Endomucin, a CD34-like sialomucin, marks hematopoietic stem cells throughout development

Area of Science:

• Hematology
• Developmental Biology
• Cell Biology

Background:

• Hematopoietic stem cells (HSCs) are crucial for blood formation.
• Identifying specific HSC markers is essential for understanding their development and function.
• Existing markers may not fully capture the heterogeneity and developmental stages of HSCs.

Purpose of the Study:

• To identify novel cell-surface molecules specific to mouse hematopoietic stem cells (HSCs).
• To characterize the expression and function of Endomucin in HSCs during development.
• To establish Endomucin as a reliable marker for long-term repopulating HSCs (LTR-HSCs).

Main Methods:

• Modified signal sequence trap applied to mouse bone marrow (BM) CD34(-)c-Kit(+)Sca-1(+)Lin(-) (CD34(-)KSL) HSCs.
• Flow cytometry and cell sorting to analyze Endomucin expression in different hematopoietic populations.
• Assessment of BM repopulating capacity and in vitro cytokine responsiveness of Endomucin-positive and -negative fractions.

Main Results:

• Endomucin was identified as a novel cell-surface molecule highly expressed on BM KSL HSCs and progenitor cells.
• LTR-HSCs were exclusively found within the Endomucin(+)CD34(-)KSL population.
• Endomucin expression delineated hematopoietic progenitor populations in the yolk sac and AGM region during embryonic development.
• Significant changes in repopulating capacity and cytokine responsiveness were observed in Endomucin-defined fractions during HSC ontogeny.

Conclusions:

• Endomucin serves as a novel and reliable cell-surface marker for LTR-HSCs throughout development.
• Endomucin expression patterns provide insights into HSC ontogeny and developmental transitions.
• This finding offers a valuable tool for future research on HSC biology and potential therapeutic applications.