DISTRIBUTION OF ALPHA-6 INTEGRIN SUBUNIT IN DEVELOPING MOUSE SUBMANDIBULAR-GLAND

We examined the development of mouse submandibular gland by light and electron microscopy and determined the distribution of the alpha6 integrin subunit and laminin in this process by immunofluorescence and immunoelectron microscopy. At Days 13.5 and 14 of gestation alpha6 was localized over the entire cell surface of undifferentiated epithelial cells of the terminal duster. On Day 15 the expression of alpha6 could no longer be detected over central cells in the proximal portion of branched terminal duster, whereas peripheral cells were stained over the entire surface. On Day 17 of gestation to day of birth, alpha6 expression was restricted to the basolateral surface of the differentiated acinotubular structure. Its expression on acinar cells was uniformly distributed throughout the basolateral membrane, but on duct cells stronger staining towards the basal surface was noted. Similar expression was observed in adult acinar and duct cells. Expression of the alpha6-subunit at the cell-cell contact in an early stage and its expression at the basolateral surface in an advanced stage indicate that integrin containing alpha6 plays a significant role in cell-cell and cell-substrate interaction. Stage and cell type-specific change of integrin expression may be significant for submandibular development.