Study identifies trigger for Huntington's disease

By Will Dunham

WASHINGTON, April 22 (Reuters) - A mistake in the way the body's cells repair their DNA may trigger onset of Huntington's disease, researchers said in a finding they hope leads to better treatment of the incurable hereditary brain disease.

Writing on Sunday in the journal Nature, the researchers said their study involving mice explains the mechanism for how Huntington's disease begins and how it becomes worse over time in people who have inherited the gene that causes it.

Scientists knew a version of a gene called "huntingtin" caused the disease, which makes brain nerve cells waste away. But they had wondered what spurred its onset, usually in middle age.

A segment of the gene grows when cells try to remove lesions caused by a process called oxidation. This happens to DNA constantly in the body and usually cells can repair themselves.

With Huntington's, normal DNA repair enzymes keep these lesions in check at first but over time the growing numbers of lesions overwhelm the repair system, said Cynthia McMurray, a professor of pharmacology at the Mayo Clinic in Rochester, Minnesota.

"The key finding is that damage to the DNA and its normal repair is actually causing mutation leading to disease," McMurray said in a telephone interview.

"Nobody has connected the dots before," McMurray said a statement.