Abstract A073: Epigenetic regulation of the Cd4 locus

Abstract

Abstract CD4 helper and CD8 cytotoxic T cells originate from progenitor cells with binary potential. Transcriptional regulatory elements are key in establishing heritable epigenetic mechanisms to ensure gene-expression programs that maintain lineage identity. We show that, during thymocyte development, the co-receptor CD4 is regulated by a stage-specific regulatory element that ensures commitment to the CD4 lineage. Sustained CD4 expression in post-selection thymocytes requires this intronic element situated 3' to a silencer element previously shown to repress cd4 in CD8 cytotoxic T cells. Despite normal CD4 expression before selection, thymocytes lacking this intronic element failed to maintain CD4 expression following positive selection and were redirected to the CD8 lineage after MHC class II–restricted selection. We find that this regulatory element is key for propagating TET enzyme–mediated locus demethylation in CD4 T cells, a process that is likely initiated by another cis-element controlling CD4 expression at the double positive stage, before lineage commitment. This locus demethylation event is critical in ensuring heritable lineage identity and disruption of this process results in unstable CD4 expression and altered gene expression profiles. Cis and trans element interactions and molecular mechanisms governing heritable expression in response to distinct signals that dictate lineage ‘choice’ during T cell development will be presented. Citation Format: Priya Issuree, Kenny Day, Dan R. Littman. Epigenetic regulation of the Cd4 locus [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A073.