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The effect of spontaneous acquisition of an extra chromosome 7 for engineered del(7q) on induced pluripotent stem cells (iPSCs) derived from patients with Shwachman Diamond Syndrome (SDS).

ABSTRACT: Monosomy 7 or deletion of 7q (del(7q)) frequently arise in inherited and acquired bone marrow failure, and are associated with progression to high grade Myelodysplastic Syndrome (MDS) and acute leukemia. Current non-transplant approaches to treat marrow failure may be complicated by potential stimulation of clonal outgrowth. To study the biological consequences of del(7q) within the context of a failing marrow, we utilized induced pluripotent stem cells (iPSCs) derived from patients with Shwachman Diamond Syndrome (SDS) and genomically engineered a deletion of (7q). Deletion of 7q failed to confer a relative fitness advantage in either pluripotent SDS iPSC or in iPSC-derived SDS CD34+ cells. The TGF-beta pathway was the top differentially regulated pathway in transcriptome analysis with the TGF pathway found activated in SDS-iPSCs, compared to SDS-del(7q) iPSCs. Increased phosphorylation of SMAD2 in SDS-iPSCs was reduced following del(7q) and increased upon restoration of 7q diploidy, in support of an effect of 7q dosage on the activation status of the TGF-beta pathway in SDS. Inhibition of the TGF-beta pathway rescued hematopoiesis in SDS-iPSCs and in primary bone marrow cells from SDS patients without improving hematopoiesis of the SDS-del(7q) cells. Together, these results utilizing an iPSC model of MDS in BMF identified a targetable vulnerability for potential therapeutic strategies to ameliorate bone marrow failure without promoting outgrowth of the del7q clone.

ORGANISM(S): Homo sapiens

PROVIDER: GSE118377 | GEO | 2019/07/26

REPOSITORIES: GEO

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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.

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The effect of spontaneous acquisition of an extra chromosome 7 for engineered del(7q) on induced pluripotent stem cells (iPSCs) derived from patients with Shwachman Diamond Syndrome (SDS).

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