| Modification Notes |
Mucin glycoproteins are major constituents of the glycocalyx that covers mucosal epithelium. There are two broad classes of mucins: membrane-associated and secretory mucins. The MUC7 gene encodes a low-molecular-mass salivary mucin, mucin 7 (also designated MG2, mucin glycoprotein 2), that lacks cysteine-rich domains and is secreted as a soluble monomer (1). The MUC7 glycoprotein (5) can bind to a variety of microbes and this binding requires a cysteine-containing domain in the N-terminal region of MUC7 (3). MUC7 is expressed in human submandibular/sublingula secretions and in mucous acinar cells (2-4). Among all normal malignant tissue samples and tumor cell lines, MUC7 is only expressed in bladder cancer cell lines and samples of invasive transitional cell carcinomas, suggesting differential MUC7 gene expression with the onset of malignant transformation of the bladder urothelium (6). MUC7 is also expressed in a variety of epithelial cancers (7). Expression of MUC7 is retinoic acid (RA)- or retinol-dependent and is mediated by the retinoid acid receptors RARa and, to a lesser extent, by RARg. Thyroid hormone T3 binds to thyroid receptors and interacts with RA to inhibit mucin gene expression (8). |
