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 inte grin subunit and laminin in this process by immunofluorescence and imm unoelectron microscopy. At Days 13.5 and 14 of gestation alpha6 was lo calized over the entire cell surface of undifferentiated epithelial ce lls of the terminal duster. On Day 15 the expression of alpha6 could n o longer be detected over central cells in the proximal portion of bra nched terminal duster, whereas peripheral cells were stained over the entire surface. On Day 17 of gestation to day of birth, alpha6 express ion was restricted to the basolateral surface of the differentiated ac inotubular structure. Its expression on acinar cells was uniformly dis tributed throughout the basolateral membrane, but on duct cells strong er staining towards the basal surface was noted. Similar expression wa s observed in adult acinar and duct cells. Expression of the alpha6-su bunit at the cell-cell contact in an early stage and its expression at the basolateral surface in an advanced stage indicate that integrin c ontaining alpha6 plays a significant role in cell-cell and cell-substr ate interaction. Stage and cell type-specific change of integrin expre ssion may be significant for submandibular development.