May function in ocular mucus homeostasis. Isoform 1 and isoform 2-6 share the first 17 amino acid residues that correspond to the signal sequence. Specifically expressed in sublingual salivary glands. Expressed by mucous cells of the submandibular gland and submucosal gland of the trachea. Expression is altered in sld (sublingual gland differentiation arrest) mutants. Contaminating sequence. Sequence of unknown origin in the N-terminal part.