Gene expression of thymic microenvironmental cells: phenotipycal and functional modifications after inactivation of the CD49e gene by RNA interference.
The thymus is a central lymphoid organ, in which bone marrow-derived T cell precursors undergo a complex process of maturation that occurs as thymocytes migrate in the context of the thymic microenvironment, a tridimensional network composed of distinct cell types. These microenvironmental cells interact with thymocytes, providing signals that regulate normal intrathymic T cell development. These signals are released in niches of the thymic microenvironment, in which a given cell type has a specific signaling pattern and influences particular thymocyte differentiation stages. In our study, we identified genes differentially expressed in cortical and medullary thymic epithelial cells. Some genes take part in the neuroendocrine regulation of the thymic epithelium, such as the thymopoietin and hormone receptors; others, VCAM and fibronectin, play a role in adhesion and migration of thymocytes in the thymic microenvironment. The identification of these genes will be helpful for a better understanding of those signals provided by the thymic microenvironment to the developing thymocytes. These signals are involved in the bidirectional cross-talk between thymocytes and microenvironmental cells, implying that such an interaction should regulate gene expression by the thymic epithelium. Accordingly, DNA microarray experiments revealed that interaction with thymocytes resulted in the modulation of 114 genes in murine cortical epithelial cells, 142 genes in medullarry epithelial cells, and more than 350 genes of the human thymicepithelium. In order to get more information on extracellular matrix-mediated thymocyte/thymic epithelial cell interactions, we performed RNA interference-induced gene silencing of CD49e (the alpha-5 chain of the fibronectin receptor VLA-5) in human thymic epithelial cells. We observed that such a strategy triggered the modulation of other molecules related to thymocyte/thymic epithelial cell interactions. Actually, at least 150 genes are modulated in the thymic epithelium after anti-CD49e RNAi treatment. Importantly, we showed that RNAigene silencing of the alpha-5 integrin chain led to a decrease in the adhesion of thymocytes to thymic epithelial cells. Overall, we showed in the present thesis that interaction of thymocytes with the thymic epithelium lead to a massive gene modulation in epithelial cells. Moreover, we showed that RNA interference induced inhibition of the fibronectin receptor VLA-5 in the thymic epithelium also generates modulation of a large variety of genes, with consequences on the interactions of these cells with thymocytes.
School:Faculdades Oswaldo Cruz
Source Type:Master's Thesis
Date of Publication:04/10/2008