A targeting construct was used for recombineering to insert an ERT2-cre-ERT2 sequence (cre fused to two mutated human estrogen receptor ligand-binding domains) into a BAC containing the Aire locus. The inducible cre cassette replaced exon 2 of Aire. The resulting linearized BAC was injected into fertilized FVB oocytes. Founder and line number information is not available.