This transgene consists of the mouse Btc cDNA downstream of the cytomegalovirus enhancer, the chicken beta-actin promoter, and rabbit beta-globin splice acceptor and upstream to the rabbit beta-globin 3'-flanking region and polyadenylation signal, is referred to as L4, and is integrated at a different site than L2. Btc is expressed ubiquitously, with highest expression in heart. lung, brain, and pancreas. (J:103364)