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 circulating

lipoprotein particles and consists of an apolipoprotein(

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 substantial

reductions in Lp(a), a causal risk factor for cardiovascular

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 intrachromosomal

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 feasibility

of using CRISPR-Cas9 to disrupt LPA in vivo, and highlights

the importance of examining the diverse consequences

of CRISPR cutting within repetitive loci and in the genome

globally.