title: Ectopic expression of Msx2 in mammalian myotubes recapitulates aspects of amphibian muscle dedifferentiation.
abstract: In contrast to urodele amphibians and teleost fish, mammals lack the regenerative responses to replace large body parts. Amphibian and fish regeneration uses dedifferentiation, i.e., reversal of differentiated state, as a means to produce progenitor cells to eventually replace damaged tissues. Therefore, induced activation of dedifferentiation responses in mammalian tissues holds an immense promise for regenerative medicine. Here we demonstrate that ectopic expression of Msx2 in cultured mouse myotubes recapitulates several aspects of amphibian muscle dedifferentiation. We found that MSX2, but not MSX1, leads to cellularization of myotubes and downregulates the expression of myotube markers, such as MHC, MRF4 and myogenin. RNA sequencing of myotubes ectopically expressing Msx2 showed downregulation of over 500 myotube-enriched transcripts and upregulation of over 300 myoblast-enriched transcripts. MSX2 selectively downregulated expression of Ptgs2 and Ptger4, two members of the prostaglandin pathway with important roles in myoblast fusion during muscle differentiation. Ectopic expression of Msx2, as well as Msx1, induced partial cell cycle re-entry of myotubes by upregulating CyclinD1 expression but failed to initiate S-phase. Finally, MSX2-induced dedifferentiation in mouse myotubes could be recapitulated by a pharmacological treatment with trichostatin A (TSA), bone morphogenetic protein 4 (BMP4) and fibroblast growth factor 1 (FGF1). Together, these observations indicate that MSX2 is a major driver of dedifferentiation in mammalian muscle cells.
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland. Electronic address: atilgany@gmail.com.
authors.forename: Atilgan
authors.initials: A
authors.lastname: Yilmaz
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland.
authors.forename: Rachel
authors.initials: R
authors.lastname: Engeler
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland; SIB Swiss Institute of Bioinformatics, Mattenstrasse 26, 4058 Basel, Switzerland.
authors.forename: Simona
authors.initials: S
authors.lastname: Constantinescu
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland.
authors.forename: Konstantinos D
authors.initials: KD
authors.lastname: Kokkaliaris
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland; SIB Swiss Institute of Bioinformatics, Mattenstrasse 26, 4058 Basel, Switzerland.
authors.forename: Christos
authors.initials: C
authors.lastname: Dimitrakopoulos
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland.
authors.forename: Timm
authors.initials: T
authors.lastname: Schroeder
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland; SIB Swiss Institute of Bioinformatics, Mattenstrasse 26, 4058 Basel, Switzerland.
authors.forename: Niko
authors.initials: N
authors.lastname: Beerenwinkel
authors.affiliation: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, Basel 4058, Switzerland; Faculty of Science, University of Basel, Basel, Switzerland. Electronic address: renato.paro@bsse.ethz.ch.
authors.forename: Renato
authors.initials: R
authors.lastname: Paro
mesh_terms: D000663:Amphibians; D000818:Animals; D002454:Cell Differentiation; D000066630:Ectopic Gene Expression / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D008322:Mammals / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*
chemical_list: D018398:Homeodomain Proteins; C084119:MSX2 protein
keywords: Homeobox genes; Muscle stem cells; Reprogramming; Skeletal muscle; Tissue regeneration; Transcription factors