In conclusion, reduced expression of PGC1β results in perturbed formation of early erythroid progenitors and impaired terminal erythroid differentiation with an accumulation of polychromatic erythroblasts and a subsequent reduction of more mature erythroblasts, a phenotype that is reminiscent of the refractory anemia seen in many MDS patients27 and the MDS-like anemia we have previously reported on in mouse21. The gene discussed is PPARGC1B; the disease is myelodysplastic syndrome.