Luo D, Renault VM, Rando TA.. The regulation of Notch signaling in muscle stem cell activation and postnatal myogenesis. Semin Cell Dev Biol 16: 612-622
Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305-5235, USA. Seminars in Cell and Developmental Biology
(Impact Factor: 6.27).
08/2005; 16(4-5):612-22. DOI: 10.1016/j.semcdb.2005.07.002
The Notch signaling pathway is an evolutionarily conserved pathway that is critical for tissue morphogenesis during development, but is also involved in tissue maintenance and repair in the adult. In skeletal muscle, regulation of Notch signaling is involved in somitogenesis, muscle development, and the proliferation and cell fate determination of muscle stems cells during regeneration. During each of these processes, the spatial and temporal control of Notch signaling is essential for proper tissue formation. That control is mediated by a series of regulatory proteins and protein complexes that enhance or inhibit Notch signaling by regulating protein processing, localization, activity, and stability. In this review, we focus on the regulation of Notch signaling during postnatal muscle regeneration when muscle stem cells ("satellite cells") must activate, proliferate, progress along a myogenic lineage pathway, and ultimately differentiate to form new muscle. We review the regulators of Notch signaling, such as Numb and Deltex, that have documented roles in myogenesis as well as other regulators that may play a role in modulating Notch signaling during satellite cell activation and postnatal myogenesis.
Available from: Jane Batt
- "Notch-1 is a transmembrane receptor protein that is sequentially cleaved upon ligand binding, releasing its “activated” intracellular domain, which translocates from the cytosol to the nucleus to influence transcription . In muscle satellite cells Notch-1 positively regulates proliferation, and decreased expression of Notch-1 coincides with the onset of terminal differentiation to myocytes , . A role for Notch-1 in mature muscle fibres has not yet been elucidated. "
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ABSTRACT: Skeletal muscle atrophy is a consequence of muscle inactivity resulting from denervation, unloading and immobility. It accompanies many chronic disease states and also occurs as a pathophysiologic consequence of normal aging. In all these conditions, ubiquitin-dependent proteolysis is a key regulator of the loss of muscle mass, and ubiquitin ligases confer specificity to this process by interacting with, and linking ubiquitin moieties to target substrates through protein∶protein interaction domains. Our previous work suggested that the ubiquitin-protein ligase Nedd4-1 is a potential mediator of skeletal muscle atrophy associated with inactivity (denervation, unloading and immobility). Here we generated a novel tool, the Nedd4-1 skeletal muscle-specific knockout mouse (myo(Cre);Nedd4-1(flox/flox)) and subjected it to a well validated model of denervation induced skeletal muscle atrophy. The absence of Nedd4-1 resulted in increased weights and cross-sectional area of type II fast twitch fibres of denervated gastrocnemius muscle compared with wild type littermates controls, at seven and fourteen days following tibial nerve transection. These effects are not mediated by the Nedd4-1 substrates MTMR4, FGFR1 and Notch-1. These results demonstrate that Nedd4-1 plays an important role in mediating denervation-induced skeletal muscle atrophy in vivo.
Available from: Christopher P Cardozo
- "DOI: 10.2164/jandrol.112.016428 Luo et al, 2005; Brack et al, 2008 "
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ABSTRACT: Nandrolone, an anabolic steroid, slows denervation atrophy of rat muscle, prevents denervation-induced nuclear accumulation of intracellular domain of the Notch receptor (NICD) and elevates expression of Numb. Numb acts as an inhibitor of Notch signaling and promotes myogenic differentiation of satellite cells. Turnover of Numb is regulated by mdm2, an E3 ubiquitin ligase. With these considerations in mind, we investigated the effects of nandrolone on the expression of Numb and mdm2 proteins and determined the effect of mdm2 on nandrolone-induced alterations in Numb protein in C2C12 myoblasts. When C2C12 cells were cultured in a medium favoring differentiation [DMEM containing 2% horse serum (HS)], nandrolone upregulated Numb protein levels in a time-dependent manner and prolonged Numb protein half-life from 10h to 18h. In contrast, nandrolone reduced the expression of mdm2 protein. To determine whether the decreased mdm2 expression induced by nandrolone was responsible for the increased levels and prolonged half-life of Numb protein in this cell line, mdm2-siRNA was employed to inhibit mdm2 expression. Compared to cells transfected with scrambled siRNA (negative control), transfection with mdm2-siRNA increased basal Numb protein expression but abolished the further increase in Numb protein levels by nandrolone. In addition, transfection of mdm2-siRNA mimicked the effect of nandrolone to prolong the half-life of Numb protein. Moreover, when C2C12 cells were forced to over-express mdm2, there was a significant decline in the expression of both basal and inducible Numb protein. Our data suggest that nandrolone, by a novel mechanism for this agent in a muscle cell type, increases Numb protein levels in C2C12 myoblasts by stabilizing Numb protein against degradation, at least in part, via suppression of mdm2 expression.
Available from: Mark A Sussman
- "The role of Notch in skeletal muscle development and adult stem cells is well established       . Recent evidence indicates that a temporary pulse of Notch activity is necessary for terminal differentiation of muscle progenitors in developing chick skeletal muscle  in contrast to prior studies in which Notch was reported to oppose myogenesis . "
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ABSTRACT: Notch signaling is critical for proper heart development and recently has been reported to participate in adult cardiac repair. Notch resides at the cell surface as a single pass transmembrane receptor, transits through the cytoplasm following activation, and acts as a transcription factor upon entering the nucleus. This dynamic and widespread cellular distribution allows for potential interactions with many signaling and binding partners. Notch displays temporal as well as spatial versatility, acting as a strong developmental signal, controlling cell fate determination and lineage commitment, and playing a pivotal role in embryonic and adult stem cell proliferation and differentiation. This review serves as an update of recent literature addressing Notch signaling in the heart, with attention to findings from noncardiac research that provide clues for further interpretation of how the Notch pathway influences cardiac biology. Specific areas of focus include Notch signaling in adult myocardium following pathologic injury, the role of Notch in cardiac progenitor cells with respect to differentiation and cardiac repair, crosstalk between Notch and other cardiac signaling pathways, and emerging aspects of noncanonical Notch signaling in heart.
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