The investigators 1) created induced pluripotent stem cells (iPSCs) from patients with PiZZ-associated A1AT deficiency; 2) designed zinc finger nucleases to specifically nick the DNA flanking the mutation in the A1AT gene; 3) replaced the region of genomic DNA containing the mutation with a fragment of DNA containing not only the corrected gene sequence, but also a transposon, which allows for selective growth of corrected iPSCs; 4) removed the transposon without leaving a trace; 5) assessed for corrected clones that had not undergone additional mutations during the procedures using deep sequencing, genome hybridization, and other approaches; and 6) differentiated the iPSCs into functional hepatocytes that were transplanted into immunodeficient mice, where they functioned to produce human albumin and the corrected A1AT protein.