Myogenic factor 6 (also known as Mrf4 or herculin) is a protein that in humans is encoded by the MYF6 gene. [5] This gene is also known in the biomedical literature as MRF4 and herculin. MYF6 is a myogenic regulatory factor (MRF) involved in the process known as myogenesis. [6] [7]
MYF6/Mrf4 is a member of the myogenic factor (MRF) family of transcription factors that regulate skeletal muscle myogenesis and muscle regeneration. Myogenic factors are basic helix-loop-helix (bHLH) transcription factors. MYF6 is a gene that encodes a protein involved in the regulation of myogenesis. The precise role(s) of Myf6/Mrf4 in myogenesis are unclear, although in mice it is able to initiate myogenesis in the absence of Myf5 and MyoD, two other MRFs. [8] The portion of the protein integral to myogenesis regulation requires the basic helix-loop-helix (bHLH) domain that is conserved among all of the genes in the MRF family.
MYF6 is expressed exclusively in skeletal muscle, and it is expressed at a higher levels in adult skeletal muscle than all of the other MRF family genes. In mouse, Myf6/Mrf4 differs somewhat from the other MRF genes due to its two-phase expression. Initially, Myf6 is transiently expressed along with Myf-5 in the somites during the early stages of myogenesis. However, it is more noticeably expressed postnatally. This suggests that it serves an important role in the maintenance and repair of adult skeletal muscle. [9]
The MYF6 gene is physically linked to the MYF5 gene on chromosome 12, and similar linkage is observed in all vertebrates. Mutations in the mouse Myf6 gene typically exhibit reduced levels of Myf5. [10] Despite reductions in muscle mass of the back and defective rib formation, Myf6 mutants still exhibit fairly normal skeletal muscle. This demonstrates that Myf6 is not essential for the formation of most myofibers, at least in the strains of mice tested.
In zebrafish, Myf6/Mrf4 is expressed in all terminally differentiated muscle examined, but expression has not been reported in muscle precursor cells. [11]
Mutations in the MYF6 gene are associated with autosomal dominant centronuclear myopathy (ADCNM) and Becker's muscular dystrophy. [12]
MyoD, also known as myoblast determination protein 1, is a protein in animals that plays a major role in regulating muscle differentiation. MyoD, which was discovered in the laboratory of Harold M. Weintraub, belongs to a family of proteins known as myogenic regulatory factors (MRFs). These bHLH transcription factors act sequentially in myogenic differentiation. Vertebrate MRF family members include MyoD1, Myf5, myogenin, and MRF4 (Myf6). In non-vertebrate animals, a single MyoD protein is typically found.
Myosatellite cells, also known as satellite cells, muscle stem cells or MuSCs, are small multipotent cells with very little cytoplasm found in mature muscle. Satellite cells are precursors to skeletal muscle cells, able to give rise to satellite cells or differentiated skeletal muscle cells. They have the potential to provide additional myonuclei to their parent muscle fiber, or return to a quiescent state. More specifically, upon activation, satellite cells can re-enter the cell cycle to proliferate and differentiate into myoblasts.
The PAX3 gene encodes a member of the paired box or PAX family of transcription factors. The PAX family consists of nine human (PAX1-PAX9) and nine mouse (Pax1-Pax9) members arranged into four subfamilies. Human PAX3 and mouse Pax3 are present in a subfamily along with the highly homologous human PAX7 and mouse Pax7 genes. The human PAX3 gene is located in the 2q36.1 chromosomal region, and contains 10 exons within a 100 kb region.
Myogenesis is the formation of skeletal muscular tissue, particularly during embryonic development.
Myogenin, is a transcriptional activator encoded by the MYOG gene. Myogenin is a muscle-specific basic-helix-loop-helix (bHLH) transcription factor involved in the coordination of skeletal muscle development or myogenesis and repair. Myogenin is a member of the MyoD family of transcription factors, which also includes MyoD, Myf5, and MRF4.
Myogenic regulatory factors (MRF) are basic helix-loop-helix (bHLH) transcription factors that regulate myogenesis: MyoD, Myf5, myogenin, and MRF4.
