Hematopoiesis under telomeric attrition at the single-cell resolution

The molecular mechanisms that drive hematopoietic stem cell (HSC) functional decline under conditions of stress are not completely understood. Here, in light of the recent advances in single-cell technologies, we sought to redefine the transcriptional and epigenetic landscape of mouse and human hematopoietic stem cells (HSCs) under telomeric stress, as that induced by pathogenic germline mutations in telomerase complex genes. These analyses revealed that telomere attrition maintains HSCs in a state of persistent metabolic activation and differentiation towards the megakaryocytic lineage through the cell-intrinsic upregulation of interferon (IFN) signaling response, which directly comprises HSCs’ self-renewal capabilities and eventually leads to their exhaustion. Telomerase reactivation completely restored HSC transcriptional homeostasis at the single-cell level, overcame enhanced megakaryocytic differentiation and significantly ameliorated HSCs’ repopulation capacity in the setting of competitive transplantation, suggesting that HSCs can repristinate their function upon telomere damage resolution. This study challenges the long-standing hypothesis that telomere attrition limits the proliferative potential of HSCs by inducing apoptosis or senescence and suggests that early intervention targeting the IFN axis could prevent bone marrow failure syndromes in patients with pathogenic mutations affecting telomere maintenance. To understand how telomeric attrition affects the function of hematopoietic stem cells (HSCs) and leads to degenerative defects in bone marrow (BM) by scRNA-seq