Fig. 2. Targeting at the Igf2/H19 ICR. The ICR was replaced by the (ChßGI)2, keeping the CTCF sites in the same orientation. The sequences involved are described in Fig. 1B. BamHI and probe a (Pr.a) blot, one clone shown. All seven clones obtained [EcoRI and probe b (Pr.b) blot] underwent conservative recombination. The neo selection cassette was flanked by loxP sites allowing for excision with Cre.