Embryonic corneal epithelial actin alters distribution in response to laminin

In the current study, laser scanning confocal image analysis was used to investigate the actin distribution in whole-mount preparations of freshly isolated and cultured corneal epithelia. Actin staining defined the cell borders and microvilli of the periderm cells. The actin was prominent as an organized network at the interface between the basal and periderm cells and in the basal compartment of the basal cells (actin cortical mat) when isolated with the basal lamina (BL). In epithelia isolated without BL, the actin in the periderm cells and the network at the periderm-basal cell interface was the same as in epithelia isolated with BL. However, the actin in the basal compartment of the basal cells was localized in the cellular blebs that projected from the basal cell surface. Epithelia isolated without BL and cultured in the presence of laminin reorganized the actin cortical mat within 2 hours. However, epithelia isolated without BL and cultured without BL proteins continued to have basal cell projections, sometimes into the pores of the filter. Treatment of epithelia with 2 microM cytochalasin D prevented the reorganization of the actin by laminin. In conclusion, the use of confocal analysis increased our understanding of actin distribution in the epithelial sheets. These results confirmed and extended previous studies using electron microscopy to determine that corneal epithelial cells respond to extracellular matrix molecules by an actin-dependent mechanism.