Recently, the MUC7 gene sequence encoding for the protein backbone of the low molecular mass salivary mucin, MG2, has been reported from two overlapping cDNA clones. The purpose of our study was to isolate and characterize a full-length MUC7 cDNA, which will be utilized for expression of MUC7. A full-length cDNA (2.34 kb) encoding the MUC7 gene product was isolated from a human submandibular gland expression library using rabbit polyclonal antisera specific for the mucin peptide. The identity of this clone was confirmed by restriction enzyme mapping, DNA cross-hybridization, and Sanger dideoxy DNA sequencing. The full-length cDNA was used as a probe for Northern blot analysis under high and low stringency hybridization conditions. Results indicated that MUC7 is expressed in human sublingual and submandibular gland tissues, but it not in rat, mouse, or hamster submandibular-sublingual gland tissues. Southern blot analysis under low stringency hybridization conditions revealed that the full-length MUC7 cDNA hybridizes to human and monkey genomic DNA, but it not in rat, mouse, or hamster genomic DNA, suggesting a MUC7 homologue in the monkey genome. This was confirmed by PCR amplification of monkey genomic DNA and subsequent DNA sequencing. Expression of MUC7 appears to be tissue specific to human submandibular and sublingual gland tissues, although the presence of a MUC7 monkey homologue suggests expression of MUC7 in monkey salivary tissue. We have also expressed MUC7 in both rabbit reticulocyte in vitro translation and pET15-b E.coli based expression systems. We are currently developing purification schemes for the recombinant MG2. Key Words: Human, Saliva, Mucin, Expression
NIH ExPorter
NIH ExPorter