...need to generate lentivirus containing the entire library (Figure 8D). This lentivirus will then be used...-occurring Acr (Anti-CRISPR) proteins can help control CRISPR activity. Acr proteins have evolved in phages...LmoCas9 and SpCas9. Acr proteins can be used to control both when and where genome editing happens. CASANOVA...Dominik Niopek’s lab , is a way to optogenetically control genome editing by fusing the anti-CRISPR protein...photosensitive LOV2 domain . Several labs have also controlled Acr activity with endogenous cell-type specific... the HDR pathway can also help. Additionally, constructs with Cas9 fused to proteins that modulate HDR...delivery to cells that are poorly transduced by lentivirus. Non-mammalian CRISPR libraries are also available...