Expression of secretory mucin genes by human conjunctival epithelia.

PURPOSE To determine whether human conjunctival epithelium expresses any of the human mucin genes designated MUC2 through MUC7. METHOD Northern blot analysis was performed using total RNA isolated from surgically removed conjunctival tissues. Complementary DNA or oligonucleotides to the tandem repeat region of each mucin gene were labeled and hybridized to conjunctival RNA. In situ hybridization also was performed to determine the distribution of mucin mRNA. RESULTS Only MUC4 and MUC5 probes hybridized to conjunctival RNA by Northern blot analysis. Both probes bound in a polydispersed pattern, which is characteristic of mucin genes. Using in situ hybridization, MUC4 mRNA was detected in the cells of the stratified conjunctival epithelium, whereas MUC5 mRNA expression was limited to goblet cells MUC4 or MUC5 probes did not hybridize to sections of corneal epithelium. CONCLUSIONS The mucins MUC4 and MUC5 are expressed by the human conjunctiva. These mucins may play an important role in forming the tear-film layer at the air and ocular surface epithelium interface.