When flies are made to lose a gene with links to Restless Legs Syndrome (RLS), they suffer the same sleep disturbances and restlessness that human patients do. The findings reported online on May 31 in Current Biology, a Cell Press publication, strongly suggest a genetic basis for RLS, a condition in which patients complain of an irresistible urge to move that gets worse as they try to rest.
"Although widely prevalent, RLS is a disorder whose pathophysiological basis remains very poorly understood," said Subhabrata Sanyal of Emory University School of Medicine. "The major significance of our study is to highlight the fact that there might be a genetic basis for RLS. Understanding the function of these genes also helps to understand and diagnose the disease and may offer more focused therapeutic options that are currently limited to very general approaches."
Sanyal's team recognized that a number of genome-wide association studies in humans had suggested connections between RLS and variation in a single gene (BTBD9).
"BTBD9 function or its relationship to RLS and sleep were a complete mystery," Sanyal said.
His team realized that there might be a way to shed some light on that mystery in fruit flies. Flies have a single, highly conserved version of the human BTBD9. They decided to test whether the gene that had turned up in those human studies would have any effect on sleep in the insects. In fact, flies need sleep just like humans do, and their sleep patterns are influenced by the same kinds of brain chemistry.
The researchers now report that flies lacking their version of the RLS-associated gene do lose sleep as they move more. When those flies were treated with a drug used for RLS, they showed improvements in their sleep.
The studies also yielded evidence about how the RLS gene works by controlling dopamine levels in the brain as well as iron balance in cells. Sanyal said his team will continue to explore other RLS-related genes that have been identified in human studies in search of more details of their interaction and function.
"Our results support the idea that genetic regulation of dopamine and iron metabolism constitute the core pathophysiology of at least some forms of RLS," the researchers write.
More broadly, they say, the study emphasizes the utility of simple animals such as fruit flies in unraveling the genetics of sleep and sleep disorders.
- Amanda Freeman, Elaine Pranski, R. Daniel Miller, Sara Radmard, Doug Bernhard, H.A. Jinnah, Ranjita Betarbet, David B. Rye, Subhabrata Sanyal. Sleep Fragmentation and Motor Restlessness in a Drosophila Model of Restless Legs Syndrome. Current Biology, 2012; DOI: 10.1016/j.cub.2012.04.027
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