A powerful CRISPR/Cas9-based method for targeted transcriptional activation

Targeted transcriptional activation of endogenous genes is important for understanding physiological transcriptional networks, synthesizing genetic circuits, and inducing cellular phenotype changes. The CRISPR/Cas9 system has great potential to achieve this purpose, however, it has not yet been successfully used to efficiently activate endogenous genes and induce changes in cellular phenotype. A powerful method for transcriptional activation by using CRISPR/Cas9 was developed. Replacement of a methylated promoter with an unmethylated one by CRISPR/Cas9 was sufficient to activate the expression of the neural cell gene OLIG2 and the embryonic stem cell gene NANOG in HEK293T cells. Moreover, CRISPR/Cas9-based OLIG2 activation induced the embryonic carcinoma cell line NTERA-2 to express the neuronal marker βIII-tubulin. Epigenome editing: A novel CRISPR/Cas9-based method for transcriptional activation through microhomology-mediated end-joining (MMEJ) was developed. CRISPR/Cas9 was used to specifically replace the methylated promotor region of a target gene with an unmethylated copy, thereby leading to efficient gene activation at levels sufficient to bring about changes in cell fate.