Ezh2 Regulates Activation-Induced CD8⁺ T Cell Cycle Progression via Repressing Cdkn2a and Cdkn1c Expression

Area of Science:

• Immunology
• Epigenetics
• Cell Biology

Background:

• Naïve CD8+ T cells must transition from resting to the cell cycle for differentiation.
• Chromatin remodeling of cell cycle inhibitors is vital for this transition but not fully understood.
• Ezh2, a component of PRC2, mediates H3K27me3, a key epigenetic mark.

Purpose of the Study:

• To investigate the role of Ezh2 in regulating the proliferation and apoptosis of naïve CD8+ T cells upon activation.
• To elucidate the molecular mechanisms by which Ezh2 controls T cell activation-induced cell cycle progression.

Main Methods:

• Utilized Ezh2 conditional knockout mouse models (Ezh2fl/flCd4Cre+ and Ezh2fl/flGzmBCre+) to delete Ezh2 at different developmental stages.
• Assessed T cell proliferation and apoptosis following antigen stimulation.
• Measured H3K27me3 levels and gene expression of cell cycle inhibitors (Cdkn2a, Cdkn1c) using qPCR and ChIP.
• Performed real-time imaging to observe cell division dynamics.

Main Results:

• Deletion of Ezh2 during thymocyte development led to impaired proliferation and increased apoptosis of CD8+ T cells.
• Deletion of Ezh2 post-activation impaired proliferation but not apoptosis, indicating temporal separation of functions.
• Ezh2 deficiency resulted in increased expression of Cdkn2a and Cdkn1c due to reduced H3K27me3.
• Real-time imaging showed prolonged cell division times in Ezh2-deficient T cells.

Conclusions:

• Ezh2-mediated repression of Cdkn2a and Cdkn1c is critical for activation-induced CD8+ T cell proliferation.
• Ezh2 plays a vital role in regulating the cell cycle progression of activated CD8+ T cells.
• Epigenetic control by Ezh2 is essential for T cell immune responses.