TGF-ß inhibitors stimulate red blood cell production by enhancing self-renewal of BFU-E erythroid progenitors

Erythroid progenitor BFU-Es are so-named based on their ability to generate in methylcellulose culture large colonies of erythroid cells that consist of “bursts” of smaller erythroid colonies derived from the later CFU-E Epo- dependent progenitors. “Early” BFU-E cells forming large BFU-E colonies presumably have higher capacities for self-renewal than do those forming small BFU-E colonies. In order to understand the mechanism underlying this heterogeneity, we conducted single cell transcriptome analysis on BFU-E cells purified from mouse embryos. Our analyses showed that there are two principal subgroups of mouse BFU-E cells and that the type III TGFß receptor (TßRIII) is a potential marker that distinguishes “early” and “late” BFU-Es. Expression of TßRIII is correlated with that of GATA1, a gene encoding an erythroid transcription factor induced during the BFU-E to CFU-E transition. The mouse and human BFU-E sub populations (TßRIII10%lo) expressing the 10% lowest amount of surface TßRIII are indeed enriched for early BFU-Es, and are significantly more responsive to glucocorticoid stimulation, which promotes BFU-E self-renewal, as compared to the total BFU-E population. The TßRIII10%lo BFU-E subpopulation presumably represents earlier BFU-Es with maximal capacity for self-renewal. Consistent with this notion, signaling by the TGFß receptor kinases RI and RII increases during the transition from early (TßRIII10%lo) to late (TßRIII10%hi) BFU-Es and then decreases in CFU-E cells. Blocking TGF-ß signaling by receptor kinase inhibitors increase TßRIII10%lo BFU-E cell self-renewal and increases total erythroblast production, suggesting the use of this type of drug in treating Epo unresponsive anemias. Overall design: Discovery of BFU-E subpopulations

48

Gao X, Lee HY, da Rocha EL, Zhang C, Lu YF, Li D, Feng Y, Ezike J, Elmes RR, Barrasa MI, Cahan P, Li H, Daley GQ, Lodish HF