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Information about Sarcoglycan

The sarcoglcyans are a family of five transmembrane proteins (α, β, γ, δ or ε) involved in the protein complex responsible for connecting the muscle fibre cytoskeleton to the extracellular matrix, preventing damage the muscle fibre sarcolemma through shearing forces.

Mutations in the α, β, γ or δ genes (not ε) encoding these proteins can lead to the associated limb-girdle muscular dystrophy.

Genes

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Histology: muscle tissue
skeletal muscle/generalepimysium, fascicle, perimysium, endomysium, muscle fiber (intrafusal, extrafusal), myofibril sarcomere (a, i, and h bands; z and m lines), myofilaments (thin filament/actin, thick filament/myosin, elastic filament/titin, nebulin), tropomyosin, troponin (T, C, I) costamere (dystrophin, α,β-dystrobrevin, syncoilin, synemin/desmuslin, dysbindin, sarcoglycan, dystroglycan, sarcospan), desmin neuromuscular junction, motor unit, muscle spindle, excitation-contraction coupling, sliding filament mechanism myoblast, satellite cell, sarcoplasm, sarcolemma, sarcoplasmic reticulum, T-tubule
cardiac musclemyocardium, intercalated disc, nebulette
smooth musclecalmodulin, vascular smooth muscle
protein complex is a group of two or more associated proteins formed by protein-protein interaction that is stable over time. Protein complexes are a form of quaternary structure.
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cytoskeleton is a cellular "scaffolding" or "skeleton" contained, as all other organelles, within the cytoplasm. It is contained in all eukaryotic cells and recent research has shown it can be present in prokaryotic cells too.
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extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.
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The sarcolemma is the cell membrane of a muscle cell. The membrane is designed to receive and conduct stimuli.

Alterations in the sarcolemmal membrane stability and repair system can lead to muscular dystrophy.
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Limb-girdle muscular dystrophy
Classification & external resources

ICD-9 359.1

DiseasesDB 32189

eMedicine neuro/189  
MeSH D049288 Limb-girdle muscular dystrophy or Erb's muscular dystrophy
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Histology (from the Greek ἱστός) is the study of tissue sectioned as a thin slice, using a microtome. It can be described as microscopic anatomy.
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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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Skeletal muscle is a type of striated muscle, usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction.
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Epimysium is a layer of connective tissue which ensheaths the entire muscle. It is composed of dense irregular connective tissue. It is continuous with fascia and other connective tissue wrappings of muscle including the endomysium, and perimysium.
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In anatomy, a fascicle is a bundle of skeletal muscle fibers surrounded by connective tissue.

Specialized muscle fibers in the heart which transmit electrical impulses from the Atrioventricular Node (AV Node) to the Purkinje Fibers are fascicles, also referred to as bundle
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Perimysium is a sheath of connective tissue which groups individual muscle fibers ( anywhere between 10 to 100 or more) into bundles or fascicles

See also

  • Endomysium

External links

  • Histology at cytochemistry.

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The endomysium, literally meaning within the muscle, is a layer of connective tissue that ensheaths a muscle fiber and is composed mostly from reticular fibers. It also contains capillaries, nerves and lymphatics.
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muscle fiber, also spelled muscle fibre (see spelling differences), also technically known as a myocyte, is a single cell of a muscle. Muscle fibers contain many myofibrils, the contractile unit of muscles.
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Intrafusal fibers are muscle fibers that comprise the muscle spindle. These fibers are walled off from the rest of the muscle by a collagen sheath. This sheath has a spindle or "fusiform" shape, hence the name "intrafusal.
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Extrafusal muscle fibers are a class of muscle fiber innervated by alpha motor neurons.

They are motor neurons and generate tension, mechanical work and allow for movement by contracting.
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Myofibrils (obsolete term: sarcostyles) are cylindrical organelles, found within muscle cells. They are bundles of actomyosin filaments that run from one end of the cell to the other and are attached to the cell surface membrane at each end.
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A sarcomere is the basic unit of a muscle's cross-striated myofibril. Sarcomeres are multi-protein complexes composed of three different filament systems.
  • The thick filament system is composed of myosin protein which is connected from the M-line to the Z-disc by Titin

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The filaments of myofibrils constructed from proteins, myofilaments, consist of 2 types, thick and thin. Thin filaments consist primarily of the protein actin; thick filaments consist primarily of the protein myosin.
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Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
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Myosins are a large family of motor proteins found in eukaryotic tissues. They are responsible for actin-based motility.

Structure and Function

Domains

Most myosin molecules are composed of both a head and a tail domain.
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Not to be confused with Tintin.


Titin, also known as connectin[1] (UniProt name: Q10466_HUMAN; accession number: Q10466), is a protein that is important in the contraction of striated muscle tissues.
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Nebulin is an actin-binding protein which is localized to the I-band the sarcomeres in skeletal muscle. It is a very large protein (600-900 kDa) and binds as many as 200 actin monomers.
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Troponin is a complex of three proteins that is integral to muscle contraction in skeletal and cardiac muscle, but not smooth muscle. Troponin is attached to the protein tropomyosin and lies within the groove between actin filaments in muscle tissue.
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Troponin T is a part of the troponin complex. It binds to tropomyosin, interlocking them to form a troponin-tropomyosin complex.

The tissue specific subtypes are:
  • Slow skeletal troponin T1, TNNT1 (19q13.

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Troponin C is a part of the troponin complex. It binds to calcium ions to produce movement.

The tissue specific subtypes are:
  • Slow troponin C, TNNC1 (3p21.3-p14.3, Mendelian Inheritance in Man (OMIM) 191040 )
  • Fast troponin C, TNNC2 (20q12-q13.

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Troponin I is a part of the troponin complex. It binds to actin in thin myofilaments to hold the troponin-tropomyosin complex in place. The letter I is given due to its inhibitory character.
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The costamere is a structural-functional component of skeletal muscle cells which, according to original descriptions in the early 1980s (which are generally still accepted), are sub-sarcolemmal protein assemblies circumferentially aligned in register with the Z-disk of peripheral
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Dystrophin is a rod-shaped cytoplasmic protein, and a vital part of a protein complex that connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane.
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Identifiers
Symbol DTNB

Entrez 1838
HUGO 3058
OMIM 602415

RefSeq NM_033147
UniProt O60941
Other data

Locus Chr. 2 p24

Dystrobrevin is a protein that binds to dystrophin in the costamere of skeletal muscle cells.
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