title: Distinct transcriptional networks in quiescent myoblasts: a role for Wnt signaling in reversible vs. irreversible arrest.
abstract: Most cells in adult mammals are non-dividing: differentiated cells exit the cell cycle permanently, but stem cells exist in a state of reversible arrest called quiescence. In damaged skeletal muscle, quiescent satellite stem cells re-enter the cell cycle, proliferate and subsequently execute divergent programs to regenerate both post-mitotic myofibers and quiescent stem cells. The molecular basis for these alternative programs of arrest is poorly understood. In this study, we used an established myogenic culture model (C2C12 myoblasts) to generate cells in alternative states of arrest and investigate their global transcriptional profiles. Using cDNA microarrays, we compared G0 myoblasts with post-mitotic myotubes. Our findings define the transcriptional program of quiescent myoblasts in culture and establish that distinct gene expression profiles, especially of tumour suppressor genes and inhibitors of differentiation characterize reversible arrest, distinguishing this state from irreversibly arrested myotubes. We also reveal the existence of a tissue-specific quiescence program by comparing G0 C2C12 myoblasts to isogenic G0 fibroblasts (10T1/2). Intriguingly, in myoblasts but not fibroblasts, quiescence is associated with a signature of Wnt pathway genes. We provide evidence that different levels of signaling via the canonical Wnt pathway characterize distinct cellular states (proliferation vs. quiescence vs. differentiation). Moderate induction of Wnt signaling in quiescence is associated with critical properties such as clonogenic self-renewal. Exogenous Wnt treatment subverts the quiescence program and negatively affects clonogenicity. Finally, we identify two new quiescence-induced regulators of canonical Wnt signaling, Rgs2 and Dkk3, whose induction in G0 is required for clonogenic self-renewal. These results support the concept that active signal-mediated regulation of quiescence contributes to stem cell properties, and have implications for pathological states such as cancer and degenerative disease.
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Sindhu
authors.initials: S
authors.lastname: Subramaniam
authors.forename: Prethish
authors.initials: P
authors.lastname: Sreenivas
authors.forename: Sirisha
authors.initials: S
authors.lastname: Cheedipudi
authors.forename: Vatrapu Rami
authors.initials: VR
authors.lastname: Reddy
authors.forename: Lingadahalli Subrahmanya
authors.initials: LS
authors.lastname: Shashidhara
authors.forename: Ravi Kumar
authors.initials: RK
authors.lastname: Chilukoti
authors.forename: Madhavi
authors.initials: M
authors.lastname: Mylavarapu
authors.forename: Jyotsna
authors.initials: J
authors.lastname: Dhawan
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D059447:Cell Cycle Checkpoints / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D002999:Clone Cells; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology* / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D009928:Organ Specificity / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics; D060449:Wnt Signaling Pathway / Q000235:genetics*; D051176:beta Catenin / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C405061:Dkk3 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; D020710:RGS Proteins; C105345:Rgs2 protein, mouse; D025521:Tumor Suppressor Proteins; D051176:beta Catenin