A 345 bp fragment containing the 3' UTR was replaced with an 855bp fragment containing the rabbit beta-globin 3' UTR and a self-excising neo cassette via homologous recombination. The self-excising neo resistance cassette was then removed during germline transmission. Quantitative RT-PCR showed that the steady-state message levels were increased in adipose tissue, kidneys, liver and heart in homozygous and heterozygous mice compared to wild-type littermates. Real-time RT-PCR indicated that the transcripts from the knock-in allele were more stable than those from the wild-type allele. (J:154767)