Scientists,led by an Indian-origin researcher,have found that a gene involved in neurodegenerative disease also plays a critical role in the proper function of the circadian clock. In a study of the common fruit fly,researchers from Northwestern University found that the gene,called Ataxin-2,keeps the clock responsible for sleeping and waking on a 24-hour rhythm. Without the gene,the rhythm of the fruit fly’s sleep-wake cycle is disturbed,making waking up on a regular schedule difficult for the fly.
The discovery is particularly interesting because mutations in the human Ataxin-2 gene are known to cause a rare disorder called spino cerebellar ataxia (SCA) and also contribute to amyotrophic lateral sclerosis (ALS),also known as Lou Gehrig’s disease.
This study linking the Ataxin-2 gene with abnormalities in the sleep-wake cycle could help pinpoint what is causing these neurode generative diseases as well as provide a deeper understanding of the human sleep-wake cycle.Period (per) is a well-studied gene in fruit flies that encodes a protein,called PER,which regulates circadian rhythm.
Ravi Allada,professor of neurobiology in the Weinberg College of Arts and Sciences,and Chunghun Lim,a postdoctoral fellow,in his lab discovered that Ataxin-2 helps activate translation of PER RNA into PER protein,a key step in making the circadian clock run properly.
“It’s possible that Ataxin-2’s function as an activator of protein translation may be central to understanding how,when you mutate the gene and disrupt its function,it may be causing or contributing to diseases such as ALS or spino cerebellar ataxia,” Allada said. The fruit fly Drosophila melano gaster is a model organism for scientists studying the sleep-wake cycle because the fly’s genes are highly conserved with the genes of humans.
Ataxin-2 is the second gene in a little more than two years that Northwestern researchers have identified as a core gear of the circadian clock,and the two genes play similar roles.
Allada,Lim and colleagues in 2011 reported their discovery of a gene,which they dubbed “twenty-four,” that plays a role in translating the PER protein,keeping the sleep-wake cycle on a 24-hour rhythm.
Researchers found the twenty-four protein sticking toATAXIN-2 and decided to investigate further. In their experiments,Allada and Lim discovered the Ataxin-2 and twenty-four genes appear to be partners in PER protein translation. “We’ve really started to define a pathway that regulates the circadian clock and seems to be especially important in a specific group of neurons that governs the fly’s morning wake-up,” Allada said. The study was published in the journal Science.