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Enhancer competition between H19 and Igf2 does not mediate their imprinting.
J V Schmidt1, J M Levorse, S M Tilghman
1Department of Molecular Biology and The Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA.
Summary
Genomic imprinting of H19 and Igf2 genes was studied. Deleting the H19 promoter in mice showed it is not required for Igf2 gene silencing, challenging the enhancer competition model.
Area of Science:
- Genetics
- Genomic Imprinting
- Gene Regulation
Background:
- The H19 and Igf2 genes are imprinted on mouse chromosome 7.
- Coordinate expression and reciprocal imprinting suggest promoter competition for shared enhancers.
Purpose of the Study:
- To test the enhancer competition model for H19 and Igf2 gene regulation.
- To investigate the role of H19 transcriptional activity in Igf2 imprinting.
Main Methods:
- Utilized Cre-loxP technology in mice.
- Generated a conditional deletion of the H19 promoter and structural gene.
Main Results:
- The H19 promoter and transcription were conditionally deleted.
- Imprinted silencing of the Igf2 gene occurred independently of H19 transcriptional activity.
Conclusions:
- H19 transcriptional activity is not required for the imprinted silencing of Igf2.
- The enhancer competition model is not supported by these findings.