How to form and maintain a monolayered epithelium: the role of integrins
Authors: Lourdes Rincón-Ortega; Acaimo González-Reyes; María Dolores Martín-Bermudo
Affiliation: Centro Andaluz de Biología del Desarrollo, CSIC-Univ. Pablo de Olavide, Sevilla, Spain
Keywords: q. epithelial sheets; t. cell junctions and adhesion
Integrins are essential proteins that connect the cell with the extracellular matrix (ECM) and have an important role in the development and maintenance of epithelia. They are implicated in many epithelial diseases and also in tumor progression. To study integrin function in epithelial homeostasis, we use the follicular epithelium(FE) of the Drosophila ovary as model system.
The monolayered FE present, in the developing egg chambers of the ovary, follicle cells (FCC), the most abundant cell type, and polar cells, that act as signaling centers for the patterning of the FE. Individual egg chambers are connected by a line of stalk cells. The FE is surrounded by a specialized ECM known as basement membrane (BM), which supports egg chambers growth during oogenesis. The FE is connected to the BM through integrins. Integrins are essential to maintain the architecture of the FE, since the absence of integrins induces extra-layers of FCC at the poles of the egg chambers (Fernández-Miñán et al., 2007). In addition, we have recently observed that lack of integrins produces alterations in the number and distribution of polar and stalk cells, which results in aberrant follicles.
In this project, we aim to understand how these phenotypes arise, thus gaining insight into the role of cell-ECM interactions mediated by integrins during epithelial morphogenesis and maintenance. Our results show that integrins control the number of polar and stalk cells by regulating the proliferation rate and activation of signaling pathways in their precursors. Furthermore, analysis of cell division in vivo, leads us to propose that the formation of extra-layers could be due to a combination of aberrant spindle orientation, cellular tension and BM mechanical properties. Taking all together, our findings show that integrins regulate epithelia development and maintenance by different molecular and cellular mechanisms, including activity of signaling pathways, spindle orientation and mechanical properties of cells and their surrounding BM.