a 60bp deletion in the right side of exon10), and (3) a 261bp deletion in the right side of exon10. The in vitro expression assay showed that the c.1431C>T variant did not affect the ITGB3 mRNA levels, but directly led to protein truncation and declined expression.

CONCLUSION: Due to its significant impact on protein expression, c.1431C>T mutation in ITGB3 could be considered a pathogenic variant of GT. This could enrich the ITGB3 mutation spectrum and provide a base for the genetic diagnosis of GT.