title: Clonal analysis reveals uniformity in the molecular profile and lineage potential of CCR9(+) and CCR9(-) thymus-settling progenitors.
abstract: The entry of T cell progenitors to the thymus marks the beginning of a multistage developmental process that culminates in the generation of self-MHC-restricted CD4(+) and CD8(+) T cells. Although multiple factors including the chemokine receptors CCR7 and CCR9 are now defined as important mediators of progenitor recruitment and colonization in both the fetal and adult thymi, the heterogeneity of thymus-colonizing cells that contribute to development of the T cell pool is complex and poorly understood. In this study, in conjunction with lineage potential assays, we perform phenotypic and genetic analyses on thymus-settling progenitors (TSP) isolated from the embryonic mouse thymus anlagen and surrounding perithymic mesenchyme, including simultaneous gene expression analysis of 14 hemopoietic regulators using single-cell multiplex RT-PCR. We show that, despite the known importance of CCL25-CCR9 mediated thymic recruitment of T cell progenitors, embryonic PIR(+)c-Kit(+) TSP can be subdivided into CCR9(+) and CCR9(-) subsets that differ in their requirements for a functional thymic microenvironment for thymus homing. Despite these differences, lineage potential studies of purified CCR9(+) and CCR9(-) TSP reveal a common bias toward T cell-committed progenitors, and clonal gene expression analysis reveals a genetic consensus that is evident between and within single CCR9(+) and CCR9(-) TSP. Collectively, our data suggest that although the earliest T cell progenitors may display heterogeneity with regard to their requirements for thymus colonization, they represent a developmentally homogeneous progenitor pool that ensures the efficient generation of the first cohorts of T cells during thymus development.
authors.affiliation: Medical School, Institute for Biomedical Research, Medical Research Council Center for Immune Regulation, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
authors.forename: Guillaume E
authors.initials: GE
authors.lastname: Desanti
authors.forename: William E
authors.initials: WE
authors.lastname: Jenkinson
authors.forename: Sonia M
authors.initials: SM
authors.lastname: Parnell
authors.forename: Amine
authors.initials: A
authors.lastname: Boudil
authors.forename: Laetitia
authors.initials: L
authors.lastname: Gautreau-Rolland
authors.forename: Bertus
authors.initials: B
authors.lastname: Eksteen
authors.forename: Sophie
authors.initials: S
authors.lastname: Ezine
authors.forename: Peter J L
authors.initials: PJ
authors.lastname: Lane
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Jenkinson
authors.forename: Graham
authors.initials: G
authors.lastname: Anderson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology; D019070:Cell Lineage; D002469:Cell Separation; D002999:Clone Cells; D004622:Embryo, Mammalian; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D054503:Lymphoid Progenitor Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D038041:Lymphopoiesis; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D042282:Microdissection; D054388:Receptors, CCR / Q000276:immunology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000196:embryology
chemical_list: C119309:CC chemokine receptor 9; D054388:Receptors, CCR