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Published on: December 3, 2015
Hematopoietic stem cell quiescence maintained by p21cip1/waf1
1Experimental Hematology, AIDS Research Center, Massachusetts General Hospital Cancer Center, Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
Science (New York, N.Y.)
|March 10, 2000
Summary
The G1 checkpoint regulator, p21, is crucial for hematopoietic stem cell (HSC) quiescence. Without p21, HSCs proliferate excessively, leading to exhaustion and failure, especially under stress.
Area of Science:
- Hematology
- Stem Cell Biology
- Molecular Biology
Background:
- Hematopoietic stem cells (HSCs) maintain quiescence, a state critical for preserving the stem cell pool.
- The G1 checkpoint regulator, cyclin-dependent kinase inhibitor p21 (p21), is implicated in controlling stem cell proliferation.
Purpose of the Study:
- To investigate the role of p21 in regulating HSC quiescence and self-renewal.
- To determine the consequences of p21 deficiency on hematopoiesis under homeostatic and stress conditions.
Main Methods:
- Utilized genetically engineered mice lacking the p21 gene (p21-/-).
- Assessed HSC proliferation, absolute numbers, and self-renewal capacity via serial bone marrow transplantation.
- Evaluated hematopoietic responses to cell cycle-specific myelotoxic injury.
Main Results:
- p21 deficiency led to increased HSC proliferation and numbers under normal conditions.
- p21-/- mice exhibited premature death and hematopoietic failure upon exposure to myelotoxic injury.
- Impaired self-renewal of primitive hematopoietic cells was observed in serially transplanted p21-/- bone marrow.
Conclusions:
- p21 acts as a critical molecular switch controlling HSC entry into the cell cycle.
- Absence of p21 results in stem cell exhaustion due to increased proliferation.
- Restricted cell cycling, regulated by p21, is essential for preventing stem cell depletion and hematopoietic failure during stress.
