Cellular origin of mucins of the ocular surface tear film.

In summary, we have demonstrated that the ocular surface epithelia express at least three mucin genes. We suggest that the gel-forming mucin MUC5AC is a major mucin forming the mucus gel of the tear film. We further suggest that MUC1 facilitates the spread of the MUC5-containing mucus on the ocular surface and, along with the mucus gel, prevents cell and debris adhesion to the ocular surface. The function of MUC4 at the ocular surface remains to be elucidated.