Dermal Real-Time Quaking-Induced Conversion Is a Sensitive Marker to Confirm Isolated Rapid Eye Movement Sleep Behavior Disorder as an Early α-Synucleinopathy.

BACKGROUND: Skin biopsy is a potential tool for the premortem confirmation of an α-synucleinopathy. OBJECTIVE: The aim was to assess the aggregation assay real-time quaking-induced conversion (RT-QuIC) of skin biopsy lysates to confirm isolated rapid eye movement sleep behavior disorder (iRBD) as an α-synucleinopathy. METHODS: Skin biopsies of patients with iRBD, Parkinson's disease (PD), and controls were analyzed using RT-QuIC and immunohistochemical detection of phospho-α-synuclein. RESULTS: α-Synuclein aggregation was detected in 97.4% of iRBD patients (78.4% of iRBD biopsies), 87.2% of PD patients (70% of PD biopsies), and 13% of controls (7.9% of control biopsies), with a higher seeding activity in iRBD compared to PD. RT-QuIC was more sensitive but less specific than immunohistochemistry. CONCLUSIONS: Dermal RT-QuIC is a sensitive method to detect α-synuclein aggregation in iRBD, and high seeding activity may indicate a strong involvement of dermal nerve fibers in these patients. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Novel Associations of BST1 and LAMP3 With REM Sleep Behavior Disorder.

OBJECTIVE: To examine the role of genes identified through genome-wide association studies (GWASs) of Parkinson disease (PD) in the risk of isolated REM sleep behavior disorder (iRBD). METHODS: We fully sequenced 25 genes previously identified in GWASs of PD in a total of 1,039 patients with iRBD and 1,852 controls. The role of rare heterozygous variants in these genes was examined with burden tests. The contribution of biallelic variants was further tested. To examine the potential effect of rare nonsynonymous BST1 variants on the protein structure, we performed in silico structural analysis. Finally, we examined the association of common variants using logistic regression adjusted for age and sex. RESULTS: We found an association between rare heterozygous nonsynonymous variants in BST1 and iRBD (p = 0.0003 at coverage >50× and 0.0004 at >30×), driven mainly by 3 nonsynonymous variants (p.V85M, p.I101V, and p.V272M) found in 22 (1.2%) controls vs 2 (0.2%) patients. All 3 variants seem to be loss-of-function variants with a potential effect on the protein structure and stability. Rare noncoding heterozygous variants in LAMP3 were also associated with iRBD (p = 0.0006 at >30×). We found no association between rare heterozygous variants in the rest of genes and iRBD. Several carriers of biallelic variants were identified, yet there was no overrepresentation in iRBD. CONCLUSION: Our results suggest that rare coding variants in BST1 and rare noncoding variants in LAMP3 are associated with iRBD. Additional studies are required to replicate these results and to examine whether loss of function of BST1 could be a therapeutic target.

Dermal phospho-alpha-synuclein deposits confirm REM sleep behaviour disorder as prodromal Parkinson's disease.

