Collagen Types and Linked Disorders

There are 29 genetically distinct collagens present in animal tissues. Collagen types I, II, III, V and XI self-assemble into D-periodic cross-striated fibrils. Here the D is approximately 67 nm and there is characteristic axial periodicity of collagen. These form the most abundant collagens in vertebrates.

Collagen types I - V

• Type I collagen is found throughout the body except in cartilaginous tissues. It is found in skin, tendon, vascular, ligature, organs and is the main component of bone. It is also synthesized in response to injury and in the fibrous nodules in fibrous diseases. Over 90% of the collagen in the body is type I.
• Type II collagen is the main component of cartilage. It is also found in developing cornea and vitreous humour. These are formed from two or more collagens or co-polymers rather than a single type of collagen.
• Type III collagen is found in the walls of arteries and other hollow organs and usually occurs in the same fibril with type I collagen.
• Type IV forms the bases of cell basement membrane

• Type V collagen and type XI collagen are minor components of tissue and occur as fibrils with type I and type II collagen respectively. Type V forms cell surfaces, hair and placenta.

Collagen linked diseases

Due to the diverse location of the collagen types they are associated with diseases. The collagen linked diseases commonly arise from genetic defects or nutritional deficiencies. These defects often cause problems in the biosynthesis of the collagen molecules, their assembly and posttranslational modification process that makes them their final end form of collagen.

There may be defects in collagen secretion and general production as well. In addition there is excess collagen formation and deposition in scleroderma.

Collagen-related diseases most commonly arise from genetic defects or nutritional deficiencies that affect the biosynthesis, assembly, postranslational modification, secretion, or other processes involved in normal collagen production.

Type Notes Gene(s) Disorders I This is the most abundant collagen of the human body. It is present in scar tissue, the end product when tissue heals by repair. It is found in tendons, skin, artery walls, the endomysium of myofibrils, fibrocartilage, and the organic part of bones and teeth. COL1A1, COL1A2 osteogenesis imperfecta, Ehlers-Danlos Syndrome, Infantile cortical hyperostosis aka Caffey's disease II Hyaline cartilage, makes up 50% of all cartilage protein. Vitreous humour of the eye. COL2A1 Collagenopathy III This is the collagen of granulation tissue, and is produced quickly by young fibroblasts before the tougher type I collagen is synthesized. Reticular fiber. Also found in artery walls, skin, intestines and the uterus COL3A1 Ehlers-Danlos Syndrome IV basal lamina; eye lens. Also serves as part of the filtration system in capillaries and the glomeruli of nephron in the kidney. COL4A1, COL4A2, COL4A3, COL4A4, COL4A5, COL4A6 Alport syndrome, Goodpasture's syndrome V most interstitial tissue, assoc. with type I, associated with placenta COL5A1, COL5A2, COL5A3 Ehlers-Danlos syndrome (Classical) VI most interstitial tissue, assoc. with type I COL6A1, COL6A2, COL6A3 Ulrich myopathy and Bethlem myopathy VII forms anchoring fibrils in dermal epidermal junctions COL7A1 epidermolysis bullosa dystrophica VIII some endothelial cells COL8A1, COL8A2 Posterior polymorphous corneal dystrophy 2 IX FACIT collagen, cartilage, assoc. with type II and XI fibrils COL9A1, COL9A2, COL9A3 - EDM2 and EDM3 X hypertrophic and mineralizing cartilage COL10A1 Schmid metaphyseal dysplasia XI cartilage COL11A1, COL11A2 Collagenopathy XII FACIT collagen, interacts with type I containing fibrils, decorin and glycosaminoglycans COL12A1 - XIII transmembrane collagen, interacts with integrin a1b1, fibronectin and components of basement membranes like nidogen and perlecan. COL13A1 - XIV FACIT collagen COL14A1 - XV - COL15A1 - XVI - COL16A1 - XVII transmembrane collagen, also known as BP180, a 180 kDa protein COL17A1 Bullous pemphigoid and certain forms of junctional epidermolysis bullosa XVIII source of endostatin COL18A1 - XIX FACIT collagen COL19A1 - XX - COL20A1 - XXI FACIT collagen COL21A1 - XXII - COL22A1 - XXIII MACIT collagen - COL23A1 - XXIV - COL24A1 - XXV - COL25A1 - XXVI - EMID2 - XXVII - COL27A1 - XXVIII - COL28A1 - XXIX epidermal collagen COL29A1 Atopic dermatitis

In addition to the above mentioned disorders, excessive deposition of collagen occurs in scleroderma.

Sources

Further Reading

• All Collagen Content
• Do Collagen Supplements Work? Science-Backed Benefits for Skin, Joints, and Muscles
• Collagen - What is Collagen?
• Collagen Molecular Structure
• Collagen Fibrillar Structure

Last Updated: Jun 17, 2023