Role of mechanometabolism in hematopoietic stem cell specification

The mechanical force generated by blood flow stimulates emergence of the first hematopoietic stem cells (HSCs) in the embryo that are critical for producing the adult blood system. Fluid force drives transition of HSC precursors from an endothelial to hematopoietic identity. Here, we provide the source data for our study exploring the molecular regulation of this fate switch. We identify a role for shear stress in driving the adaptation of mitochondrial composition, ultrastructure, and function, which we show are essential for hematopoietic fate specification and engraftment potential. Data in support of characterization of Ncx1 cardiac mutants and ex vivo shear stress cultures are supplied for all graphs in our study. Briefly, we show that shear stress remodels mitochondria by promoting mitochondrial gene transcription and protein synthesis. Laminar fluid flow selectively initiates translation of 5’terminal polypyrimidine (5’TOP) motif-containing transcripts, which commonly encode ribosome and translation machinery. The metabolic reprogramming induced by flow depends upon mTOR activation and is blocked when ribosome activity or mTOR is inhibited. Conversely, chemical activation of mTOR mimics the effects of fluid shear stress on mitochondria and blood reconstituting potential. Further, we demonstrate that pharmacological activation of mTOR can also partially rescue hematopoiesis in heartbeat mutants in utero. These data reveal that mechanometabolism is a physiologically relevant determinant of hematopoietic fate that could be leveraged for improved engineering of HSCs for disease modeling and treatment.

Methods
The source data provided are derived from a comprehensive collection of methods for analysis of gene expression, hematopoietic and endothelial cell type classification, mitochondrial and bioenergetic features, protein synthesis and regulatory sequences that dictate translation of specific mRNA transcripts, hematopoietic progenitor and stem cell function, intracellular signaling pathways, and tissue concentration of drugs in the embryo following in utero administration to mothers. Detailed methods are provided in the published work associated with this study.