Project description:In anemia-stressed mice, compensatory RBC production occurs primarily in the spleen. We have compared erythropoiesis across the three models with a multiplexed single cell-RNA sequencing experiment of formalin-fixed spleen cell suspensions of one spherocytosis (Spta), two sickle cell disease (Berk) and one thalassemia (Thal) spleen. After de-multiplexing, batch correction, and Leiden clustering, Ptprc (CD45) negative cells were extracted, and pseudotimes were calculated to establish the erythropoietic differentiation trajectory. Along this trajectory, three cell populations could be delineated representing (1) Kit+Runx3+ hematopoietic stem cells (2) highly proliferative Mki67+Gata1+ Klf1+ Epor+ Tfrc+ early-stage erythropoietic progenitors; and (3) Gypa+ Xpo+ late-stage erythropoietic progenitors with active heme synthesis (Alas2+).
Project description:Dhh negatively regulates multiple stages of erythrocyte differentiation. In Dhh-deficient bone marrow, the common myeloid progenitor (CMP) population was increased, but differentiation from CMP to granulocyte/macrophage progenitor was decreased, and the mature granulocyte population was decreased, compared with wild-type (WT). In contrast, differentiation from CMP to megakaryocyte/erythrocyte progenitor was increased, and the megakaryocyte/erythrocyte progenitor population was increased. In Dhh-deficient spleen and bone marrow, BFU-Es and erythroblast populations were increased compared with WT. During recovery of hematopoiesis after irradiation, and under conditions of stress-induced erythropoiesis, erythrocyte differentiation was accelerated in both spleen and bone marrow of Dhh-deficient mice compared with WT. To investigate possible mechanisms for its regulation of erythropoiesis we carried out RNAsequencing on Facs-sorted erythroblast population II (CD71+Ter119+) cells from Dhh-/-, Dhh+/- and WR mice.
Project description:Extramedullary erythropoiesis is not expected in healthy adult mice, but erythropoietic gene expression was elevated in lineage-depleted spleen cells from cd47−/− mice. Elevated expression of several genes associated with early stages of erythropoiesis was observed in mice lacking CD47 or its signaling ligand thrombospondin-1, consistent with previous evidence that this signaling pathway inhibits expression of multipotent stem cell transcription factors in spleen. In contrast, cells expressing markers of committed erythroid progenitors including erythropoietin receptor, aquaporin-1, glycophorin A, and erythrocyte membrane-associated protein were more abundant in cd47−/− spleens but significantly depleted in thbs1−/− spleens. Single cell transcriptome analysis indicated that loss of CD47 is associated with accumulation and increased proliferation of CD34− committed erythroid progenitors in spleen, consistent with the known function of CD47 to limit turnover of aging erythrocytes. Conversely, loss of thrombospondin-1 delays turnover, which suppresses erythropoiesis in thbs1−/− spleens relative to the basal level in wild type mice.
Project description:Extramedullary erythropoiesis is not expected in healthy adult mice, but erythropoietic gene expression was elevated in lineage-depleted spleen cells from cd47−/− mice. Elevated expression of several genes associated with early stages of erythropoiesis was observed in mice lacking CD47 or its signaling ligand thrombospondin-1, consistent with previous evidence that this signaling pathway inhibits expression of multipotent stem cell transcription factors in spleen. In contrast, cells expressing markers of committed erythroid progenitors including erythropoietin receptor, aquaporin-1, glycophorin A, and erythrocyte membrane-associated protein were more abundant in cd47−/− spleens but significantly depleted in thbs1−/− spleens. Single cell transcriptome analysis indicated that loss of CD47 is associated with accumulation and increased proliferation of CD34− committed erythroid progenitors in spleen, consistent with the known function of CD47 to limit turnover of aging erythrocytes. Conversely, loss of thrombospondin-1 delays turnover, which suppresses erythropoiesis in thbs1−/− spleens relative to the basal level in wild type mice.
