MYCT1 CONTROLS ENVIRONMENTAL SENSING IN HUMAN HEMATOPOIETIC STEM CELLS

ABSTRACT: Hematopoietic stem cells (HSC) rely on a unique regulatory machinery that facilitates life-long blood production and enables reconstitution of the entire hematopoietic system upon transplantation. However, the biological processes governing human HSC self-renewal and engraftment ability are poorly understood and challenging to recapitulate ex vivo to facilitate robust human HSC expansion. We discovered a novel HSC regulatory protein, MYCT1 (MYCT target 1), that is selectively expressed in endothelial cells (EC) and undifferentiated human HSPCs but becomes drastically downregulated during HSC culture. Lentiviral knockdown of MYCT1 in human foetal liver and cord blood HSPCs revealed a critical role for MYCT1 in governing human HSPC expansion and engraftment ability. Single cell RNAseq of human CB HSPCs after MYCT1 knockdown and overexpression revealed that MYCT1 governs HSC functional competence and modulates cellular properties essential for HSC stemness, such as low mitochondrial metabolic activity. Indeed, restoring the compromised MYCT1 expression in cultured human CB HSPCs improved ex vivo expansion of the most undifferentiated human HSPCs and enhanced their engraftment ability. We found that MYCT1 is localized in the endosomal membrane and interacts with vesicle trafficking regulators and signalling machinery essential for HSC and EC function. Loss of MYCT1 led to excessive endocytosis and hyperactive signalling responses to cytokines, whereas restoring MYCT1 expression in cultured CB HSPCs balanced the abnormal endocytosis associated with prolonged culture and fine-tuned signalling responses. Our work identifies MYCT1-moderated endocytosis and environmental sensing as an essential regulatory mechanism required to preserve human HSC stemness, and pinpoints silencing of MYCT1 as a critical contributor to the dysfunction of cultured human HSCs that needs to be addressed to improve human HSC culture strategies.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Yasi Jami  

LAB HEAD: yasaman jami

PROVIDER: PXD042257 | Pride | 2024-04-15

REPOSITORIES: Pride