Figure 4

Targeting of a LacZ transgene to the Hnf3αΔNeo locus. a) A targeting vector (materials and methods) containing a LacZ transgene was introduced into Hnf3αΔpgk-Neo ES cells by electroporation and cells were cultured in media containing G418. The genotype of ES cell clones that were resistant to G418 was determined by Southern blot analysis of genomic DNA digested with HindIII and EcoRV. A wild type 8.0 kb Hnf3α fragment and a 3.5 kb " pgk-Neo targeted" fragment from Hnf3αΔpgk-Neo ES cells (lane 1) was identified using probe A. The 3.5 kb " pgk-Neo targeted" fragment was replaced with a 2.7 kb EcoRV fragment in all fifteen G418 resistant clones examined due to the introduction of a novel EcoRV site that lies within the LacZ transgene (Hnf3αLacZ, lanes 2-16). b) Embryos at 10.5 days of gestation that were derived from Hnf3αLacZ ES cells express β-galactosidase (blue) throughout the developing hindgut (hg), foregut (fg), liver (l) and stomach (s).