Collagen mutations cause disorders
Structural proteins such as collagen are made in large amounts, and any variation in their make-up is very noticeable. There are more than 30 different genes for collagen in humans, and genetic mutations can weaken the structures supported by collagen. Some mutations are fatal; others can cause problems such as slow growth and bones that break easily. Brittle bone disease, or osteogenesis imperfecta, arises from mutations in one type of collagen (read our Real Voices interview with Samantha Renke for more on this condition).
Alterations to some other forms of collagen affect connective tissue. People with Ehlers–Danlos syndrome, which is also caused by a range of different mutations, may have very stretchy skin that bruises easily and heals badly. Ehlers–Danlos syndrome can also cause weakness in heart valves, weakness in the walls of the bladder or uterus, and floppy joints.
Some of these problems arise directly from changes in collagen protein sequences. Others are caused by changes in the enzymes that alter some amino acids after the basic protein is made, a process called post-translational modification.
Those enzymes – that convert proline to hydroxyproline or lysine to hydroxylysine – also depend on vitamin C. Many of the symptoms of scurvy (vitamin C deficiency) are seen in connective tissue. Leaky capillaries cause bleeding under the skin, teeth come loose, and wounds no longer heal.