Novel Mutations in Chinese Patients with Multiple Osteochondromas Identified Using Whole Exome Sequencing

Multiple osteochondromas (MO) are an autosomal-dominant disease characterized by the growth of multiple cartilage-capped prominences in the growth plate region of the metaphysis in long and flat bones. To detect genetic mutations related to MO, a three-generation Chinese family with MO was evaluated using whole exome sequencing for mutation screening. The candidate pathogenic mutation was validated by Sanger sequencing. A novel frameshift (NM_000401.3:c.1321del:p.Leu441TrpfsTer28) in exon 8 of the exotosin 2 (EXT2) gene was identified in two affected individuals. Codons 441 and 468 in the EXT2 gene are highly conserved among vertebrates as demonstrated by multiple sequence alignment. The c.1321 del C resulted in an amino acid change at codon 441, which generated a premature stop codon at position 468, causing complete loss of the glycosyltransferase domain. A novel frameshift mutation c.1321delC detected in the EXT2 gene may help in prenatal genetic screening and early diagnosis of MO.