Defining the molecular basis controlling hematopoietic stem cell symmetric and asymmetric divisions -supplement

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PROJECT SUMMARY AND ABSTRACT Hematopoietic stem cells (HSCs) maintain blood homeostasis through a delicate balance in fate choices of self-renewal and commitment to differentiation. An imbalance in HSC fate choices is the key contributor to hematologic diseases that affect millions of people. HSC fate choices is maintained by coordinated symmetric self-renewal, symmetric commitment and asymmetric divisions. Thus, understanding the control of HSC division choices holds therapeutic potential for hematopoietic diseases. However, our knowledge on the control of HSC divisions is still lacking. Here, I aim to fill the gap by implementing novel systems and high-throughput assays to interrogate HSC fate choices. We recently revealed a unique role of m6A RNA methylation that is essential for HSC symmetric commitment, the division choice that is critical for the rapid replenishment of mature blood cells upon stress. Hence, I propose to leverage the m6A deficient HSCs as a novel system to elucidate the m6A-associated molecular programs in controlling HSC symmetric commitment. To uncover novel regulators in HSC fate choices, I aim to define the role of the understudied RBP NYNRIN, which is a stemness factor identified from my preliminary data and our recent AML-iPSC study, in controlling HSC divisions. I also aim to implement FATE-seq, a novel method involves HSC barcoding followed by in vitro division and single cell RNAseq that allows for a global assessment of HSC divisions. FATE-seq as an orthogonal system will identify novel regulators of HSC fate choices. The Specific Aims are: (1): Characterize the HSC-like intermediate state controlled by m6A RNA methylation. (2): Determine the molecular programs driven by m6A RNA methylation in controlling HSC symmetric commitment. (3): Uncover novel regulators in HSC symmetric and asymmetric fate decisions. Success of this work will define the novel regulators of HSC fate control and provide novel therapeutic opportunities for hematological diseases and stem cell expansion. Dr. Hanzhi Luo is currently a postdoc fellow in the Molecular Pharmacology program at the Memorial Sloan Kettering Cancer Center. Her initial achievements include uncovering m6A's role in HSC symmetric commitment, as well as revealing the RUNX1 dependency in leukemia stem cells with the AML-iPSC model. Both studies were recently published in Cell Reports. Her long-term goal is to establish a research team with an emphasis on molecular mechanisms of HSC fate choices with a strong commitment to translate basic sdiscoveries into the clinic. The proposed research will provide new training for Dr. Luo in hematopoiesis and RNA regulators. This work will be performed at the MSKCC, an exciting research environment with cutting- edge facilities. Dr. Luo will be mentored by Dr. Michael Kharas, a leading expert in studying RNA regulators in normal and malignant stem cells, and a dedicated supporter for young trainees. Together, this career development plan will help Dr. Luo establish her independent research lab at a research-oriented academic institute and become a leader in the field of hematopoiesis.