question: Is Growth factor independence 1b (GFI1B) important for hematopoiesis?
answer: Yes. Gfi-1B is a transcriptional repressor essential for the regulation of erythropoiesis and megakaryopoiesis.  Gfi-1b(-/-) embryonic stem cells fail to contribute to red cells of adult chimeras. Gfi-1b(-/-) embryos exhibit delayed maturation of primitive erythrocytes and subsequently die with failure to produce definitive enucleated erythrocytes.