Wellington, R. | bioRxiv Science

bioRxiv2024

Multiplexed single cell transcriptomics optimizes mesodermal patterning and hemogenic endothelial output from murine embryonic stem cells

BackgroundEarly patterning of mesodermal precursor populations is a key step of hematopoietic development in the embryo. To better understand this process, we employed sci-Plex, a high-throughput method of measuring multiplexed perturbations at the single-cell level, to evaluate the transcriptional response of mouse embryonic stem cells subjected to a gradient of two key morphogens in early mesoderm/hematopoietic development, Activin and BMP4. Resultssci-Plex revealed varying combinations of Activin and BMP4 temporally influenced mesoderm patterning in vitro and subsequent production of cell types reflecting their in vivo counterparts. We leveraged sci-Plex data to further optimize the generation of intraembryonic-like hemogenic endothelial cells that serve as the precursors of definitive hematopoietic lineages, including hematopoietic stem cells. ConclusionsThis study highlights the utility of sci-Plex to dissect how dose and temporal integration of interacting signal pathways determines cell fates and serves as a resource to analyze cell fate choices in early mesoderm patterning at single cell resolution.

developmental biology↗

bioRxiv2023

Differentiation latency and dormancy signatures define fetal liver HSCs at single cell resolution

Decoding the gene regulatory mechanisms and signaling interactions that orchestrate the self-renewal of hematopoietic stem cells (HSCs) during their expansion in the fetal liver (FL) could unlock novel therapeutic strategies to expand transplantable HSCs, a long-standing challenge. Here, to explore intrinsic and extrinsic regulation of FL-HSC self-renewal at the single cell level, we engineered a culture platform designed to recapitulate the FL endothelial niche, which supports the ex vivo amplification of serially engraftable HSCs. Leveraging this platform in combination with single cell index flow cytometry, live imaging, serial transplantation assays, and single cell RNA-sequencing, we uncovered previously unrecognized heterogeneity within immunophenotypically defined FL-HSCs. Specifically, we demonstrated that differentiation latency, symmetric cell divisions, and transcriptional signatures of biosynthetic dormancy and lipid metabolism are distinguishing properties of rare FL-HSCs capable of serial, long-term multilineage hematopoietic reconstitution. Our findings support a paradigm in which intrinsic programs and extrinsic signals combinatorially facilitate the symmetric self-renewal and expansion of nascent HSCs in the FL niche while delaying their active participation in hematopoiesis. Additionally, our study provides a valuable resource for future investigations into the intrinsic and niche-derived signaling pathways that govern FL-HSC self-renewal.

developmental biology↗