title: The secreted lymphangiogenic factor CCBE1 is essential for fetal liver erythropoiesis.
abstract: The secreted protein CCBE1 is required for lymphatic vessel growth in fish and mice, and mutations in the CCBE1 gene cause Hennekam syndrome, a primary human lymphedema. Here we show that loss of CCBE1 also confers severe anemia in midgestation mouse embryos due to defective definitive erythropoiesis. Fetal liver erythroid precursors of Ccbe1 null mice exhibit reduced proliferation and increased apoptosis. Colony-forming assays and hematopoietic reconstitution studies suggest that CCBE1 promotes fetal liver erythropoiesis cell nonautonomously. Consistent with these findings, Ccbe1(lacZ) reporter expression is not detected in hematopoietic cells and conditional deletion of Ccbe1 in hematopoietic cells does not confer anemia. The expression of the erythropoietic factors erythropoietin and stem cell factor is preserved in CCBE1 null embryos, but erythroblastic island (EBI) formation is reduced due to abnormal macrophage function. In contrast to the profound effects on fetal liver erythropoiesis, postnatal deletion of Ccbe1 does not confer anemia, even under conditions of erythropoietic stress, and EBI formation is normal in the bone marrow of adult CCBE1 knockout mice. Our findings reveal that CCBE1 plays an essential role in regulating the fetal liver erythropoietic environment and suggest that EBI formation is regulated differently in the fetal liver and bone marrow.
authors: Department of Medicine and Cardiovascular Institute, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors: Zhiying
authors: Z
authors: Zou
authors: David R
authors: DR
authors: Enis
authors: Hung
authors: H
authors: Bui
authors: Eugene
authors: E
authors: Khandros
authors: Vinayak
authors: V
authors: Kumar
authors: Zoltan
authors: Z
authors: Jakus
authors: Christopher
authors: C
authors: Thom
authors: Yiqing
authors: Y
authors: Yang
authors: Veerpal
authors: V
authors: Dhillon
authors: Mei
authors: M
authors: Chen
authors: Minmin
authors: M
authors: Lu
authors: Mitchell J
authors: MJ
authors: Weiss
authors: Mark L
authors: ML
authors: Kahn
mesh_terms: D000740:Anemia / Q000196:embryology* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000818:Animals; D001853:Bone Marrow / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D020964:Embryo Loss / Q000235:genetics; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D004900:Erythroblasts / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D004920:Erythropoiesis; D004921:Erythropoietin / Q000235:genetics / Q000378:metabolism; D005333:Fetus / Q000378:metabolism* / Q000473:pathology; D017353:Gene Deletion; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008208:Lymphatic System / Q000196:embryology; D051379:Mice; D019089:Stem Cell Factor / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; C572375:Ccbe1 protein, mouse; D019089:Stem Cell Factor; D025521:Tumor Suppressor Proteins; D004921:Erythropoietin