The mechanism of androgen-dependent differentiation of the duct system in the submandibular gland

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In regard to the differentiation of rodent submandibular glands (SMG), we have obtained the following results :1)In the mouse SMG, the expression of the transcription factor JunD is localized to the duct system and much more abundant in the female than in the male gland. During the postnatal development and testosterone-induced GCT cell differentiation, JunD expression is temporarily induced in the nuclei of striated duct cells and dispappeares as they differentiated into GCT cells (Reference 1).2)The expression and localization of menin, a nuclear protein that binds JunD, showed the same pattern in the mouse SMG as that of JunD, suggesting that JunD-menin complex is responsible for the duct differentiation.3)In the SMG of hypophysectomized rats, the induction of the protease inhibitor cystatin S by the b-adrenergic agonist isoproterenol is much less than that in the control. Administration of one of the pituitary-dependent hormones, i.e., testosterone, estradiol, dexamethasone and thyroxine, together with isoproterenol results in marked recovery of cystatin S expression (Reference 2).These results suggest the role of cross-talks between multiple signaling pathways, including that of androgens, in the differentiation of rodent SMG.4)We have cloned a novel animal lectin specifically expressed in the rat sublingual gland and named it STAMP (sublingual gland acinar membrane protein). SLAMP is localized to the membrane of ER-Golgi intermediate compartment (ERGIC), suggesting its role in the early secretory pathway of mucin glycoproteins.