Phylogenetic tree of von Willebrand D domains in human and chicken mucins. A neighbor-joining tree was obtained by ClustalW using 1000 bootstrap replicates. Bootstrap percentages above 50 are shown. Groups containing the VWD1, VWD2, VWD3 and VWD4 domains of mucin type are shown with a shaded background. Animals represented are human (h), mouse (m) and chicken (c).