This post was contributed by guest bloggers Dominik Paquet and Dylan Kwart from Ludwig-Maximilians-University in Munich and Marc Tessier-Lavigne’s lab at the Rockefeller University in NYC.
The CRISPR/Cas9 system is a versatile tool for precise gene editing in many organisms and model systems. We have used CRISPR/Cas9 extensively for the purpose of making sequence-specific changes in human induced pluripotent stem cells (iPSCs). The CRISPR/Cas9 complex is very efficient at introducing double stranded breaks (DSBs) into genomic DNA in many cell types and often results in biallelic modifications. Most commonly, DSBs are repaired by the nonhomologous end-joining (NHEJ) pathway, leading to nonspecific nucleotide insertions, deletions or other mutations, referred to as ‘indels’. While this is convenient for generating gene knockouts, NHEJ repair does not allow introduction of specific sequence changes.