Epigenetic Mechanisms of Genomic Imprinting: Common Themes in the Regulation of Imprinted Regions in Mammals, Plants, and Insects

Figure 3

Creation of the Drosophila mini-X chromosome and the resulting imprinted expression of the garnet marker gene. The Dp(1:f)LJ9 mini-X chromosome was generated through an inversion followed by a large deletion by X-ray irradiation. In the resulting mini-X chromosome, garnet is placed next to a region centric of heterochromatin containing an imprinting center. (a) Paternal transmission of the mini-X chromosome results in silencing of garnet, as a result of H3K9 methylation and heterochromatin formation. (b) Maternal transmission of the mini-X chromosome results in active transcription of the garnet gene, maintained by CTCF counteracting heterochromatin formation.