Project description:Study was performed to improve understanding of erythropoiesis (EP) induced by acute anemia in Atlantic salmon. Fish was injected with a low dose of hemolytic compound phenylhydrazine (PHZ). Treatment resulted in moderate but significant reduction of hematocrit (Hct) and increased transcription of cardiac erythropoietin (epo) at 2 days post challenge (dpc), and epo receptor (epor) in spleen from 2 to 4 dpc. Oligonucleotide microarrays were used to characterize the events of EP in the spleen. These results were compared to gene expression profiles of untreated mature red blood cells (RBC) in order to search for erythroid-specific genes. Splenic responses suggested a prevalence of protective mechanisms at the first stage, characterized by induced xenobiotic metabolism and responses to oxidative and protein stress. Erythroid-specific regulation was evident at 2 dpc and enhanced by 4 dpc, and gene expression profiles witnessed a rapid establishment of RBC phenotype although Hct levels remained low. A large group of genes showed a strong correlation to globins by expression profiles. In addition to epor this included genes of heme and iron metabolism, scavengers of free radicals and chaperones, channels and transporters, markers of erythrocytes, regulators of proliferation and cell cycle arrest and many genes with unidentified roles in RBC differentiation. Induced EP in spleen was characterized by specific features, such as upregulation of virus-responsive genes and sustained high expression of proapoptotic genes including caspases. Transcriptome changes suggested an association between EP and suppression of several developmental programs including adaptive immune responses. In conclusion, acute hemolysis and resulting anemia rapidly induced EP in the spleen of Atlantic salmon, which showed both common characteristics for all vertebrates as well as fish-specific properties. Atlantic salmon was injected with a single dose of PHZ (6 mg/kg body mass) or saline. Spleen samples for microarray analyses were collected after 2 and 4 days. Additonally, red blood cells (RBC) were compared with spleen
Project description:Study was performed to improve understanding of erythropoiesis (EP) induced by acute anemia in Atlantic salmon. Fish was injected with a low dose of hemolytic compound phenylhydrazine (PHZ). Treatment resulted in moderate but significant reduction of hematocrit (Hct) and increased transcription of cardiac erythropoietin (epo) at 2 days post challenge (dpc), and epo receptor (epor) in spleen from 2 to 4 dpc. Oligonucleotide microarrays were used to characterize the events of EP in the spleen. These results were compared to gene expression profiles of untreated mature red blood cells (RBC) in order to search for erythroid-specific genes. Splenic responses suggested a prevalence of protective mechanisms at the first stage, characterized by induced xenobiotic metabolism and responses to oxidative and protein stress. Erythroid-specific regulation was evident at 2 dpc and enhanced by 4 dpc, and gene expression profiles witnessed a rapid establishment of RBC phenotype although Hct levels remained low. A large group of genes showed a strong correlation to globins by expression profiles. In addition to epor this included genes of heme and iron metabolism, scavengers of free radicals and chaperones, channels and transporters, markers of erythrocytes, regulators of proliferation and cell cycle arrest and many genes with unidentified roles in RBC differentiation. Induced EP in spleen was characterized by specific features, such as upregulation of virus-responsive genes and sustained high expression of proapoptotic genes including caspases. Transcriptome changes suggested an association between EP and suppression of several developmental programs including adaptive immune responses. In conclusion, acute hemolysis and resulting anemia rapidly induced EP in the spleen of Atlantic salmon, which showed both common characteristics for all vertebrates as well as fish-specific properties.
Project description:Acute anemia induces rapid expansion of erythroid precursors and accelerated differentiation to replenish erythrocytes. Paracrine signals – involving cooperation between SCF/c-Kit signaling and other signaling inputs – are required for the activation and function of erythroid precursors in anemia. Our prior work revealed that the Sterile Alpha Motif (SAM) Domain 14 (Samd14) gene is transcriptionally upregulated in a model of acute anemia. Samd14 expression increases the regenerative capacity of the erythroid system and promotes stress-dependent c-Kit signaling. However, the mechanism underlying Samd14’s role in stress erythropoiesis is unknown. We identified a protein-protein interaction between Samd14 and the α- and β heterodimers of the F-actin capping protein (CP) complex. Knockdown of the CP β subunit increased erythroid maturation in ex vivo cultures and decreased colony forming potential of stress erythroid precursors. In a genetic complementation assay for Samd14 activity, our results revealed that the Samd14-CP interaction is a determinant of erythroid precursor cell levels and function. Samd14-CP promotes SCF/c-kit signaling in CD71med spleen erythroid precursors.