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Shedding light on Restless Legs Syndrome via the Human Genome

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1 Shedding light on Restless Legs Syndrome via the Human Genome
Pharmacogenomic Implications Shedding light on Restless Legs Syndrome via the Human Genome David B. Rye Professor of Neurology Director, Emory University Program in Sleep Atlanta, GA David Rye, MD, PhD Professor of Neurology Director, Emory Healthcare Program in Sleep

2 RLS Affects Tens of Millions in the United States alone
RLS is more prevalent than originally believed1 RLS affects approximately 10% of the US adult population, yet often goes undiagnosed2 Approximately 12 million Americans suffer from moderate to severe ‘primary’ RLS2,3 RLS is more prevalent than originally believed1 RLS affects approximately 10% of the US adult population, yet often goes undiagnosed2 Approximately 12 million Americans suffer from moderate to severe primary RLS2,3 63% of patients with RLS report having at least one first-degree relative with the condition4 Hening W. Clin Neurophysiol. 2004;115: Hening W, et al. Sleep Med. 2004;5: NINDS, NIH; NIH Publication No References 1Hening W. The clinical neurophysiology of the restless legs syndrome and periodic limb movements. Part I: diagnosis, assessment, and characterization. Clin Neurophysiol. 2004;115: ; 2Hening W, Walters AS, Allen RP, et al. Impact, diagnosis and treatment of restless legs syndrome (RLS) in a primary care population: the REST (RLS epidemiology, symptoms, and treatment) primary care study. Sleep Med. 2004;5: ; 3Restless Legs Syndrome Fact Sheet. Bethesda, Md: National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH); NIH Publication No ; 4Montplaisir J, Boucher S, Poirier G, et al. Clinical, polysomnographic, and genetic characteristics of restless legs syndrome: a study of 133 patients diagnosed with new standard criteria. Mov Disord. 1997;12:61-65.

3 Burden of RLS is Significant
Depressed mood (OR = 2.6) Stroke & Cardiovascular disease (OR= ) Hypertension (OR = 1.5; *PLMs > 30/hr OR = 2.3) Ulfberg J, Nystrom B, Carter N, Edling C. Prevalence of restless legs syndrome among men aged 18 to 64 years: an association with somatic disease and neuropsychiatric symptoms. Mov Disord 2001;16: Winkelman J, Finn L, Young T. Prevalence and correlates of restless legs syndrome in the Wisconsin sleep cohort. Sleep 2005;28(Abst Suppl):A – Sleep Medicine 2006-May 30th (epub ahead of print) *Personal observations; Winkelman et al. (2008) Neurology 70:35-42


5 RLS remains a clinical diagnosis: IRLSSG/NIH Diagnostic Criteria for RLS
Urge to move legs, usually accompanied by uncomfortable leg sensations Onset or worsening of symptoms at rest or inactivity, such as when lying or sitting Relief with movement—partial or total relief from discomfort by walking or stretching Worsening of symptoms in the evening and at night A 2002 Workshop on RLS, held by the National Institutes of Health (NIH) in collaboration with the International RLS Study Group (IRLSSG), established four essential criteria—meaning that in this system all four are required to make the diagnosis. The four are An urge to move the legs. Although some patients have only motor symptoms, most patients who seek treatment have also had sensory symptoms. The involuntary movements of RLS must be distinguished from unconscious repetitive movements such as foot tapping Onset or worsening during rest or inactivity. As resting begins, motor and sensory symptoms may both be absent, but the likelihood and the intensity of each side of RLS increases as resting goes on. Ordinary discomfort such as stiffness from prolonged immobility is not RLS Relief with movement. The relief is generally described as prompt, but it may not be complete, and in severe RLS it may have been possible only at earlier stages Worsening (or occurrence) only in the evening or at night. In severe RLS with symptoms night and day, this too may be only the patient’s memory of earlier stages Allen RP, et al, for the International Restless Legs Syndrome Study Group. Sleep Med. 2003;4: Reference Allen RP, Picchietti D, Hening WA, et al, for the International Restless Legs Syndrome Study Group. Restless legs syndrome: diagnostic criteria, special considerations, and epidemiology. A report from the restless legs syndrome diagnosis and epidemiology workshop at the National Institutes of Health. Sleep Med. 2003;4:

6 Periodic leg movements in sleep (PLMs) in RLS appear to exhibit heritability (at least as much as, if not more than, sensory symptoms)!


