Fig. 1. (A) Gene regulation at the Igf2 and H19 loci. (M), Maternal allele; (P), Paternal allele. (B) Nucleotide structure of the 2.4 kb ICR and the 2.4 kb (ChßGI)2. Vertical lines are CpGs or GpCs. CTCF-binding sites are indicated (gray rectangles) and are in the 5'-CCGCnnGGnGGCAG-3' orientation. Sequence of the ICR is as published elsewhere (Ishihara et al., 1998) (GenBank Accession Number, AF049091) and is defined here as a BglII fragment at –2.0 to –4.4 kb RTSS of H19. To obtain the ChßGI sequence, we sequenced the outer 1.2 kb XbaI fragment of plasmid pJC13-1 (Chung et al., 1993). This sequence has been deposited with GenBank (Accession Number, AY040835). (C) Comparison of the present ICR substitution (gray bar) with three independent ICR deletions (open bars): deletion a (Thorvaldsen et al., 1998), deletion b (Drewell et al., 2000) and deletion c (Srivastava et al., 2000). H19 transcription start site (arrow). X, XbaI; B, BamHI; Bg, BglII; H, HindIII; Bs, BspEI; K, KpnI.
