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Updated: Aug 16, 2026
A Non-random Mouse Model for Pharmacological Reactivation of Mecp2 on the Inactive X Chromosome
Published on: May 22, 2019
Rescue of Mdm4-deficient mice by Mdm2 reveals functional overlap of Mdm2 and Mdm4 in development
Heather A Steinman1, Kathleen M Hoover, Marilyn L Keeler
1Department of Cell Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Abstract:
The Mdm2 and Mdm4 genes are amplified and overexpressed in a variety of human cancers and encode structurally related oncoproteins that bind to the p53 tumor suppressor protein and inhibit p53 activity. Mice deleted for either Mdm2 or Mdm4 die during embryogenesis, and the developmental lethality of either mouse model can be rescued by concomitant deletion of p53. However, the phenotypes of Mdm2 and Mdm4-deficient mice suggest that Mdm2 and Mdm4 play nonoverlapping roles in regulating p53 activity during development, with Mdm2 regulating p53-mediated cell death and Mdm4 regulating p53-mediated inhibition of cell growth. Here, we describe complete rescue of Mdm4-deficient mice by expression of an Mdm2 transgene, and demonstrate that Mdm2 can regulate both p53-mediated apoptosis and inhibition of cell growth in the absence of Mdm4 in primary cells. Furthermore, deletion of Mdm4 enhances the ability of Mdm2 to promote cell growth and tumor formation, indicating that Mdm4 has antioncogenic properties when Mdm2 is overexpressed.
Insights
Mdm2 and Mdm4 proteins regulate the p53 tumor suppressor. Mdm2 can compensate for Mdm4 loss, controlling cell growth and death, but Mdm4 deletion enhances Mdm2-driven tumor formation.
Area of Science:
- Molecular Biology
- Cancer Biology
- Genetics
Background:
- Mdm2 and Mdm4 oncoproteins are overexpressed in human cancers, inhibiting the p53 tumor suppressor.
- Mice lacking Mdm2 or Mdm4 exhibit embryonic lethality, which is rescued by p53 deletion.
- Mdm2 and Mdm4 appear to have distinct roles in p53 regulation during development.
Purpose of the Study:
- To investigate the functional overlap between Mdm2 and Mdm4 in p53 regulation.
- To determine if Mdm2 can rescue Mdm4-deficient mice and regulate p53 in the absence of Mdm4.
- To explore the role of Mdm4 in tumor suppression when Mdm2 is overexpressed.
Main Methods:
- Generating Mdm4-deficient mice rescued by an Mdm2 transgene.
- Analyzing primary cells from rescued mice to assess Mdm2's function without Mdm4.
- Evaluating the impact of Mdm4 deletion on Mdm2-driven cell growth and tumor formation.
Main Results:
- Mdm2 transgene expression completely rescued Mdm4-deficient mice.
- Mdm2 regulated both p53-mediated apoptosis and cell growth inhibition in primary cells lacking Mdm4.
- Mdm4 deletion enhanced Mdm2's ability to promote cell growth and tumor formation.
Conclusions:
- Mdm2 can functionally replace Mdm4 in regulating p53 activity, including apoptosis and cell growth inhibition.
- Mdm4 possesses tumor-suppressive functions, particularly when Mdm2 is overexpressed, highlighting its antioncogenic potential.
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