A targeting construct was designed to insert a FLAG-tagged-mCherry fluorescent protein and a Cre Recombinase sequence, separated by two different viral 2A oligopeptides that mediate ribosomal skipping (P2A [from porcine teschovirus-1] and T2A [from insect Thosea asigna virus], into the coding sequence of the Mafb (v-maf musculoaponeurotic fibrosarcoma oncogene family, protein B (avian)) gene. A frt-flanked neomycin resistance (neo) cassette was inserted 3' of the cre sequence. Resulting mice were bred to FLP1 exspressing mice to remove the neo cassette.