Single-cell roadmap of megakaryocyte development

• Applicant: Dr. Zoltan Nagy
• Subject Area: Hematology, Oncology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 519246588

Megakaryocytes (MKs) are large cells within the bone marrow responsible for the production of blood platelets, which are essential for blood clotting. Platelet transfusions, administered in a variety of medical contexts, are critical for patients at high risk of bleeding. With the current demographic shifts, an increase in platelet shortages is projected, leading to the exploration of in vitro-generated platelets as a potential alternative strategy to donor-derived platelets. However, despite recent advances, MK maturation in vitro remains notably inefficient, and the signalling pathways guiding the development of MK progenitors into fully mature cells remain largely enigmatic. This programme aims to identify central molecular hubs driving MK maturation and platelet biogenesis by building on two major discoveries we made recently. We observed a striking reduction in many transcripts in MKs and an associated maturation defect while investigating transgenic mice with low platelet count deficient in a certain MK-specific protein. These findings suggest that this protein triggers an MK-specific transcriptional programme. Concurrently, by studying platelets from another transgenic mouse strain also exhibiting low platelet count, we found a selective increase in the level of ribosomal proteins. Interestingly, ribosomal proteins are eliminated shortly after platelet biogenesis, suggesting that this signalling protein could be involved in regulating their turnover. This is of significance as there are drugs known to modulate these pathways, which alter platelet count in patients. The key objectives of this programme are to uncover the molecular mechanisms of how these proteins control transcription and influence the elimination of ribosomal proteins. We will utilize newly established single-cell transcriptomics and (phospho-)proteomics technologies, signalling studies and transgenic mice, along with patient samples. We aim to generate CRISPR knockout MKs of potential effector genes and determine their function in MK maturation, transcription, and platelet generation using innovative imaging, and novel in vitro and in vivo assays. The insights gained from these studies will enhance our understanding of MK development and platelet biogenesis. The successful identification of the molecular mechanisms underlying these phenotypes could pave the way for future applications, potentially enabling us to manipulate these processes to generate highly mature MKs in vitro or to adjust platelet count in patients.

• DFG Programme: Independent Junior Research Groups