Fig. 1. Clustal alignment detects 47% sequence identity between Sotv and human EXT2. Identical residues are bold and boxed in dark gray, while similarities are boxed in light gray. A strongly hydrophobic region likely to represent a transmembrane domain is indicated by a double-headed arrow. Vertical arrows indicate positions of nonsense mutations in the five characterized sotv alleles. The dumbbell highlights a DXD motif conserved in UDP-sugar-dependent glycosyltransferases.