Phosphorylated alpha-synuclein (p-alpha-syn) deposits, one of the neuropathological hallmarks of Parkinson's disease (PD), have recently been detected in dermal nerve fibres in PD patients with good specificity and sensitivity. Here, we studied whether p-alpha-syn may serve as a biomarker in patients with a high risk of developing PD, such as those with REM sleep behaviour disorder (RBD). We compared the presence and distribution of p-alpha-syn deposits in dermal nerve fibres in 18 patients with RBD, 25 patients with early PD and 20 normal controls. Skin biopsy was taken at C7, Th10, and the upper and lower leg. Presynaptic dopamine transporter imaging using FP-CIT-SPECT was performed in all patients with RBD and in 11 patients with PD. All RBD patients underwent olfactory function testing. The likelihood ratio (LR) for prodromal PD was calculated for each patient based on published research criteria. Skin serial sections were assessed by double-immunofluorescence labelling with antibodies to pSer129-alpha-syn under blinded conditions. P-alpha-syn was visualized in 10/18 patients with RBD (sensitivity of 55.6%) and in 20/25 early PD patients (sensitivity of 80%) but in none of the controls (specificity of 100%). The percentage of dermal structures innervated by p-alpha-syn-positive fibres was negatively correlated with dopamine transporter binding in the FP-CIT-SPECT (ρ = -0.377, p = 0.048), with olfactory function (ρ = -0.668, p = 0.002), and positively correlated with the total LR for RBD to present prodromal PD (ρ = 0.531, p = 0.023). Dermal p-alpha-syn can be considered a peripheral histopathological marker of synucleinopathy and can be detected in a subgroup of RBD patients presumably representing prodromal PD. Dermal p-alpha-syn is detectable in RBD patients without PD motor symptoms, thereby stratifying a patient group that is of great interest for clinical trials testing disease-modifying drugs.

The influence of intraoperative microelectrode recordings and clinical testing on the location of final stimulation sites in deep brain stimulation for Parkinson's disease.

BACKGROUND: The goal of our study was to investigate the influence of intraoperative microelectrode recordings and clinical testing on the location of the final stimulation site in deep brain stimulation in Parkinson's disease. METHODS: In 22 patients with Parkinson's disease we compared magnetic resonance imaging (MRI)-based and atlas-based targets with the adjusted stimulation sites after intraoperative, multitrack microelectrode recording (MER) and intraoperative and postoperative clinical testing. The investigation included 176 target/stimulation sites in 44 subthalamic nuclei (STNs), which were related to a standardised three-dimensional, MRI-defined STN. RESULTS: Atlas-based targets were positioned more superior and more medial than the MRI-based targets, which were located in the centre of the MRI-STN. The optimal stimulation sites, found intraoperatively after MER and clinical testing, were located more lateral and slightly more superior than both planned targets. In the majority of the cases the location of the active contact was the most superior and most lateral of all target sites. The differences in the distributions of those four targets reached statistical significance. However, final active contacts were distributed throughout the MRI-defined STN and its immediate surroundings. CONCLUSIONS: The adoption of microelectrode recordings and extensive clinical testing allows the adjustment of anatomical targeting even to unexpected stimulation sites in and around the MRI-defined STN.

Expression of solute carrier 7A4 (SLC7A4) in the plasma membrane is not sufficient to mediate amino acid transport activity.

Member 4 of human solute carrier family 7 (SLC7A4) exhibits significant sequence homology with the SLC7 subfamily of human cationic amino acid transporters (hCATs) [Sperandeo, Borsani, Incerti, Zollo, Rossi, Zuffardi, Castaldo, Taglialatela, Andria and Sebastio (1998) Genomics 49, 230-236]. It is therefore often referred to as hCAT-4 even though no convincing transport activity has been shown for this protein. We expressed SLC7A4 in Xenopus laevis oocytes, but could not detect any transport activity for cationic, neutral or anionic amino acids or for the polyamine putrescine. In addition, human glioblastoma cells stably overexpressing a fusion protein between SLC7A4 and the enhanced green fluorescent protein (EGFP) did not exhibit an increased transport activity for l-arginine. The lack of transport activity was not due to a lack of SLC7A4 protein expression in the plasma membrane, as in both cell types SLC7A4-EGFP exhibited a similar subcellular localization and level of protein expression as functional hCAT-EGFP proteins. The expression of SLC7A4 can be induced in NT2 teratocarcinoma cells by treatment with retinoic acid. However, also for this endogenously expressed SLC7A4, we could not detect any transport activity for l-arginine. Our data demonstrate that the expression of SLC7A4 in the plasma membrane is not sufficient to induce an amino acid transport activity in X. laevis oocytes or human cells. Therefore, SLC7A4 is either not an amino acid transporter or it needs additional (protein) factor(s) to be functional.