The self-inactivating KamiCas9 system for the editing of CNS disease genes

Neurodegenerative disorders are a major public health problem because of the highfrequency of these devastating diseases in the population. Genome editing with theCRISPR/Cas9 system is making it possible, for the first time, to modify the sequenceof genes linked to these diseases in the adult brain. Here, a self-inactivatingCRISPR/Cas9 system, kamiCas9, was designed for transient expression of the Cas9protein and high editing efficiency. In the first application of this technology toneurodegenerative disorders, the gene responsible for Huntington’s disease (HD) wastargeted in adult mouse neuronal and glial cells. Mutant huntingtin (HTT) wasefficiently inactivated in mouse models of HD, leading to an improvement in keymarkers of the disease. Sequencing of potential off-targets with the constitutive Cas9system in differentiated human iPS cells, revealed a very low incidence with only onesite above background level. Importantly, the off-target frequency was drasticallyreduced with the kamiCas9 system. These results demonstrate the potential of theself-inactivating CRISPR/Cas9 editing for applications in the context ofneurodegenerative diseases.