Gene editing in hematopoietic stem cells by co-delivery of Cas9/sgRNA ribonucleoprotein and templates for homology-directed repair in 'all-in-one' lentivirus-derived nanoparticles
Repair of double-strand DNA breaks generated by site-directed endonucleases, like Cas9, is the hallmark of gene editing based on homology-directed repair (HDR). HDR uses an exogenous DNA template to restore the cleaved DNA sequence and can facilitate specific gene corrections as well as insertion of genes or partial cDNA sequences. For CRISPR/Cas-directed gene editing, co-administration of the Cas9/single guide RNA (sgRNA) ribonucleoprotein (RNP) complex and a DNA template typically involves two different delivery strategies or different types of vehicles. This requires exquisite timing of delivery and may potentially challenge safety and therapeutic applicability. There is a need therefore for technologies that can ferry complete editing tool kits into cells. Here, we demonstrate the use of lentivirus-derived nanoparticles (LVNPs) to transport both RNP complexes and vector RNA, which upon reverse transcription serves as donor for HDR-directed repair. These 'all-in-one' LVNPs support targeted gene insertion with reduced off-target effects relative to nucleofection procedures. We show potent editing in the HBB gene in human erythroid progenitor cells as well as HDR-directed editing in hematopoietic stem and progenitor cells. Our findings mark a first step toward using a single virus-derived vehicle for delivering a full HDR gene editing kit. Overall design: HUDEP-2 cells homozygous for the sickle cell disease variant are treated with lentivirus-derived nanoparticles that deliver Cas9, sgRNA targeting the hemoglobin beta gene and a homology donor for correction of the mutation. Paired end sequencing of amplicons spanning the edited region is analyzed in CRISPResso2 with the untreated sample as reference sample.