RESUMO
How a single cell gives rise to progeny with differing fates remains poorly understood. We examined cells lacking methyl CpG binding domain protein-2 (MBD2), a molecule that has been proposed to link DNA methylation to silent chromatin. Helper T cells from Mbd2(-/-) mice exhibit disordered differentiation. IL-4, the signature of a restricted set of progeny, is expressed ectopically in Mbd2(-/-) parent and daughter cells. Loss of MBD2-mediated silencing renders the normally essential activator, Gata-3, dispensable for IL-4 induction. Gata-3 and MBD2 act in competition, wherein each factor independently, and quantitatively, regulates the binary choice of whether heritable IL-4 expression is established. Gata-3 functions, in part, to displace MBD2 from methylated DNA. These results suggest that activating and silencing signals integrate to provide spatially and temporally restricted patterns of gene activity.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Inativação Gênica , Transativadores/metabolismo , Animais , Ligação Competitiva , Diferenciação Celular , Linhagem Celular , Linhagem da Célula , Cromatina/metabolismo , Ilhas de CpG/genética , Metilação de DNA , Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/genética , Citometria de Fluxo , Fator de Transcrição GATA3 , Deleção de Genes , Interleucina-4/genética , Interleucina-4/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Linfócitos T Auxiliares-Indutores/citologia , Linfócitos T Auxiliares-Indutores/metabolismo , Transativadores/deficiência , Transativadores/genéticaRESUMO
Type 1 helper T (T(H)1) cells are essential for cellular immunity, but their ontogeny, maturation and durability remain poorly understood. By constructing a dominant-negative form of T-bet, we were able to determine the role played by this lineage-inducing trans-activator in the establishment and maintenance of heritable T(H)1 gene expression. Optimal induction of interferon-gamma (IFN-gamma) expression required genetic interaction between T-bet and its target, the homeoprotein Hlx. In fully mature T(H)1 cells, reiteration of IFN-gamma expression and stable chromatin remodeling became relatively independent of T-bet activity and coincided with demethylation of DNA. In contrast, some lineage attributes, such as expression of IL-12R beta 2 (interleukin 12 receptor beta 2), required ongoing T-bet activity in mature T(H)1 cells and their progeny. These findings suggest that heritable states of gene expression might be maintained by continued expression of the inducing factor or by a mechanism that confers a stable imprint of the induced state.