The H19 Differentially Methylated Region Marks the Parental Origin of a Heterologous Locus without Gametic DNA Methylation

Abstract

Igf2 and H19 are coordinately regulated imprinted genes physically linked on the distal end of mouse chromosome 7. Genetic analyses demonstrate that the differentially methylated region (DMR) upstream of the H19 gene is necessary for three distinct functions: transcriptional insulation of the maternal Igf2 allele, transcriptional silencing of paternal H19 allele, and marking of the parental origin of the two chromosomes. To test the sufficiency of the DMR for the third function, we inserted DMR at two heterologous positions in the genome, downstream of H19 and at the alpha-fetoprotein locus on chromosome 5. Our results demonstrate that the DMR alone is sufficient to act as a mark of parental origin. Moreover, this activity is not dependent on germ line differences in DMR methylation. Thus, the DMR can mark its parental origin by a mechanism independent of its own DNA methylation.

We thank Marisa Bartolomei, Tamara Davis, and Jacquetta Trasler for providing protocols and advice for the direct sequencing assay for DNA methylation.

This work was supported by the Intramural Research program of the National Institute for Child Health and Human Development.