Myogenin: A myogenic regulatory factor that controls myogenesis. Myogenin is induced during differentiation of every skeletal muscle cell line that has been investigated, in contrast to the other myogenic regulatory factors that only appear in certain cell types.MyoD Protein: A myogenic regulatory factor that controls myogenesis. Though it is not clear how its function differs from the other myogenic regulatory factors, MyoD appears to be related to fusion and terminal differentiation of the muscle cell.Myogenic Regulatory Factors: A family of muscle-specific transcription factors which bind to DNA in control regions and thus regulate myogenesis. All members of this family contain a conserved helix-loop-helix motif which is homologous to the myc family proteins. These factors are only found in skeletal muscle. Members include the myoD protein (MYOD PROTEIN); MYOGENIN; myf-5, and myf-6 (also called MRF4 or herculin).Myogenic Regulatory Factor 5: A SKELETAL MUSCLE-specific transcription factor that contains a basic HELIX-LOOP-HELIX MOTIF. It plays an essential role in MUSCLE DEVELOPMENT.Muscle Development: Developmental events leading to the formation of adult muscular system, which includes differentiation of the various types of muscle cell precursors, migration of myoblasts, activation of myogenesis and development of muscle anchorage.Muscle Proteins: The protein constituents of muscle, the major ones being ACTINS and MYOSINS. More than a dozen accessory proteins exist including TROPONIN; TROPOMYOSIN; and DYSTROPHIN.Myoblasts: Embryonic (precursor) cells of the myogenic lineage that develop from the MESODERM. They undergo proliferation, migrate to their various sites, and then differentiate into the appropriate form of myocytes (MYOCYTES, SKELETAL; MYOCYTES, CARDIAC; MYOCYTES, SMOOTH MUSCLE).Muscle, Skeletal: A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.Muscles: Contractile tissue that produces movement in animals.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.MEF2 Transcription Factors: Activating transcription factors of the MADS family which bind a specific sequence element (MEF2 element) in many muscle-specific genes and are involved in skeletal and cardiac myogenesis, neuronal differentiation and survival/apoptosis.Rhabdomyosarcoma, Embryonal: A form of RHABDOMYOSARCOMA arising primarily in the head and neck, especially the orbit, of children below the age of 10. The cells are smaller than those of other rhabdomyosarcomas and are of two basic cell types: spindle cells and round cells. This cancer is highly sensitive to chemotherapy and has a high cure rate with multi-modality therapy. (From Holland et al., Cancer Medicine, 3d ed, p2188)Helix-Loop-Helix Motifs: Recurring supersecondary structures characterized by 20 amino acids folding into two alpha helices connected by a non-helical "loop" segment. They are found in many sequence-specific DNA-BINDING PROTEINS and in CALCIUM-BINDING PROTEINS.Transcription Factor 7-Like 1 Protein: A transcription factor that takes part in WNT signaling pathway where it may play a role in the differentiation of KERATINOCYTES. The transcriptional activity of this protein is regulated via its interaction with BETA CATENIN.Myoblasts, Skeletal: Precursor cells destined to differentiate into skeletal myocytes (MYOCYTES, SKELETAL).Satellite Cells, Skeletal Muscle: Elongated, spindle-shaped, quiescent myoblasts lying in close contact with adult skeletal muscle. They are thought to play a role in muscle repair and regeneration.Rhabdomyosarcoma, Alveolar: A form of RHABDOMYOSARCOMA occurring mainly in adolescents and young adults, affecting muscles of the extremities, trunk, orbital region, etc. It is extremely malignant, metastasizing widely at an early stage. Few cures have been achieved and the prognosis is poor. "Alveolar" refers to its microscopic appearance simulating the cells of the respiratory alveolus. (Holland et al., Cancer Medicine, 3d ed, p2188)Muscle Fibers, Skeletal: Large, multinucleate single cells, either cylindrical or prismatic in shape, that form the basic unit of SKELETAL MUSCLE. They consist of MYOFIBRILS enclosed within and attached to the SARCOLEMMA. They are derived from the fusion of skeletal myoblasts (MYOBLASTS, SKELETAL) into a syncytium, followed by differentiation.Rhabdomyosarcoma: A malignant solid tumor arising from mesenchymal tissues which normally differentiate to form striated muscle. It can occur in a wide variety of sites. It is divided into four distinct types: pleomorphic, predominantly in male adults; alveolar (RHABDOMYOSARCOMA, ALVEOLAR), mainly in adolescents and young adults; embryonal (RHABDOMYOSARCOMA, EMBRYONAL), predominantly in infants and children; and botryoidal, also in young children. It is one of the most frequently occurring soft tissue sarcomas and the most common in children under 15. (From Dorland, 27th ed; Holland et al., Cancer Medicine, 3d ed, p2186; DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, pp1647-9)Muscle Denervation: The resection or removal of the innervation of a muscle or muscle tissue.Desmin: An intermediate filament protein found predominantly in smooth, skeletal, and cardiac muscle cells. Localized at the Z line. MW 50,000 to 55,000 is species dependent.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.PAX7 Transcription Factor: A paired box transcription factor that is involved in EMBRYONIC DEVELOPMENT of the CENTRAL NERVOUS SYSTEM and SKELETAL MUSCLE.DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.Inhibitor of Differentiation Protein 1: A negative regulator of BASIC HELIX-LOOP-HELIX TRANSCRIPTION FACTORS that blocks activation of CYCLIN-DEPENDENT KINASE INHIBITOR P16 and is de-regulated in a variety of NEOPLASMS.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Creatine Kinase, MM Form: An isoenzyme of creatine kinase found in the MUSCLE.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.TCF Transcription Factors: A family of DNA-binding proteins that are primarily expressed in T-LYMPHOCYTES. They interact with BETA CATENIN and serve as transcriptional activators and repressors in a variety of developmental processes.Myosin Heavy Chains: The larger subunits of MYOSINS. The heavy chains have a molecular weight of about 230 kDa and each heavy chain is usually associated with a dissimilar pair of MYOSIN LIGHT CHAINS. The heavy chains possess actin-binding and ATPase activity.Trans-Activators: Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins.Gene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Promoter Regions, Genetic: DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Myostatin: A growth differentiation factor that is a potent inhibitor of SKELETAL MUSCLE growth. It may play a role in the regulation of MYOGENESIS and in muscle maintenance during adulthood.Creatine Kinase: A transferase that catalyzes formation of PHOSPHOCREATINE from ATP + CREATINE. The reaction stores ATP energy as phosphocreatine. Three cytoplasmic ISOENZYMES have been identified in human tissues: the MM type from SKELETAL MUSCLE, the MB type from myocardial tissue and the BB type from nervous tissue as well as a mitochondrial isoenzyme. Macro-creatine kinase refers to creatine kinase complexed with other serum proteins.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.