LPA Disruption with AAV-CRISPR Potently Lowers Plasma Apo(a) in Transgenic Mouse Model: A Proof-of-concept Study.

Lipoprotein(a) (Lp(a)) represents a unique subclass of circu-lating lipoprotein particles and consists of an apolipopro-tein(a) (apo(a)) molecule covalently bound to apolipoprotein B-100. The metabolism of Lp(a) particles is distinct from that of low-density lipoprotein (LDL) cholesterol, and currently approved lipid-lowering drugs do not provide sub-stantial reductions in Lp(a), a causal risk factor for cardiovas-cular disease. Somatic genome editing has the potential to be a one-time therapy for individuals with extremely high Lp(a). We generated an LPA transgenic mouse model expressing apo(a) of physiologically relevant size. Adeno-associated virus (AAV) vector delivery of CRISPR-Cas9 was used to disrupt the LPA transgene in the liver. AAV-CRISPR nearly completely eliminated apo(a) from the circulation within a week. We performed genome-wide off-target assays to determine the specificity of CRISPR-Cas9 editing within the context of the human genome. Interestingly, we identified intrachromoso-mal rearrangements within the LPA cDNA in the transgenic mice as well as in the LPA gene in HEK293T cells, due to the repetitive sequences within LPA itself and neighboring pseudogenes. This proof-of-concept study establishes the feasi-bility of using CRISPR-Cas9 to disrupt LPA in vivo, and high-lights the importance of examining the diverse consequences of CRISPR cutting within repetitive loci and in the genome globally.