Mutational Analysis of EXT1in a Chinese Family Affected by Hereditary Multiple Osteochondroma.

Guangzhi Yuan,Wei Hou,Wenjun Liao,Linke Huang,Qiang Su,Huayu Wu,Peng Wang,Paul Harrison

doi:10.1155/2021/8888948

Abstract

Objectives To discuss the mutational features and their relationships with disease in a family with hereditary multiple osteochondroma (HMO) from Guangxi Province (GXBB-1 family), China. Methods Genomic DNA and total mRNA were extracted from peripheral blood cells of GXBB-1 family members. Whole elements of the EXT1gene and its transcript, including exons, introns, exon-intron boundaries, and coding sequence (CDS) clones, were amplified and sequenced. Allele-specific PCR was used to confirm the position and type of mutation. Results All patients from the GXBB-1 family harbored the cosegregating heterozygous c.1056+1G>A mutation located in EXT1at an exon-intron boundary. Another three single-nucleotide polymorphisms (SNPs) were also detected in the patients, including IVS2+1G>A in intron 2, c.1844 T>C [p.Pro (CCT) 614Pro (CCC)] in exon 3, and c.2534G>A [p.Glu (GAG) 844Glu (GAA)] in exon 9. The latter two SNPs were synonymous variations. Conclusions The heterozygous c.1056+1G>A mutation cosegregated with the phenotype, indicating that it is a pathogenic mutation in the GXBB-1 family. This mutation is reported for the first time in Chinese HMO patients. IVS2+1G>A and c.2534G>A have no relationship with the occurrence of disease. However, c.1844 T>C and c.1056+1G>A are linked, and their interaction needs to be further studied. c.1844T>C is a new SNP that has not been reported internationally.

Highlights

Hereditary multiple osteochondromas (HMOs), previously called hereditary multiple exostoses (HMEs), are rare autosomal dominant developmental bone disorders that usually affect cartilage ossification and are characterized by multiple benign osteocartilaginous masses that grow outward from the metaphyses of long bones, such as the ends of femurs and tibias in the lower limbs or the humerus and forearm of the upper limbs [1]
In the Western population, mutations in the EXT1 and EXT2 genes are responsible for 40%~75% and 20%–40% of HMO cases, respectively [3,4,5], compared with 14~53% and 33% ~40% in the Chinese population, respectively [6, 7]
Genomic DNA and RNA were extracted from peripheral blood samples according to the manufacturer’s instructions. cDNA was obtained by reverse transcription using RNA as a template

Summary

Introduction

Hereditary multiple osteochondromas (HMOs), previously called hereditary multiple exostoses (HMEs), are rare autosomal dominant developmental bone disorders that usually affect cartilage ossification and are characterized by multiple benign osteocartilaginous masses that grow outward from the metaphyses of long bones (exostosis cartilaginea), such as the ends of femurs and tibias in the lower limbs or the humerus and forearm of the upper limbs [1]. HMO patients often have shortened stature, bony deformities, and restricted joint motion. Most HMO patients harbor pathogenic mutations in the EXT gene family. 21-44% of cases are caused by genetic mutations in EXT1 and EXT2, respectively [2]. The mutational frequencies in these two genes vary among ethnic groups. In the Western population, mutations in the EXT1 and EXT2 genes are responsible for 40%~75% and 20%–40% of HMO cases, respectively [3,4,5], compared with 14~53% and 33% ~40% in the Chinese population, respectively [6, 7]

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Conclusion