The alterations in hematopoiesis observed in patients with MDS have previously been shown to result from dysfunctional HSCs.31,32,38 To determine whether this was also true of the altered hematopoiesis observed in Rpl22-deficient mice, we performed competitive bone marrow transplantation assays using allotype-marked (CD45.2) Rpl22−/− or Rpl22+/+ HSCs combined with whole bone marrow competitor (WBM; CD45.1). This evidence concerns the gene RPL22 and myelodysplastic syndrome.