title: Role of Hedgehog signalling at the transition from double-positive to single-positive thymocyte.
abstract: In the thymus, developing T cells receive signals that determine lineage choice, specificity, MHC restriction and tolerance to self-antigen. One way in which thymocytes receive instruction is by secretion of Sonic hedgehog (Shh) from thymic epithelial cells. We have previously shown that Hedgehog (Hh) signalling in the thymus decreases the CD4:CD8 single-positive (SP) thymocyte ratio. Here, we present data indicating that double-positive (DP) thymocytes are Hh-responsive and that thymocyte-intrinsic Hh signalling plays a role in modulating the production of CD4(+)  (SP4), CD8(+)  (SP8) and unconventional T-cell subsets. Repression of physiological Hh signalling in thymocytes altered the proportions of DP and SP4 cells. Thymocyte-intrinsic Hh-dependent transcription also attenuated both the production of mature SP4 and SP8 cells, and the establishment of peripheral T-cell compartments in TCR-transgenic mice. Additionally, stimulation or withdrawal of Hh signals in the WT foetal thymus impaired or enhanced upregulation of the CD4 lineage-specific transcription factor Gata3 respectively. These data together suggest that Hh signalling may play a role in influencing the later stages of thymocyte development.
authors.affiliation: Immunobiology Unit, Institute of Child Health, University College London, London, UK. a.furmanski@ucl.ac.uk
authors.forename: Anna L
authors.initials: AL
authors.lastname: Furmanski
authors.forename: Jose Ignacio
authors.initials: JI
authors.lastname: Saldana
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Rowbotham
authors.forename: Susan E
authors.initials: SE
authors.lastname: Ross
authors.forename: Tessa
authors.initials: T
authors.lastname: Crompton
mesh_terms: D000818:Animals; D015704:CD4 Antigens / Q000235:genetics / Q000378:metabolism; D016827:CD8 Antigens / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D019070:Cell Lineage; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D004847:Epithelial Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology; D053823:Hedgehog Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D060168:Thymocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology* / Q000196:embryology / Q000254:growth & development; D015533:Transcriptional Activation / Q000235:genetics
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens; D053823:Hedgehog Proteins; C465570:Shh protein, mouse
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