CRISPR–Cas9-mediated genome editing and guide RNA design

CRISPR and CRISPR-associated (Cas) proteins, which in nature comprise the RNA-based adaptive immune system in bacteria and archaea, have emerged as particularly powerful genome editing tools owing to their unrivaled ease of use and ability to modify genomes across mammalian model systems. As such, the CRISPR-Cas9 system holds promise as a "system of choice" for functional mammalian genetic studies across biological disciplines. Here we briefly review this fast moving field, introduce the CRISPR-Cas9 system and its application to genome editing, with a focus on the basic considerations in designing the targeting guide RNA sequence.