Project description:Myelodysplastic syndromes (MDS) with ring sideroblasts are hematopoietic stem celldisorders with erythroid dysplasia and mutations in the SF3B1 splicing factor gene. MDS patientswith SF3B1 mutations often accumulate excessive tissue iron, even in the absence oftransfusions, but the mechanisms that are responsible for their parenchymal iron overload areunknown. Body iron content, tissue distribution, and the supply of iron for erythropoiesis arecontrolled by the hormone hepcidin, which is regulated by erythroblasts through secretion of theerythroid hormone erythroferrone (ERFE). Here, we identified an alternative ERFE transcript inMDS patients with the SF3B1 mutation. Induction of this ERFE transcript in primary SF3B1-mutated bone marrow erythroblasts generated a variant protein that maintained the capacity tosuppress hepcidin transcription. Plasma concentrations of ERFE were higher in MDS patientswith a SF3B1 gene mutation than in patients with SF3B1 wild-type MDS. Thus, hepcidinsuppression by a variant erythroferrone is likely responsible for the increased iron loading inpatients with SF3B1-mutated MDS, suggesting that ERFE could be targeted to prevent ironmediated toxicity. The expression of the variant ERFE transcript that was restricted to SF3B1-mutated erythroblasts decreased in lenalidomide-responsive anemic patients, identifying variantERFE as a specific biomarker of clonal erythropoiesis.
Project description:The splicing factor SF3B1 is the most commonly mutated gene in the myelodysplastic syndromes (MDS), particularly in patients with refractory anemia with ring sideroblasts (RARS). MDS is a disorder of the hematopoietic stem cell and we thus studied the transcriptome of CD34+ cells from MDS patients with SF3B1 mutations using RNA-sequencing. Genes significantly differentially expressed at the transcript and/or exon level in SF3B1 mutant compared to wildtype cases include genes involved in MDS pathogenesis (ASXL1, CBL), iron homeostasis and mitochondrial metabolism (ALAS2, ABCB7, SLC25A37) and RNA splicing/processing (PRPF8, HNRNPD). Many genes regulated by a DNA damage-induced BRCA1-BCLAF1-SF3B1 protein complex showed differential expression/splicing in SF3B1 mutant cases. Our data indicate that SF3B1 plays a critical role in MDS by affecting the expression and splicing of genes involved in specific cellular processes/pathways, many of which are relevant to the known RARS pathophysiology, suggesting a causal link. RNA-Seq was performed to compare the transcriptome of bone marrow CD34+ cells from eight MDS patients with SF3B1 mutation, four MDS patients with no known splicing mutation and five healthy controls.
Project description:Recent studies have shown that multiple components of the mRNA splicing machinery are mutated in myelodysplastic syndrome (MDS) patients. SF3B1 is frequently mutated in refractory anemia with ringed sideroblasts (RARS)-MDS patients, however, the pathophysiological role of SF3B1 mutations has not been elucidated yet. In this study, we examined the function of Sf3b1 in murine hematopoiesis. Since Sf3b1 null homozygotes died during preimplantation development, in this study, we utilized Sf3b1 heterozygous mice showing grossly normal growth. We harvested bone marrow stem/progenitor (LSK) cells from wild type (WT) and Sf3b1+/- mice (n=4) at 20 weeks old. In addition, to exclude the possibility of indirect effect from bone marrow environment, we transplanted total bone marrow cells from WT or Sf3b1+/- (CD45.2+) mice into lethally irradiated CD45.1+ recipient mice, and then harvested (CD45.2+) LSK cells from the recipients (n=5) at 9 months-post transplantation.
Project description:Recurrent mutations in splicing factors, in particular the splicing factor 3B subunit 1 (SF3B1), are commonly seen in lower-risk (LR) myelodysplastic neoplasms (MDS) and result in various aberrantly spliced transcripts. The cell type-specific changes and their contribution to immune dysregulation in MDS remain vaguely understood. In this study, we performed RNA sequencing on classical monocytes isolated from patients with an isolated SF3B1K700E hotspot mutation. Our analysis revealed downregulated expression of genes involved in inflammatory cytokine signaling, as well as differential mRNA splicing of several genes involved in the regulation of the defense response and cytokine signaling, mRNA metabolism, apoptotic signaling, and mitotic cell cycle.
Project description:SF3B1 mutations, which occur in 20% of patients with myelodysplastic syndromes (MDS), are the hallmarks of a specific MDS subtype, MDS with ringed sideroblasts (MDS-RS), which is characterized by the accumulation of erythroid precursors in the bone marrow.
Project description:The aim of this experiment was to compare the transcriptomes of SF3B1 mutant and wildtype isogenic cells at the whole cell, nuclear and cytoplasmic levels. Mutations in SF3B1 are often found in the malignant cells of patients suffering from myelodysplastic syndromes and more rarely in other cancer types. The human K-562 leukaemia cell line was modified using CRISPR/Cas9 to integrate an A>G mutation in the SF3B1 consensus coding sequence to change the 700th codon from lysine to glutamic acid (K700E). RNA-Seq was ribo-depleted and randomly primed using SMARTer® Stranded Total RNA Sample Prep Kit. Sequencing used an Illumina NextSeq.
Project description:Recent studies have shown that multiple components of the mRNA splicing machinery are mutated in myelodysplastic syndrome (MDS) patients. SF3B1 is frequently mutated in refractory anemia with ringed sideroblasts (RARS)-MDS patients, however, the pathophysiological role of SF3B1 mutations has not been elucidated yet. In this study, we examined the function of Sf3b1 in murine hematopoiesis.
Project description:The splicing factor SF3B1 is the most commonly mutated gene in the myelodysplastic syndromes (MDS), particularly in patients with refractory anemia with ring sideroblasts (RARS). MDS is a disorder of the hematopoietic stem cell and we thus studied the transcriptome of CD34+ cells from MDS patients with SF3B1 mutations using RNA-sequencing. Genes significantly differentially expressed at the transcript and/or exon level in SF3B1 mutant compared to wildtype cases include genes involved in MDS pathogenesis (ASXL1, CBL), iron homeostasis and mitochondrial metabolism (ALAS2, ABCB7, SLC25A37) and RNA splicing/processing (PRPF8, HNRNPD). Many genes regulated by a DNA damage-induced BRCA1-BCLAF1-SF3B1 protein complex showed differential expression/splicing in SF3B1 mutant cases. Our data indicate that SF3B1 plays a critical role in MDS by affecting the expression and splicing of genes involved in specific cellular processes/pathways, many of which are relevant to the known RARS pathophysiology, suggesting a causal link.