(a) The structure of the human ABCG5/ABCG8 transgene. A P1 clone (35B6; Incyte Genomics Inc.) containing a 90-kb insert was linearized with NotI, purified, and injected into fertilized embryos as described in Methods. The insert contains the entire coding regions of human ABCG5 and ABCG8, exons 6–13 of the putative gene CGI-60 at the 3′ end of ABCG5, and 6 kb of flanking sequence at the 3′ end of ABCG8. (b) Tissue distribution of human ABCG5 and ABCG8 mRNA in the transgenic mice. Total RNA was extracted from tissues of wild-type and transgenic mice consuming a chow diet. A total of 15 μg of RNA was fractionated on a 1% formaldehyde gel, transferred to a nylon membrane, and hybridized with 1 × 10⁶ cpm/ml of [α-³²P]-labeled cDNA probes for human and mouse ABCG5 and ABCG8 at 65°C in Rapid-hyb Buffer (Amersham Biosciences Corp.). After stringent washing, the membrane was exposed to Kodak X-OMAT Blue XB-1 films (Eastman Kodak Co., Rochester, New York, USA) for 12–36 h at –80°C. This experiment was repeated, and the results were similar.