Functional domains in the MUC4 protein sequence and the predicted secondary structures. Six functional domains and/or signatures (boxes) were annotated by aligning MUC4 protein sequence in PROSITE protein domain database . The boundaries of each signature are listed. Among six SNPs tested in this study (stars), rs882605 and rs2688513 (black) were found in two different long-loop regions, 300-319 and 4,134-4,158, respectively (bold letters refer to amino acid substitution sites). The SNP rs2246901 (gray) was found in a type D von Willebrand factor (VWFD) domain. The MUC4 reference sequence can be located at National Center for Biotechnology Information databank NP_060876.4.