GPI-80 Defines Self-Renewal Ability In Hematopoietic Stem Cells During Human Development

Advances in pluripotent stem cell and reprogramming technologies have provided hope of generating transplantable hematopoietic stem cells (HSC) in culture. However, better understanding of the identity and regulatory mechanisms that define the self-renewing HSC during human development is required. We discovered that the glycophosphatidylinositol-anchored surface protein GPI-80 (Vanin-2), previously implicated in neutrophil diapedesis, distinguishes a functionally distinct subpopulation of human fetal hematopoietic stem and progenitor cells (HSPC) that possess self-renewal ability. CD34+CD90+CD38-GPI80+ HSPCs were the only population that could maintain proliferative potential and undifferentiated state in co-culture on supportive stroma, and displayed engraftment potential in sublethally irradiated NSG mice. GPI-80 expression also enabled tracking of human HSC during development as they migrate across fetal hematopoietic niches, including early fetal liver and bone marrow. Microarray analysis comparing CD34+CD90+CD38-GPI80+ HSPC to their immediate progeny (CD34+CD90+CD38-GPI80-) identified novel candidate self-renewal regulators. Knockdown of GPI80, or the top enriched transcripts encoding surface proteins (ITGAM) or transcription factors (HIF3a) documented the necessity of all three molecules in sustaining human fetal HSC self-renewal. These findings provide new insights to the poorly understood regulation of human HSC development and suggest that human fetal HSCs utilize common mechanisms with leukocytes to enable cell-cell interactions critical for HSC self-renewal.