The allele was generated by homologous recombination in embryonic stem cells targeting a Cre-Ert2-V2A-tdTomato-Frt-PGK-neo-Frt cassette into the start codon of the Aurkb locus. The PGK-Neo cassette was removed by breeding the initial progeny to mice expressing Flpe recombinase. (J:309046)