Whole Exome Sequencing Identifies The Causative Gene Mutation In A Chinese Family With Hereditary Multiple Exostoses

Objective:Hereditary multiple exostoses(HME;OMIM:133700)is an autosomal dominant skeletal disorder characterized by the formation of multiple benign cartilage-capped tumor.Besides suffering complications caused by the pressure of these exostoses on the surrounding tissues,HME patients are at an increased risk for malignant chondrosarcoma.In this study,we detected the gene of a typical Chinese family with HME in order to find out the pathogenic mutation of the family.To provide help for genetic counseling and prenatal diagnosis of the family,and lay a foundation for the study of the pathogenic mechanism of HME.Methods:We collected a four-generation HME pedigree incluing 15 members.Four patients with HME(?3??1??2??1)in the family,inherited from generation to generation and four unaffected family members(?1??2??4??5)were enrolled in the present study.The clinical data of families were collected,and the peripheral anticoagulant venous blood of the above 8 family members were collected to extract genomic DNA.Whole exome sequencing was performed on the proband(?1),and then bioinformatics analysis of the sequencing results was carried out,including quality control,filtering,alignment,variation identification,variation filtering,variation annotation of the raw data,in order to screen suspected pathogenic mutation sites,Then it was verified by PCR and Sanger sequencing to check whether it conformed to pedigree co-segregation.At the same time,conservative analysis,protein function prediction,and ANNOVAR annotation results were used to query the gene frequency and disease prediction results.Results:Through whole exome sequencing,bioinformatics analysis and Sanger sequencing,it was found that 4 patients in the HME family carried the EXT1 c.1258G>T(p.E420X)mutation,while the normal family did not carry the mutation,and the mutation was co-segregated in the family.The mutation is a new heterozygous nonsense mutation,which occurs in exon 4 of EXT1 gene.The translation termination signal is introduced in advance,resulting in a truncated EXT1 protein with a carboxyl terminal deletion of 326 amino acids,and the loss of the important functional domain of EXT1protein-"glycosyltransferase domain".Conclusion:In this study,a new pathogenic EXT1 mutation c.1258G>T(p.E420X)was found in a HME family,which confirmed the gene diagnosis for the family,laid a theoretical foundation for further research on the molecular pathogenesis of HME,and enriched the mutation spectrum of HME.