In vivo expression of Epo-R in hematopoietic and mesenchymal cells. (A) In vivo lineage-tracing model to map the expression pattern of the Epo-R. Epo-R-Cre knock-in mice²⁰  were crossed with Rosa26 yellow fluorescent protein (eYFP) reporter mice, resulting in eYFP labeling of cells, which has expressed Epo-R at any time of its development. FACS analysis of eYFP expression in (B) early erythroid progenitors depicting a representative plot (left) and quantification (right), (C) mature erythroid progenitors, and total Ter119⁺ cells showing a representative plot (left) and quantification (right), and representative plots of (D) HSCs, (E) B-cell progenitors, and (F) osteoblastic and endothelial cell fractions.^22,26  Data are presented as mean ± SEM; n = 4.