May 2 (UPI) -- Researchers at Brown University have unlocked the method genetic mutations use to disrupt communication between neurons and muscles in spinal muscular atrophy, or SMA.
SMA is incurable and fatal in early childhood in its most severe form, but the first treatment for the disease was approved for use by the Food and Drug Administration in December 2016.
The disease affects one in 8,000 children and occurs when mutations in both copies of the gene responsible for the survival motor neuron, or SMN, protein stops its production resulting in the dysfunction of motor neurons that control muscles along with atrophy and weakness.
In its most acute form, children die by age 2 when muscles that control breathing become compromised.
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The first breakthrough in the disease came in the form of spinal cord injections of the newly approved drug nusinersen, which restores some motor function and prolongs life.
"If we can figure out what is going wrong, then maybe we can have combinatorial therapies -- one that raises SMN levels and one that helps neurons survive the challenge of too little SMN," Anne Hart, professor of neuroscience at Brown University, said in a press release.
Researchers at Brown in collaboration with the University of Cologne Germany identified a complex cause-and-effect sequence in both C. elegans worm and mouse models of SMA. Lacking SMN disrupts the working of the protein Gemin3, which lessens the activity of a particular microRNA needed to prevent the overexpression of a motor neuron receptor known as m2R.
Too many m2R receptors caused by overexpression in SMA causes the motor neurons to be too sensitive to their acetylcholine output, which causes them to shut off its release prematurely affecting muscle function.
Researchers discovered that the link between the SMA and the regulation of protein translation was the Gemin3 protein.
"If you decrease the activity of these receptors, it could be beneficial," Hart said. "This needs to be tried in other models, too."
Researchers were able to trace the entire mechanism and address it at several stages to restore healthy neuron development and muscle function in worms.
The study was published in the journal eLife.
