https://orcid.org/0000-0001-5503-2809
Key Points
Distinct, induced Ras pathway lesions share shunting to myeloid lineages but have opposing effects on hematopoietic stem cells.
Strong oncogenic Ras signals are incompatible with a metabolically quiescent state of hematopoietic stem- and progenitor- cells.
Aberrantly elevated Ras signals, triggered by various distinct genetic mutations, are frequent features in myeloid leukemias. Normal hematopoiesis requires perpetual and balanced production of different blood cell lineages by multipotent hematopoietic stem cells (HSC). Stem- and progenitor- cells combine dormancy with proliferative drive and require finely tuned metabolism and protein translation rates. Due to the scarcity of stem cells, it has remained largely unknown how aberrantly elevated Ras signals may impact frequency, lineage potential, and quiescent metabolism in rare HSC. Using single cell proteomics and computational analyses, we characterized the effects of induced oncogenic mutant KRasG12D or overexpression of the Ras activator RasGRP1, compared to normal native hematopoiesis. The two Ras pathway lesions drive shared profound skewing towards and expansion of mature myeloid cells. The resolution of CyTOF unmasked opposing patterns for the HSC- and progenitor- compartments: Overexpression of RasGRP1 induced expansion of both subsets, whereas KRASG12D resulted in depletion. By combining spectral flow with SCENITHÔ, a method to quantitate protein translation as a proxy for metabolic state, we first corroborated that immature cells display low metabolic SCENITHÔ rates. Both RasGRP1 and KRASG12D drive elevated, mean SCENITHÔ signals in immature hematopoietic cells. However, RasGRP1-overexpressing stem cells retain a metabolically quiescent cell-fraction, whereas this fraction is incompatible with KRASG12D. Our temporal proteomics and metabolomics datasets provide mechanistic insights into altered hematopoiesis at single cell resolution and support the idea that the exact identity and duration of signals from Ras lesions has profound impacts on stem cell maintenance and lineage-potential.
