A targeting vector is designed to insert FRT-flanked PGK-Neo-promoterless, ATG-less hygromycin cassette 500 bp downstream of the 3' UTR of the Col1a1 locus. Flpe recombinase is then used to FLP-IN a tetO-Plk4-EYFP plasmid. The Plk4-EYFP plasmid contained mouse Plk4 open reading frame (ORF) C-terminally tagged with EYFP downstream of the tetracycline response element (tetO) and CMV minimal promoter. (J:272389)