Refinement oftheMultiple Exostoses Locus(EXT2) toa 3-cMInterval on ChromosomeII

Summary Hereditary multiple exostoses (EXT)isanautosomal dominant skeletal disorder characterized bytheformation ofmultiple exostoses onthelongbones. EXTis genetically heterogeneous, withatleast three loci involved: one(EXT1) intheLanger-Giedion region on 8q23-q24, asecond (EXT2) inthepericentromeric region ofchromosome 11,andathird (EXT3) onchromosome19p.Inthis study, linkage analysis inseven extended EXTfamilies, all linked totheEXT2locus, refined thelocalization oftheEXT2gene toa3-cMregion flanked byD11S1355 andD11S1361/D11S554. This implies that theEXT2geneislocated attheshort arm ofchromosome 11,inbandllpll-pl2. Therefined localization ofEXT2excludes anumber ofputative candidate genes located inthepericentromeric region of chromosome 11andfacilitates theprocess ofisolating theEXT2gene.