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Cell Cycle. 2009 Apr 1;8(7):1003-6. Epub 2009 Apr 2.

mTORC1 signaling governs hematopoietic stem cell quiescence.

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Department of Medical Oncology, Dana-Farber Cancer Institute and Department of Medicine and Genetics, Harvard Medical School, Boston, Massachusetts, USA.


The stringent regulation of hematopoietic stem cell (HSC) quiescence versus cell cycle progression is essential for the preservation of a pool of long-term self-renewing cells and vital for sustaining an adequate supply of all blood lineages throughout life. Cell growth, the process that is mass increase, serves as a trigger for cell cycle progression and is regulated predominantly by mammalian target of rapamycin complex 1 (mTORC1) signaling. Emerging data from various mice models show deletion of several mTORC1 negative regulators, including PTEN, TSC1, PML and Fbxw7 result in similar HSC phenotypes characterized as HSC hyper-proliferation and subsequent exhaustion, and defective repopulating potential. Further pharmacological approaches show that PTEN, TSC1 and PML regulate HSC maintenance through mTORC1. mTORC1-mediated cell growth regulatory circuits thus play a critical role in the regulation of HSC quiescence.

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