Function of CEBPα to drive the phagocyte program has been conserved from a unicellular organism. (A) Mouse CEBPα and its homologs from tunicate, sponge, and Capsaspora were transduced into pro-B cells, which were analyzed by flow cytometry 4 days later. (B,E,H-I) pro-B cells (B), MkPs (E), ErPs (H) and DN3 cells (I) were transduced with mouse, tunicate, sponge, or Capsaspora CEBPα and then examined by flow cytometry for the indicated lineage markers. Data are representative of 2 to 4 independent experiments. (C,F) The CD11b⁺ cells generated by transduction with various CEBPα homologs into pro-B cells (C) and MkPs (F) were sorted and their cytology was examined by Wright-Giemsa staining (left). Their phagocytic activity was evaluated by engulfment of pHrodo-green beads (right). (D,G) Phagocytic activities of the generated CD11b⁺ cells from pro-B cells (D) and MkPs (G) was evaluated by flow cytometry. (J) Wright-Giemsa stain of neutrophil-like cells with ring-shaped or multilobulated nuclei generated by transduction with mouse CEBPα into pro-B cells. (K) Frequency of cell types evaluated by cytology with Wright-Giemsa staining. Cells (n = 100) transduced with mouse, tunicate, or sponge CEBPα were examined. (L) Relative expression of neutrophil-associated genes in pro-B cells 2 days after CEBPα transduction. Relative expression levels (day 0 = 1) with 2^−ΔΔCT values normalized with β-actin were shown. Data are mean ± standard error of the mean of 3 replicates. ∗∗P < .01, ∗∗∗P < .001. DN3, double-negative 3; ErPs, erythroid progenitors; MkPs, megakaryocyte progenitors.