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Function of MicroRNA-146a and NF-κB in Physiologic and Pathologic Hematopoiesis


Zhao, Jimmy Liu (2013) Function of MicroRNA-146a and NF-κB in Physiologic and Pathologic Hematopoiesis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/99A5-DR49.


During inflammation and infection, hematopoietic stem and progenitor cells (HSPCs) are stimulated to proliferate and differentiate into mature immune cells, especially of the myeloid lineage. MicroRNA-146a (miR-146a) is a critical negative regulator of inflammation. Deletion of the gene encoding miR-146a—expressed in all blood cell types—produces effects that appear as dysregulated inflammatory hematopoiesis, leading to a decline in the number and quality of hematopoietic stem cells (HSCs), excessive myeloproliferation, and, ultimately, to exhaustion of the HSCs and hematopoietic neoplasms. Six-week-old deleted mice are normal, with no effect on cell numbers, but by 4 months bone marrow hypercellularity can be seen, and by 8 months marrow exhaustion is becoming evident. The ability of HSCs to replenish the entire hematopoietic repertoire in a myelo-ablated mouse also declines precipitously as miR-146a-deficient mice age. In the absence of miR-146a, LPS-mediated serial inflammatory stimulation accelerates the effects of aging. This chronic inflammatory stress on HSCs in deleted mice involves a molecular axis consisting of upregulation of the signaling protein TRAF6 leading to excessive activity of the transcription factor NF-κB and overproduction of the cytokine IL-6. At the cellular level, transplant studies show that the defects are attributable to both an intrinsic problem in the miR-146a-deficient HSCs and extrinsic effects of miR-146a-deficient lymphocytes and non-hematopoietic cells. This study has identified a microRNA, miR-146a, to be a critical regulator of HSC homeostasis during chronic inflammatory challenge in mice and has provided a molecular connection between chronic inflammation and the development of bone marrow failure and myeloproliferative neoplasms. This may have implications for human hematopoietic malignancies, such as myelodysplastic syndrome, which frequently displays downregulated miR-146a expression.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:inflammation, immunology, hematopoiesis, NF-kappaB, cancer
Degree Grantor:California Institute of Technology
Major Option:Biology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Baltimore, David L.
Thesis Committee:
  • Patterson, Paul H. (chair)
  • Mazmanian, Sarkis K.
  • Rao, Dinesh S.
  • Baltimore, David L.
Defense Date:5 February 2013
Funding AgencyGrant Number
Record Number:CaltechTHESIS:04122013-165433477
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7613
Deposited By: Jimmy Zhao
Deposited On:06 Apr 2015 22:39
Last Modified:07 Dec 2020 23:04

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