Membrane-associated and secretory mucins are high molecular weight glycoproteins of the glycocalyx (polysaccharide biofilm) that protects mucosal epithelium from particulate matter and microorganisms. The mucin family consists of Mucins 1-4, Mucin 5 (AC and B), Mucins 6-8, Mucins 11-13 and Mucins 15-17. A family of four related Mucin genes (MUC2, MUC5AC, MUC5B and MUC6) encode the major secreted mucins. Mucin 12 contains a predicted transmembrane domain; two extracellular cysteine-rich EGF-like domains; a coiled-coil region; and a domain consisting of serine-, threonine-, and proline-rich degenerate tandem repeats of 28 amino acids, a structural feature typical of mucins. Mucin 12 transcript (>12 kb) is present in colon, pancreas, prostate and uterus. Colorectal tumors can have low Mucin 12 transcript levels in comparison to normal colon tissues.
Function:
Human MUC12 (Mucin 12) is a novel mucin of epithelial mucins, which are large, secreted or cell surface glycoproteins involved in epithelial cell protection, adhesion modulation, and signaling. Using differential display on RNA from paired normal colonic mucosa and primary colorectal tumor, MUC12 is identified as one of the 2 partial cDNAs representing novel mucin genes as well as MUC11. They are downregulated in colorectal tumors.The deduced MUC12 protein contains a predicted transmembrane domain, 2 extracellular cysteine-rich EGF-like domains, a coiled-coil region, and a domain consisting of serine-, threonine-, and proline-rich degenerate tandem repeats of 28 amino acids, a structural feature typical of mucins. Human MUC12 shares high sequence homology with MUC3 and MUC4 . Northern blot analysis of 50 different normal tissues detected MUC12 expression in colon, pancreas, prostate, and uterus, with highest expression in colon. The MUC12 transcript is large, estimated to be longer than 12 kb. Expression of MUC12 was downregulated or absent in 6 of 15 (40%) colorectal tumors, as compared with matched normal colonic tissues. MUC12 expression was not detected in any of 6 colorectal cancer cell lines examined.
Subcellular Location:
Cell Membrane
Tissue Specificity:
Ubiquitous, with higher expression in colon. Down-regulated in colorectal cancer as well as in the colon of patients with ulcerative colitis (UC) and Crohn's disease (CD).
Similarity:
Contains 1 EGF-like domain.
Contains 1 SEA domain.
SWISS:
Q9UKN1
Gene ID:
10071
Database links:
Entrez Gene: 10071 Human
Omim: 60929 Human
SwissProt: Q9UKN1 Human
Unigene: 489355 Human
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