Project description:Skeletal muscle possesses remarkable regenerative potential due to satellite cells, a stem cell population located beneath the muscle basal lamina. By lineage tracing of progenitor cells expressing the Twist2 (Tw2) transcription factor in mice, we discovered a unique myogenic lineage that resides outside the basal lamina of adult muscle and contributes specifically to type IIb/x myofibers during adulthood and muscle regeneration. Tw2+ progenitors are molecularly and anatomically distinct from satellite cells, are highly myogenic in vitro and can fuse with satellite cells. Transplantation of Tw2+ progenitors into adult mice is sufficient to reconstitute new myofibers, and genetic ablation of endogenous Tw2+ progenitors causes wasting of type IIb myofibers. We show that Tw2 expression maintains progenitor cells in an undifferentiated state that is poised to initiate myogenesis in response to appropriate cues that suppress Tw2 expression. Tw2-expressing progenitors represent a previously unrecognized, fiber-type specific progenitor cell involved in muscle growth and regeneration.
Project description:Skeletal muscle possesses remarkable regenerative potential due to satellite cells, a stem cell population located beneath the muscle basal lamina. By lineage tracing of progenitor cells expressing the Twist2 (Tw2) transcription factor in mice, we discovered a unique myogenic lineage that resides outside the basal lamina of adult muscle and contributes specifically to type IIb/x myofibers during adulthood and muscle regeneration. Tw2+ progenitors are molecularly and anatomically distinct from satellite cells, are highly myogenic in vitro and can fuse with satellite cells. Transplantation of Tw2+ progenitors into adult mice is sufficient to reconstitute new myofibers, and genetic ablation of endogenous Tw2+ progenitors causes wasting of type IIb myofibers. We show that Tw2 expression maintains progenitor cells in an undifferentiated state that is poised to initiate myogenesis in response to appropriate cues that suppress Tw2 expression. Tw2-expressing progenitors represent a previously unrecognized, fiber-type specific progenitor cell involved in muscle growth and regeneration.
Project description:Skeletal muscle possesses remarkable regenerative potential due to satellite cells, a stem cell population located beneath the muscle basal lamina. By lineage tracing of progenitor cells expressing the Twist2 (Tw2) transcription factor in mice, we discovered a unique myogenic lineage that resides outside the basal lamina of adult muscle and contributes specifically to type IIb/x myofibers during adulthood and muscle regeneration. Tw2+ progenitors are molecularly and anatomically distinct from satellite cells, are highly myogenic in vitro and can fuse with satellite cells. Transplantation of Tw2+ progenitors into adult mice is sufficient to reconstitute new myofibers, and genetic ablation of endogenous Tw2+ progenitors causes wasting of type IIb myofibers. We show that Tw2 expression maintains progenitor cells in an undifferentiated state that is poised to initiate myogenesis in response to appropriate cues that suppress Tw2 expression. Tw2-expressing progenitors represent a previously unrecognized, fiber-type specific progenitor cell involved in muscle growth and regeneration.
Project description:Skeletal muscle possesses remarkable regenerative potential due to satellite cells, an injury-responsive stem cell population located beneath the muscle basal lamina that expresses Pax7. By lineage tracing of progenitor cells expressing the Twist2 (Tw2) transcription factor in mice, we discovered a myogenic lineage that resides outside the basal lamina of adult skeletal muscle. Tw2+ progenitors are molecularly and anatomically distinct from satellite cells, are highly myogenic in vitro, and can fuse with themselves and with satellite cells. Tw2+ progenitors contribute specifically to type IIb/x myofibres during adulthood and muscle regeneration, and their genetic ablation causes wasting of type IIb myofibres. We show that Tw2 expression maintains progenitor cells in an undifferentiated state that is poised to initiate myogenesis in response to appropriate cues that extinguish Tw2 expression. Tw2-expressing myogenic progenitors represent a previously unrecognized, fibre-type-specific stem cell involved in postnatal muscle growth and regeneration.
