title: Conditional Fas-associated death domain protein (FADD): GFP knockout mice reveal FADD is dispensable in thymic development but essential in peripheral T cell homeostasis.
abstract: Fas-associated death domain protein (FADD)/mediator of receptor-induced toxicity-1 is required for signaling induced by death receptors such as Fas. In earlier studies, FADD-deficient mice died in utero, and a FADD deficiency in embryonic stem cells inhibited T cell production in viable FADD-/- -->RAG-1-/- chimeras. To analyze the temporal requirement of FADD in the development and function in the T lineage, it is necessary to establish viable mutant mice producing detectable FADD-deficient T cells. We generated mice that express a functional FADD:GFP fusion gene reconstituting normal embryogenesis and lymphopoiesis in the absence of the endogenous FADD. Efficient T cell-specific deletion of FADD:GFP was achieved, as indicated by the presence of a high percentage of GFP-negative thymocytes and peripheral T cells in mice expressing Lck-Cre or CD4-Cre. Sorted GFP-negative thymocytes and peripheral T cells contained undetectable levels of FADD and were resistant to apoptosis induced by Fas, TNF, and TCR restimulation. These T cell-specific FADD-deficient mice contain normal thymocyte numbers, but fewer peripheral T cells. Purified peripheral FADD-deficient T cells failed to undergo extensive homeostatic expansion after adoptive transfer into lymphocyte-deficient hosts, and responded poorly to proliferation induced by ex vivo TCR stimulation. Furthermore, deletion of FADD in preactivated mature T cells using retrovirus-Cre resulted in no proliferation. These results demonstrate that FADD plays a dispensable role during thymocyte development, but is essential in maintaining peripheral T cell homeostasis and regulating both apoptotic and proliferation signals.
authors.affiliation: Kimmel Cancer Center, Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Yuhang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Stephen
authors.initials: S
authors.lastname: Rosenberg
authors.forename: Hanming
authors.initials: H
authors.lastname: Wang
authors.forename: Hongxia Z
authors.initials: HZ
authors.lastname: Imtiyaz
authors.forename: Ying-Ju
authors.initials: YJ
authors.lastname: Hou
authors.forename: Jianke
authors.initials: J
authors.lastname: Zhang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D053200:Fas-Associated Death Domain Protein; D049452:Green Fluorescent Proteins / Q000235:genetics; D006706:Homeostasis; D019426:Integrases / Q000502:physiology; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology*; D013950:Thymus Gland / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C505534:Fadd protein, mouse; D053200:Fas-Associated Death Domain Protein; D011948:Receptors, Antigen, T-Cell; D049452:Green Fluorescent Proteins; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); C045073:Cre recombinase; D019426:Integrases