COL6A3 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Aliases | COL6A3 , DYT27, BTHLM1, UCMD1, collagen type VI alpha 3, collagen type VI alpha 3 chain | ||||||||||||||||||||||||||||||||||||||||||||||||||
External IDs | OMIM: 120250 MGI: 88461 HomoloGene: 37917 GeneCards: COL6A3 | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Collagen alpha-3(VI) chain is a protein that in humans is encoded by the COL6A3 gene. [5] [6] [7] This protein is an alpha chain of type VI collagen that aids in microfibril formation. [8] As part of type VI collagen, this protein has been implicated in Bethlem myopathy, Ullrich congenital muscular dystrophy (UCMD), and other diseases related to muscle and connective tissue. [7] [9] [10]
This gene encodes the alpha 3 chain, one of the three alpha chains of type VI collagen, a beaded filament collagen found in most connective tissues. The alpha 3 chain of type VI collagen is much larger than the alpha 1 and 2 chains. This difference in size is largely due to an increase in the number of subdomains, similar to von Willebrand Factor type A domains, found in the amino terminal globular domain of all the alpha chains. In addition to the full length transcript, four transcript variants have been identified that encode proteins with N-terminal globular domains of varying sizes. [7]
The alpha 3 type VI chain has been shown to bind extracellular matrix proteins, an interaction that explains the importance of this collagen in organizing matrix components. [7] Microfibril formation has been traced to interactions between its N-terminal subdomain N5 and its C-terminal C5 domain in adjacent type VI collagen monomers. [8]
Mutations in the type VI collagen genes are associated with Bethlem myopathy and Ullrich congenital muscular dystrophy (UCMD). [7] [9] Typically, both Bethlem myopathy and autosomal recessive UCMD patients are heterozygous for mutations in the three type VI collagen alpha chains, but only the former exhibit symptoms. Of the three alpha chains, COL6A3 mutations contribute to only 18% of the Bethlem myopathy and UCMD cases. [9] A study on UCMD mutations by Zhang et al found only one non-pathogenic mutation in COL6A3. [10] Nonetheless, knockdown of mutant COL6A3 in patient fibroblast cells using siRNA has successfully improved cellular deposition of type VI collagen in autosomal dominant UCMD, and may become a promising treatment for it. [9] Though high expression levels of COL6A3 have been correlated with obesity and diabetes in mice, this relationship was not observed in humans. [11] Other disorders involving muscle and connective tissue include weakness, joint laxity and contractures, and abnormal skin. [9]
Laminins are a family of glycoproteins of the extracellular matrix of all animals. They are major constituents of the basement membrane, namely the basal lamina. Laminins are vital to biological activity, influencing cell differentiation, migration, and adhesion.
Congenital muscular dystrophies are autosomal recessively-inherited muscle diseases. They are a group of heterogeneous disorders characterized by muscle weakness which is present at birth and the different changes on muscle biopsy that ranges from myopathic to overtly dystrophic due to the age at which the biopsy takes place.
Bethlem myopathy is predominantly an autosomal dominant myopathy, classified as a congenital form of muscular dystrophy. There are two types of Bethlem myopathy, based on which type of collagen is affected.
Collagen alpha-1(V) chain is a protein that in humans is encoded by the COL5A1 gene.
Collagen alpha-1(VII) chain is a protein that in humans is encoded by the COL7A1 gene. It is composed of a triple helical, collagenous domain flanked by two non-collagenous domains, and functions as an anchoring fibril between the dermal-epidermal junction in the basement membrane. Mutations in COL7A1 cause all types of dystrophic epidermolysis bullosa, and the exact mutations vary based on the specific type or subtype. It has been shown that interactions between the NC-1 domain of collagen VII and several other proteins, including laminin-5 and collagen IV, contribute greatly to the overall stability of the basement membrane.
Collagen alpha-5(IV) chain is a protein that in humans is encoded by the COL4A5 gene.
Collagen alpha-3(IV) chain is a protein that in humans is encoded by the COL4A3 gene.
Collagen alpha-1(IV) chain (COL4A1) is a protein that in humans is encoded by the COL4A1 gene on chromosome 13. It is ubiquitously expressed in many tissues and cell types. COL4A1 is a subunit of the type IV collagen and plays a role in angiogenesis. Mutations in the gene have been linked to diseases of the brain, muscle, kidney, eye, and cardiovascular system. The COL4A1 gene also contains one of 27 SNPs associated with increased risk of coronary artery disease.
Collagen alpha-4(IV) chain is a protein that in humans is encoded by the COL4A4 gene.
Collagen alpha-1(VI) chain is a protein that in humans is encoded by the COL6A1 gene.
Laminin subunit beta-1 is a protein that in humans is encoded by the LAMB1 gene.
Laminin subunit alpha-2 is a protein that in humans is encoded by the LAMA2 gene.
Collagen alpha-2(VI) chain is a protein that in humans is encoded by the COL6A2 gene.
Laminin subunit alpha-4 is a protein that in humans is encoded by the LAMA4 gene.
Collagen alpha-1(XII) chain is a protein that in humans is encoded by the COL12A1 gene.
Collagen alpha-3(V) chain is a protein that in humans is encoded by the COL5A3 gene.
Collagen alpha-1(XVI) chain is a protein that in humans is encoded by the COL16A1 gene.
Ullrich congenital muscular dystrophy (UCMD) is a form of congenital muscular dystrophy. There are two forms: UCMD1 and UCMD2.
Collagen VI (ColVI) is a type of collagen primarily associated with the extracellular matrix of skeletal muscle. ColVI maintains regularity in muscle function and stabilizes the cell membrane. It is synthesized by a complex, multistep pathway that leads to the formation of a unique network of linked microfilaments located in the extracellular matrix (ECM). ColVI plays a vital role in numerous cell types, including chondrocytes, neurons, myocytes, fibroblasts, and cardiomyocytes. ColVI molecules are made up of three alpha chains: α1(VI), α2(VI), and α3(VI). It is encoded by 6 genes: COL6A1, COL6A2, COL6A3, COL6A4, COL6A5, and COL6A6. The chain lengths of α1(VI) and α2(VI) are about 1,000 amino acids. The chain length of α3(VI) is roughly a third larger than those of α1(VI) and α2(VI), and it consists of several spliced variants within the range of 2,500 to 3,100 amino acids.