The Tumor Suppressor EXT-like GeneEXTL2Encodes an α1, 4-N-Acetylhexosaminyltransferase That TransfersN-Acetylgalactosamine andN-Acetylglucosamine to the Common Glycosaminoglycan-Protein Linkage Region : THE KEY ENZYME FOR THE CHAIN INITIATION OF HEPARAN SULFATE

We established a database of hereditary multiple exostoses for the state of Washington, on the basis of a retrospective review of the medical records and a clinical evaluation of family members, to determine the prevalence, clinical range of expression, and rate of malignant degeneration. The database comprised forty-six kindreds with 113 affected members; all kindreds had at least one member living in the state of Washington. The over-all prevalence was at least one in 50,000. Approximately 10 per cent of the subjects had no family history of multiple exostoses. With the use of twenty-three pedigrees that demonstrated an adequate multigenerational history for determination of penetrance of the gene, we identified one unaffected individual among twenty-six obligate heterozygotes, a rate of penetrance of 96 per cent. There was no evidence for a substantial reduction of penetrance in female subjects. The median age at the time of the diagnosis in the 113 affected individuals was three years (range, birth to twelve years). In a cohort of eighty-four subjects for whom we had complete information, the clinical range of expression was wide: thirty-three (39 per cent) had an obvious deformity of the forearm, eight (10 per cent) had an inequality in the lengths of the limbs, seven (8 per cent) had an angular deformity of the knee, and two (2 per cent) had a deformity of the ankle. The average number of operations for the patients for whom the operative history was known was two.(ABSTRACT TRUNCATED AT 250 WORDS) Show more

Hereditary multiple exostoses, characterized by multiple cartilaginous tumors, is ascribed to mutations at three distinct loci, denoted EXT1-3. Here, we report the purification of a protein from bovine serum that harbored the D-glucuronyl (GlcA) and N-acetyl-D-glucosaminyl (GlcNAc) transferase activities required for biosynthesis of the glycosaminoglycan, heparan sulfate (HS). This protein was identified as EXT2. Expression of EXT2 yielded a protein with both glycosyltransferase activities. Moreover, EXT1, previously found to rescue defective HS biosynthesis (McCormick, C., Leduc, Y., Martindale, D., Mattison, K., Esford, L. E., Dyer, A. P., and Tufaro, F. (1998) Nat. Genet. 19, 158-161), was shown to elevate the low GlcA and GlcNAc transferase levels of mutant cells. Thus at least two members of the EXT family of tumor suppressors encode glycosyltransferases involved in the chain elongation step of HS biosynthesis. Show more

Hereditary multiple exostoses (EXT) is an autosomal dominant bony disorder characterized by the formation of cartilage-capped juxta-epiphyseal prominences on the long bones. Recently, a disease gene (EXT 1) has been mapped to chromosome 8q23-q24 by linkage analysis in informative families. Here, we report on the genetic mapping of a second locus (EXT 2) to the short arm of chromosome 19 by linkage to a microsatellite DNA marker at the D19S221 locus, which gives additional support to the view that EXT is a genetically heterogeneous condition. Show more