Project description:Activation of mostly quiescent hematopoietic stem cells (HSC) is a prerequisite for life-long blood production1, 2. This process requires major molecular adaptations to meet the regulatory and metabolic requirements for cell division3-8. The mechanisms governing cellular reprograming upon stem cell activation and their subsequent return to quiescence are still not fully characterized. Here, we describe a role for chaperone-mediated autophagy (CMA)9, a selective form of lysosomal protein degradation, in sustaining adult HSC function. CMA is required for stem cell protein quality control and upregulation of fatty acid metabolism upon HSC activation. We identify that CMA activity decreases with age in HSC and show that genetic or pharmacological activation of CMA can restore functionality of old HSC. Together, our findings provide mechanistic insights into a new role for CMA in sustaining quality control, appropriate energetics and overall long-term hematopoietic stem cell function. Our work supports that CMA may be a promising therapeutic target to enhance hematopoietic stem cell function in conditions such as aging or stem cell transplantation.
Project description:To investigate the translatome change due to loss of MYSM1 in CD34+CD45RA-CD90+ cells We performed ribosome profiling followed by NGS sequencing where only ribosome protected RNA was extracted to make the library, which mostly are in active translation
Project description:Long-term hematopoietic stem cells are rare, highly quiescent stem cells of the hematopoietic system with life-long self-renewal potential and the ability to transplant and reconstitute the entire hematopoietic system of conditioned recipients. Most of our understanding of these rare cells has relied on cell surface identification, epigenetic and transcriptomic analyses. Our knowledge of protein synthesis, folding, modification and degradation – broadly termed protein homeostasis or “proteostasis” – in these cells is still in its infancy. Here we report the requirement of the small phospho-binding adaptor proteins, the cyclin dependent kinase subunits (Cks1 and Cks2), for maintaining ordered hematopoiesis and long-term hematopoietic stem cell reconstitution. Cks1 and Cks2 are critical regulators of a myriad of key intracellular signalling pathways that govern hematopoietic stem cell biology and together they balance protein homeostasis and restrain reactive oxygen species to ensure healthy hematopoietic stem cell function.
Project description:<p><strong>BACKGROUND:</strong> Hematopoietic stem cell transplantation is a curative procedure for a variety of conditions. Despite major advances, a plethora of adverse clinical outcomes can develop post-transplantation including graft-versus-host disease and infections, which remain the major causes of morbidity and mortality. There is increasing evidence that the gastrointestinal microbiota is associated with clinical outcomes post-hematopoietic stem cell transplantation. Herein, we investigated the longitudinal dynamics of the gut microbiota and metabolome and potential associations to clinical outcomes in pediatric hematopoietic stem cell transplantation at a single centre.</p><p><strong>RESULTS:</strong> On admission (baseline), the majority of patients presented with a different gut microbial composition in comparison to healthy control children with a significantly lower alpha diversity. A further, marked decrease in alpha diversity was observed immediately post-transplantation and in most microbial diversity, and composition did not return to baseline status while hospitalized. Longitudinal trajectories identified continuous fluctuations in microbial composition, with the dominance of a single taxon in a significant proportion of patients. Using pam clustering, three clusters were observed in the dataset. Cluster 1 was common pre-transplantation, characterized by a higher abundance of <em>Clostridium XIVa</em>, <em>Bacteroides</em> and <em>Lachnospiraceae</em>; cluster 2 and cluster 3 were more common post-transplantation with higher abundance of <em>Streptococcus</em> and <em>Staphylococcus</em> in the former whilst <em>Enterococcus</em>, <em>Enterobacteriaceae</em> and <em>Escherichia</em> predominated in the latter. Cluster 3 was also associated with a higher risk of viraemia. Likewise, further multivariate analysis reveals <em>Enterobacteriaceae</em>, viraemia, use of total parenteral nutrition and various antimicrobials contributing towards cluster 3, <em>Streptococcaceae</em>, <em>Staphylococcaceae</em>, <em>Neisseriaceae</em>, vancomycin and metronidazole contributing towards cluster 2. <em>Lachnospiraceae</em>, <em>Ruminococcaceae</em>, <em>Bifidobacteriaceae</em> and not being on total parenteral nutrition contributed to cluster 1. Untargeted metabolomic analyses revealed changes that paralleled fluctuations in microbiota composition; importantly, low fecal butyrate was associated with higher risk of viraemia.</p><p><strong>CONCLUSIONS:</strong> These findings highlight the frequent shifts and dominations in the gut microbiota of pediatric patients undergoing hematopoietic stem cell transplantation. The study reveals associations between the fecal microbiota, metabolome and viraemia. To identify and explore the potential of microbial biomarkers that may predict risk of complications post-HSCT, larger multi-centre studies investigating longitudinal microbial profiling in pediatric hematopoietic stem cell transplantation are warranted.</p>