Targeted disruption of the Hx gene. (A) Structure of the Hx gene (top), the targeting vector (middle) containing a LacZ-PGKneo cassette in the first exon of the Hx gene, and the predicted structure of the disrupted allele after homologous recombination (bottom). Only the relevant restriction sites are shown: C, ClaI site; E,EcoRV site; B, BamHI site. Solid boxes represent exons 1-6. The position of the 3′ external probe is indicated. (B) Southern blot analysis of EcoRV-digested genomic DNA from ES clones. Filter was hybridized with the 3’ external probe shown in (A). The wild-type and mutant alleles are indicated by 10- and 8-kbEcoRV fragments, respectively. (C) Northern blot analysis of total RNA extracted from the liver of a wild-type, an Hx +/−, and an Hx −/− mouse. Filter was hybridized sequentially with an Hx probe and a β-actin probe. Hx transcript was reduced in Hx +/− liver and absent in Hx −/− liver. (D) β-Galactosidase staining of liver sections from a wild-type and an Hx −/− mouse. The majority of hepatocytes were labeled in Hx knockouts. Bar, 10 μm.