Sunday, August 10, 2014

How XPD/ ERCC2 cause XP .....

More than 24 mutations in the XPD/ERCC2 gene have been identified in people with Xeroderma Pigmentosum (XP). In USA, mutations in XPD gene are the second most common cause of XP.

The XPD/ERCC2 gene mutations prevent the TFIIH complex from repairing damaged DNA effectively. As a result, abnormalities accumulate in DNA, causing cells to malfunction and eventually the cells become cancerous or die. These problems with DNA repair cause people with XP to be extremely sensitive to UV rays from sunlight. When UV rays damage genes which control cell growth and division, cells can grow too fast and in an uncontrolled way. As a result, people with XP have a greatly increased risk of developing cancer. These cancers occur most frequently in areas of the body exposed to the sun such as the skin and eyes.

When XP is caused by XPD/ERCC2 gene mutations, it is often associated with progressive neurological abnormalities such as hearing loss, poor coordination, difficulty walking, movement problems, loss of intellectual function, difficulty swallowing & talking, seizures etc. The neurological abnormalities are thought to result from a buildup of DNA damage, although the brain is not exposed to UV rays. Researchers suspect that other factors damage DNA in nerve cells. It is unclear why some people with XP develop neurological abnormalities while others do not.

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