The Genes....[JEB]

What genes are related to Junctional Epidermolysis Bullosa?

Junctional Epidermolysis Bullosa [JEB] is caused due to the mutations in the LAMA3, LAMB3, LAMC2 and COL17A1 genes. Mutations in each of these genes can cause Herlitz JEB or non-Herlitz JEB. LAMB3 gene mutations are the most common causing almost 70% of all cases of JEB.

Each of the LAMA3, LAMB3 and LAMC2 gene provides instructions for making one part (subunit) of a protein called ‘Laminin 332’. This protein plays an important role in strengthening and stabilizing the skin by helping the top layer of skin (the epidermis) to attach with the underlying layers. Mutations in any of the three ‘Laminin 332’ genes lead to the production of a defective or non-functional version of this protein. Without functional laminin 332, cells in the epidermis become fragile and easily damaged. Friction or other minor trauma can cause the skin layers to separate, causing the formation of blisters.

The COL17A1 gene provides instructions for making a protein which used to assemble type ‘XVII collagen’. Collagen provides structure and strength to connective tissues such as skin, tendons and ligaments throughout the body. Type XVII collagen helps the epidermis to attach with underlying layers of skin, making the skin strong and flexible. Mutations in the COL17A1 gene prevent the normal formation of collagen XVII — as a result, the skin become less resistant to friction which leads to the formation of blisters due to minor trauma. Most COL17A1 gene mutations cause non-Herlitz JEB, although a few individuals with mutations in this gene have had the more severe Herlitz JEB.