RNA-seq of mouse myeloid progenitors reveals two independent pathways for monocyte production via GMPs and MDPs

Granulocyte-monocyte progenitors (GMPs) and monocyte-dendritic cell progenitors (MDPs) produce monocytes during homeostasis and in response to increased demand during infection. Both progenitor populations are thought to derive from common myeloid progenitors (CMPs), and a hierarchical relationship (CMP-GMP-MDP-monocyte) is presumed to underlie monocyte differentiation. Here, however, we demonstrate that mouse MDPs arose from CMPs independently of GMPs, and that GMPs and MDPs produced monocytes via similar, but distinct, monocyte-committed progenitors. GMPs and MDPs yielded classical (Ly6Chi) monocytes with gene expression signatures that were defined by their origins and impacted their function. GMPs produced a subset of “neutrophil-like” monocytes, whereas MDPs gave rise to a subset of monocytes that yielded monocyte-derived dendritic cells. GMPs and MDPs were also independently mobilized to produce specific combinations of myeloid cell types following the injection of microbial components. Thus, the balance of GMP and MDP differentiation shapes the myeloid cell repertoire during homeostasis and following infection. Overall design: RNA-seq of myeloid progenitors and Ly6Chi monocytes from mouse bone marrow. 4 progenitor fractions (GMPs, MDPs, GPs and a mixed fraction of MPs + cMoPs) were isolated from the pooled bone marrow of 20 mice. GMPs and MDPs were also cultured in vitro and the monocyte-committed progenitors and Ly6Chi monocytes they produced were also harvested. RNA was extracted from the 4 ex vivo progenitor fractions, and the 4 populations derived in vitro (GMP-derived monocyte progenitors = MP; MDP-derived monocyte progenitors = cMoP; GMP-derived Ly6Chi monocytes = G-mono; MDP-derived Ly6Chi monocytes = M-mono). The whole process was repeated using 20 additional mice to obtain a replicate set of samples.

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Yáñez A, Coetzee SG, Olsson A, Muench DE, Berman BP, Hazelett DJ, Salomonis N, Grimes HL, Goodridge HS