Objectives: The effect of environmental and lifestyle factors on patients with LRRK2 (leucine‐rich repeat kinase 2) p.Gly2019Ser (LRRK2⁺/PD⁺) compared to idiopathic PD (iPD) has yet to be thoroughly investigated.Methods: In a homogeneous Tunisian Arab Berber population, we recruited 200 idiopathic PD and 199 LRRK2 p.Gly2019Ser mutation carriers, of whom 142 had PD (LRRK2⁺/PD⁺) and 57 were unaffected (LRRK2⁺/PD⁻). Case report form (CRF) questionnaires (motor and non‐motor symptoms) including the Geoparkinson Questionnaire were used to assess environmental and lifestyle factors.Results: In LRRK2⁺/PD⁺, tobacco use was significantly associated with a later median age at onset (AAO). The median AAO was 60 years (interquartile range = 52–67.25) for tobacco users, compared to 52 years (interquartile range = 45.25–61) for non‐users (P= 0.0042 at adjusted α = 0.025). Additionally, we observed an independent but additive effect of black tea consumption and tobacco use.Conclusions: Our data suggest that tobacco and black tea have a protective effect on age at onset in LRRK2⁺/PD⁺. © 2020 The Authors.Movement Disorderspublished by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Background: Although most cases of Parkinson´s disease (PD) are idiopathic with unknown cause, an increasing number of genes and genetic risk factors have been discovered that play a role in PD pathogenesis. Many of the PD-associated proteins are involved in mitochondrial quality control, e.g., PINK1, Parkin, and LRRK2, which were recently identified as regulators of mitochondrial-endoplasmic reticulum (ER) contact sites (MERCs) linking mitochondrial homeostasis to intracellular calcium handling. In this context, Miro1 is increasingly recognized to play a role in PD pathology. Recently, we identified the first PD patients carrying mutations in RHOT1, the gene coding for Miro1. Here, we describe two novel RHOT1 mutations identified in two PD patients and the characterization of the cellular phenotypes. Methods: Using whole exome sequencing we identified two PD patients carrying heterozygous mutations leading to the amino acid exchanges T351A and T610A in Miro1. We analyzed calcium homeostasis and MERCs in detail by live cell imaging and immunocytochemistry in patient-derived fibroblasts. Results: We show that fibroblasts expressing mutant T351A or T610A Miro1 display impaired calcium homeostasis and a reduced amount of MERCs. All fibroblast lines from patients with pathogenic variants in Miro1, revealed alterations of the structure of MERCs. Conclusion: Our data suggest that Miro1 is important for the regulation of the structure and function of MERCs. Moreover, our study supports the role of MERCs in the pathogenesis of PD and further establishes variants in RHOT1 as rare genetic risk factors for neurodegeneration.

Rare denovo variants represent a significant cause of neurodevelopmental delay and intellectual disability (ID). Exome sequencing was performed on 4351 patients with global developmental delay, seizures, microcephaly, macrocephaly, motor delay, delayed speech and language development, or ID according to Human Phenotype Ontology (HPO) terms. All patients had previously undergone whole exome sequencing as part of diagnostic genetic testing with a focus on variants in genes implicated in neurodevelopmental disorders up to January 2017. This resulted in a genetic diagnosis in 1336 of the patients. In this study, we specifically searched for variants in 14 recently implicated novel neurodevelopmental disorder (NDD) genes. We identified 65 rare, protein-changing variants in 11 of these 14 novel candidate genes. Fourteen variants in CDK13, CHD4, KCNQ3, KMT5B, TCF20, and ZBTB18 were scored pathogenic or likely pathogenic. Of note, two of these patients had a previously identified cause of their disease, and thus, multiple molecular diagnoses were made including pathogenic/likely pathogenic variants in FOXG1 and CDK13 or in TMEM237 and KMT5B. Looking for pathogenic variants in newly identified NDD genes enabled us to provide a molecular diagnosis to 14 patients and their close relatives and caregivers. This underlines the relevance of re-evaluation of existing exome data on a regular basis to improve the diagnostic yield and serve the needs of our patients.

