By contrast, Sf3b1K700E/+ animals showed a small but significant increase in the number of Gr1+/Mac1+ double-positive bone marrow cells (Supplementary Figure 5b), and in the erythroid compartment there were no differences in the frequency of Ter119+/CD71+ early erythroid cells, but a relative decrease of the more mature Ter119+/CD71low/FSClow population24 (Figure 2b), indicative of impaired terminal erythroid differentiation similar to that observed in human MDS.25 Here, TFRC is linked to myelodysplastic syndrome.