Transformation of the intestinal epithelium by the MSI2 RNA binding protein
Ontology highlight
ABSTRACT: The MSI2 RNA binding protein has recently emerged as a potent oncogene playing key roles in hematopoietic stem cell homeostasis and malignant hematopoiesis. Here we demonstrate that MSI2 is expressed in the intestinal stem cell compartment, that its expression is elevated in colorectal adenocarcinomas, and that MSI2 loss of function abrogates colorectal cancer cell growth. We thus examined the oncogenic consequences of MSI2 gain of function in the intestinal epithelium with a drug inducible mouse model. Strikingly, MSI2 induction alone was sufficient to phenocopy the majority of morphological and molecular consequences of acute loss of the APC tumor suppressor in the intestinal epithelium. We demonstrate that this phenotype is independent of both the activation of the other oncogenic Musashi family member, Msi1, and of canonical Wnt pathway activation. Transcriptome-wide RNA-binding analysis indicates that MSI2 acts as a pleiotropic inhibitor of known intestinal tumor suppressors including Lrig1, Bmpr1a, Cdkn1a, and Pten. Finally, we demonstrate that inhibition of the PDK-AKT-mTORC1 axis downstream of Pten rescues oncogenic consequences of MSI2 induction. Taken together, our findings identify MSI2 as a central component in an unappreciated oncogenic pathway promoting intestinal transformation. 2 wild-type samples, 2 TRE-Msi2 samples
Project description:The MSI2 RNA binding protein has recently emerged as a potent oncogene playing key roles in hematopoietic stem cell homeostasis and malignant hematopoiesis. Here we demonstrate that MSI2 is expressed in the intestinal stem cell compartment, that its expression is elevated in colorectal adenocarcinomas, and that MSI2 loss of function abrogates colorectal cancer cell growth. We thus examined the oncogenic consequences of MSI2 gain of function in the intestinal epithelium with a drug inducible mouse model. Strikingly, MSI2 induction alone was sufficient to phenocopy the majority of morphological and molecular consequences of acute loss of the APC tumor suppressor in the intestinal epithelium. We demonstrate that this phenotype is independent of both the activation of the other oncogenic Musashi family member, Msi1, and of canonical Wnt pathway activation. Transcriptome-wide RNA-binding analysis indicates that MSI2 acts as a pleiotropic inhibitor of known intestinal tumor suppressors including Lrig1, Bmpr1a, Cdkn1a, and Pten. Finally, we demonstrate that inhibition of the PDK-AKT-mTORC1 axis downstream of Pten rescues oncogenic consequences of MSI2 induction. Taken together, our findings identify MSI2 as a central component in an unappreciated oncogenic pathway promoting intestinal transformation.
Project description:Loss of the APC tumor suppressor in the intestinal epithelium initiates the majority of human colorectal adenocarcinomas. Constitutive β-catenin activation is thought to underlie tumorigenesis induced by loss of APC, however β-catenin activation alone does not recapitulate all APC-loss phenotypes, suggesting that additional pathways are required. We demonstrate that aberrant activation of the Msi1 RNA binding protein occurs upon APC loss and that constitutive Msi1 activation alone is sufficient to phenocopy APC loss in the intestinal epithelium. Msi1 elicits these effects through binding of mRNAs encoding pleiotropic tumor suppressors resulting in promiscuous activation of quiescent intestinal stem cells, proliferative expansion of the stem cell compartment, crypt fission, and blocked differentiation. Further, we find these phenotypes to be largely dependent on mTORC1 activity, and demonstrate that loss of Msi activity is sufficient to abrogate tumorigenesis in mouse and human systems. Our findings implicate Msi1 as a central coordinator of APC loss-induced intestinal stem cell transformation and adenocarcinoma progression. 2 wild-type, 2 transgenic samples
