The mouse submaxillary gland protein (mSMGP) gene is highly expressed in the submandibular and lacrimal glands of the adult mouse. As a first step in elucidating the role of the mSMGP in the submandibular gland, gene expression in the developing mouse was examined. Using reverse transcriptase polymerase chain reaction (RT-PCR), Southern and Northern blot analyses, mSMGP gene expression in the prenatal submandibular gland was det cted as early as embryonic day 14 (E14), the approximate time at which submandibular gland development begins. By 'in situ' hybridization studies of the embryonic gland, mSMGP gene expression was localized to the acinar cells, the major secretory cells of the submandibular gland. The early and continued expression of the mSMGP gene in the embryo suggests that the mSMGP may be integral during submandibular gland development in the mouse. Sequence analysis of the mSMGP in our laboratory has revealed the presence of a signal peptide, suggesting that the mSMGP is a secreted protein. (Abstract shortened by UMI.)