Mario Ezquerra

Background The neuropathology of Parkinson's disease (PD) associated with leucine‐rich repeat kinase 2 (LRRK2) mutations (LRRK2‐PD) is heterogeneous and varies with the type of mutation. There are only a few studies evaluating seeding aggregation assays to detect α‐synuclein (α‐syn) in patients with LRRK2‐PD. Objective We aimed to investigate whether α‐syn real‐time quaking induced conversion (RT‐QuIC) is a sensitive biomarker of synucleinopathy in LRRK2‐PD. Methods We studied α‐syn RT‐QuIC in brain tissue and postmortem ventricular cerebrospinal fluid (CSF) of LRRK2‐PD cases with and without Lewy‐type pathology. Results The accuracy of α‐syn RT‐QuIC in substantia nigra and CSF samples of patients with LRRK2‐PD was 100%. The test also obtained 100% sensitivity to detect misfolded α‐syn in substantia nigra of cases with idiopathic PD and was negative in the substantia nigra of all the control brains without Lewy‐type pathology. Conclusions Substantia nigra and ventricular CSF RT‐QuIC discriminates with high sensitivity and specificity LRRK2 cases with Lewy‐type pathology from those without it. RT‐QuIC assay could be of particular interest in the selection of cases for clinical trials in this genetic form of PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Background Isolated rapid eye movement sleep behavior disorder (IRBD) is a well‐established clinical risk factor for Lewy body diseases (LBDs), such as Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Objective To elucidate whether serum microRNA (miRNA) deregulation in IRBD can antedate the diagnosis of LBD by performing a longitudinal study in different progression stages of IRBD before and after LBD diagnosis and assessing the predictive performance of differentially expressed miRNAs by machine learning–based modeling. Methods Using genome‐wide miRNA analysis and real‐time quantitative polymerase chain reaction validation, we assessed serum miRNA profiles from patients with IRBD stratified by dopamine transporter (DaT) single‐photon emission computed tomography into DaT‐negative IRBD (n = 17) and DaT‐positive IRBD (n = 21), IRBD phenoconverted into LBD (n = 13), and controls (n = 20). Longitudinally, we followed up the IRBD cohort by studying three time point serum samples over 26 months. Results We found sustained cross‐sectional and longitudinal deregulation of 12 miRNAs across the RBD continuum, including DaT‐negative IRBD, DaT‐positive IRBD, and LBD phenoconverted IRBD (let‐7c‐5p, miR‐19b‐3p, miR‐140, miR‐22‐3p, miR‐221‐3p, miR‐24‐3p, miR‐25‐3p, miR‐29c‐3p, miR‐361‐5p, miR‐425‐5p, miR‐4505, and miR‐451a) (false discovery rate P < 0.05). Age‐ and sex‐adjusted predictive modeling based on the 12 differentially expressed miRNA biosignatures discriminated IRBD and PD or DLB from controls with an area under the curve of 98% (95% confidence interval: 89–99%). Conclusions Besides clinical diagnosis of IRBD or imaging markers such as DaT single‐photon emission computed tomography, specific miRNA biosignatures alone hold promise as progression biomarkers for patients with IRBD for predicting PD and DLB clinical outcomes. Further miRNA studies in other PD at‐risk populations, such as LRRK2 mutation asymptomatic carriers or hyposmic subjects, are warranted. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society