Project description:The Musashi-2 (Msi2) RNA-binding protein maintains stem cell self-renewal and promotes oncogenesis by enhancing cell proliferation in hematopoietic and gastrointestinal tissues. However, it is unclear how Msi2 recognizes and regulates mRNA targets in vivo and whether Msi2 primarily controls cell growth in all cell types. Here we identified Msi2 targets with HITSCLIP and revealed that Msi2 primarily recognizes mRNA 3UTRs at sites enriched in multiple copies of UAG motifs in epithelial progenitor cells. RNA-seq and ribosome profiling demonstrated that Msi2 promotes targeted mRNA decay without affecting translation efficiency. Unexpectedly, the most prominent Msi2 targets identified are key regulators that govern cell motility with a high enrichment in focal adhesion and extracellular matrix-receptor interaction, in addition to regulators of cell growth and survival. Loss of Msi2 stimulates epithelial cellmigration, increases the number of focal adhesion and also compromises cell growth. These findings provide new insights into the molecular mechanisms of Msi2âs recognition and repression of targets and uncover a key function of Msi2 in restricting epithelial cell migration. Identification of direct Musashi-2 targets in keratinocytes through the use of RNA-Seq, Ribosome-Profiling, and Msi2-HITS-CLIP
Project description:We demonstrate that Msi2 is the predominant form expressed in hematopoietic stem cells (HSC), and its knockdown leads to reduced engraftment and depletion of HSCs in vivo. Overexpression of Msi2 in a mouse model increases HSC cell cycle progression and cooperates with BCR-ABL1 to induce an aggressive leukemia. MSI2 is over-expressed in human myeloid leukemia, and expression levels directly correlate with decreased patient survival, thereby defining MSI2 expression as a novel prognostic marker in acute myeloid leukemia (AML). Depletion of MSI2 in human myeloid leukemia cells leads to decreased proliferation and apoptosis. These data implicate the MSI2 RNA binding protein in myeloid leukemogenesis and identify a novel potential target for therapy in AML. Hematopoietic stem cells and progenitor cells (LineageLow, Sca1-, Kit+; LK) from control and transgenic MSI2-inducible mice were isolated and RNA was extracted using Qiagen RNeasy Micro Kit according to manufacturers instruction. cDNA was fragmented and biotinylated before hybridization onto Affymetrix Mouse Expression Array 430 2.0.
Project description:Recent studies have shown that the RNA binding protein Musashi 2 (Msi2) plays prominent roles during development and leukemia. Additionally, in embryonic stem cells (ESC) undergoing the early stages of differentiation, Msi2 has been shown to associate with Sox2, which is required for the self-renewal of ESC. These findings led us to examine the effects of Msi2 on the behavior of ESC. Using an shRNA sequence that targets Msi2 and a scrambled shRNA sequence, we determined that knockdown of Msi2 disrupts the self-renewal of ESC and promotes their differentiation. Collectively, our findings argue that Msi2 is required to support the self-renewal and pluripotency of ESC. We used microarrays to better understand global changes in ESC gene expression following the knockdown of the RNA-binding protein Msi2 as compared to control ESC expressing a scrambled shRNA. Mouse embryonic stem cells (D3) were treated with lentivirus engineered for the expression of a Msi2 targeting shRNA sequence or scrambled (control) shRNA sequence. Following selection for infected cells with puromycin, cells were subcultured at low density and allowed to grow for 4 days (see treatment protocol) before RNA was extracted. RNA was collected and analyzed one time for each of the two samples.
