Project description:TRAF-interacting protein with forkhead-associated domain B (TIFAB) is a haploinsufficient gene in del(5q) Myelodysplastic syndrome (MDS). Hematopoietic-specific deletion of Tifab results in progressive bone marrow (BM) and blood defects, including skewed hematopoietic stem/progenitor cells (HSPC) proportions, altered myeloid differentiation, and progressive cytopenia. A subset of mice transplanted with Tifab knockout (KO) hematopoietic cells develop a bone marrow failure (BMF)-like disease with neutrophil dysplasia and cytopenia. In competitive transplants, Tifab KO HSPC are out-competed by wild-type (WT) cells, suggesting a cell-intrinsic HSPC defect. Gene expression analysis of Tifab KO HSPC identified dysregulation of immune-related signatures, and hypersensitivity to Toll-like receptor 4 (TLR4) stimulation. TIFAB also forms a complex with TRAF6, a mediator of immune signaling, and reduces TRAF6 protein stability by a lysosome-dependent mechanism. In contrast, TIFAB loss increases TRAF6 protein and the dynamic range of TLR4 signaling in HSPC, contributing to ineffective hematopoiesis. Moreover, combined deletion of TIFAB and miR-146a, two genes associated with del(5q) MDS/AML, results in a cooperative increase in TRAF6 expression and hematopoietic dysfunction in vivo. Re-expression of TIFAB in human del(5q) leukemic cells results in attenuated TLR4 signaling and reduced cell viability. These findings underscore the importance of efficient regulation of innate immune/TRAF6 signaling within HSPC by TIFAB, and its cooperation with miR-146a as it relates to the pathogenesis of hematopoietic malignancies, such as del(5q) MDS/AML.
Project description:TRAF-interacting protein with forkhead-associated domain B (TIFAB) is a haploinsufficient gene in del(5q) Myelodysplastic syndrome (MDS). Hematopoietic-specific deletion of Tifab results in progressive bone marrow (BM) and blood defects, including skewed hematopoietic stem/progenitor cells (HSPC) proportions, altered myeloid differentiation, and progressive cytopenia. A subset of mice transplanted with Tifab knockout (KO) hematopoietic cells develop a bone marrow failure (BMF)-like disease with neutrophil dysplasia and cytopenia. In competitive transplants, Tifab KO HSPC are out-competed by wild-type (WT) cells, suggesting a cell-intrinsic HSPC defect. Gene expression analysis of Tifab KO HSPC identified dysregulation of immune-related signatures, and hypersensitivity to Toll-like receptor 4 (TLR4) stimulation. TIFAB also forms a complex with TRAF6, a mediator of immune signaling, and reduces TRAF6 protein stability by a lysosome-dependent mechanism. In contrast, TIFAB loss increases TRAF6 protein and the dynamic range of TLR4 signaling in HSPC, contributing to ineffective hematopoiesis. Moreover, combined deletion of TIFAB and miR-146a, two genes associated with del(5q) MDS/AML, results in a cooperative increase in TRAF6 expression and hematopoietic dysfunction in vivo. Re-expression of TIFAB in human del(5q) leukemic cells results in attenuated TLR4 signaling and reduced cell viability. These findings underscore the importance of efficient regulation of innate immune/TRAF6 signaling within HSPC by TIFAB, and its cooperation with miR-146a as it relates to the pathogenesis of hematopoietic malignancies, such as del(5q) MDS/AML. We performed an expression analysis on sorted lineage-Sca1+cKit+ (LSK) isolated from bone marrow (BM) of 3 month old mice transplanted with Tifab+/+ (WT) or Tifab-/- (KO) BM cells (n = 3 mice/group). We selected this time point to capture the gene expression profile of Tifab-/- LSK after engraftment but prior to overt hematopoietic failure. Total RNA was extracted, purified, reverse transcribed, labeled, and hybridized onto the GeneChip MoGene 2.0 ST Array (Affymetrix). Comparison comprises mRNA expression profile of Tifab+/+ LSK vs. Tifab-/- LSK.
