Project description:Anemia is a significant cause of morbidity and mortality in myeloid malignances. Cytogenetic changes are recurrent within malignant hematopoietic stem and progenitor cells, yet their role in anemia pathogenesis remains unknown. One recurrent karyotypic abnormality in myeloid neoplasms is the deletion of part or all of chromosome 7 [-7/del(7q)], which harbors the transcription factor and tumor suppressor gene, CUX1. CUX1 knockdown mouse models develop myeloid disease similar to that seen in humans, including a spontaneous, cell intrinsic, and lethal anemia that develops with age. Here, we elucidate the cellular and molecular mechanisms by which CUX1 regulates erythropoiesis. We demonstrate CUX1 knockdown mice have an aberrant stress erythropoiesis response and decreased survival after acute anemia induction. CUX1 insufficient erythroblasts undergo accelerated cell cycling and increased apoptosis. In line with these phenotypes, transcriptome profiling indicates that CUX1-knockdown elicits increased proliferation and decreased erythroid differentiation gene signatures. ATAC-sequencing demonstrated dramatic, global chromatin opening in CUX1-knockdown erythroblasts. As measured by fluorescence lifetime imaging, this increased chromatin accessibility is concomitant with a disruption in nuclear condensation, which is normally requisite in mammalian erythroblasts for nuclear eviction and terminal differentiation. Finally, we show that CUX1 mediates chromatin compaction by promoting histone deacetylation. Thus, rather than a transcriptional role, our data implicate in an epigenetic regulatory role for CUX1 in erythropoiesis. Furthermore, these results suggest therapeutic targeting of epigenetic regulators, such as histone acetyl transferases, may have clinical benefit for the anemias associated with loss of CUX1.
Project description:LOUCY cells were resuspended in Opti-MEM (Gibco) and electroporated in 4 mm cuvettes (300 V, 1000 F; Genepulser XCell, Bio-Rad) using Stealth siRNAs (Ambion) against CUX1 or negative control duplexes. Cells were rested for 15 min following electroporation before dilution into normal RPMI 10 percent FBS growth media. RNA prepared from cells 48-72 h later using an RNeasy mini kit (Qiagen) was used for cDNA preparation for microarrays according to manufacturers instructions (Illumina).
Project description:-7/del(7q) is genetic event prevalent in high-risk myeloid neoplasms. For reasons that are unclear, gain-of-function mutations in the RAS pathway frequently co-occur with monosomy 7. Here we identify a genetic interaction between RAS and the 7q-encoded transcription factor, CUX1. Concomitant mutations in RAS genes and CUX1 are wide-spread across tumor types, suggesting cooperativity in tumorigenesis. To test this, we generated mice with oncogenic NrasG12D and Cux1 knockdown. Double mutant mice developed myeloid malignancies with higher penetrance and faster onset than either single allele alone, with leukemic transformation in one third of cases. Oncogenic RAS imparts increased self-renewal on CUX1-deficient hematopoietic stem and progenitor cells (HSPCs). Reciprocally, CUX1 knockdown amplifies RAS signaling through decreased transcriptional expression of negative regulators of RAS and PI3K signaling. Accordingly, NrasG12D;Cux1-knockdown HSPCs have heighted growth factor-sensitivity and downstream RAS pathway activation. Double mutant HSPCs were responsive to PIK3 or MEK inhibition, suggesting that these may be promising therapeutic targets in patients with 7/del(7q) malignancies. Our results implicate the loss of CUX1 as the underlying explanation for the association of -7/del(7q) with oncogenic RAS. Furthermore, we report the unexpected convergence of an oncogene and tumor suppressor gene on the same pathway.
Project description:DNA-binding factor Tis7 (Ifrd1) shows increased ribosome recruitment during eIF2 phosphorylation during proteotoxic stress in erythroblasts. Here, we examine the effect of Tis7 knockdown on RNA expression at different time points after tunicamycin exposure.
