CD34+ cells from RCMD-RS and RARS patients display a particular expression profile of mitochondria-related genes;17, 20 we observed upregulation of ALAS2 (heme biosynthesis enzyme) and downregulation of ABCB7 (involved in the transport of iron from the mitochondria to the cytoplasm) in SF3B1 mutants compared with wild type and control, in agreement with our previous reports.17, 20SLC25A37, encoding a mitochondrial iron importer, and GLRX5, encoding another mitochondrial protein, were both significantly upregulated in CD34+ cells of SF3B1 mutants compared with wild type and control. This evidence concerns the gene ALAS2 and myelodysplastic syndrome with ring sideroblasts.