Project description:Members of the Msi family of RNA-binding proteins have recently emerged as potent oncoproteins in a range of malignancies. MSI2 is highly expressed in hematopoietic cancers, where it is required for disease maintenance. In contrast to the hematopoietic system, colorectal cancers can express both Msi family members, MSI1 and MSI2. Here, we demonstrate that, in the intestinal epithelium, Msi1 and Msi2 have analogous oncogenic effects. Further, comparison of Msi1/2-induced gene expression programs and transcriptome-wide analyses of Msi1/2-RNA-binding targets reveal significant functional overlap, including induction of the PDK-Akt-mTORC1 axis. Ultimately, we demonstrate that concomitant loss of function of both MSI family members is sufficient to abrogate the growth of human colorectal cancer cells, and Msi gene deletion inhibits tumorigenesis in several mouse models of intestinal cancer. Our findings demonstrate that MSI1 and MSI2 act as functionally redundant oncoproteins required for the ontogeny of intestinal cancers.
Project description:Msi2 is a critical regulatior of myeoid leukemia, and these data identify genes that are changed following Msi2 deletion in bcCML and de novo AML stem cells. Leukemic stem cells were extracted from wild-type and Msi2 mutant MLL-AF9 driven AML and BCR-ABL/NUP98-HOXA9 driven bcCML, in triplicate. RNA was extracted and hybridized on Affymetrix microarrays. The mouse strain was a genetic trap Msi2 mutant made by Center for Animal Resources and Development (CARD) of Kumamoto University. They call their strain B6;CB-Msi2Gt(pU-21T)2Imeg, see also http://cardb.cc.kumamoto-u.ac.jp/transgenic/strainsDetailAction.do?strainId=834
Project description:Comparison of gene expression in intestinal epithelial cells in the presence or absence of ectopic induction of MSI2 in vivo Total RNA was isolated from preparations of total intestinal epithelial cells taken from the jejunum from 3 control (R26-M2rtTA +doxycycline for 24 hrs) and 3 experimental (TRE-MSI2::R26-M2rtTA +doxycycline for 24 hrs) and subjected to profiling on affymetrix Gene 1.0ST arrays
Project description:Leukemia stem cells (LSCs) are found in most aggressive myeloid diseases and contribute to therapeutic resistance. Genetic and epigenetic alterations cause a dysregulated developmental program in leukemia. The MSI2 RNA binding protein has been previously shown to predict poor survival in leukemia. We demonstrate that the conditional deletion of Msi2 results in delayed leukemogenesis, reduced disease burden and a loss of LSC function. Gene expression profiling of the Msi2 ablated LSCs demonstrates a loss of the HSC/LSC and an increase in the differentiation program. The gene signature from the Msi2 deleted LSCs correlates with survival in AML patients. MSI2’s maintains the MLL self-renewal program by interacting with and retaining efficient translation of Hoxa9, Myc and Ikzf2. We further demonstrate that shRNA depletion of the MLL target gene Ikzf2 also contributes to MLL leukemia cell survival. Our data provides evidence that MSI2 controls efficient translation of the oncogenic LSC self-renewal program and a rationale for clinically targeting MSI2 in myeloid leukemia. RNA-Seq was performed on sorted c-Kit high leukemic cells from 2 Msi2 -/- and 2 Msi2 f/f mice.
Project description:Leukemia stem cells (LSCs) are found in most aggressive myeloid diseases and contribute to therapeutic resistance. Genetic and epigenetic alterations cause a dysregulated developmental program in leukemia. The MSI2 RNA binding protein has been previously shown to predict poor survival in leukemia. We demonstrate that the conditional deletion of Msi2 results in delayed leukemogenesis, reduced disease burden and a loss of LSC function. Gene expression profiling of the Msi2 ablated LSCs demonstrates a loss of the HSC/LSC and an increase in the differentiation program. The gene signature from the Msi2 deleted LSCs correlates with survival in AML patients. MSI2’s maintains the MLL self-renewal program by interacting with and retaining efficient translation of Hoxa9, Myc and Ikzf2. We further demonstrate that shRNA depletion of the MLL target gene Ikzf2 also contributes to MLL leukemia cell survival. Our data provides evidence that MSI2 controls efficient translation of the oncogenic LSC self-renewal program and a rationale for clinically targeting MSI2 in myeloid leukemia.