In Vivo Tissue-Specific DNA Demethylation in Mouse Liver Through a Hydrodynamic Tail Vein Injection

A new technique called the dCas9-SunTag and scFv-TET1CD epigenome editing system has recently been developed to edit the DNA methylation status of specific genes. The transfection of an all-in-one vector containing this system into cells is feasible and induces the DNA demethylation of specific genes; however, due to the large size of the vector, difficulties are associated with its introduction into mice. We herein used a hydrodynamic tail vein injection (HTVi) to introduce the all-in-one vector into mice for in vivo epigenome editing. HTVi needs to be considered for inducing the targeted DNA demethylation of particular genes in the mouse liver.

[The Efficiency of Gene Activation Using CRISPR/dCas9-Based Transactivation Systems Depends on the System Run Time]

Transactivation systems are a promising application based on the CRISPR/Cas9 system and allow targeted control of gene expression levels in cell culture. However, their performance has been reported to vary considerably depending on the cell type and the activator system. Three activator systems (dCas9-VP160, dCas9-SunTag, and dCas9-VPR) were compared for the efficiency of activating expression of OCT4, NANOG, PDX1, FOXA2, NKX2-2, and NKX6-1 in an immortalized human skin fibroblast line. The activation efficiency was found to depend on the activation system type; the extent of activation depended on the system run time.

Genomic Targeting of TET Activity for Targeted Demethylation Using CRISPR/Cas9

Methylation of DNA at cytosine bases is an important DNA modification underlying normal development and disease states. Despite decades of research into the biological function of DNA methylation, most of the observations so far have relied primarily on associative data between observed changes in DNA methylation states and local changes in transcriptional activity or chromatin state processes. This is primarily due to the lack of molecular tools to precisely modify DNA methylation in the genome. Recent advances in genome editing technologies have allowed repurposing the CRISPR-Cas9 system for epigenome editing by fusing the catalytically dead Cas9 (dCas9) to epigenome modifying enzymes. Moreover, methods of recruiting multiple protein domains, including the SunTag system, have increased the efficacy of epigenome editing at target sites. Here, we describe an end-to-end protocol for efficient targeted removal of DNA methylation by recruiting multiple catalytic domain of TET1 enzymes to the target sites with the dCas9-SunTag system, including sgRNA design, molecular cloning, delivery of plasmid into mammalian cells, and targeted DNA methylation analysis.