title: Cellular networks of human thymic medullary stromas coordinated by p53-related transcription factors.
abstract: The final elimination step of self-reactive T cells occurs in the medulla of the thymus where a complex framework provided by stromal cells supports an optimal milieu for their selection. Here we present evidence that tight junctions (TJs) widely join medullary stromal cells of the human thymus. Occludin (OCLN) and claudin-1 (CLDN-1) of TJ-associated molecules were dominantly expressed in medullary thymic epithelial cells (mTECs), and CLDN-4 and CLDN-7 were also localized in some mTECs near Hassall's corpuscles. Interestingly, p53-like transcription factors were found to upregulate OCLN and CLDN-1 in human TEC lines, as recently suggested in the regulation of mTEC function. Furthermore, dendritic cells (DCs) of the medulla, with a major role for selection of thymocytes, expressed CLDN-1 and OCLN as well, implying that the interposition of DCs within the mTEC scaffold is also helped by TJs. Analysis of freeze-fracture replicas of the thymus revealed TJ strand structures in the vicinity of gap junction plaques through which small molecules might move, as implied by dye-transfer analysis of a medullary cell line. Thus, it is thought that p53-like molecules regulate TJ-associated interactions of medullary stromal cells and that this mechanism might be associated with an intercellular communication network, probably for preserving the medullary niches.
authors.affiliation: Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, Japan. ichimiya@sapmed.ac.jp
authors.forename: Shingo
authors.initials: S
authors.lastname: Ichimiya
authors.forename: Takashi
authors.initials: T
authors.lastname: Kojima
mesh_terms: D002450:Cell Communication; D002460:Cell Line; D002675:Child, Preschool; D062445:Claudin-1; D062506:Claudin-4; D057167:Claudins; D003713:Dendritic Cells / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis; D062793:Occludin; D017154:Stromal Cells / Q000166:cytology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D019108:Tight Junctions / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: C568108:CLDN1 protein, human; C568157:CLDN4 protein, human; C473255:CLDN7 protein, human; D062445:Claudin-1; D062506:Claudin-4; D057167:Claudins; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53