Close correlation between the distribution of tenascin and that of actin filaments in the mouse urethral mesenchyme during active morphogenesis.

The distribution of tenascin, an extracellular matrix glycoprotein, and that of actin filaments were studied in the developing urethra of mouse embryos by antitenascin immunofluorescent and rhodamine-phalloidin staining. Tenascin appeared transiently in the urethral mesenchyme at the site of active morphogenesis in which the urethral epithelium separated from the surface epithelia of the glans and prepuce, being tubular, and the bilateral mesenchymes lining the preexisting urethral epithelium were seamed together in the ventral side of the tubular urethra immediately after the epithelial separation. The spatially and temporally restricted distribution of tenascin corresponded well to that of mesenchymal cells which possessed many actin filaments. These observations suggest that tenascin is involved in the cytoskeletal organization of mesenchymal cells in the active phase of morphogenesis.