Project description:Chromosome 5q deletions (del(5q)) are common in high-risk (HR) Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML); however, the gene regulatory networks that sustain these aggressive diseases are unknown. Reduced miR-146a expression in del(5q) HR-MDS/AML and miR-146a-/- hematopoietic stem/progenitor cells (HSPC) results in TRAF6/NF-κΒ activation. Increased survival and proliferation of HSPC from miR-146alow HR-MDS/AML is sustained by a neighboring haploid gene, SQSTM1 (p62), expressed from the intact 5q allele. Overexpression of p62 from the intact allele occurs through NF-κB-dependent feedforward signaling mediated by miR-146a deficiency. p62 is necessary for TRAF6-mediated NF-κB signaling, as disrupting the p62-TRAF6 signaling complex results in cell cycle arrest and apoptosis of MDS/AML cells. Thus, del(5q) HR-MDS/AML employs an intrachromosomal gene network involving loss of miR-146a and haploid overexpression of p62 via NF-κB to sustain TRAF6/NF-κB signaling for cell survival and proliferation. Interfering with the p62-TRAF6 signaling complex represents a therapeutic option in miR-146a-deficient and aggressive del(5q) MDS/AML.
Project description:Chromosome 5q deletions (del(5q)) are common in high-risk (HR) Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML); however, the gene regulatory networks that sustain these aggressive diseases are unknown. Reduced miR-146a expression in del(5q) HR-MDS/AML and miR-146a-/- hematopoietic stem/progenitor cells (HSPC) results in TRAF6/NF-M-NM-:M-NM-^R activation. Increased survival and proliferation of HSPC from miR-146alow HR-MDS/AML is sustained by a neighboring haploid gene, SQSTM1 (p62), expressed from the intact 5q allele. Overexpression of p62 from the intact allele occurs through NF-M-NM-:B-dependent feedforward signaling mediated by miR-146a deficiency. p62 is necessary for TRAF6-mediated NF-M-NM-:B signaling, as disrupting the p62-TRAF6 signaling complex results in cell cycle arrest and apoptosis of MDS/AML cells. Thus, del(5q) HR-MDS/AML employs an intrachromosomal gene network involving loss of miR-146a and haploid overexpression of p62 via NF-M-NM-:B to sustain TRAF6/NF-M-NM-:B signaling for cell survival and proliferation. Interfering with the p62-TRAF6 signaling complex represents a therapeutic option in miR-146a-deficient and aggressive del(5q) MDS/AML. Four del(5q) MDS/AML patients with low miR-146a expression (5284, 8839, 8285, 4233) and 5 with high miR-146a expression (7957, 5534, 4688, 4982, 8412) were selected for microarray assay. RNA was reverse transcribed and labeled, and hybridized onto the GeneChip Human Gene 1.0 ST Array. A total of nine samples were included, and two groups are assigned based on miR-146a expression. Comparison comprises mRNA expression profile of low miR-146a group v.s. high miR-146a group.
Project description:Interstitial deletion of a single copy of chromosome 5q is the most frequent cytogenetic alteration in Myelodysplastic Syndromes (MDS), which results in reduced dosage of numerous genes. Furthermore, the extent of the 5q deletion determines disease severity, suggesting cooperation between deleted genes in the proximal and distal regions of del(5q). Although the contribution of individual genes to the pathogenesis of del(5q) MDS has been investigated, less is known about the epistatic interactions and/or cooperation between neighboring deleted genes. Deletion of TRAF-interacting protein with forkhead-associated domain B (TIFAB) and miR-146a, two haploinsufficient genes in del(5q) MDS, has been previously reported to activate the Toll-like receptor (TLR) signaling cascade in hematopoietic stem/progenitor cells (HSPC) by increasing TRAF6 protein stability and mRNA translation, respectively. To investigate the epistasis of TIFAB and miR-146a, we generated a mouse model in which Tifab and miR-146a were simultaneously deleted (Tifab-/-;miR-146a-/-, dKO). Herein, we report that combined hematopoietic-specific deletion of Tifab and miR-146a results in more rapid and severe cytopenia, and progression to a fatal bone marrow (BM) failure-like disease as compared to Tifab- or miR-146adeficiency alone. HSPC from Tifab-/-, miR-146a-/-, and dKO mice exhibit enrichment of gene 69 regulatory networks associated with innate immune signaling. Moreover, a subset of the differentially expressed genes is controlled synergistically following deletion of Tifab and miR-146a. Notably, nearly half of these defined synergy response genes identified in the mouse models were aberrantly expressed in del(5q) MDS HSPC when TIFAB (5q31) and miR-146a (5q33.3) were both deleted. Thus, synergistic control of gene expression following deletion of epistatic haploinsufficient genes in del(5q) MDS may be an underlying mechanism of the diseased state.
