Identificación y estudio de nuevos mecanismos moleculares implicados en la morfogénesis epitelial: mecanotransducción, orientación del huso mitótico y endocitosis

Abstract

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 11-07-2014Epithelial cells represent the founding stone at the dawn of metazoan evolution. Epithelial cell polarity is apparent in the organization of different membrane domains, which carry out essential functions in the animal, such as nutrient uptake and excretion. Epithelial tissues are frequently convoluted and wrapped inside the animal body, in the form of tubes, providing protection from the environment and augmenting the exchange surface for different physiological functions. Epithelial organ morphogenesis is the process by which epithelial cells proliferate and organize the three-dimensional architecture of the final organ while generating and maintaining the polarized phenotype. Using the 3D-MDCK cell culture system and zebrafish gut morphogenesis as in vitro and in vivo models of epithelial morphogenesis we have investigated three mechanisms that regulate epithelial morphogenesis in vertebrates. Firstly, through use of adhesive micropatterns, we have characterized that spatial confinement of cell adhesion provides essential mechanophysical cues for the acquisition of 3D epithelial polarity. Second, through the analysis of the small GTPase Cdc42, a master regulator of cell polarity, we have found that mitotic spindle formation and orientation are required for the maintenance of planar symmetric cell divisions, which is necessary for single lumen formation. Finally, we characterized a specific gene set induced in vivo and in vitro during epithelial morphogenesis, and we contributed to elucidate that one of these genes is responsible for the fine regulation of endocytosis during development to control the process of epithelial morphogenesis and differentiation. In conclusion, we have analyzed three mechanisms involved in the process of epithelial morphogenesis in vertebrates. Furthermore, these mechanisms are common to most epithelial glands, and therefore provide essential knowledge on how polarity and proliferation are controlled during development, and point to new approaches to unravel the process of polarity loss and dysplasia at the origin of carcinomagenesi