F9 embryonal carcinoma cells can differentiate in vitro into either parietal (PE) or visceral (VE) endoderm, depending upon specific retinoic acid (RA) treatment and growth conditions. In differentiated aggregates of F9 cells (EB), the VE is a polarized monolayer surrounding a core of undifferentiated cells. Within 7 days of treatment the cells organize their cytoskeleton and synthesize large amounts of extracellular matrix proteins to form a basal lamina under the newly formed epithelium. All these changes are likely to involve integrin expression and organization. In this study we have analyzed the spatio-temporal changes in the pattern and level of expression of β1, β34, α5, α6A, and α6B integrin subunits. We found that the organization of the VE monolayer in F9 aggregates involves both qualitative and quantitative changes in integrin expression. β1 is downregulated and accumulates in the forming epithelium. The same occurs for α5, although its location on the surface of the aggregate appears to be transient as in fully differentiated EB its distribution is uniform. β4 and α6A are also mainly localized in the VE but they are undetectable in undifferentiated aggregates and their expression is induced by RA treatment. An important exception is represented by α6B whose distribution and expression remain almost unchanged throughout treatment.
ASJC Scopus subject areas
- Cell Biology