Epigenome Editing (CRISPRoff/CRISPRon) — Gene Therapy & Genetic Interventions
Programmable epigenetic silencing or activation of target genes without altering DNA sequence, using CRISPR-based tools.
Overview
CRISPRoff and CRISPRon are engineered CRISPR-based tools that modify gene expression through epigenetic mechanisms (DNA methylation or demethylation) rather than cutting DNA. CRISPRoff uses a catalytically dead Cas9 (dCas9) fused to DNMT3A and KRAB domains to silence target genes via de novo methylation. CRISPRon uses dCas9 fused to TET1 and transcriptional activators to demethylate and activate silenced genes. These modifications are heritable through cell division but potentially reversible, offering advantages over permanent DNA editing for therapeutic applications.
Indications
- Gene silencing for gain-of-function disease mutations
- Gene activation for loss-of-function diseases
- Epigenetic reprogramming of age-related gene expression changes
- Cancer immunotherapy (reactivation of silenced tumor suppressors)
- Reversible gene modulation research
Mechanism of Action
sgRNA directs dCas9 fusion protein to specific genomic locus without cutting DNA
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| CRISPRoff (dCas9-DNMT3A-KRAB) | Study-specific | Single treatment | AAV or LNP delivery; gene silencing is heritable |
| CRISPRon (dCas9-TET1-VPR) | Study-specific | Single treatment | Gene activation and demethylation |
Safety & Contraindications
- Off-target epigenetic modifications at unintended loci
- Long-term stability of epigenetic modifications in vivo requires characterization
- Immunogenicity of dCas9 fusion proteins
- Potential for unintended gene network effects from silencing/activating single genes
- No human clinical trials for epigenome editing tools
- Delivery efficiency to target tissues remains a challenge