{"doi":"10.1016/j.ymthe.2021.06.021","title":"Adenine base editing reduces misfolded protein accumulation and toxicity in alpha-1 antitrypsin deficient patient iPSC-hepatocytes","abstract":"Alpha-1 antitrypsin deficiency (AATD) is most commonly caused by the Z mutation, a single-base substitution that leads to AAT protein misfolding and associated liver and lung disease. In this study, we apply adenine base editors to correct the Z mutation in patient induced pluripotent stem cells (iPSCs) and iPSC-derived hepatocytes (iHeps). We demonstrate that correction of the Z mutation in patient iPSCs reduces aberrant AAT accumulation and increases its secretion. Adenine base editing (ABE) of differentiated iHeps decreases ER stress in edited cells, as demonstrated by single-cell RNA sequencing. We find ABE to be highly efficient in iPSCs and do not identify off-target genomic mutations by whole-genome sequencing. These results reveal the feasibility and utility of base editing to correct the Z mutation in AATD patient cells. Alpha-1 antitrypsin deficiency (AATD) is most commonly caused by the Z mutation, a single-base substitution that leads to AAT protein misfolding and associated liver and lung disease. In this study, we apply adenine base editors to correct the Z mutation in patient induced pluripotent stem cells (iPSCs) and iPSC-derived hepatocytes (iHeps). We demonstrate that correction of the Z mutation in patient iPSCs reduces aberrant AAT accumulation and increases its secretion. Adenine base editing (ABE) of differentiated iHeps decreases ER stress in edited cells, as demonstrated by single-cell RNA sequencing. We find ABE to be highly efficient in iPSCs and do not identify off-target genomic mutations by whole-genome sequencing. These results reveal the feasibility and utility of base editing to correct the Z mutation in AATD patient cells. IntroductionAlpha-1 antitrypsin deficiency (AATD) is a common heritable cause of both lung and liver disease. AATD results from mutations in the SERPINA1 gene, which encodes the antiprotease alpha-1 antitrypsin (AAT). AAT is produced in high abundance by hepatocytes1Schultz H.E. Heremans J.F. Synthesis of the Plasma Proteins. Elsevier, New York1966: 321-349Google Scholar and functions primarily to neutralize neutrophil elastase. The most prevalent disease-causative mutation is a single-base substitution from guanine (G) to adenine (A), which results in a glutamic acid-to-lysine substitution (Glu342Lys) and production of a mutant protein prone to misfolding and aggregation, termed “Z-AAT.”2Brantly M. Nukiwa T. Crystal R.G. Molecular basis of alpha-1-antitrypsin deficiency.Am. J. Med. 1988; 84: 13-31Abstract Full Text PDF PubMed Scopus (396) Google Scholar Reduced Z-AAT secretion and associated diminished circulating AAT levels3Wewers M.D. Casolaro M.A. Sellers S.E. Swayze S.C. McPhaul K.M. Wittes J.T. Crystal R.G. Replacement therapy for alpha 1-antitrypsin deficiency associated with emphysema.N. Engl. J. Med. 1987; 316: 1055-1062Crossref PubMed Scopus (494) Google Scholar result in a protease/antiprotease imbalance in the lungs that over time predisposes affected individuals to injury, most commonly manifested as emphysema.4Brantly M.L. Paul L.D. Miller B.H. Falk R.T. Wu M. Crystal R.G. Clinical features and history of the destructive lung disease associated with alpha-1-antitrypsin deficiency of adults with pulmonary symptoms.Am. Rev. Respir. Dis. 1988; 138: 327-336Crossref PubMed Scopus (264) Google Scholar In addition, accumulation of polymerized Z-AAT in the liver can result in toxic gain-of-function effects in hepatocytes, leading to liver disease in both neonates and adults.5Lomas D.A. Evans D.L. Finch J.T. Carrell R.W. The mechanism of Z alpha 1-antitrypsin accumulation in the liver.Nature. 1992; 357: 605-607Crossref PubMed Scopus (886) Google Scholar,6Eriksson S. Carlson J. Velez R. Risk of cirrhosis and primary liver cancer in alpha 1-antitrypsin deficiency.N. Engl. J. Med. 1986; 314: 736-739Crossref PubMed Scopus (475) Google ScholarAlthough infusion of pooled human AAT protein (“augmentation therapy”) has been shown to slow progression of lung disease in AATD patie","journal":"Molecular Therapy","year":2021,"id":166290,"datarank":0.5375278407684165,"base_score":3.58351893845611,"endowment":3.58351893845611,"self_citation_contribution":0.5375278407684165,"citation_network_contribution":0.0,"self_endowment_contribution":0.5375278407684165,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":35,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9514,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":691178,"name":"Joseph E. 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