Research Funded by RLS Foundation is Getting Results

An excerpt from the Winter 2017 edition of NightWalkers, the Foundation's quarterly magazine.

From the seeds of an RLS Foundation grant, researcher Byron Jones, PhD, has grown a genetic reference population of mice that is poised to serve as an animal model for RLS research. In 2004, the RLS Foundation awarded Byron Jones, PhD, an $8,000 grant for a project to start a mouse colony that could be used in research to help identify RLS-related genes. Over the course of 12 years and many mouse generations, Jones has employed a genetic reference colony that not only has helped unearth three possible RLS genes, but also may provide a model for studying RLS and testing treatments. Jones’s program is summarized in a recent review article in Sleep Medicine (1).

“The human genome informs the mouse genome,” says Jones. “It’s partly tongue in cheek, but also serious. … Genetic information in the mouse is, 90 percent or better, the same as in humans.”

“We need to understand how things happen at the cellular, molecular level,” he says. “The drugs we use are superficial – not cures. I want to go after what is causing RLS, and how we can intervene to prevent this [disease]. You need to know how it works before you can cure it.”

BXD40: A Match for RLS Iron Regulation

In the RLS-funded project, Jones (then at Penn State) set out to find an inbred mouse strain whose genetics, when deprived of iron, produced the same biological characteristics (phenotypes) as RLS. He obtained mice known to be different in all kinds of phenotypes, and tested them for differences in their response to iron deficiency. Jones’s team studied over 30 strains of mice to identify a strain called BXD40 that met their criteria. When fed an iron-deficient diet, the BXD40 females showed great loss of iron in the substantia nigra region of the brain, but hardly any loss in the periphery – matching the iron deficiency profile of RLS in humans.

During the project, Jones was invited by Johns Hopkins researchers Christopher Earley, MD, PhD, and Richard Allen, PhD, to collaborate on researching genetics and iron regulation in the brain. Allen showed that BXD40 mice had phenotype characteristics the same as people with RLS – namely, altered sleep patterns and problems with their sensory systems.

This team identified three genes seemingly involved in iron regulation that were not previously known to play a role in RLS – among them, the gene BTBD9.

“We literally stumbled upon these mice, but it was a planned stumbling,” says Jones. “We struck a homer.”

Other scientists like Yuqing Li, PhD, an RLS Foundation grant recipient, at the University of Florida, are using these findings to further explore BTBD9 in genetic models of RLS.

A ‘Perfect Experimental Platform’

Jones subsequently was awarded two R01 grants from the National Institutes of Health – one to continue this work on genetic regulation of iron in the brain, and the other to study the effects of chronic stress on alcohol consumption. His research team (now at the University of Tennessee) has controlled breeding within the colony to create strains with fixed genotype so that all are genetically alike. They have grown the mouse colony, generation by generation, to include over 100 strains of mice. Jones calls this a “perfect experimental platform.” Scientists can now look at the effects of the different genes by going into the colony, choosing mice with a particular genetic profile, and testing them to answer scientific questions. Strains can also be tested in different laboratories to tease out the effects of environmental factors.

“We get remarkable replication of experimental results across all laboratories,” says Jones.

Matching RLS Behaviors and Response to Medication

In recent work, Jones and collaborator Erica Unger, PhD (at Lebanon Valley College in Anville, Pennsylvania), matched the BXD40 model with RLS behaviors. Unger analyzed the 24-hour activity levels of BXD40 mice compared with five other BX strains. The BXD40 showed that with dietary iron deficiency, the BXD40 mice had an increase in activity in the last part of their active cycle and first part of their rest cycle – matching the cycle of RLS symptoms in humans. No other strain showed this circadian change in behavior. Unger also tested this model with RLS medications. Preliminary data showed that treating the BXD40 animals with levodopa or quinpirole significantly reversed the decreased rest time and increased activity.

The result: a potential RLS animal model in the iron-deficient BXD40 mouse which shows the many characteristics of RLS in humans – iron regulation, behaviors, and response to dopaminergic drugs. Jones plans to use this animal model to build on his RLS research.

“We were able to find some animal verifications of what was going on with humans, and that’s always cool,” says Jones. “Now, if we find out how the protein BTBD9 operates in the brain in iron management, then instead of treating RLS with a dopamine agonist, we might find some agent that alters the expression of this gene.”

1 Allen RP, Donelson NC, Jones BC, Li Y, Manconi M, Rye DB, Sanyal S, Winkelmann J. “Animal models of RLS phenotypes.” Sleep Medicine 2016 Sep 2 (Epub ahead of print).

In 2016 the Foundation's Research Grant Program has pledged to increase its RLS research funding to $200,000 annually for up to eight pilot grants. Since 1997 The Foundation has funded nearly $1.6 million in competitive research grants for the study of RLS. Read more about the other funded research here.