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Savol, Andrej J

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Savol

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Andrej J

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Savol, Andrej J

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    Prolonged Mek1/2 suppression impairs the developmental potential of embryonic stem cells
    (Springer Nature, 2017) Choi, Jiho; Huebner, Aaron; Clement, Kendell; Walsh, Ryan M.; Savol, Andrej J; Lin, Kaixuan; Gu, Hongcang; Di Stefano, Bruno; Brumbaugh, Justin; Kim, Sang-Yong; Sharif, Jafar; Rose, Christopher M.; Mohammad, Arman; Odajima, Junko; Charron, Jean; Shioda, Toshihiro; Gnirke, Andreas; Gygi, Steven; Koseki, Haruhiko; Sadreyev, Ruslan; Xiao, Andrew; Meissner, Alexander; Hochedlinger, Konrad
    Concomitant activation of the Wnt pathway and suppression of Mapk signalling by two small molecule inhibitors (2i) in the presence of leukaemia inhibitory factor (LIF) (hereafter termed 2i/L) induces a naive state in mouse embryonic stem (ES) cells that resembles the inner cell mass (ICM) of the pre-implantation embryo1. Since the ICM exists only transiently in vivo, it remains unclear how sustained propagation of naive ES cells in vitro affects their stability and functionality. Here we show that prolonged culture of male mouse ES cells in 2i/L results in irreversible epigenetic and genomic changes that impair their developmental potential. Furthermore, we find that female ES cells cultured in conventional serum plus LIF medium phenocopy male ES cells cultured in 2i/L. Mechanistically, we demonstrate that the inhibition of Mek1/2 is predominantly responsible for these effects, in part through the downregulation of DNA methyltransferases and their cofactors. Finally, we show that replacement of the Mek1/2 inhibitor with a Src inhibitor preserves the epigenetic and genomic integrity as well as the developmental potential of ES cells. Taken together, our data suggest that, although short-term suppression of Mek1/2 in ES cells helps to maintain an ICM-like epigenetic state, prolonged suppression results in irreversible changes that compromise their developmental potential.
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    IRF3 and type I interferons fuel a fatal response to myocardial infarction
    (Springer Nature, 2017) King, Kevin R; Aguirre, Aaron; Ye, Yu-Xiang; Sun, Yuan; Roh, Jason; Ng, Richard; Kohler, Rainer; Arlauckas, Sean; Iwamoto, Yoshiko; Savol, Andrej J; Sadreyev, Ruslan; Kelly, Mark; Fitzgibbons, Timothy P; Fitzgerald, Katherine A; Mitchison, Timothy; Libby, Peter; Nahrendorf, Matthias; Weissleder, Ralph
    Interferon regulatory factor 3 (IRF3) and type I interferons (IFNs) protect against infections and cancer, but excessive IRF3 activation and type I IFN production cause autoinflammatory conditions such as Aicardi–Goutières syndrome and STING-associated vasculopathy of infancy (SAVI)3. Myocardial infarction (MI) elicits inflammation5, but the dominant molecular drivers of MI-associated inflammation remain unclear. Here we show that ischemic cell death and uptake of cell debris by macrophages in the heart fuel a fatal response to MI by activating IRF3 and type I IFN production. In mice, single-cell RNA-seq analysis of 4,215 leukocytes isolated from infarcted and non-infarcted hearts showed that MI provokes activation of an IRF3–interferon axis in a distinct population of interferon-inducible cells (IFNICs) that were classified as cardiac macrophages. Mice genetically deficient in cyclic GMP-AMP synthase (cGAS), its adaptor STING, IRF3, or the type I IFN receptor IFNAR exhibited impaired interferon-stimulated gene (ISG) expression and, in the case of mice deficient in IRF3 or IFNAR, improved survival after MI as compared to controls. Interruption of IRF3-dependent signaling resulted in decreased cardiac expression of inflammatory cytokines and chemokines and decreased inflammatory cell infiltration of the heart, as well as in attenuated ventricular dilation and improved cardiac function. Similarly, treatment of mice with an IFNAR-neutralizing antibody after MI ablated the interferon response and improved left ventricular dysfunction and survival. These results identify IRF3 and the type I IFN response as a potential therapeutic target for post-MI cardioprotection.