Project description: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.
Project description:We identified a novel HSC (hematopoietic stem cell) regulatory gene, MYCT1 (MYC target 1), that is selectively expressed in undifferentiated human HSPC and is critical for human HSC expansion and engraftment. To define the molecular function of MYCT1 we performed cell fractionation, immunofluorescence, and immunoprecipitation coupled with high sensitivity mass spectrometry of V5-tagged MYCT1 in KG1 hematopoietic cells and human endothelial cells (E4-immortalized HUVEC, E4EC (Butler et al. 2012)). We found that MYCT1 localizes in the endosomal membrane and interacts with vesicle trafficking regulators and signalling machinery essential for HSC and endothelial cell function. We performed RNAseq to asses the expression of the identified MYCT1 interactors in KG1 and E4EC cell lines.
Project description:We identified a novel HSC regulatory gene, MYCT1 (MYC target 1), that is selectively expressed in undifferentiated human HSPC and is critical for human HSC expansion and engraftment. MYCT1 knockdown (KD) in human fetal liver and cord blood (CB) HSPCs impaired expansion ex vivo and engraftment after transplantation, whereas restoring the compromised MYCT1 expression via lentiviral overexpression (OE) in cultured human CB HSPCs improved ex vivo expansion of the most undifferentiated human HSPCs (CD34+CD38-CD90+CD45RA-EPCR+ITGA3+) and enhanced their engraftment ability. We performed single cell RNAseq of uncultured human CB HSPCs, as well as 72 hours after MYCT1 KD and OE to identify MYCT1-regulated programs in HSC and understand the role of MYCT1 in governing human HSPC expansion and engraftment ability. Functional enrichment analysis linked the loss of MYCT1 in HLF+ HSCs to a profound dysregulation of multiple cellular programs essential for HSC stemness, such as oxidative phosphorylation or proteostasis, while MYCT1 OE had the opposite effect and showed closer similarity to uncultured HLF+ HSCs. These data indicate that the loss or gain of MYCT1 expression elicits major effects on programs regulating human HSC functional competence.
Project description:We identified a novel HSC regulatory gene, MYCT1 (MYC target 1), that is selectively expressed in undifferentiated human HSPC and is critical for human HSC expansion and engraftment. MYCT1 knockdown (KD) in human fetal liver and cord blood (CB) HSPCs impaired expansion ex vivo and engraftment after transplantation, whereas restoring the compromised MYCT1 expression via lentiviral overexpression (OE) in cultured human CB HSPCs improved ex vivo expansion of the most undifferentiated human HSPCs (CD34+CD38-CD90+CD45RA-EPCR+ITGA3+) and enhanced their engraftment ability. We performed single cell RNAseq of uncultured human CB HSPCs, as well as 72 hours after MYCT1 KD and OE to identify MYCT1-regulated programs in HSC and understand the role of MYCT1 in governing human HSPC expansion and engraftment ability. Functional enrichment analysis linked the loss of MYCT1 in HLF+ HSCs to a profound dysregulation of multiple cellular programs essential for HSC stemness, such as oxidative phosphorylation or proteostasis, while MYCT1 OE had the opposite effect and showed closer similarity to uncultured HLF+ HSCs. These data indicate that the loss or gain of MYCT1 expression elicits major effects on programs regulating human HSC functional competence. Mechanistically, we found that MYCT1 governs endocytosis. Therefore, we performed scRNAseq of cultured HSPCs (CD34+CD38-CD90+EPCR+) with low, medium or high levels of endocytosis and found that low endocytosis HSCs had higher MYCT1 expression and favorable transcriptomic profiles of HSC functional competence.
Project description:Purpose: To obtain the differentially expressed LncRNA, mRNAs and miRNAs between the two groups of cells. Results: We identified 174 LncRNAs, 327 mRNAs and 235 miRNAs differentially expressed in MYCT1-overexpressed Hep2 cells compared to the controls.