Apoa1, a safe harbor locus for therapeutic genome editing in the liver
Clinical application of somatic genome editing requires therapeutics that are generalizable to a broad range of patients. Targeted insertion of promoterless transgenes can ensure that edits are permanent, broadly applicable, while minimizing risks of off-target integration. In the liver, the Albumin locus is currently the only well characterized site for promoterless transgene insertion. Using an unbiased ChIP-seq approach, we here identify Apolipoprotein a1 (Apoa1) as one of the most highly expressed and accessible loci in mouse and human liver. We target the Apoa1 locus with Adeno-Associated Viral (AAV) delivery of CRISPR/Cas9, and achieve rates of 6 to 16% with no evidence of toxicity. We further show that the endogenous Apoa1 promoter can drive robust and sustained expression of therapeutic proteins such as factor IX (FIX) or apolipoprotein E (APOE). Finally, we demonstrate that Apoa1-targeted fumarylacetoacetate hydrolase (FAH) can correct and rescue the severe metabolic liver disease hereditary tyrosinemia type I. In summary, we identify and validate Apoa1 as novel safe harbor site for genome editing therapeutics. Overall design: ChIPmentation for H3K27ac and background control in primary mouse hepatocytes