title: Vagaries of fluorochrome reporter gene expression in Foxp3+ regulatory T cells.
abstract: CD4(+)CD25(+) regulatory T (Treg) cell lineage commitment and expression of the transcription factor Foxp3 can be induced at the CD4(+)CD8(+) double-positive (DP) and CD4(+)CD8(?) single-positive stages of thymic development, as well as in postthymic CD4(+) T cells in peripheral lymphoid tissues. The availability of transgenic mice with Foxp3-dependent fluorochrome reporter gene expression has greatly facilitated studies on the intra- and extrathymic generation of murine Foxp3(+) Treg cells. Here, we performed a comparative analysis of thymic Treg cell development and peripheral compartments of mature Treg cells in various transgenic strains with gene targeted and bacterial artificial chromosome (BAC)-driven Foxp3-fluorochrome expression. These studies revealed a relative deficiency of Foxp3(+) DP thymocytes selectively in mice with targeted insertion of the fluorochrome reporter gene coding sequence into the endogenous Foxp3 gene. While Foxp3 BAC-driven fluorochrome expression in ex vivo CD4(+) T cells was found to faithfully reflect Foxp3 protein expression, we provide evidence that Foxp3 BAC transgenesis can result in sizable populations of Foxp3(+) Treg cells that lack fluorochrome reporter expression. This could be attributed to both timely delayed up-regulation of BAC expression in developing Treg cells and the accumulation of peripheral Foxp3(+) Treg cells with continuous transcriptional inactivity of the Foxp3 BAC transgene.
authors.affiliation: Immunotolerance in Regeneration, CRTD/DFG-Center for Regenerative Therapies Dresden, Technical University Dresden, Dresden, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Schallenberg
authors.forename: Cathleen
authors.initials: C
authors.lastname: Petzold
authors.forename: Pei-Yun
authors.initials: PY
authors.lastname: Tsai
authors.forename: Tim
authors.initials: T
authors.lastname: Sparwasser
authors.forename: Karsten
authors.initials: K
authors.lastname: Kretschmer
mesh_terms: D000818:Animals; D019070:Cell Lineage / Q000276:immunology; D003433:Crosses, Genetic; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D015870:Gene Expression; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000378:metabolism; D019426:Integrases / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology
chemical_list: D005456:Fluorescent Dyes; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D049452:Green Fluorescent Proteins; C045073:Cre recombinase; D019426:Integrases