Mice deficient in glucuronyltransferase-I.

Chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), and heparin (Hep) are a class of glycosaminoglycans (GAGs) that are distributed on the surface of virtually all cells and in the extracellular matrices. CS/DS and HS/Hep chains share a common carbohydrate-protein linkage region structure, GlcAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser. Glucuronyl transfer to the Gal residue, the final biosynthetic step in the common linkage region, is catalyzed by a key enzyme, beta1,3-glucuronyltransferase, which is termed glucuronyltransferase I (GlcAT-I). As it has been reported that the expression level of GlcAT-I correlates well with the amount of GAGs, GlcAT-I is thought to regulate the expression of GAGs. In fact, a defect in the squashed vulva 8 (sqv-8) gene which encodes GlcAT-I in Caenorhabditis elegans eliminates the expression of GAGs and the mutant worms show not only a perturbation in vulval invagination but also a defect in the cytokinesis in fertilized eggs, resulting in alternating cell division and cell fusion. Here, we summarize the recent knowledge on the roles of GlcAT-I in mammalian GAG biosynthesis and embryonic cell division using GlcAT-I knock-out mice.