FIGURE 3.

Molecular mechanism of alternative imprinting gene expression: (A) in the maternally expressed imprinted genes (MEGs) pathway, differential methylation of both maternal alleles occurs (green color), i.e., DEMETER (DME) downregulates DNA methylation by the hypomethylation process resulted in parental allele normal expression (red color), but increased methylation by DMT and polycomb repressive complex 2 (PRC2) causes histone methylation resulted in allele suppression, (B) in the paternally expressed imprinted genes (PEGs) pathway, the hypermethylated parental allele switches from the silent to active state under the action of PRC2 due to a halt in methylation by DMT, contrastingly hypomethylated maternal allele switches the active to silent state under the action of PRC2 via histone methylation.