Project description:While del(5q) MDS patients comprise a well-defined hematological subgroup, the molecular basis underlying its origin and the reason behind the relapse to lenalidomide remains unknown. Using scRNAseq on CD34+ progenitor cells from patients with del(5q) MDS we were able to identify cells harboring the deletion, enabling us to deeply characterize the transcriptional impact of this genetic insult on disease pathogenesis and treatment response. We found, across all patients, an enrichment of del(5q) cells in GMP and megakaryocyte-erythroid progenitors not described to date. Interestingly, both del(5q) and non-del(5q) cells presented similar transcriptional lesions when compared to progenitors from healthy individuals, indicating that all cells, and not only those harboring the deletion, are altered in these patients and may contribute to aberrant hematopoietic differentiation. However, GRN analysis revealed a group of regulons with aberrant activity in del(5q) cells that could be responsible for triggering altered hematopoiesis, pointing to a more prominent role of these cells in the phenotype of these patients. An analysis of del(5q) MDS patients achieving hematological response upon lenalidomide treatment showed that the drug reverted several transcriptional alterations in both del(5q) and non-del(5q) cells, but other lesions remained, which may be responsible for potential future relapses. Moreover, lack of hematological response was associated with the inability of lenalidomide to reverse transcriptional alterations. Collectively, this study provides a deep characterization of del(5q) and non-del(5q) cells at single-cell resolution, revealing previously unknown transcriptional alterations that could contribute to disease pathogenesis, or lack of responsiveness to lenalidomide.
Project description:Despite the high response rates of individuals with myelodysplastic syndrome (MDS) with deletion of chromosome 5q (del(5q)) to treatment with lenalidomide (LEN) and the recent identification of cereblon (CRBN) as the molecular target of LEN, the cellular mechanism by which LEN eliminates MDS clones remains elusive. Here we performed an RNA interference screen to delineate gene regulatory networks that mediate LEN responsiveness in an MDS cell line, MDSL. We identified GPR68, which encodes a G-protein-coupled receptor that has been implicated in calcium metabolism, as the top candidate gene for modulating sensitivity to LEN. LEN induced GPR68 expression via IKAROS family zinc finger 1 (IKZF1), resulting in increased cytosolic calcium levels and activation of a calcium-dependent calpain, CAPN1, which were requisite steps for induction of apoptosis in MDS cells and in acute myeloid leukemia (AML) cells. In contrast, deletion of GPR68 or inhibition of calcium and calpain activation suppressed LEN-induced cytotoxicity. Moreover, expression of calpastatin (CAST), an endogenous CAPN1 inhibitor that is encoded by a gene (CAST) deleted in del(5q) MDS, correlated with LEN responsiveness in patients with del(5q) MDS. Depletion of CAST restored responsiveness of LEN-resistant non-del(5q) MDS cells and AML cells, providing an explanation for the superior responses of patients with del(5q) MDS to LEN treatment. Our study describes a cellular mechanism by which LEN, acting through CRBN and IKZF1, has cytotoxic effects in MDS and AML that depend on a calcium- and calpain-dependent pathway.
