In Vivo Genome Editing Partially Restores Alpha1-Antitrypsin in a Murine Model of AAT Deficiency

CRISPR (clustered regularly interspaced short palindromic repeats) genome editing holds promise in the treatment of genetic diseases that currently lack effective long-term therapies. Patients with alpha-1 antitrypsin (AAT) deficiency develop progressive lung disease due to the loss of AAT's antiprotease function and liver disease due to a toxic gain of function of the common mutant allele. However, it remains unknown whether CRISPR-mediated AAT correction in the liver, where AAT is primarily expressed, can correct either or both defects. Here we show that AAV delivery of CRISPR can effectively correct Z-AAT mutation in the liver of a transgenic mouse model. Specifically, we co-injected two AAVs: one expressing Cas9 and another encoding an AAT guide RNA and homology-directed repair template. In both neonatal and adult mice, this treatment partially restored M-AAT in the serum. Furthermore, deep sequencing confirmed both indel mutations and precise gene correction in the liver, permitting careful analysis of gene editing events in vivo. This study demonstrates a proof of concept for the application of CRISPR-Cas9 technology to correct AAT mutations in vivo and validates continued exploration of this approach for the treatment of patients with AAT deficiency.