IGF2 and Prader-Willi syndrome: We found that the average rate of DNA methylation in the KCNQ1/KCNQ1OT1 and SNURF-SNRPN/UBE3A (Prader–Willi syndrome (PWS)-ICR) ICRs was strikingly higher (about 18% methylated CpGs), when compared to the H19/IGF2, DLK1-DIO3/MEG3, and PEG3/ZIM ICRs in human germ cells, which showed complete loss of DNA methylation (Fig. 3d and Supplementary Fig. 3f).