Gene Editing in the NSG mouse strain and its genetic derivatives

Abstract

Abstract The NSG (NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ) mouse strain is highly immunodeficient and has dramatically improved the ability to work with human tumors in an organismal context using xenograft approaches. Technical innovations have expanded the utility of this personalized tumor platform via the reconstitution of parts of the human immune system. An example of this is the NSG-SGM3 inbred mouse strain, in which transgenes expressing human IL3, GMCSF and SCF have been stably integrated into the NSG background, and can effectively support the stable engraftment of human myeloid lineages and the regulatory T cell populations. Direct modification of the NSG genome in mouse embryos was a key to attain this NSG “derivative” strain rapidly and avoid extensive breeding. Modification of NSG, which is built on the parental NOD/ShiLtJ background, a commonly utilized polygenic model of autoimmune type 1 diabetes, can optimize the engraftment of other human lineages. Modern genome modification technology must overcome strain specific characteristics. DNA repair is involved in creating mutations by resolving double strand breaks. The SCID mutation (Prkdcscid) in the NSG background compromises some DNA repair pathways. It was not clear whether nuclease assisted recombination technologies would be a robust tool to modify NSG genomes at the zygote stage. We demonstrate CRISPR-Cas9 is an effective tool for introducing genome modifications in NSG and present a specific example using the Hprt locus. We will also present our experience modifying NSG and its derivatives, demonstrating that direct modification of these genomes is technically feasible and is enabling the rapid sequential genetic tailoring in this high value immunodeficient strain.