title: De novo DNA methylation is required to restrict T helper lineage plasticity.
abstract: Naïve CD4+ T cells are highly plastic and can differentiate into discrete lineages with unique functions during an immune response. Once differentiated, helper T cells maintain a stable transcriptional memory of their initial lineage choice and resist redifferentiation. During embryogenesis, de novo DNA methylation operates on the hypomethylated genome of the blastocyst to achieve tissue-specific patterns of gene expression. Similarly, the ifnγ promoter is hypomethylated in naïve T cells, but Th2, Th17, and iTreg differentiation is accompanied by substantial de novo DNA methylation at this locus. To determine whether de novo DNA methylation is required to restrict T helper lineage plasticity, we used mice with T cell-specific deletion of the methyltransferase DNMT3a. Induction of lineage-specific cytokines occurred normally in the absence of DNMT3a, however, DNMT3a-deficient Th2, Th17, and iTreg completely failed to methylate the ifnγ promoter. This was accompanied by an increase in the transcriptionally permissive trimethyl H3K4 mark, and a reduction in inhibitory H3K27 methylation at the ifnγ locus. Failed de novo methylation resulted in failed silencing of the ifnγ gene, as DNMT3a-deficient Th2, Th17, and iTreg cells produced significant levels of IFNγ following restimulation in the presence of IL-12. Therefore, DNMT3a-mediated DNA methylation restricts T helper plasticity by establishing an epigenetically silent chromatin structure at regulatory regions of the ifnγ gene.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine and The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Rajan M
authors.initials: RM
authors.lastname: Thomas
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Gamper
authors.forename: Brian H
authors.initials: BH
authors.lastname: Ladle
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Powell
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Wells
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000276:immunology; D019070:Cell Lineage / Q000276:immunology*; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000276:immunology; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000502:physiology*; D000090205:DNA Methyltransferase 3A; D044127:Epigenesis, Genetic / Q000276:immunology; D020868:Gene Silencing / Q000276:immunology; D006706:Homeostasis / Q000276:immunology*; D007371:Interferon-gamma / Q000235:genetics / Q000276:immunology; D051379:Mice; D057507:Mice, 129 Strain; D008817:Mice, Mutant Strains; D011401:Promoter Regions, Genetic / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000166:cytology* / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology; D058504:Th17 Cells / Q000166:cytology / Q000276:immunology
chemical_list: D016207:Cytokines; C000715535:Dnmt3a protein, mouse; D007371:Interferon-gamma; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A