Distinct, strict requirements for Gfi-1b in adult bone marrow red cell and platelet generation.
The zinc finger transcriptional repressor Gfi-1b is essential for erythroid and megakaryocytic development in the embryo. Its roles in the maintenance of bone marrow erythropoiesis and thrombopoiesis have not been defined. We investigated Gfi-1b's adult functions using a loxP-flanked Gfi-1b allele in combination with a novel doxycycline-inducible Cre transgene that efficiently mediates recombination in the bone marrow. We reveal strict, lineage-intrinsic requirements for continuous adult Gfi-1b expression at two distinct critical stages of erythropoiesis and megakaryopoiesis. Induced disruption of Gfi-1b was lethal within 3 wk with severely reduced hemoglobin levels and platelet counts. The erythroid lineage was arrested early in bipotential progenitors, which did not give rise to mature erythroid cells in vitro or in vivo. Yet Gfi-1b(-/-) progenitors had initiated the erythroid program as they expressed many lineage-restricted genes, including Klf1/Eklf and Erythropoietin receptor. In contrast, the megakaryocytic lineage developed beyond the progenitor stage in Gfi-1b's absence and was arrested at the promegakaryocyte stage, after nuclear polyploidization, but before cytoplasmic maturation. Genome-wide analyses revealed that Gfi-1b directly regulates a wide spectrum of megakaryocytic and erythroid genes, predominantly repressing their expression. Together our study establishes Gfi-1b as a master transcriptional repressor of adult erythropoiesis and thrombopoiesis.
Cancer Center, 2 Center for Regenerative Medicine, and 3 Department of Pathology, Massachusetts General Hospital, 4 Harvard Medical School, Boston, MA 02114.
Adlen
A
Foudi
Daniel J
DJ
Kramer
Jinzhong
J
Qin
Denise
D
Ye
Anna-Sophie
AS
Behlich
Scott
S
Mordecai
Frederic I
FI
Preffer
Arnaud
A
Amzallag
Sridhar
S
Ramaswamy
Konrad
K
Hochedlinger
Stuart H
SH
Orkin
Hanno
H
Hock
D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D001853:Bone Marrow / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D053595:Embryonic Stem Cells / Q000378:metabolism; D004912:Erythrocytes / Q000502:physiology*; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000235:genetics*; D005822:Genetic Vectors; D006410:Hematopoiesis / Q000502:physiology*; D053208:Kaplan-Meier Estimate; D051379:Mice; D008822:Mice, Transgenic; D046228:Microarray Analysis; D008856:Microscopy, Fluorescence; D016296:Mutagenesis; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
D017931:DNA Primers; C486395:Gfi1b protein, mouse; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins