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mdm2 deletion does not alter growth characteristics of p53-deficient embryo fibroblasts
K M McMasters1, R Montes de Oca Luna, J R Peña
1Department of Surgical Oncology, University of Texas MD Anderson Cancer Center, Houston 77030, USA.
Abstract:
The mdm2 gene encodes a protein that is necessary for the negative regulation of p53 function in vivo. Deletion of the mdm2 gene in mice results in early embryonic death while concomitant mdm2 and p53 deletion results in viable offspring. The viability of these mice prompted us to ask if MDM2 had an important growth regulatory function independent of p53. We established mouse embryo fibroblasts null for both p53 and mdm2 and compared them with p53-null fibroblasts. The cells did not differ in their growth rates or their ability to bypass a G1 arrest. Both cell lines formed colonies efficiently when plated at low density and showed a similar degree of genetic instability. Thus, the analysis of several growth parameters indicated no difference between p53-null and p53/mdm2-null cell lines.
Insights
The MDM2 protein regulates p53. Removing both MDM2 and p53 genes allows mice to survive embryonic development, suggesting MDM2
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- The MDM2 gene product is crucial for inhibiting p53 activity in vivo.
- Mice lacking the MDM2 gene experience embryonic lethality.
- Simultaneous deletion of MDM2 and p53 genes in mice leads to viable offspring.
Purpose of the Study:
- To investigate the potential growth-regulatory role of MDM2 independent of p53.
- To compare the cellular behavior of cells lacking both p53 and MDM2 with those lacking only p53.
Main Methods:
- Generation of mouse embryo fibroblasts lacking both p53 and MDM2.
- Comparison of p53-null and p53/mdm2-null cell lines.
- Assessment of cell growth rates, G1 arrest bypass, low-density colony formation, and genetic instability.
Main Results:
- No significant differences were observed in growth rates between p53-null and p53/mdm2-null cells.
- Both cell lines demonstrated similar abilities to bypass G1 arrest.
- Efficient colony formation at low density and comparable levels of genetic instability were noted in both cell types.
Conclusions:
- The study found no discernible difference in key growth parameters between cells lacking p53 and cells lacking both p53 and MDM2.
- These findings suggest that MDM2's critical growth regulatory functions, if any, may be largely dependent on p53.
- Further research is needed to fully elucidate the independent functions of MDM2 in cellular growth and development.