Secretoglobins: Sexually dimorphic expression of androgen-binding protein mRNA in mouse lacrimal glands

PURPOSE. This study was conducted to seek sex differences in mRNA expression in normal mouse lacrimal glands. Gene expression differences in the lacrimal gland may contribute to susceptibility to lacrimal gland or ocular surface disease. METHODS. A differential display analysis was performed on poly(A)⁺ RNA isolated from male and female Swiss Webster mouse exorbital lacrimal glands. Four potential gender-specific products were subcloned and sequenced. Full-length cDNAs of each product were obtained using RACE-PCR. ³²P-labeled fragments of each clone were hybridized to a blot of male and female mouse poly(A)⁺ RNA isolated from harderian, lacrimal, submandibular, sublingual, and parotid glands and the liver. RESULTS. GenBank database alignments indicated that the four clones were members of the secretoglobin family. The most closely related sequences were the mouse salivary androgen- binding protein (ABP) subunits α, β and γ. We named the four lacrimal clones the δ, ε, ζ, and η subunits of ABP. Northern blot analysis showed that mRNAs for each of these four ABP sub-units were lacrimal-gland-specific. The δand ζ subunits of ABP were expressed primarily in male mouse lacrimal gland. CONCLUSIONS. Sequence attributes predict that the ABP subunits expressed in lacrimal glands comprise proteins that are secreted in tears. These data imply compositional differences in ABPs secreted by mouse lacrimal and submandibular glands, and in ABPs secreted by male and female mouse lacrimal glands.