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Flk-2 is a marker in hematopoietic stem cell differentiation: a simple method to isolate long-term stem cells
J L Christensen1, I L Weissman
1Departments of Pathology and Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305-5324, USA. juliech@stanford.edu
Summary
Long-term hematopoietic stem cells (HSCs) lack Flk-2 expression, indicating a primitive state. Flk-2 expression marks the transition to short-term HSCs, signifying loss of self-renewal capacity in HSC maturation.
Area of Science:
- Hematology
- Stem Cell Biology
- Immunology
Background:
- Hematopoietic stem cells (HSCs) are crucial for blood cell formation.
- The c-kit(+) lineage(-) Sca-1(+) (KLS) population contains HSCs and progenitors.
- Long-term (LT) and short-term (ST) HSCs are distinguished by Thy-1.1 expression levels.
Purpose of the Study:
- To determine if the Flk-2/Flt3 receptor tyrosine kinase is expressed on primitive LT-HSCs.
- To investigate the role of Flk-2 in HSC self-renewal and differentiation.
Main Methods:
- Purification of multipotent stem and progenitor cells based on Flk-2 surface expression.
- Competitive reconstitution assays using sorted cell populations.
- Analysis of Flk-2 and Thy-1.1 expression on the KLS subset of adult mouse bone marrow.
Main Results:
- Low numbers of Flk-2(-) HSCs achieved long-term multilineage reconstitution.
- Flk-2(+) multipotent cells primarily resulted in short-term reconstitution.
- Three distinct populations were identified: LT-HSCs (Thy-1.1(lo) Flk-2(-)), ST-HSCs (Thy-1.1(lo) Flk-2(+)), and progenitors (Thy-1.1(-) Flk-2(+)).
Conclusions:
- Loss of Thy-1.1 and gain of Flk-2 expression signifies the loss of self-renewal during HSC maturation.
- Flk-2(-) KLS cells represent the most primitive LT-HSCs.
- Flk-2 antibody can aid in the direct isolation of LT-HSCs from adult mouse bone marrow.