Rasgrf1 imprinting is regulated by a CTCF-dependent methylation-sensitive enhancer blocker

Area of Science:

• Genetics
• Epigenetics
• Molecular Biology

Background:

• Genomic imprinting regulates parent-of-origin-specific gene expression.
• Imprinted methylation of the paternal Rasgrf1 allele in mice occurs at a differentially methylated domain (DMD).
• A repeat sequence 3' of the DMD is crucial for regulating imprinted methylation and expression.

Purpose of the Study:

• To elucidate the mechanism by which DNA methylation controls Rasgrf1 imprinting.
• To investigate the role of the DMD and repeat sequences in regulating imprinted expression.

Main Methods:

• Investigated the function of the DMD as an enhancer blocker.
• Assessed the methylation-sensitive binding of CTCF to the DMD.
• Analyzed the impact of repeat-mediated methylation on CTCF binding and gene expression.
• Examined enhancer-blocking activity in vitro and in vivo.

Main Results:

• The DMD functions as an enhancer blocker, binding CTCF in a methylation-sensitive manner.
• CTCF binding to the unmethylated maternal allele silences expression.
• Repeat-mediated methylation of the paternal allele prevents CTCF binding, allowing Rasgrf1 expression.
• In vivo studies demonstrated that bypassing the enhancer blocker abolishes imprinting.

Conclusions:

• The repeats and DMD act as a binary switch regulating Rasgrf1 imprinting.
• Methylation-sensitive CTCF binding to the DMD is the key mechanism controlling imprinted expression.
• This study provides novel insights into the epigenetic regulation of imprinted genes.