 The Grb10 gene in mice has a bivalent domain that uses H3K4me3 and H3K27me3 modifications as a tool to express genes from one parent while the other is silenced.This allows the gene to be expressed by only one parent in a specific tissue.In most somatic tissues, the Grb10 gene is expressed from the maternal allele, except in the brain where it is expressed from the paternal allele.