Regulating CRISPR/Cas9 Function through Conditional Guide RNA Control

Conditional control of CRISPR/Cas9 has been developed by using a variety of different approaches, many focusing on manipulation of the Cas9 protein itself. However, more recent strategies for governing CRISPR/Cas9 function are based on guide RNA (gRNA) modifications. They include control of gRNAs by light, small molecules, proteins, and oligonucleotides. These designs have unique advantages compared to other approaches and have allowed precise regulation of gene editing and transcription. Here, we discuss strategies for conditional control of gRNA function and compare effectiveness of these methods. Different strategies have been developed to control guide RNA function in the CRISPR/Cas9 system. Both external and cellular triggers, including light, small molecules, proteins, and oligonucleotides, were used for convenient and precise regulation of genome editing and transcriptional activation in cells. These methods provide spatial and temporal resolution for gene editing and might find future therapeutic applications.