An E-box is a DNA response element found in some eukaryotes that acts as a protein-binding site and has been found to regulate gene expression in neurons, muscles, and other tissues. Its specific DNA sequence, CANNTG, with a palindromic canonical sequence of CACGTG, is recognized and bound by transcription factors to initiate gene transcription. Once the transcription factors bind to the promoters through the E-box, other enzymes can bind to the promoter and facilitate transcription from DNA to mRNA.
Transcription factor 3, also known as TCF3, is a protein that in humans is encoded by the TCF3 gene. TCF3 has been shown to directly enhance Hes1 expression.
Myocyte-specific enhancer factor 2C also known as MADS box transcription enhancer factor 2, polypeptide C is a protein that in humans is encoded by the MEF2C gene. MEF2C is a transcription factor in the Mef2 family.
Serum response factor, also known as SRF, is a transcription factor protein.
Myocyte-specific enhancer factor 2A is a protein that in humans is encoded by the MEF2A gene. MEF2A is a transcription factor in the Mef2 family. In humans it is located on chromosome 15q26. Certain mutations in MEF2A cause an autosomal dominant form of coronary artery disease and myocardial infarction.
Paired-like homeodomain transcription factor 2 also known as pituitary homeobox 2 is a protein that in humans is encoded by the PITX2 gene.
Cysteine and glycine-rich protein 3 also known as cardiac LIM protein (CLP) or muscle LIM protein (MLP) is a protein that in humans is encoded by the CSRP3 gene.
Class A basic helix-loop-helix protein 15 (bHLHa15) also known as class B basic helix-loop-helix protein 8 (bHLHb8) or muscle, intestine and stomach expression 1 (MIST-1) is a protein that in humans is encoded by the BHLHA15 gene.
Myosin-8 is a protein that in humans is encoded by the MYH8 gene.
"Basic helix-loop-helix family, member e41", or BHLHE41, is a gene that encodes a basic helix-loop-helix transcription factor repressor protein in various tissues of both humans and mice. It is also known as DEC2, hDEC2, and SHARP1, and was previously known as "basic helix-loop-helix domain containing, class B, 3", or BHLHB3. BHLHE41 is known for its role in the circadian molecular mechanisms that influence sleep quantity as well as its role in immune function and the maturation of T helper type 2 cell lineages associated with humoral immunity.
Ryanodine receptor 1 (RYR-1) also known as skeletal muscle calcium release channel or skeletal muscle-type ryanodine receptor is one of a class of ryanodine receptors and a protein found primarily in skeletal muscle. In humans, it is encoded by the RYR1 gene.
In molecular biology, the myogenic determination factor 5 proteins are a family of proteins found in eukaryotes. This family includes the Myf5 protein, which is responsible for directing cells to the skeletal myocyte lineage during development. Myf5 is likely to act in a similar way to the other MRF4 proteins such as MyoD which perform the same function. These are histone acetyltransferases and histone deacetylases which activate and repress genes involved in the myocyte lineage.
Myogenic factor 5 is a protein that in humans is encoded by the MYF5 gene. It is a protein with a key role in regulating muscle differentiation or myogenesis, specifically the development of skeletal muscle. Myf5 belongs to a family of proteins known as myogenic regulatory factors (MRFs). These basic helix loop helix transcription factors act sequentially in myogenic differentiation. MRF family members include Myf5, MyoD (Myf3), myogenin, and MRF4 (Myf6). This transcription factor is the earliest of all MRFs to be expressed in the embryo, where it is only markedly expressed for a few days. It functions during that time to commit myogenic precursor cells to become skeletal muscle. In fact, its expression in proliferating myoblasts has led to its classification as a determination factor. Furthermore, Myf5 is a master regulator of muscle development, possessing the ability to induce a muscle phenotype upon its forced expression in fibroblastic cells.
Margaret Buckingham, is a British developmental biologist working in the fields of myogenesis and cardiogenesis. She is an honorary professor at the Pasteur Institute in Paris and emeritus director in the Centre national de la recherche scientifique (CNRS). She is a member of the European Molecular Biology Organization, the Academia Europaea and the French Academy of Sciences.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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