Functional characterisation of new molecular mechanisms involved in epithelial lumen morphogenesis


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Fernando Martin-Belmonte1
1CSIC-UAM Centro de BiologĂ­a Molecular Severo Ochoa

Abstract

Epithelial organs such as lungs, kidneys or the gut are made of cavities (alveoli, cysts or acini) and tubules (the nephron tubules). These components are lined by a monolayer of polarised cells, with an apical surface facing a lumen and a basolateral surface lining the cell-to-cell junctions and subjacent extracellular matrix (ECM). After polarisation, acquisition of a central lumen is the major event during epithelial organs development. Although epithelial cell polarisation has been widely studied, the molecular mechanisms that lead to lumen formation are poorly understood. MDCK cells plated in ECM (3D cultures) form spherical structures enclosing a central lumen (cysts) that resemble the epithelial organ structure, which is a powerful model for the study of lumen morphogenesis. In order to identify genes necessary for lumen morphogenesis we performed a transcriptional and functional screening. First, a microarray analysis was done to identify upregulated genes during lumen morphogenesis. Microarray data was validated by quantitative PCR, and finally a set of genes was selected to perform a functional analysis by siRNA silencing. We confirmed induction of 48 genes. The siRNA analysis indicated that 16 genes (33%) were required for normal lumen phenotype in 3D cultures. Furthermore, most of these genes are downregulated in epithelial cancers. The identification of these genes opens new ways for the understanding of the key molecular mechanisms that lead to the development of epithelial organs, and identify new targets to treat epithelial tumours.

Supported by grants of the Human Frontiers Science Program (HFSP-CDA 00011/2009), Marie Curie (IRG-209382),MICINN (BFU2008-01916) and (CONSOLIDER CSD2009-00016) to FM-B; and JAE fellowships (MICINN) to AERF and SV; and a FPI fellowship (MICINN) to MG.