Neogenin-1 distinguishes between myeloid-biased and balanced mouse long-term hematopoietic stem cells.

Hematopoietic stem cells (HSCs) self-renew and generate all blood cells. Recent studies with single cell transplants and lineage tracing suggest that adult HSCs are diverse in their reconstitution and lineage potentials. However, prospective isolation of these subpopulations has remained challenging. Here, we identify Neogenin-1 (NEO1) as a unique surface marker on a fraction of mouse HSCs labeled with , a specific reporter of long-term HSCs (LT-HSCs). We show that NEO1 LT-HSCs expand with age and respond to myeloablative stress in young mice while NEO1 LT-HSCs exhibit no significant change in number. Furthermore, NEO1 LT-HSCs are more often in the G/S cell cycle phase compared to NEO1 LT-HSCs in both young and old bone marrow. Upon serial transplantation, NEO1 LT-HSCs exhibit myeloid-biased differentiation and reduced reconstitution while NEO1 LT-HSCs are lineage-balanced and stably reconstitute recipients. Gene expression analysis reveals erythroid and myeloid priming in the NEO1 fraction and association of quiescence and self-renewal-related transcription factors with NEO1 LT-HSCs. Finally, transplanted NEO1 LT-HSCs rarely generate NEO1 LT-HSCs while NEO1 LT-HSCs repopulate both LT-HSC fractions. This supports a model in which dormant, balanced NEO1 LT-HSCs can hierarchically precede active, myeloid-biased NEO1 LT-HSCs.