Project description:Toll-like receptors (TLR) activation contributes to premalignant hematologic conditions, such as myelodysplastic syndromes (MDS). TRAF6, a TLR effector with ubiquitin (Ub) ligase activity, is overexpressed in MDS hematopoietic stem/progenitor cells (HSPCs). We found that TRAF6 overexpression in mouse HSPC results in impaired hematopoiesis and bone marrow failure. Using a global Ub screen, we identified hnRNPA1, an RNA-binding protein and auxiliary splicing factor, as a substrate of TRAF6. TRAF6 ubiquitination of hnRNPA1 regulated alternative splicing of Arhgap1, which resulted in activation of the GTP-binding Rho family protein Cdc42 and accounted for hematopoietic defects in TRAF6-expressing HSPCs. These results implicate Ub signaling in coordinating RNA processing by TLR pathways during an immune response and in premalignant hematologic diseases, such as MDS.
Project description:CFU-PreB colonies are reduced in number and size in Hspa9+/- mice compared to wildtype littermates. We compared the expression profiles of these colonies to gain insight into the mechanism driving this difference. HSPA9 is located on chromosome 5q31.2 in humans, a region that is commonly deleted in patients with myeloid malignancies [del(5q)], including myelodysplastic syndromes (MDS). HSPA9 expression is reduced by 50% in patients with del(5q)-associated MDS, consistent with haploinsufficient levels. Zebrafish mutants and knockdown studies in human and mouse cells have implicated a role for HSPA9 in hematopoiesis. To comprehensively evaluate the effects of Hspa9 haploinsufficiency on hematopoiesis, we generated an Hspa9 knockout mouse model. While homozygous knockout of Hspa9 is embryonic lethal, mice with heterozygous deletion of Hspa9 (Hspa9+/-) are viable and have a 50% reduction in Hspa9 expression. Hspa9+/- mice have normal basal hematopoiesis and do not develop MDS. However, Hspa9+/- mice have a cell-intrinsic reduction in bone marrow CFU-PreB colony formation without alterations in the number of B-cell progenitors in vivo, consistent with a functional defect in Hspa9+/- B-cell progenitors. We further reduced Hspa9 expression (<50%) using RNAi and observe reduced B-cell progenitors in vivo, indicating that appropriate levels (≥50%) of Hspa9 are required for normal B-lymphopoiesis in vivo. Knockdown of Hspa9 in an IL-7 dependent mouse B-cell line reduced Stat5 phosphorylation following IL-7 receptor stimulation, supporting a role for Hspa9 in Stat5 signaling in B-cells. Collectively, these data implicate a role for Hspa9 in B-lymphopoiesis and Stat5 activation downstream of IL-7 signaling. Bone marrow cells from 5 Hspa9+/+ and 5 Hspa9+/- mice were independently cultured in CFU-PreB methylcellulose medium for 7 days. PreB colonies were isolated and B220+ cells were flow sorted for RNA isolation.
Project description:Microarray analysis with 40,000 cDNA gene chip arrays determined differential gene expression profiles (GEPs) in CD34+ marrow cells from myelodysplastic syndrome (MDS) patients compared to normal individuals. Using focused bioinformatics analyses, we found 1175 genes significantly differentially expressed by MDS vs Normal, requiring a minimum of 39 genes to separately classify these patients. Major GEP differences were demonstrated between Normal and MDS patients and between several MDS subgroups: (1) those whose disease remained stable (sMDS) and those who subsequently transformed (tMDS) to acute myeloid leukemia (AML); (2) between del(5q) and other MDS patients. A 6-gene ‘poor risk’ signature was defined which was associated with AML transformation and provided additive prognostic information for IPSS Intermediate-1 patients. Over-expression of genes generating ribosomal proteins and for other signaling pathways was demonstrated in the tMDS patients. Comparison of del(5q) to the remaining MDS patients showed 1924 differentially expressed genes, with under-expression of 1014 genes, 11 of which were within the 5q31-32 Commonly Deleted Region. These data demonstrated (1) GEPs distinguishing MDS patients from normal and between those with differing clinical outcomes (tMDS vs sMDS) and cytogenetics [eg, del(5q)] ; and (2) molecular criteria refining prognostic categorization and associated biologic processes in MDS. Gene expression profiles from CD34+ cells of 35 MDS subjects and 6 Normals were compared.