Background Hepatocyte Growth Factor (HGF) is a pleiotropic cytokine of mesenchymal origin that mediates a characteristic array of biological activities including cell proliferation, survival, motility and morphogenesis. of Magic-F1 gene CCNB1 into adult mice promoted muscular hypertrophy and decreased myocyte apoptosis. Magic-F1 transgenic mice displayed constitutive muscular hypertrophy, improved running performance and accelerated muscle regeneration following injury. Crossing of Magic-F1 transgenic mice with -sarcoglycan knock-out mice Ca mouse model of muscular dystrophyC or adenovirus-mediated Magic-F1 gene delivery resulted in amelioration of the dystrophic phenotype as measured by both anatomical/histological analysis and functional tests. Conclusions/Significance Because of these features Magic-F1 represents a novel molecular tool to counteract muscle wasting in major muscular diseases such as cachexia or muscular dystrophy. Introduction Hepatocyte Growth Factor (HGF), also known as Scatter Factor (SF), is a pleiotropic cytokine of mesenchymal origin that mediates a characteristic array of biological activities including cell proliferation, survival, Cilliobrevin D IC50 motility and morphogenesis [1]C[3]. Its high affinity receptor, the tyrosine kinase Met, is expressed by a wide range of tissues including epithelial, endothelial, hematopoietic, neuronal and muscular cells [4], [5]. Embryonic muscle precursor cells express Met and migrate following HGF gradients during embryo development [6]C[10]. Genetic impairment of HGF-Met signaling in mice leads to abnormal muscle development in the limbs, thorax and tongue [11]C[13], and newborns -which are ataxic and have breathing problems- die a few hours later because they cannot suck mother’s milk [14]. In the adult, the HGF-Met pathway is involved in muscle regeneration following injury. Muscle satellite cells, which reside in the stroma of muscular tissues and express both Cilliobrevin D IC50 HGF and Met [15], represent a pool of muscle precursors that are activated and stimulated to divide when muscle regeneration or adaptive growth is needed [16], [17]. Autocrine HGF-Met stimulation plays a key role in mediating activation and early division of satellite cells, but is shut off in a second phase in order to allow the cells to exit the cell cycle and to enter the differentiation process [18], [19]. HGF stimulation of cultured satellite cells promotes cell proliferation and inhibits myogenic differentiation [20]. Magic Factor-1 (Met-Activating Genetically Improved Chimeric Factor-1 or Magic-F1) is an HGF-derived, engineered protein that contains two Met-binding domains repeated in tandem. It has a reduced affinity for Met and, in contrast to HGF, it elicits activation of the AKT but not the ERK signaling pathway. As a result of its partial ability to activate Met signaling, Magic-F1 is not mitogenic but conserves the ability to protect cells against apoptosis. We have analyzed the effects of Magic-F1 on muscular cells both and in mice. We show that Magic-F1 protects myogenic precursors against apoptosis and thus enhances the differentiation process, which is naturally accompanied by cell death. This pro-differentiative effect is observed both in cultured myogenic cell systems and in two different models. Remarkably, constitutive or transient expression of Magic-F1 in Cilliobrevin D IC50 a mouse model of muscular dystrophy partially rescues the dystrophic phenotype and allows animals to perform better in a classic tread mill functional test. These features make Magic-F1 a novel, potential molecular tool to counteract muscle wasting in major muscular diseases including cachexia and muscular dystrophy. Results Engineering of Magic-F1, a bivalent Met ligand Mature HGF is a dimeric molecule consisting of a – and a -chain joint by a disulphide bridge [21]. The -chain contains a leader peptide for secretion, an N-domain similar to the activation domain of plasminogen, and four kringle domains (K 1C4) typical of the blood clotting cascade proteases [22]. In functional terms, HGF is a bivalent molecule containing two distinct Met binding sites, one in the -chain high affinity; [23] and one at in the -chain low affinity; [24]. Isolated HGF domains containing only one receptor binding site (HGF NK1, HGF NK2, HGF -chain, HGF -chain) can bind to the Met receptor but do not activate it [22]C[25], thus suggesting that a bivalent molecule is necessary to achieve receptor activation. Consistent with this idea, some monovalent scatter factor subdomains (HGF NK1, HGF NK2) display a partial agonistic activity when they are stabilized in a dimeric form by extracellular matrix proteoglycans [26]. To generate new recombinant proteins capable of inducing specific patterns of biological responses, we engineered several artificial molecules containing different HGF domain in various combination. Magic-F1,.