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Yalcin S.,Mount Sinai School of Medicine | Marinkovic D.,Mount Sinai School of Medicine | Mungamuri S.K.,Mount Sinai School of Medicine | Zhang X.,Mount Sinai School of Medicine | And 4 more authors.
EMBO Journal | Year: 2010

Reactive oxygen species (ROS) participate in normal intracellular signalling and in many diseases including cancer and aging, although the associated mechanisms are not fully understood. Forkhead Box O (FoxO) 3 transcription factor regulates levels of ROS concentrations, and is essential for maintenance of hematopoietic stem cells. Here, we show that loss of Foxo3 causes a myeloproliferative syndrome with splenomegaly and increased hematopoietic progenitors (HPs) that are hypersensitive to cytokines. These mutant HPs contain increased ROS, overactive intracellular signalling through the AKT/mammalian target of rapamycin signalling pathway and relative deficiency of Lnk, a negative regulator of cytokine receptor signalling. In vivo treatment with ROS scavenger N-acetyl-cysteine corrects these biochemical abnormalities and relieves the myeloproliferation. Moreover, enforced expression of Lnk by retroviral transfer corrects the abnormal expansion of Foxo3 -/- HPs in vivo. Our combined results show that loss of Foxo3 causes increased ROS accumulation in HPs. In turn, this inhibits Lnk expression that contributes to exaggerated cytokine responses that lead to myeloproliferation. Our findings could explain the mechanisms by which mutations that alter Foxo3 function induce malignancy. More generally, the work illustrates how deregulated ROS may contribute to malignant progression. © 2010 European Molecular Biology Organization | All Rights Reserved. Source

Josowitz R.,Mount Sinai School of Medicine | Carvajal-Vergara X.,CSIC - National Center for Metallurgical Research | Lemischka I.R.,Black Family Stem Cell Institute | Gelb B.D.,Mount Sinai School of Medicine
Current Opinion in Cardiology | Year: 2011

Purpose of review: The development of induced pluripotent stem cell (iPSC) technology has led to many advances in the areas of directed cell differentiation and characterization. New methods for generating iPSC-derived cardiomyocytes provide an invaluable resource for the study of certain cardiovascular disorders. This review highlights the current technology in this field, its application thus far to the study of genetic disorders of the RAS/MAPK pathway and long-QT syndrome (LQTS), and future directions for the field. Recent findings: Enhanced methods increase the efficiency of generating and stringently purifying iPSC-derived cardiomyocytes. The use of cardiomyocytes derived from patients with LEOPARD syndrome and LQTS has shed light on the molecular mechanisms of disease and validated their use as reliable human disease models. Summary: The use of iPSC-derived cardiomyocytes to study genetic cardiovascular disorders will enable a deeper and more applicable understanding of the molecular mechanisms of human disease, as well as improving our ability to achieve successful cell-based therapies. Methods to efficiently generate these cells are improving and provide promise for future applications of this technology. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins. Source

Saunders A.,Black Family Stem Cell Institute | Saunders A.,Mount Sinai School of Medicine | Faiola F.,Black Family Stem Cell Institute | Wang J.,Black Family Stem Cell Institute | Wang J.,Mount Sinai School of Medicine
Stem Cells | Year: 2013

Pluripotent embryonic stem cells and induced pluripotent stem cells hold great promise for future use in tissue replacement therapies due to their ability to self-renew indefinitely and to differentiate into all adult cell types. Harnessing this therapeutic potential efficiently requires a much deeper understanding of the molecular processes at work within the pluripotency network. The transcription factors Nanog, Oct4, and Sox2 reside at the core of this network, where they interact and regulate their own expression as well as that of numerous other pluripotency factors. Of these core factors, Nanog is critical for blocking the differentiation of pluripotent cells, and more importantly, for establishing the pluripotent ground state during somatic cell reprogramming. Both mouse and human Nanog are able to form dimers in vivo, allowing them to preferentially interact with certain factors and perform unique functions. Recent studies have identified an evolutionary functional conservation among vertebrate Nanog orthologs from chick, zebrafish, and the axolotl salamander, adding an additional layer of complexity to Nanog function. Here, we present a detailed overview of published work focusing on Nanog structure, function, dimerization, and regulation at the genetic and posttranslational levels with regard to the establishment and maintenance of pluripotency. The full spectrum of Nanog function in pluripotent stem cells and in cancer is only beginning to be revealed. We therefore use this evidence to advocate for more comprehensive analysis of Nanog in the context of disease, development, and regeneration. © AlphaMed Press. Source

Takikawa S.,Black Family Stem Cell Institute | Wang X.,Black Family Stem Cell Institute | Ray C.,Black Family Stem Cell Institute | Vakulenko M.,Black Family Stem Cell Institute | And 2 more authors.
Epigenetics | Year: 2013

Genomic imprinting is a common epigenetic phenomenon in mammals. Dysregulation of genomic imprinting has been implicated in a variety of human diseases. ZFP57 is a master regulator in genomic imprinting. Loss of ZFP57 causes loss of DNA methylation imprint at multiple imprinted regions in mouse embryos, as well as in embryonic stem (ES) cells. Similarly, mutations in human ZFP57 result in hypomethylation at many imprinted regions and are associated with transient neonatal diabetes and other human diseases. Mouse and human Zfp57 genes are located in the same syntenic block. However, mouse and human ZFP57 proteins only display about 50% sequence identity with different number of zinc fingers. It is not clear if they share similar mechanisms in maintaining genomic imprinting. Here we report that mouse and human ZFP57 proteins are functionally interchangeable. Expression of exogenous wild-type human ZFP57 could maintain DNA methylation imprint at three imprinted regions in mouse ES cells in the absence of endogenous mouse ZFP57. However, mutant human ZFP57 proteins containing the mutations found in human patients could not substitute for endogenous mouse ZFP57 in maintaining genomic imprinting in ES cells. Like mouse ZFP57, human ZFP57 and its mutant proteins could bind to mouse KAP1, the universal cofactor for KRAB zinc finger proteins, in mouse ES cells. Thus, we conclude that mouse and human ZFP57 are orthologs despite relatively low sequence identity and mouse ES cell system that we had established before is a valuable system for functional analyses of wild-type and mutant human ZFP57 proteins. © 2013 Landes Bioscience. Source

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