Epigenetic engineering is a novel aspect of genomic control, which makes such regulation with precision, programmability, and reversibility capable of controlling gene expression far beyond the capabilities of other genome methods. The method is essential to the development of personalized medicine, synthetic biology, and functional genomics in that it allows for a change in chromatin states without causing permanent changes to DNA, so it may potentially address irreversible mutagenesis.

Programmable proteins (such as deactivated Cas9 (dCas9), zinc-finger domains, and TALE fusions) are used as epigenetic switches to activate or silence epigenetic marks to create tunable and heritable gene expression. Experimental evidence of Saccharomyces cerevisiae has shown that epigenetic switching provides a selective benefit during unstable environments by swapping cellular identity states as fast as possible by switching the expression state of genes, but also adapts cellular identity in genetic silence by avoiding genetic mutations. Modular CRISPR-dCas9 systems have been used to target methylation and demethylation stability at specific loci within genomic systems (e.g., BACH2, HNF1A, IL6ST, MGAT3) to induce long-lasting transcriptional effects up to 30 days following transfection in mammalian systems. Also, optimization of dCas9-fusion protein expression reduces off-target epigenomic activities, thus increasing specificity and biosafety.

All this evidence shows that combinatorially designed high-resolution epigenetic switches coupled with advances in synthetic biology revolutionize genomic interventions. The modality is a safer, reversible, and more accurate modality for personalized therapies and disease modeling, as well as more flexible and specific synthetic biology applications due to higher functional flexibility and specificity.