Project description:Monosomy 7 (-7) and del(7q) are high-risk cytogenetic abnormalities common in myeloid malignancies. We previously reported that CUX1, a homeodomain-containing transcription factor encoded on 7q22, is frequently inactivated in myeloid neoplasms, and CUX1 myeloid tumor suppressor activity is conserved from humans to Drosophila. CUX1-inactivating mutations are recurrent in clonal hematopoiesis of indeterminate potential as well as myeloid malignancies, in which they independently carry a poor prognosis. To determine the role for CUX1 in hematopoiesis, we generated 2 short hairpin RNA-based mouse models with ∼54% (Cux1mid) or ∼12% (Cux1low) residual CUX1 protein. Cux1mid mice develop myelodysplastic syndrome (MDS) with anemia and trilineage dysplasia, whereas CUX1low mice developed MDS/myeloproliferative neoplasms and anemia. In diseased mice, restoration of CUX1 expression was sufficient to reverse the disease. CUX1 knockdown bone marrow transplant recipients exhibited a transient hematopoietic expansion, followed by a reduction of hematopoietic stem cells (HSCs), and fatal bone marrow failure, in a dose-dependent manner. RNA-sequencing after CUX1 knockdown in human CD34+ cells identified a -7/del(7q) MDS gene signature and altered differentiation, proliferative, and phosphatidylinositol 3-kinase (PI3K) signaling pathways. In functional assays, CUX1 maintained HSC quiescence and repressed proliferation. These homeostatic changes occurred in parallel with decreased expression of the PI3K inhibitor, Pik3ip1, and elevated PI3K/AKT signaling upon CUX1 knockdown. Our data support a model wherein CUX1 knockdown promotes PI3K signaling, drives HSC exit from quiescence and proliferation, and results in HSC exhaustion. Our results also demonstrate that reduction of a single 7q gene, Cux1, is sufficient to cause MDS in mice.
Project description:CUX1, a homeodomain-containing transcription factor, is recurrently deleted or mutated in multiple tumor types. In myeloid neoplasms, CUX1 deletion or mutation carries a poor prognosis. We have previously established that CUX1 functions as a tumor suppressor in hematopoietic cells across multiple organisms. Others, however, have described oncogenic functions of CUX1 in solid tumors, often attributed to truncated CUX1 isoforms, p75 and p110. Given the clinical relevance, it is imperative to clarify these discrepant activities. Herein, we sought to determine the CUX1 isoforms expressed in hematopoietic cells, and find that they express the full-length p200 isoform. Through the course of this analysis, we found no evidence of the p75 alternative transcript in any cell type examined. Using an array of orthogonal approaches, including biochemistry, proteomics, CRISPR/Cas9 genomic editing, and analysis of functional genomics datasets across a spectrum of normal and malignant tissue types, we found no data to support the existence of the CUX1 p75 isoform generated by an alternative transcriptional start site. Based on these results, prior studies of p75 require reevaluation, including the interpretation of oncogenic roles attributed to CUX1.
Project description:Therapy-related myeloid neoplasms (t-MN) are a high-risk, late effect in cancer survivors with poorly understood pathogenesis. It has been postulated that, in some cases, hematopoietic stem and progenitor cells (HSPCs) harboring mutations are selected for by cytotoxic exposures and transform. Here, we elucidate this model in the context of deficiency of CUX1, a transcription factor encoded on chromosome 7q. We report that CUX1 has a critical, early role in the DNA repair process in HSPCs. Mechanistically, CUX1 recruits the histone methyltransferase EHMT2 to DNA breaks to promote H3K27 methylation, phospho-ATM retention, subsequent γH2AX foci formation and propagation and, ultimately, 53BP1 recruitment. Despite significant unrepaired DNA damage sustained in CUX1-deficient murine HSPCs after cytotoxic exposures, they continue to proliferate and expand, mimicking clonal hematopoiesis in patients post-chemotherapy. As a consequence, preexisting CUX1 deficiency predisposes mice to highly penetrant and rapidly fatal therapy-related erythroleukemias. These findings establish the importance of epigenetic regulation of DNA repair and position CUX1 as a gatekeeper in myeloid transformation.