title: Dicer Regulates the Balance of Short-Lived Effector and Long-Lived Memory CD8 T Cell Lineages.
abstract: MicroRNAs constitute a major post-transcriptional mechanism for controlling protein expression, and are emerging as key regulators during T cell development and function. Recent reports of augmented CD8 T cell activation and effector differentiation, and aberrant migratory properties upon ablation of Dicer/miRNAs in naïve cells have established a regulatory role of miRNAs during priming. Whether miRNAs continue to exert similar functions or are dispensable during later stages of CD8 T cell expansion and memory differentiation remains unclear. Here, we report a critical role of Dicer/miRNAs in regulating the balance of long-lived memory and short-lived terminal effector fates during the post-priming stages when CD8 T cells undergo clonal expansion to generate a large cytotoxic T lymphocyte (CTL) pool and subsequently differentiate into a quiescent memory state. Conditional ablation of Dicer/miRNAs in early effector CD8 T cells following optimal activation and expression of granzyme B, using unique dicerfl/fl gzmb-cre mice, led to a strikingly diminished peak effector size relative to wild-type antigen-specific cells in the same infectious milieu. Diminished expansion of Dicer-ablated CD8 T cells was associated with lack of sustained antigen-driven proliferation and reduced accumulation of short-lived effector cells. Additionally, Dicer-ablated CD8 T cells exhibited more pronounced contraction after pathogen clearance and comprised a significantly smaller proportion of the memory pool, despite significantly higher proportions of CD127Hi memory precursors at the effector peak. Combined with previous reports of dynamic changes in miRNA expression as CD8 T cells differentiate from naïve to effector and memory states, these findings support distinct stage-specific roles of miRNA-dependent gene regulation during CD8 T cell differentiation.
authors.affiliation: The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA, United States of America.
authors.forename: Florian M
authors.initials: FM
authors.lastname: Baumann
authors.affiliation: The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA, United States of America.
authors.forename: Yevgeniy
authors.initials: Y
authors.lastname: Yuzefpolskiy
authors.affiliation: Department of Pediatrics, Division of Hematology and Oncology, University of Washington School of Medicine, Seattle, WA, United States of America; Ben Towne Center for Childhood Cancer Research, Seattle Children's Research Institute, Seattle, WA, United States of America.|Department of Pathology, University of Washington School of Medicine, Seattle, WA, United States of America.
authors.forename: Surojit
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Department of Pediatrics, Division of Hematology and Oncology, University of Washington School of Medicine, Seattle, WA, United States of America; Ben Towne Center for Childhood Cancer Research, Seattle Children's Research Institute, Seattle, WA, United States of America.
authors.forename: Vandana
authors.initials: V
authors.lastname: Kalia
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000502:physiology; D019070:Cell Lineage / Q000276:immunology / Q000502:physiology; D007156:Immunologic Memory / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000502:physiology; D043244:Ribonuclease III / Q000502:physiology*
chemical_list: D035683:MicroRNAs; D043244:Ribonuclease III