title: Sonic Hedgehog regulates thymic epithelial cell differentiation.
abstract: Sonic Hedgehog (Shh) is expressed in the thymus, where it regulates T cell development. Here we investigated the influence of Shh on thymic epithelial cell (TEC) development. Components of the Hedgehog (Hh) signalling pathway were expressed by TEC, and use of a Gli Binding Site-green fluorescence protein (GFP) transgenic reporter mouse demonstrated active Hh-dependent transcription in TEC in the foetal and adult thymus. Analysis of Shh-deficient foetal thymus organ cultures (FTOC) showed that Shh is required for normal TEC differentiation. Shh-deficient foetal thymus contained fewer TEC than wild type (WT), the proportion of medullary TEC was reduced relative to cortical TEC, and cell surface expression of MHC Class II molecules was increased on both cortical and medullary TEC populations. In contrast, the Gli3-deficient thymus, which shows increased Hh-dependent transcription in thymic stroma, had increased numbers of TEC, but decreased cell surface expression of MHC Class II molecules on both cortical and medullary TEC. Neutralisation of endogenous Hh proteins in WT FTOC led to a reduction in TEC numbers, and in the proportion of mature Aire-expressing medullary TEC, but an increase in cell surface expression of MHC Class II molecules on medullary TEC. Likewise, conditional deletion of Shh from TEC in the adult thymus resulted in alterations in TEC differentiation and consequent changes in T cell development. TEC numbers, and the proportion of mature Aire-expressing medullary TEC were reduced, and cell surface expression of MHC Class II molecules on medullary TEC was increased. Differentiation of mature CD4 and CD8 single positive thymocytes was increased, demonstrating the regulatory role of Shh production by TEC on T cell development. Treatment of human thymus explants with recombinant Shh or neutralising anti-Shh antibody indicated that the Hedgehog pathway is also involved in regulation of differentiation from DP to mature SP T cells in the human thymus.
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK.
authors.forename: José Ignacio
authors.initials: JI
authors.lastname: Saldaña
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK.
authors.forename: Anisha
authors.initials: A
authors.lastname: Solanki
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK.
authors.forename: Ching-In
authors.initials: CI
authors.lastname: Lau
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK.
authors.forename: Hemant
authors.initials: H
authors.lastname: Sahni
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK.
authors.forename: Susan
authors.initials: S
authors.lastname: Ross
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Furmanski
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ono
authors.affiliation: Weatherall Institute of Molecular Medicine, and Department of Paediatrics, University of Oxford, UK.
authors.forename: Georg
authors.initials: G
authors.lastname: Holländer
authors.affiliation: Immunobiology Section, UCL Institute of Child Health, 30 Guilford Street London WC1N 1EH, UK. Electronic address: t.crompton@ucl.ac.uk.
authors.forename: Tessa
authors.initials: T
authors.lastname: Crompton
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism*; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D015398:Signal Transduction; D060168:Thymocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*
chemical_list: D053823:Hedgehog Proteins
keywords: MHCII; Morphogen; Sonic hedgehog; T cell; Thymic epithelium; cTEC; mTEC