Adeno-Associated Virus Serotype 3 (AAV3) shares 82% sequence homology with AAV2, and like AAV2, requires the Heparan Sulfate Proteoglycan (HSPG) receptor for cell attachment. AAV3 vectors transduce human liver cancer cells extremely efficiently because AAV3 utilizes the human Hepatocyte Growth Factor Receptor (hHGFR) as a co-receptor for viral entry, which is highly expressed in these cells. Both the extracellular and intracellular kinase domains of hHGFR are required for AAV3-mediated transgene expression.Cas9 is an endonuclease enzyme that introduces a double stranded break into the DNA when recruited to a specific DNA sequence by the sgRNA (single guide RNA). This double stranded break is repaired in mammalian cells either through Non-Homologous End Joining or Homologous Recombination. Non-Homologous End Joining often results in the deletion or insertion of several base pairs at the cut site, which, when resulting in a frameshift, causes the functional inactivation of the gene.SaCas9 (Staphylococcus aureus CRISPR-associated protein 9) has demonstrated high cutting efficiency in mammalian cells, and its smaller size makes it ideal for packaging into AAV. SaCas9 recognizes a longer protospacer adjacent motif (PAM) site, 5'-NNGRRT-3', than the more traditional SpCas9 (Streptococcus pyogenes CRISPR-associated protein 9). These AAV particles constitutively express SaCas9 under the control of a CMV promoter.