title: Disruption of Smad5 gene leads to enhanced proliferation of high-proliferative potential precursors during embryonic hematopoiesis.
abstract: SMAD proteins are downstream signal transducers of the transforming growth factor beta (TGF-beta) superfamily, which serve as pleiotropic regulators in embryonic and adult hematopoiesis. SMAD5, initially considered to mediate bone morphogenetic proteins (BMPs) signals, can also transduce the inhibitory signal of TGF-beta1 on proliferation of hematopoietic progenitors derived from human bone marrow. To define its specific role in regulation of primitive multipotential progenitors during early embryonic hematopoiesis, we examined Smad5(-/-) yolk sacs at E9.0 to 9.5 and detected an elevated number of high-proliferative potential colony-forming cells (HPP-CFCs) with enhanced replating potential. To exclude the possible influence of microenvironmental deficit on embryonic hematopoiesis in vivo, we performed in vitro embryonic stem (ES) cell differentiation assay and investigated the HPP-CFCs in particular. Smad5(-/-) embryoid bodies (EBs) contained an elevated number of blast colony-forming cells (BL-CFCs), the in vitro equivalent of hemangioblast, in contrast to reduced proliferation of primitive erythroid precursors (Ery/Ps) within the mutant EBs. More importantly, profoundly increased frequency of HPP-CFCs, featured with a gene-dosage effect, was detected within day 6 Smad5(-/-) EBs compared with the wild type. In addition, Smad5(-/-) HPP-CFCs displayed enhanced self-renewal capacity and decreased sensitivity to TGF-beta1 inhibition, suggesting a critical role of Smad5 in TGF-beta1 regulation of embryonic HPP-CFCs. Consistently, reverse transcription-polymerase chain reaction analysis detected alterations of the transcription factors including GATA-2 and AML1 as well as cytokine receptors in Smad5(-/-) HPP-CFC colonies. Together, these data define an important function of SMAD5 in negative regulation of high-proliferative potential precursors during embryonic hematopoiesis.
authors.affiliation: Department of Cell Biology, Institute of Basic Medical Sciences, Beijing, Peoples' Republic of China.
authors.forename: Bing
authors.initials: B
authors.lastname: Liu
authors.forename: Yanxun
authors.initials: Y
authors.lastname: Sun
authors.forename: Feizi
authors.initials: F
authors.lastname: Jiang
authors.forename: Shuangxi
authors.initials: S
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.forename: Yu
authors.initials: Y
authors.lastname: Lan
authors.forename: Xiao
authors.initials: X
authors.lastname: Yang
authors.forename: Ning
authors.initials: N
authors.lastname: Mao
mesh_terms: D000818:Animals; D002455:Cell Division; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004622:Embryo, Mammalian / Q000166:cytology; D015672:Erythroid Precursor Cells / Q000166:cytology; D004921:Erythropoietin / Q000494:pharmacology; D018628:Gene Dosage; D005914:Globins / Q000037:antagonists & inhibitors; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D051379:Mice; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D051902:Smad5 Protein; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D015017:Yolk Sac / Q000166:cytology
chemical_list: D004268:DNA-Binding Proteins; D010750:Phosphoproteins; D051902:Smad5 Protein; C497798:Smad5 protein, mouse; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D004921:Erythropoietin; D005914:Globins