Fig. 1

 A map of chromosome 11p15. Normally, the maternal allele is methylated at differentially methylated region 2 (DMR2), and the paternal allele is methylated at differentially methylated region 1 (DMR1). Unmethylated DMR1 on the maternal chromosome permits binding of the insulator protein CTCF, which blocks access of enhancers to the IGF2 promoter. Therefore, the maternal copy of H19 uses enhancers and is transcribed. Methylated DMR1 on the paternal chromosome prevents binding of the CTCF. Therefore, enhancers can access the IGF2 promoter, which is transcribed. On the maternal chromosome, DMR2 is methylated, and KCNQ1 and CDKN1C are transcribed. On the paternal chromosome, DMR2 is unmethylated, and KCNQ1OT1 is transcribed. IGF2 positively and CDKN1C negatively regulates cell growth and proliferation. Green triangles indicate enhancers. Lollipops indicate methylated DMR. Genes normally expressed from the maternal chromosome are depicted as red boxes, and genes normally expressed from the paternal chromosome are depicted as blue boxes. Arrows indicate the orientation of transcription. Tel = telomere. Cen = centromere