RB1 and myelodysplastic syndrome: In murine models, genetic ablation of the retinoic acid receptor gamma (Rar-γ) or retinoblastoma (Rb) genes in BM stromal cells have been reported to promote MPN development [49, 50], whereas inactivation of the microRNA-processing enzyme dicer in immature OSTERIX- (OSX) expressing osteoprogenitors caused myelodysplastic syndrome (MDS) [4].