Heterogeneity of high-potency multilineage hematopoietic stem cells and identification of "Super" transplantability

Hematopoietic stem cells (HSCs) are heterogeneous, and the quality of HSCs-that is, transplantability-is a key determinant for posttransplant hematopoietic reconstitution. However, molecular modalities of high-potency HSCs with superior transplantability still remain poorly understood. Here, we conducted large-scale single-clone serial-transplant experiments and tracked descendant cells of 288 HSC clones to quantify their intrinsic capability for hematopoietic reconstitution. Using integrated single-cell transcriptional, immunophenotypical, and Bayesian dynamic analyses, we uncovered 3 classes of HSC clones ("Super," "Flash," and "Trickle") that had higher output in the first generation but exhibited markedly different behavior in later generations. The Super-class HSC clones comprised 4% of the HSCs and manifested persistent superior transplantability and balanced myeloid/lymphoid-lineage outputs across generations in serial transplants. The Super-class HSCs had a unique molecular signature, including low expression of CD27, that was distinct from previously known classical HSC signatures. Validation experiments indicated that CD27- HSCs had superior transplantability compared with CD27+ HSCs. Our study asserted an operational definition for Super transplantability of HSCs, defined its molecular program, and suggested new directions for enriching high-potency HSCs in grafts.