The effect of histone deacetylase inhibitors on the efficiency of the CRISPR/Cas9 system

Abstract

The CRISPR/Cas9 technology is a prominent genome-editing tool capable of producing a double-strand break in the genome. However, the modification of hematopoietic stem cells via the homology-directed repair pathway is still inefficient. Therefore, we hypothesize that histone deacetylase inhibitors, such as valproic acid (VPA) and sodium butyrate (NaB), could enhance HDR efficiency by increasing the accessibility of the genome-editing machinery. To address the potential utilization of HDAC inhibitors therapeutically, we began by assessing the effect of VPA and NaB on two cell lines representative of the two hematopoietic stem cell lineages. No statistically significant effect on cell growth or viability was observed at concentrations as high as 5 mM. At a concentration as low as 0.005 mM NaB, an enhancement in CRISPR cutting efficiency was evidenced in both cell lines. This enhancement did not appear to be locus-specific. However, an enhancement in cutting efficiency following VPA treatment does appear to be. HDR efficiency was enhanced greater than two-fold with the use of 0.005 mM VPA. These results are promising and suggest the consideration of treatment with an HDAC inhibitor in CRISPR/Cas9 genome editing protocols. Highlights: • Sodium butyrate and valproic acid are two histone deactylase inhibitors. • Concentrations up to 0.5 mM valproic acid and sodium butyrate is well tolerated by blood cells. • Sodium butyrate and valproic acid can enhance the cutting efficiency of the CRISPR/Cas9 system. • The effect of valproic acid on the cutting efficiency of CRISPR/Cas9 appears to be locus specific. • Valproic acid can enhance the targeting efficiency of CRISPR/Cas9 via the HDR repair pathway.

Keywords

• CRISPR
• Gene editing
• Histone deacetylase inhibitors
• Valproic acid
• Sodium butyrate