Similar ChIP in human cells shows that the CpG island of NDN and the Prader-Willi syndrome imprinting center (located in exon 1 of the SNRPN gene) carry H3K4me2 and H3K4me3 marks on the expressed paternal allele but not on the nonexpressed maternal allele [64,65]. Here, SNRPN is linked to Prader-Willi syndrome.