Variants in the Neuronal Nitric Oxide Synthase (nNOS, NOS1) Gene are Associated with Restless Legs Syndrome
Juliane Winkelmann1,2,3, Peter Lichtner1,3, Barbara Schormair1,3, Manfred Uhr2, Stephanie Hauk1,3, Karin Stiasny-Kolster4, Claudia Trenkwalder5, Walter Paulus6, Ines Peglau7, Ilonka Eisensehr8, Thomas Illig9, H.-Erich Wichmann9, Hildegard Pfister2, Jelena Golic3, Thomas Bettecken2, Benno Pütz2, Florian Holsboer2, Thomas Meitinger1,3, Bertram Müller-Myhsok2
1Institute of Human Genetics, GSF-National Research Center for Environment and Health, Munich, Germany, 2Max Planck Institute of Psychiatry, Munich, Germany, 3Technical University, Institute of Human Genetics, Munich, Germany, 4Philipps University Marburg, Dept. of Neurology, Marburg, Germany, 5Paracelsius-Elena Klinik, Kassel, Germany, 6University of Göttingen, Dept. of Neurophysiology, Göttingen, Germany, 7Neurologische Praxis, Berlin, Germany, 8Neurologische Praxis Sendlingerstrasse, Munich, Germany, 9Institute of Epidemiology, GSF-National Research Center for Environment and Health, Munich, Germany

Objective: To identify genes related to RLS we performed a three-stage association study (explorative study, replication study, high-density mapping) in two Caucasian RLS case-control samples of altogether 918 independent cases and controls.

Methods: In the explorative study (367 cases and controls, respectively) we screened 1536 SNPs in 366 genes in a 21 Mb region encompassing the RLS1 critical region on chromosome 12.

Results: Armitage trend test revealed three genomic regions which were significant (p< 0.05). In the replication study (551 cases and controls, respectively) we genotyped the most significant SNPs of stage 1. After correction for multiple testing, association was observed with SNP rs7977109 (pnominal= 0.00175, pWestfall-Young= 0.04895, OR= 0.76228, 95% CI= 0.64310-0.90355) which is in the neuronal nitric oxide synthase (NOS1) gene. High-density mapping using altogether 34 tagging and coding SNPs of the NOS1 gene in both case-control samples further confirmed the significant association results to NOS1. Ten more SNPs revealed significance with nominal p-values from 0.0001-0.0482 (genotypic test and Armitage test).

Conclusion: Altogether, this study provides evidence for an association of variants in the NOS1 gene and RLS and suggests the involvement of the NO/arginine pathway in the pathogenesis of RLS. Potential usage of NO modulating agents as new treatment options for RLS have become a challenging aspect for future research of this disorder.