title: Thymocytes inLyve1-CRE/S1pr1f/fMice Accumulate in the Thymus due to Cell-Intrinsic Loss of Sphingosine-1-Phosphate Receptor Expression.
abstract: T cell emigration from the thymus is essential for immunological homeostasis. While stromal cell-produced sphingosine-1-phosphate (S1P) has been shown to promote thymocyte egressviathe S1P receptor, S1PR1, the significance of S1P/S1PR1 signaling in the thymic stromal cells that surround T cells remains unclear. To address this issue, we developed conditional knockout mice (Lyve1-CRE/S1pr1f/fmice) in whichS1pr1was selectively targeted in cells expressing the lymphatic endothelial cell marker, Lyve1. In these mice, T cells were significantly reduced in secondary lymphoid tissues, and CD62L+mature CD4 and CD8 single-positive (SP) T cells accumulated in the medulla failed to undergo thymus egress. Using aLyve1reporter strain in which Lyve1 lineage cells expressed tdTomato fluorescent protein, we unexpectedly found that a considerable proportion of the thymocytes were fluorescently labeled, indicating that they belonged to the Lyve1 lineage. The CD4 and CD8 SP thymocytes inLyve1-CRE/S1pr1f/fmice exhibited an egress-competent phenotype (HSAlow, CD62Lhigh, and Qa-2high), but were CD69highand lacked S1PR1 expression. In addition, CD4 SP thymocytes from these mice were unable to migrate to the periphery after their intrathymic injection into wild-type (WT) mice. In contrast, WT T cells could migrate to the periphery in both WT andLyve1-CRE/S1pr1f/fthymuses. These results demonstrated that thymocyte egress is mediated by T cell-expressed, but not stromal cell-expressed, S1PR1 and caution against using theLyve1-CREsystem for selectively gene deletion in lymphatic endothelial cells.
authors.affiliation: MediCity Research Laboratory, University of Turku , Turku , Finland.
authors.forename: Akira
authors.initials: A
authors.lastname: Takeda
authors.affiliation: MediCity Research Laboratory, University of Turku , Turku , Finland.
authors.forename: Mohammad Shahadat
authors.initials: MS
authors.lastname: Hossain
authors.affiliation: MediCity Research Laboratory, University of Turku , Turku , Finland.
authors.forename: Pia
authors.initials: P
authors.lastname: Rantakari
authors.affiliation: Department of Immunology and Cell Biology, Graduate School of Medicine and Frontier Biosciences, Osaka University, Suita, Japan; WPI Immunology Frontier Research Center, Osaka University, Suita, Japan.
authors.forename: Szandor
authors.initials: S
authors.lastname: Simmons
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University , Suita , Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Sasaki
authors.affiliation: MediCity Research Laboratory, University of Turku, Turku, Finland; Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland.
authors.forename: Marko
authors.initials: M
authors.lastname: Salmi
authors.affiliation: MediCity Research Laboratory, University of Turku , Turku , Finland.
authors.forename: Sirpa
authors.initials: S
authors.lastname: Jalkanen
authors.affiliation: MediCity Research Laboratory, University of Turku, Turku, Finland; WPI Immunology Frontier Research Center, Osaka University, Suita, Japan; Interdisciplinary Program for Biomedical Sciences, Institute for Academic Initiatives, Osaka University, Suita, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyasaka
keywords: Lyve1; S1PR1; egress; sphingosine-1-phosphate; thymus