mRNA in mouse lacrimal glands with homolooy to salivary androgen-binding protein

Purpose: The exorbital and infraorbital lacrimal glands from mice were examined using molecular techniques to identify unique or differentially expressed mRNA. Methods The exorbital and infraorbital glands were dissected from adult male and female Swiss Webster mice. Poly (A)+ RNA was isolated from the tissues and reverse transcribed. The resulting cDNA was then amplified using polymerase chain reaction (PCR) and compared by differential display (DDRT) on silver stained polyacrylamide gels. The cDNA fragments of interest were reamplified, subcloned and sequenced. The BLAST program was used to search for data base sequence homologies. Results: The initial DDRT studies indicated that the exorbital and infraorbital lacrimal glands of mice are very similar tissues. One of the clones of interest isolated from the lacrimal tissues has some sequence homology (75%) to the alpha subunit of a low molecular weight androgen-binding protein (ABP) present in relatively high quantities in mouse salivary glands and saliva. Northern blots showed this mRNA is expressed at approximately equal levels in both male and female lacrimal tissue. Salivary ABP is unrelated to the androgen binding protein in Sertoli cells or the sex hormone binding globulin circulating in the plasma. Conclusions: mRNA for a protein related to salivary ABP is expressed in mouse lacrimal tissue suggesting that this protein may be synthesized and secreted into the tear fluid. ABP-like proteins have not previously been identified in lacrimal tissue or in tears. The function for ABP is not known.