Nat. Biotechnol., https://doi.org/10.1038/nbt.4166 (2018).

Targetable nucleases have made genetic engineering of animals for research a much more tractable endeavor. But, efficient transfer of large insertion products remains challenging and inefficient, despite several recent innovations. To date, most reported techniques transformed zygotes for generation of engineered mouse lines. Authors of a new manuscript took a different approach and introduced CRISPR/Cas9 reagents to two-cell zygotes so as to take advantage of the extended G2 phase—post-DNA replication and pre-mitosis—to increase the time during which recombination could occur. Investigators also used a streptavidin tagged Cas9 in combination with a biotinylated repair template to increase efficient construct interaction and thereby improve recombination. With these alterations, transformation efficiency improved several fold over conventional methods.