👤 L Vits

Hereditary multiple osteochondromas (MO) is an autosomal dominant bone disorder characterized by the presence of bony outgrowths (osteochondromas or exostoses) on the long bones. MO is caused by mutations in the EXT1 or EXT2 genes, which encode glycosyltransferases implicated in heparan sulfate biosynthesis. Standard mutation analysis performed by sequencing analysis of all coding exons of the EXT1 and EXT2 genes reveals a mutation in approximately 80% of the MO patients. We have now optimized and validated a denaturing high-performance liquid chromatography (DHPLC)-based protocol for screening of all EXT1- and EXT2-coding exons in a set of 49 MO patients with an EXT1 or EXT2 mutation. Under the optimized DHPLC conditions, all mutations were detected. These include 20 previously described mutations and 29 new mutations - 20 new EXT1 and nine new EXT2 mutations. The protocol described here, therefore, provides a sensitive and cost-sparing alternative for direct sequencing analysis of the MO-causing genes. Show less

Hereditary multiple exostosis (EXT) is an autosomal dominant condition mainly characterized by the presence of multiple exostoses on the long bones. These exostoses are benign cartilaginous tumors (enchondromata). Three different EXT loci on chromosomes 8q (EXT1), 11p (EXT2) and 19p (EXT3) have been reported, and recently the EXT1 gene was identified by positional cloning. To isolate the EXT2 gene, we constructed a contig of yeast artificial chromosomes (YAC) and P1 clones covering the complete EXT2 candidate region on chromosome 11p11-p12. One of the transcribed sequences isolated from this region corresponds to a novel gene with homology to the EXT1 gene, and harbours inactivating mutations in different patients with hereditary multiple exostoses. This indicates that this gene is the EXT2 gene. EXT2 has an open reading frame encoding 718 amino acids with an overall homology of 30.9% with EXT1, suggesting that a family of related genes might be responsible for the development of EXT. Show less