One possible explanation for the lack of erythropoietic defects in Sf3b1heterozygous mice could be due to the fact that haploinsufficiency does not manifest an erythroid phenotype in mice similar to the reported for RPS19 for Diamond-Blackfan anemia [56] and for Sec23B for congenital dyserythropoietic anemia type II [57]. The gene discussed is RPS19; the disease is congenital dyserythropoietic anemia type 2.