Parkinson’s disease (PD) is a progressive neurodegenerative disorder. Genetic modifiers, environmental factors and gene–environment interactions have been found to modify PD risk and disease progression. The objective of this study was to evaluate the association of smoking, caffeine and anti-inflammatory drugs with age at onset (AAO) in a large PD cohort. A total of 35,963 American patients with idiopathic PD (iPD) from the Fox Insight Study responded to health and lifestyle questionnaires. We compared the median AAO between different groups using the non-parametric Mann–Whitney U test. Non-parametric Spearman’s correlation was used for correlation assessments and regression analysis was used to assess interaction between variables. We found that smoking (p < 0.0001), coffee drinking (p < 0.0001) and aspirin intake (p < 0.0001) show an exploratory association with AAO in PD, that was further supported by multivariate regression models. The association of aspirin with PD AAO was replicated in another cohort (EPIPARK) (n = 237 patients with PD).

While many genetic causes of movement disorders have been identified, modifiers of disease expression are largely unknown. X-linked dystonia-parkinsonism (XDP) is a neurodegenerative disease caused by a SINE-VNTR-Alu(AGAGGG)_n retrotransposon insertion in TAF1, with a polymorphic (AGAGGG)_n repeat. Repeat length and variants in MSH3 and PMS2 explain ∼65% of the variance in age at onset (AAO) in XDP. However, additional genetic modifiers are conceivably at play in XDP, such as repeat interruptions. Long-read nanopore sequencing of PCR amplicons from XDP patients (n = 202) was performed to assess potential repeat interruption and instability. Repeat-primed PCR and Cas9-mediated targeted enrichment confirmed the presence of identified divergent repeat motifs. In addition to the canonical pure SINE-VNTR-Alu-5′-(AGAGGG)_n, we observed a mosaic of divergent repeat motifs that polarized at the beginning of the tract, where the divergent repeat interruptions varied in motif length by having one, two, or three nucleotides fewer than the hexameric motif, distinct from interruptions in other disease-associated repeats, which match the lengths of the canonical motifs. All divergent configurations occurred mosaically and in two investigated brain regions (basal ganglia, cerebellum) and in blood-derived DNA from the same patient. The most common divergent interruption was AGG [5′-SINE-VNTR-Alu(AGAGGG)₂AGG(AGAGGG)_n], similar to the pure tract, followed by AGGG [5′-SINE-VNTR-Alu(AGAGGG)₂AGGG(AGAGGG)_n], at median frequencies of 0.425 (IQR: 0.42–0.43) and 0.128 (IQR: 0.12–0.13), respectively. The mosaic AGG motif was not associated with repeat number (estimate = −3.8342, P = 0.869). The mosaic pure tract frequency was associated with repeat number (estimate = 45.32, P = 0.0441) but not AAO (estimate = −41.486, P = 0.378). Importantly, the mosaic frequency of the AGGG negatively correlated with repeat number after adjusting for age at sampling (estimate = −161.09, P = 3.44 × 10⁻⁵). When including the XDP-relevant MSH3/PMS2 modifier single nucleotide polymorphisms into the model, the mosaic AGGG frequency was associated with AAO (estimate = 155.1063, P = 0.047); however, the association dissipated after including the repeat number (estimate = −92.46430, P = 0.079). We reveal novel mosaic divergent repeat interruptions affecting both motif length and sequence (DRILS) of the canonical motif polarized within the SINE-VNTR-Alu(AGAGGG)_n repeat. Our study illustrates: (i) the importance of somatic mosaic genotypes; (ii) the biological plausibility of multiple modifiers (both germline and somatic) that can have additive effects on repeat instability; and (iii) that these variations may remain undetected without assessment of single molecules.

Objective Our study investigated the presence of regional differences in hexanucleotide repeat number in postmortem brain tissues of 2 patients with X-linked dystonia-parkinsonism (XDP), a combined dystonia-parkinsonism syndrome modified by a (CCCTCT)_n repeat within the causal SINE-VNTR-Alu retrotransposon insertion in the TAF1 gene. Methods Genomic DNA was extracted from blood and postmortem brain samples, including the basal ganglia and cortex from both patients and from the cerebellum, midbrain, and pituitary gland from 1 patient. Repeat sizing was performed using fragment analysis, small-pool PCR-based Southern blotting, and Oxford nanopore sequencing. Results The basal ganglia (p < 0.001) and cerebellum (p < 0.001) showed higher median repeat numbers and higher degrees of repeat instability compared with blood. Conclusions Somatic repeat instability may predominate in brain regions selectively affected in XDP, thereby hinting at its potential role in disease manifestation and modification.