A PGK-Neo cassette was inserted into intron 3 and three loxP sites around exons 2 and 3 and the PGK-Neo. Chimeras were mated to Tg(ACTB-cre)13Miya mice to remove exons 2 and 3 and the PGK-Neo cassette. Northern blot analysis and RT-PCR confirmed absence of RNA. (J:102924)