Project description:This SuperSeries is composed of the following subset Series: GSE16432: MSI2 regulates hematopoiesis and accelerates leukemogenesis GSE22773: Musashi 2 regulates normal hematopoiesis and accelerates leukemogenesis (LK and MS12-inducible) GSE22774: Musashi 2 regulates normal hematopoiesis and accelerates leukemogenesis (LSK and LK) GSE22775: Musashi 2 regulates normal hematopoiesis and accelerates leukemogenesis (Leukemia cell lines) Refer to individual Series
Project description:The Musashi family of mRNA translational regulators control both physiological and pathological stem cell self-renewal primarily by repressing targets that promote differentiation. In response to differentiation cues, Musashi can switch from a repressor to an activator of target mRNA translation. However, the molecular events that distinguish Musashi-mediated translational activation from repression are not understood. We have previously reported that Musashi function is required for the maturation of Xenopus oocytes, and specifically for translational activation of specific dormant maternal mRNAs. Here, we employed mass spectrometry to identify cellular factors necessary for Musashi-dependent mRNA translational activation. We report a requirement for association of Musashi1 with the embryonic poly(A) binding protein (ePABP) or the canonical somatic cell poly(A) binding protein PABPC1 for activation of Musashi target mRNA translation. Co-immunoprecipitation studies demonstrated an increased Musashi1 interaction with ePABP during oocyte maturation. Attenuation of endogenous ePABP activity severely compromised Musashi function, preventing downstream signaling and blocking oocyte maturation. Recovery of Musashi-dependent mRNA translational activation and maturation of ePABP attenuated oocytes was achieved through ectopic expression of either ePABP or PABPC1. Consistent with the findings in Xenopus oocytes, PABPC1 remained associated with Musashi under conditions of Musashi target mRNA de-repression and translation during mammalian stem cell differentiation. Since association of Musashi1 with poly(A) binding proteins has previously only been implicated in repression of Musashi target mRNAs, our findings reveal distinct context-dependent roles for the interaction of Musashi with poly[A] binding protein family members in response to extracellular cues that control cell fate.
Project description:Clonal hematopoiesis plays a critical role in the initiation and development of hematologic malignant diseases. FOXM1, a well-known transcription factor, is often downregulated in CD34+ cells from patients with del(5q) Myelodysplastic Syndrome (MDS). Here we show that Foxm1 haploinsufficiency disturbs normal hematopoiesis and confers a competitive repopulation advantage to hematopoietic stem cells (HSCs) for a short period, but disrupts the long-term self-renewal capacity of HSCs, recapitulating the phenotypes of abnormal HSCs in MDS patients. Moreover, heterozygous inactivation of Foxm1 leads to an increase in DNA damage in hematopoietic stem/progenitor cells (HSPCs). Foxm1 haploinsufficiency induces an MDS-like disease in a mouse model with LPS-induced chronic inflammation, and accelerates AML-ETO9a-mediated leukemogenesis. We also identified PARP1, an important enzyme responding to various kinds of DNA lesions, as a previously unrecognized target of Foxm1. Foxm1 haploinsufficiency inhibits DNA damage response (DDR) in HSCs by downregulating PARP1 expression in HSPCs. Given that PARP1 inhibitors increase the risk of MDS and AML in clinical therapy for solid tumors, our results suggest that downregulation of the Foxm1-PARP1 molecular axis plays a pivotal role in the pathogenesis of MDS by promoting clonal hematopoiesis and reducing genome stability.