Epithelial-mesenchymal interactions as a system to study alternative splicing regulation by extracellular signals

FEDERICO PELISCH; MATÍAS BLAUSTEIN; ALBERTO R. KORNBLIHTT; ANABELLA SREBROW

Bariloche, Argentina

Congreso; Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas - SAIB; 2003

Our group studies the effect of extracellular signals on the alternative splicing of the fibronectin (FN) pre-mRNA. In the case of the murine FN gene, a single primary transcript gives rise to up to 12 different mRNAs and polypeptides as the result of cell-specific alternative splicing, occurring in three different regions: EDII, EDI and IIICS. We have reported previously that a mammary mesenchymal cell line expresses higher proportions of EDI+ fibronectin than a mammary epithelial one. Furthermore, soluble factors secreted by mesenchymal cells (MC-conditioned medium) stimulate the inclusion of EDI in epithelial cells and induce cell scattering. These observations led us to speculate that the upregulation of EDI inclusion could be due to an epithelial-mesenchymal transition. Preliminary results indicate that most of the cells remain epithelial after treatment with MC-conditioned medium, as judged by the maintenance of cytokeratin, an epithelial marker, and the isoform of the FGF receptor expressed. We investigated the splicing pattern of the other FN alternative exons in these two cell types and asked whether the MC-conditioned medium had any effect on the splicing of this two exons. While mesenchymal cells express higher levels of EDII+ and IIICS+ FN than epithelial cells, only the alternative splicing of IIICS is regulated by this treatment.