Zebrafish mutations in genes encoding enzymes essential for the synthesis of HS-PGs such as exostosin 2 (ext2; dackel; dak) and 3′-phosphoadenosine 5′-phosphosulfate transporter 1 (Papst1; pinscher; pic), model the human disease condition, Hereditary Multiple Exostoses (Clement et al., 2008, Wiweger et al. 2011). This evidence concerns the gene EXT2 and hereditary multiple exostoses.