Fig. 3

Hypothetical model for the regulation of the DNA methylation at the PWS/AS region by AS-IC and PWS-IC. Circles denote CpGs showing differential methylation patterns in a parent-of-origin-specific manner. Solid circles represent methylated CpGs, and the open ones unmethylated CpGs. P denotes paternally inherited allele, and M maternally derived allele. Deleted regions are shown by gray boxes in each case. a Mechanism regulating the DNA methylation at the PWS/AS region in normal individuals. On the P allele, CpGs in PWS-IC and the promoter of paternally expressed genes in the 5′ upstream region of ICR are unmethylated, and CpGs located sparsely in the SNORD116s cluster are methylated. The unmethylated PWS-IC on the P allele is thought to lead to CpGs with a paternal methylation pattern at CpGs in both the upstream region (unmethylated, shown by white arrows) and the SNORD116s cluster (methylated, shown by black arrows). AS-IC on the P allele methylated CpGs in the SNORD116s cluster. On the M allele, PWS-IC and CpGs in iDMRs of upstream imprinted genes are methylated, and CpGs in the SNORD116s cluster are unmethylated. AS-IC on the M allele methylated PWS-IC. Maternal methylation pattern (methylated in the upstream region and unmethylated in the SNORD116s cluster) is the default state. b Regulation of the DNA methylation in cases with various microdeletions involving AS-IC, PWS-IC, or SNORD116s cluster. The cases with deletions in the paternally inherited allele are shown in the upper part and those in the maternally derived allele in the lower part. In the second left case with a deletion involving only PWS-IC in the paternally inherited allele, the methylation pattern in the SNORD116s cluster is depicted according to the results of a previous report [14]. c DNA methylation pattern in cases with large deletions involving the entire PWS/AS region. AS-IC and PWS-IC seemed to control DNA methylation status cooperatively or separately at the PWS/AS region