Fine-mapping of SNCA in REM sleep behavior disorder and overt synucleinopathies.
Krohn L., Wu RY., Heilbron K., Ruskey JA., Laurent SB., Blauwendraat C., Alam A., Arnulf I., Hu MTM., Dauvilliers Y., Högl B., Toft M., Bjørnarå KA., Stefani A., Holzknecht E., Monaca CC., Beatriz A., Plazzi G., Antelmi E., Ferini-Strambi L., Young P., Heidbreder A., Cochen De Cock V., Mollenhauer B., Sixel-Döring F., Trenkwalder C., Sonka K., Kemlink D., Figorilli M., Puligheddu M., Dijkstra F., Viaene M., Oertel W., Toffoli M., Gigli GL., Valente M., Gagnon J-F., Nalls MA., Singleton AB., 23andMe Research Team None., Desautels A., Montplaisir JY., Cannon P., Ross OA., Boeve BF., Dupré N., Fon EA., Postuma RB., Pihlstrøm L., Rouleau GA., Gan-Or Z.
OBJECTIVE: REM-sleep behavior disorder (RBD) is a prodromal synucleinopathy, as >80% will eventually convert to overt synucleinopathy. We performed an in-depth analysis of the SNCA locus to identify RBD-specific risk variants. METHODS: Full sequencing and genotyping of SNCA was performed in isolated/idiopathic RBD (iRBD, n=1,076), Parkinson's disease (PD, n=1,013), and dementia with Lewy bodies (DLB, n=415), and in control subjects (n=6,155). iRBD cases were diagnosed with RBD prior to neurodegeneration, although some have since converted. A replication cohort from 23andMe of PD patients with probable RBD (pRBD) was also analyzed (cases n=1,782, controls n=131,250). Adjusted logistic regression models and meta-analyses were performed. Effects on conversion rate were analyzed in 432 RBD patients with available data using Kaplan-Meier survival analysis. RESULTS: A 5'-region SNCA variant (rs10005233) was associated with iRBD (OR=1.43, p=1.1E-08), which was replicated in pRBD. This variant is in linkage disequilibrium (LD) with other 5' risk variants across the different synucleinopathies. An independent iRBD-specific suggestive association (rs11732740) was detected at the 3' of SNCA (OR=1.32, p=4.7E-04, not statistically significant after Bonferroni correction). Homozygous carriers of both iRBD-specific SNPs were at highly increased risk for iRBD (OR=5.74, p=2E-06). The known top PD-associated variant (3' variant rs356182) had an opposite direction of effect in iRBD compared to PD. INTERPRETATION: There is a distinct pattern of association at the SNCA locus in RBD as compared to PD, with an opposite direction of effect at the 3' of SNCA. Several 5' SNCA variants are associated with iRBD and with pRBD in overt synucleinopathies. This article is protected by copyright. All rights reserved.