What is elastin and what does it do in the skin?
Elastin is a protein that is essential for skin health and, you guessed it, essential for elasticity in the skin.
Sohte ELN gene encodes for a protein, called tropoelastin, which is one of two components of elastic fibers.
These elastic fibers maintains the elasticity to our numerous tissues, that supports body’s joints and organs. An intricate lattice is formed by the elastic fibers, found in the space between cells. This is where they give structural support to organs and tissues, like the heart, skin, lungs, ligaments and blood vessels.
Striae distensae, more commonly known as stretch marks. Before stretch marks appear, the skin will become thin, flattened and pink, sometimes feeling itchy. They initially appear as red, purple or pinkish lines. The often appear scar like, and occur in parallel lines or patches in the skin. In the beginning, the lines are slightly raised, before the eventually flatten. When the start to flatten they also start to fade in colour and become white and after time are less noticeable.
Stretch marks are just as the name explains, they usually result from sudden weight gain or growth. The stretching causes the middle skin layer to tear, allowing deeper skin layers to show through, appearing as a stretch mark. The tear in the dermis often allows blood vessels below to be seen, that is why they’re often red or purple in colour.
The dermis is made up of inter-connected fibers allowing your body to stretch as it grows. Stretch marks are estimated to be prevalent from 50 to 80%. The factors that play a role in the development of stretch marks are excessive skin distension (this can occur during pregnancy, growth spurts in puberty or rapid weight gain), prolonged exposure to cortisol, used in treatment of Cushing’s syndrome and genetics.
To date there are no isolated gene variants associated with stretch marks. A genome-wide association analysis of stretch marks in a discovery cohort using 23andMe participants of European descent. The conclusion that men we less likely to report stretch marks, 25% men vs. 55% of women.
Four regions were significantly associated with stretch marks. The most strongly associated gene associated variant in the first region with stretch marks is the ELN gene. It was also associated with stretch marks during pregnancy.
The A allele is the risk allele, and the AA genotype is found in over 40% of Europeans and in the general population at around 10%.
Elastin is a major component of elastic fibers, that are thin bundles of protein that provide flexibility and strength to connective tissue. Elastin helps these tissues to keep their form after stretching or contracting. The gene variant in elastin, result in a loss of mature elastin, which can also results in the below conditions.
There have been the identification of at least 16 ELN gene mutations with skin disorder called cutis laxa. This disorder is characterised by sagging skin, the increased risk of an aneurysm in the large blood vessel, the aorta and a lung disease emphysema, which makes it difficult to breathe. The ELN mutations that lead to cutis laxa produce very long tropoelastin. This interferes with the formation of mature elastin and assembling of the supportive elastic fiber network. This will weaken connective tissue in the skin and blood vessels. The defective connective tissue underlies the characteristics of cutis laxa.
In Williams syndrome, the ELN gene of chromosome 7 is deleted, this means that people will be missing one copy. This means that elastin production is reduced by 50%. The normal elastic fiber structure will no longer support blood vessels. This means that blood vessels are often thicker, form narrowings and are less resilient.
This syndrome, is associated with connective tissue abnormalities, such as joint problems, loose skin and cardiovascular disease.
Another condition linked to over 60 ELN gene mutations. It is called supravalvular aortic stenosis, a heart defect present from birth. Most of the gene mutations that cause this defect decrease the production of tropoelastin. This reduces the amount of mature elastin available to make up the elastic fibers. This results in the fibers making up the aorta to be thinner than normal. As compensation the smooth muscle thickens, the aorta becomes less flexible. This can damage the aorta over time. The narrowing of the aorta means the heart has to work harder which can lead to shortness of breath and heart failure.