(A) Gene schematic and Southern blotting strategy for mapping Ndst1 alleles. Filled triangles represent loxP recombination sites; bar indicates target sequence of Ndst1 probe; restriction sites for BglII and HindIII and expected fragment sizes are also indicated. (B) Southern blot to determine Cre-mediated recombination of Ndst1 floxed alleles. Hepatocyte genomic DNA was digested with BglII/HindIII and probed for Ndst1 alleles. The deleted allele gave a BglII/HindIII fragment at 3.2 kb, and the Ndst1^f and wild-type alleles gave BglII/HindIII fragments at 2.6 kb. The Ndst1^f BglII/HindIII fragment was slightly larger than 2.6 kb due to the inserted 34-bp loxP site. DNA in each lane was isolated from individual mice. Quantification of bands indicated 65%–75% recombination in AlbCre⁺ hepatocytes. (C) The HS chains are depicted using the indicated symbol nomenclature for the individual sugar residues. Heparinases degrade the chains to disaccharides (dashed lines), which can then be separated according the number and pattern of sulfate groups (Table 1). HS chains from the mutant contain less sulfate and iduronic acid because Ndst1 creates the preferred substrates for epimerization and O-sulfation. The residual sulfation presumably arises from incomplete inactivation of Ndst1 and the expression of Ndst2.