8 Iron is central to RLS symptomatology
RLS symptoms occur in > 40% of subjects with iron deficiency Akyol et al., Clin Neurol Neurosurg Dec;106: In vivo and in vitro iron depletion in dopamine rich brain regions of RLS patients Allen et al., Neurology Jan 56: Connor et al., Neurology Aug 61: Iron deficiency adversely affects dopamine signaling Allen et al, Sleep Med Jul 5:385-91 Oral and intravenous iron can ameliorate RLS symptoms. Earley, Heckler and Allen Sleep Med May 5:

9 Iron trafficking appears to be awry in RLS/PLMs – A “leaky” bucket
RLS Patient Earley, Heckler and Allen, Sleep Medicine (2005) 6: 301

10 Treatment Options Oral or intravenous iron repletion when iron deficiency confirmed (9-50% of cases) Dopaminergics – 1st line treatment as per American Sleep Disorders Assoc. Standards of Practice Committee and the Medical Advisory Board of the RLS Foundation Pramipexole ( mg) – Ropinirole ( mg) minutes before typical symptom onset–FDA approved for idiopathic, moderate-severe RLS Off-label: Opioids – Anticonvulsants – gabapentin Benzodiazepines –

11 RLS Aggravators Alcohol (tanins; GABAAReceptor modulation)
SNRIs > SSRIs >> SDRIs Antidopaminergic medications – e.g., metaclopramide; prochlorperazine (compazine) Anti-histamines (e.g., diphenhydramine) Over-the-counter sleep aids and cold remedies (ephedrines)

12 A genetic-linkage analysis of RLS in Iceland
Funded in part by the Restless Legs Syndrome Foundation in collaboration with deCODE Genetics, Reykjavik, Iceland Homogeneity Excellent genealogic records Excellent record keeping in health care Highest literacy rate in the world Participation in clinical studies is high (80-85%)

13 4 recently identified gene variants account for at
least 80% of the population attritubable risk for RLS

14 To everyone’s surprise/dismay:
None of the implicated genes directly or indirectly affect iron or dopamine. The implicated regions are intronic or intergenic and suggest regulatory roles. The functions are in many cases not well known.

15 SNPs associating to RLS are intimately related to the disease biology:
Multiple SNPs in at least the BTBD9 and Meis1 genes are related in a dose dependent fashion to PLMs – bearing ZERO relationship to RLS rating scales Multiple SNPs in the BTBD9 gene are inversely related in a dose dependent fashion to low iron stores At-risk SNP frequencies in disparate ethnic groups mirrors the large range of ethnic differences in RLS prevalence

16 RLS at-risk variants are COMMON and considerably impact population risk for RLS
Allele Gene OR Frequency PAR p value BTBD (0.656) x10-7 – x10-18 MEIS (0.114) ~ x10-3 – x10-16 MAP2K (0.692) ~ x10-2 – x10-5 PTPRD (0.13) <0.10 (X.XX) = allele frequency in Icelandic population controls

17 Homozygous for BTBD9 Younger or Asian Uremia

18 Pondering the Genetics Landscape:
Will genotypes correlate with specific phenotypes? Can genetic testing inform diagnosis and treatment decisions? What are the downstream molecular networks that effect disease expression?

19 Pharmacogenics for RLS – targets?
Treatment stratification Dopaminergics vs. opioids vs. iron vs. ? Complication stratification Dopaminergic augmentation Aggravators (e.g., antihistamines; metaclopramide) Predictive Health End-Stage Renal Disease Pregnancy

20 RLS pharmacogenomics - challenges
RLS genes Despite high ORs, commonality of at-risk SNPs necessitates large ( ) sample sizes Choice of (endo) phenotype Latent or incipient disease Non-RLS genes

21 Dissecting disease biology

22 Acknowledgements Emory Program in Sleep Emory Dept. of Cell Biology deCODE Genetics Dr. Donald Bliwise Dr. S. Sanyal Dr. Hreinn Stefansson Dr. Michael Decker Dr. KristleifurKristjansson Dr. Alex Iranzo Emory Dept. of Genetics Dr. Andrew Hicks Dr. Jeffrey Durmer Dr. Steve Warren Dr. Larus Gudmundsson Dr. Lynn-Marie Trotti Dr. Mark Bouzyk Ingibjorg Eiriksdottir, RN Dr. Lisa Billars Dr. Jeffrey Gulcher Dr. Reddiah Mumanenni Dr. Kari Stefansson Dr. Glenda Keating Emory Dept. of Neurology Dr. Amanda Freeman Dr. Allan Levey Landspitali Dr. Tom Genetta Dr. Salina Waddy J Max Beck Ami Rosen Dr. Thordur Sigmundsson Gillian Hue CRIN Staff Dr. Albert Pal Sigdursson Daniel Miller Kaniyika Freeman Emory School of Public Health Dr. Harland Austin Funding RLS Foundation Arthur L. Williams Jr. Foundation Woodruff Health Sciences

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