title: RNA interference-mediated knockdown of CD49e (α5 integrin chain) in human thymic epithelial cells modulates the expression of multiple genes and decreases thymocyte adhesion.
abstract: BACKGROUND
  The thymus is a central lymphoid organ, in which bone marrow-derived T cell precursors undergo a complex process of maturation. Developing thymocytes interact with thymic microenvironment in a defined spatial order. A component of thymic microenvironment, the thymic epithelial cells, is crucial for the maturation of T-lymphocytes through cell-cell contact, cell matrix interactions and secretory of cytokines/chemokines. There is evidence that extracellular matrix molecules play a fundamental role in guiding differentiating thymocytes in both cortical and medullary regions of the thymic lobules. The interaction between the integrin α5β1 (CD49e/CD29; VLA-5) and fibronectin is relevant for thymocyte adhesion and migration within the thymic tissue. Our previous results have shown that adhesion of thymocytes to cultured TEC line is enhanced in the presence of fibronectin, and can be blocked with anti-VLA-5 antibody.
  
  
  RESULTS
  Herein, we studied the role of CD49e expressed by the human thymic epithelium. For this purpose we knocked down the CD49e by means of RNA interference. This procedure resulted in the modulation of more than 100 genes, some of them coding for other proteins also involved in adhesion of thymocytes; others related to signaling pathways triggered after integrin activation, or even involved in the control of F-actin stress fiber formation. Functionally, we demonstrated that disruption of VLA-5 in human TEC by CD49e-siRNA-induced gene knockdown decreased the ability of TEC to promote thymocyte adhesion. Such a decrease comprised all CD4/CD8-defined thymocyte subsets.
  
  
  CONCLUSIONS
  Conceptually, our findings unravel the complexity of gene regulation, as regards key genes involved in the heterocellular cell adhesion between developing thymocytes and the major component of the thymic microenvironment, an interaction that is a mandatory event for proper intrathymic T cell differentiation.
authors.affiliation: Laboratory on Thymus Research, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro, RJ, 21040-360, Brazil.
authors.forename: Leandra
authors.initials: L
authors.lastname: Linhares-Lacerda
authors.forename: Marcelo
authors.initials: M
authors.lastname: Ribeiro-Alves
authors.forename: Ana Cristina Martins de Almeida
authors.initials: AC
authors.lastname: Nogueira
authors.forename: Daniella Areas
authors.initials: DA
authors.lastname: Mendes-da-Cruz
authors.forename: Danielle Aparecida
authors.initials: DA
authors.lastname: Magalhães
authors.forename: Mireille
authors.initials: M
authors.lastname: Dardenne
authors.forename: Geraldo Aleixo
authors.initials: GA
authors.lastname: Passos
authors.forename: Wilson
authors.initials: W
authors.lastname: Savino
mesh_terms: D002448:Cell Adhesion / Q000235:genetics / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics*; D055785:Gene Knockdown Techniques; D006801:Humans; D039482:Integrin alpha5 / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D013601:T-Lymphocytes / Q000502:physiology*; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D005353:Fibronectins; D039482:Integrin alpha5