Rewriting the epigenome: CRISPR tools for biological discovery and therapeutics.

The eukaryotic epigenome plays a central role in regulating gene expression, cellular identity, and development through dynamic, multilayered biochemical modifications to DNA, histones, and chromatin architecture. Disruption of these regulatory mechanisms contributes to a wide range of human diseases, including cancer, neurodegenerative disorders, and immunological conditions. Targeted epigenome editing offers promising discovery and therapeutic strategies by enabling the correction of aberrant epigenetic states without the need for permanent changes to the DNA sequence. The catalytically inactive CRISPR-Cas (dCas) molecule fused to epigenetic effector domains has emerged as a versatile platform for programmable, locus-specific modulation of chromatin states. These CRISPR-based epigenetic editors can deposit or remove desired epigenetic marks and alter three-dimensional genome organization to fine-tune gene expression with high specificity. Recent developments have expanded the CRISPR epigenome editing toolbox by introducing new effector domains, improving multiplexing capabilities, and enabling large-scale genetic screening, leading to novel insights into the functional genomics across various cellular contexts. However, clinical translation remains challenged by inefficient delivery and suboptimal editing efficacy in vivo. This review highlights recent advances in CRISPR-based epigenetic editing, with a focus on applications in primary cells, new tool development, and the translational potential of epigenome modulation for safe, durable, and precise therapies.