Developing CRISPR Tools to Reprogram the Mammalian Genome

The genetic reprogramming of mammalian cell fate and identity requires efficient tools for genome engineering. The bacterial immune system CRISPR has emerged as a powerful approach for directed genome editing in diverse organisms via an RNA-guided Cas9 nuclease. In addition to its utility in genome editing, we have developed the CRISPR system as a versatile synthetic biology toolset for transcriptional regulation, epigenetic modification, and chromatin imaging in mammalian cells. We repurposed the catalytically inactive Cas9 (dCas9) that lacks the nuclease activity as synthetic transcription factors for sequence-specific activation or repression of endogenous genes. When coupled with RNA- or protein-interacting peptide domains, the system could be used for highly efficient, inducible, and multiplexable gene regulation. In sum, the CRISPR tools for gene regulation offer a new powerful approach for genetically reprogramming the mammalian cells and tissues.