Getting the wires crossed: New research identifies cause of mirror movements

By Christine Zeindler

Ever notice when babies kick, both legs move at the same time? This “mirror movement” between the left and right side of the body is normal for infants. However, as the brain and motor systems develop, we learn to move our right and left limbs independent of one another. Some people however, may never master this and movements on the right side are mimicked by the left into adulthood. For example, when an adult with mirror movement taps his right foot to music, his left foot will also keep beat.
Now new research has identified a mutation in a gene called DCC that affects the nervous system and causes this inability to independently move one side and not the other.
“Adult mirror movement is very rare, but it is a phenomena observed throughout the world,” says lead author Dr. Myriam Srour, a pediatric neurologist at The Montreal Children’s Hospital of the McGill University Health Centre. “Although parents may find this trait disturbing, children do learn to adapt by suppressing the undesired movement so the condition is less obvious.”
Dr. Srour along with her colleagues from the Université de Montréal, CHU Sainte-Justine, Centre Hospitalier de l'Université de Montréal, Institut de Recherches Cliniques de Montreal, Montreal Heart Institute and Jundishapour University of Medical Sciences, analyzed the genes from four generations of a French-Canadian family affected by mirror movement. All had the same DCC mutation. Mutations in the same gene were found in an Iranian family with the same condition.
“Discovery of this mutation is significant as it is the first to indicate a role for DCC in human brain development and provides clues as to how the brain is wired,” says Dr. Srour. “Now that we know the gene mutation responsible our next steps are to see if this disrupts any other body systems at a subtle level.”
The study results were published in the journal Science in April, 2010. The study was funded by the Canadian Institutes of Health Research.
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