3046 – DECIPHERING THE CONNECTIONS BETWEEN CELL STATE AND CELL FATE IN HUMAN FETAL HEMATOPOIESIS

• Published in: Experimental hematology 2022, Vol.111, p.S67-S68
• Main Authors: Chabra, Shirom, Haltalli, Myriam, Calderbank, Emily, Wilson, Nicola, Kucinski, Iwo, Haniffa, Muzlifah, Laurenti, Elisa, Göttgens, Bertie
• Format: Article
• Language: English
• ISSN: 0301-472X; 1873-2399
• DOI: 10.1016/j.exphem.2022.07.102

The blood and immune systems arise from hematopoietic stem cells during hematopoiesis. Underlying this process is a carefully coordinated series of cell fate decisions which enables the output of mature lineages to be fine-tuned to match changing demands on blood production. To explore the molecular mechanisms underlying fate determination during human hematopoiesis we adapted the LARRY scRNA-seq barcoding technique (Weinreb et al., 2020, Science) to connect initial cell state with eventual cell fate. For this study, Hematopoietic Stem and Progenitor Cells (HSPCs) were isolated from human fetal liver, transduced with a lentiviral vector expressing the barcode library and cultured in vitro to promote pan-differentiation into mature blood cells. To track clonal progression along differentiation, samples of the culture were taken at early, intermediate, and late timepoints for scRNA-seq. Alongside in vitro experiments, barcoded cells were transplanted into humanized mice to allow differentiation in vivo. We have established pipelines to link scRNA-seq measurements to clonal barcodes with high fidelity. This has enabled tracking >230 clones in real time as they traverse the transcriptional landscape from HSPCs towards differentiated progeny. We are extracting three types of clonal relationships which provide key information on: (i) the symmetry of early fetal HSPC divisions; (ii) how differences in initial cell state determine fate; (iii) how transcriptional signatures change during differentiation; and (iv) the phylogenetic relationships between different cell fates. This work will have implications beyond life in utero, as it will provide a healthy blueprint to contrast and understand perturbed hematopoiesis (such as in leukemias, primary immunodeficiencies and anemias), and its insights may pave the way for novel fate manipulation methods for regenerative medicine.