Expression of Single mRNA Constructs Encoding Both CRISPR-Cas9 Protein and Guide RNAs for Future Gene Therapy Applications

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The basis of many life-threatening diseases is disruption in key genes. In many cases, repairing these disruptions can prevent or reverse disease. The development of CRISPR-Cas9 technology, which consists of Cas9 nuclease directed to specific genomic locations by guide RNA (gRNA), has significantly progressed in the past decade and has shown signs of promise for treating diseases such as Alzheimer’s and cystic fibrosis. One integral issue of gene editing therapy is the method and effectiveness of delivery. Current approaches such as lentiviral and adeno-associated virus vectors suffer from either stable, constant expression of CRISPR components that causes unintended gene editing or an inability to efficiently carry large cargoes such as two independent genes: Cas9 and guide RNA. To begin to bypass these cargo limitations, we created a CRISPR-Cas9 mRNA structure that encompasses all of the necessary components for gene editing on a single RNA. These constructs consist of a promoter, followed by a Cas9 open reading frame, a triplex region from MALAT1 that protects the Cas9 open reading frame, and then either 1, 2, or 4 gRNAs that target specific reporters, with each gRNA between two self-cleaving ribozyme sequences. These constructs successfully drove Cas9 editing of two distinct reporters in human cells and thus open the door for many more experiments such as incorporation into various delivery constructs to further develop this technology for gene editing therapy.