To examine whether chronic hyperglycemia combined with Alk1 haploinsufficiency is associated with damage of the glomerular endothelial surface layer, kidney cryostat sections taken from mice eight weeks after the onset of diabetes were stained with wheat germ agglutinin (WGA), a lectin that binds to negatively charged sugar residues of glycoproteins, such as sialic acid, and with heparanase, an endo-beta-D-glucuronidase that specifically cleaves the heparan sulfate chain of negatively-charged proteoglycans. The gene discussed is ACVRL1; the disease is diabetes mellitus.