Abstract
The recent development of genome editing systems, such as zinc-finger nucleases, transcription activator-like effectors, CRISPR-Cas nucleases, and base editors has enabled the unprecedented capability to engineer the genomes of living cells. The ever-increasing demand for genome editors with improved accuracy, activity, and functionality has stimulated significant efforts to further engineer the genome editing systems. Directed evolution represents a promising strategy to improve the existing genome editing systems and enable new editing functions. Here, we review recent representative strategies to harness the power of directed evolution to improve genome editing systems, which have led to state-of-the-art genome editors that have significant implications for diverse applications in both laboratories and clinics.