Examples of altered GAG sulfation involving sulfotransferases that cause abnormalities have been identified for both: mutations in chondroitin-6-sulfotransferase-1 (C6ST-1) which are associated with chondrodysplasia and progressive spinal involvement (Thiele et al., 2004), while mice deficient in chondroitin-4-sulfotransferase (C4ST-1) exhibit a more severe chrondrodysplasia. This evidence concerns the gene CHST3 and chondrodysplasia.