Expression and localization of the transcription factor JunD in the duct system of mouse submandibular gland.

We studied the expression and localization of JunD, a component of the transcription factor activator protein-1 (AP-1), in the mouse submandibular gland with immunoblotting and immunohistochemistry. In adult mice, all seven Jun and Fos family members constituting the AP-1 complex were expressed more abundantly in the female gland than in the male gland, and JunD was the most abundant of the members. Immunoreactivity for JunD was localized exclusively in the duct system of the gland, in which it was localized to the nuclei of intercalated duct (ID) cells and a subpopulation of striated duct (SD) cells located adjacent to ID. In contrast, granular convoluted tubule (GCT) cells, which are much more abundant in the male gland, were devoid of JunD. During postnatal development of the male gland, JunD was lost from the duct cells as they differentiated to GCT cells at 3-5 weeks postpartum. When GCT differentiation was induced in adult female gland by testosterone administration, many JunD-negative SD cells were temporarily induced to express JunD after 6-24 hr, but those cells lost JunD as they completely converted to GCT cells by 48 hr. These results suggested that JunD is involved in the differentiation of the duct system of mouse submandibular gland, in which there is crosstalk between the androgen/androgen receptor system and the AP-1 complex.