Dupré, Nicolas

Abstract:The autosomal recessive cerebellar ataxias (ARCAs) compose a clinically and genetically heterogeneous group of neurodegenerative diseases characterized by prominent cerebellar ataxia, dysmetria, dysarthria, and nystagmus that are inherited in an autosomal recessive fashion. The diagnosis of ARCAs is challenging because of their low prevalence, poor medical recognition, and heterogeneous clinical presentation with many overlapping features between entities. There currently exist no disease-modifying therapies for most ARCAs, and treatment is mainly symptomatic, aimed at prolonging independence and maintaining the quality of life. As knowledge of the common pathogenic pathways underlying several ARCAs grows, so do these pathways to target with new drugs. Chelation or enzyme replacement therapies are available for some specific ataxias caused by amenable metabolic alterations. A large number of drug trials are ongoing and aim to identify new therapeutic approaches to expand the options in our repertoire. Improved protocols of motor rehabilitation and noninvasive cerebellar stimulation have been shown to delay disease progression and maintain quality of life. Furthermore, recent progress in gene and molecular targeting therapies is rapidly expanding and holds promise for repairing defective genes. Neurotransplantation of grafted stem cells, which is still at the experimental preclinical stage, has opened new therapeutic strategies aimed at delaying cell degeneration and facilitating compensatory functions. This article is an overview of the current management and treatment strategies with an emphasis on promising perspectives for patients with ARCAs.

Objective Rapid eye movement 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 disease (PD, n = 1,013), dementia with Lewy bodies (DLB, n = 415), and control subjects (n = 6,155). The 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 (n = 1,782 cases; n = 131,250 controls). 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 (odds ratio [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. ANN NEUROL 2020;87:584–598

ABSTRACT Background: MAPT haplotypes are associated with PD, but their association with rapid eye movement sleep behavior disorder is unclear. Objective: To study the role of MAPT variants in rapid eye movement sleep behavior disorder. Methods: Two cohorts were included: (A) PD (n = 600), rapid eye movement sleep behavior disorder (n = 613) patients, and controls (n = 981); (B) dementia with Lewy bodies patients with rapid eye movement sleep behavior disorder (n = 271) and controls (n = 950). MAPT ‐associated variants and the entire coding sequence of MAPT were analyzed. Age‐, sex‐, and ethnicity‐adjusted analyses were performed to examine the association between MAPT , PD, and rapid eye movement sleep behavior disorder. Results: MAPT‐ H2 variants were associated with PD (odds ratios: 0.62‐0.65; P = 0.010‐0.019), but not with rapid eye movement sleep behavior disorder. In PD, the H1 haplotype odds ratio was 1.60 (95% confidence interval: 1.12‐2.28; P = 0.009), and the H2 odds ratio was 0.68 (95% confidence interval: 0.48‐0.96; P = 0.03). The H2/H1 haplotypes were not associated with rapid eye movement sleep behavior disorder. Conclusions: Our results confirm the protective effect of the MAPT ‐H2 haplotype in PD, and define its components. Furthermore, our results suggest that MAPT does not play a major role in rapid eye movement sleep behavior disorder, emphasizing different genetic background than in PD in this locus. © 2018 International Parkinson and Movement Disorder Society