Stage-specific epigenetic regulation of CD4 expression by coordinated enhancer elements during T cell development

Area of Science:

• Immunology
• Epigenetics
• Molecular Biology

Background:

• Epigenetic regulation governs gene expression inheritance during T cell differentiation.
• The precise mechanisms establishing and maintaining epigenetic landscapes in T cells remain unclear.

Purpose of the Study:

• To investigate the role of stage-specific cis-elements in regulating Cd4 transcription during T cell differentiation.
• To elucidate the epigenetic mechanisms governing Cd4 locus accessibility and expression in thymic and peripheral T cells.

Main Methods:

• Analysis of Cd4 cis-elements (E4p and E4m) and their role in Cd4 transcription.
• Investigation of DNA demethylation mediated by TET1 and TET3.
• Assessment of cis-element function in developing thymocytes versus mature peripheral T cells.

Main Results:

• Two cis-elements, E4p and E4m, coordinate Cd4 transcription in mature T cells, partly via the Wnt pathway.
• E4p enables E4m to induce DNA demethylation by TET1/3, priming the Cd4 locus for peripheral T cell transcription.
• Cd4 locus demethylation is essential for Cd4 transcription in activated peripheral T cells, but cis-elements become dispensable.
• Loss of TET1/3 in developing thymocytes does not impact Cd4 transcription, indicating uncoupled epigenetic modification and transcription.

Conclusions:

• Thymic cis-elements play a critical role in controlling peripheral gene expression through heritable epigenetic mechanisms.
• DNA demethylation orchestrated by specific enhancers is a key step in T cell epigenetic programming.
• The findings reveal a novel mechanism linking early epigenetic events to later gene expression patterns in T cells.