A floxed neo selection cassette was placed upstream of exon 7 in the SmaI restriction site and an additional loxP site was inserted downstream of exon 9. Correct targeting was confirmed by genomic PCR. LoxP-flanked (floxed) sequence encoded residues 707?870 of the interferon-inducible form of ADAR1 (GenBankTM/EBI accession number AAK16102), including essential regions for editing activity.