Project description:Cu (Cu) is essential for several biochemical pathways due to its role as a catalytic cofactor or allosteric regulator of enzymes. Its import and distribution are tightly controlled by transporters and metallochaperones and Cu homeostasis is maintained by balancing Cu uptake and export. Genetic diseases are caused by impaired Cu transporters CTR1, ATP7A, or ATP7B but little is known about the regulatory mechanisms by which these proteins meet the fluctuating demands of Cu in specific tissues. Cu is required for differentiation of skeletal myoblasts to myotubes. Here, we demonstrate that ATP7A is needed for myotube formation and that its increased abundance during differentiation is mediated by stabilization of Atp7a mRNA via the 3' untranslated region. Increased ATP7A levels during differentiation resulted in increased Cu delivery to lysyl oxidase, a secreted cuproenzyme that needed for myotube formation. These studies identify a previously unknown role for Cu in regulating muscle differentiation and have broad implications for understanding Cu-dependent differentiation in other tissues.
Project description:Exercise has profound benefits for brain function in animals and humans. In rodents, voluntary wheel running increases the production of new neurons and upregulates neurotrophin levels in the hippocampus, as well as improving synaptic plasticity, memory function and mood. The underlying cellular mechanisms, however, remain unresolved. Recent research indicates that peripheral organs such as skeletal muscle, liver and adipose tissue secrete factors during physical activity that may influence neuronal function. Here we used an in vitro cell assay and proteomic analysis to investigate the effects of proteins secreted from skeletal muscle cells on adult hippocampal neural progenitor cell (aNPC) differentiation. We also sought to identify the relevant molecules driving these effects. Specifically, we treated rat L6 skeletal muscle cells with the AMP-kinase (AMPK) agonist 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) or vehicle (distilled water). We then collected the conditioned media (CM) and fractionated it using high-performance liquid chromatography (HPLC). Treatment of aNPCs with a specific fraction of the AICAR-CM upregulated expression of doublecortin (DCX) and Tuj1, markers of immature neurons. Proteomic analysis of this fraction identified proteins known to be involved in energy metabolism, cell migration, adhesion and neurogenesis. Culturing differentiating aNPCs in the presence of one of the factors, glycolytic enzyme glucose-6-phosphate isomerase (GPI), or AICAR-CM, increased the proportion of neuronal (Tuj1+) and astrocytic, glial fibrillary acidic protein (GFAP+) cells. Our study provides further evidence that proteins secreted from skeletal muscle cells may serve as a critical communication link to the brain through factors that enhance neural differentiation.
Project description:Satellite cells, also known as muscle stem cells, are responsible for skeletal muscle growth and repair in mammals. Pax7 and Pax3 transcription factors are established satellite cell markers required for muscle development and regeneration, and there is great interest in identifying additional factors that regulate satellite cell proliferation, differentiation, and/or skeletal muscle regeneration. Due to the powerful regenerative capacity of many zebrafish tissues, even in adults, we are exploring the regenerative potential of adult zebrafish skeletal muscle. Here, we show that adult zebrafish skeletal muscle contains cells similar to mammalian satellite cells. Adult zebrafish satellite-like cells have dense heterochromatin, express Pax7 and Pax3, proliferate in response to injury, and show peak myogenic responses 4-5 days post-injury (dpi). Furthermore, using a pax7a-driven GFP reporter, we present evidence implicating satellite-like cells as a possible source of new muscle. In lieu of central nucleation, which distinguishes regenerating myofibers in mammals, we describe several characteristics that robustly identify newly-forming myofibers from surrounding fibers in injured adult zebrafish muscle. These characteristics include partially overlapping expression in satellite-like cells and regenerating myofibers of two RNA-binding proteins Rbfox2 and Rbfoxl1, known to regulate embryonic muscle development and function. Finally, by analyzing pax7a; pax7b double mutant zebrafish, we show that Pax7 is required for adult skeletal muscle repair, as it is in the mouse.