Sporadic Parkinson's Disease Patients Research Articles

Genetic study of the NUS1 gene variants in Han Chinese patients with Parkinson’s disease

Aim: Parkinson’s disease (PD) is the second most common progressive neurodegenerative disease linked to genetic and other factors. The NUS1 dehydrodolichyl diphosphate synthase subunit gene (NUS1) variants were reported to be associated with PD. In this PD-control cohort, we aimed to explore the potential role of the NUS1 gene variants in PD. Methods: A cohort of 512 Han Chinese sporadic PD patients and 516 ethnically and age-matched controls underwent clinical evaluation. Peripheral blood samples were then collected, and whole-exome sequencing was performed. The potential PD-related variants identified through screening were verified using Sanger sequencing, further classified, and subsequently analyzed by bioinformatics analysis tools. Statistical analysis was conducted to assess the association between the variants and PD. Results: Three NUS1 heterozygous missense variants, including c.127G>T (p.Ala43Ser, rs1327892878), c.487G>C (p.Asp163His, rs369403261), and c.537T>A (p.Asp179Glu, rs28362519), were identified. Two rare variants, c.127G>T and c.487G>C, were exclusively found in PD patients, while the low-frequency variant c.537T>A was detected both in patients and controls. Combined with bioinformatics analysis, a potentially pathogenic role of c.127G>T and c.487G>C may exert in PD risk, though no significant association was shown by statistical analysis (all P > 0.05). Conclusion: Our findings suggested that the NUS1 variants seem to not cause monogenic PD, and variants like c.127G>T and c.487G>C may, at most, exert a susceptibility to PD.

Pre-clinical safety and efficacy of human induced pluripotent stem cell-derived products for autologous cell therapy in Parkinson's disease.

Pre-clinical safety and efficacy of human induced pluripotent stem cell-derived products for autologous cell therapy in Parkinson's disease.

Generation of hiPSCs lines from three sporadic Parkinson's disease patients.

Generation of hiPSCs lines from three sporadic Parkinson's disease patients.

The α-Synuclein Seeding Amplification Assay for Parkinson's Disease.

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. Currently, PD is incurable, and the diagnosis of PD mainly relies on clinical manifestations. The central pathological event in PD is the abnormal aggregation and deposition of misfolded α-synuclein (α-Syn) protein aggregates in the Lewy body (LB) in affected brain areas. Behaving as a prion-like seeding, the misfolded α-syn protein can induce and facilitate the aggregation of native unfolded α-Syn protein to aggravate α-Syn protein aggregation, leading to PD progression. Recently, in a blood-based α-Syn seeding amplification assay (SAA), Kluge et al. identified pathological α-Syn seeding activity in PD patients with Parkin (PRKN) gene variants. Additionally, pathological α-syn seeding activity was also identified in sporadic PD and PD patients with Leucine-rich repeat kinase 2 (LRRK2) or glucocerebrosidase (GBA) gene variants. Principally, the α-Syn SAA can be used to detect pathological α-Syn seeding activity, which will significantly enhance PD diagnosis, progression monitoring, prognosis prediction, and anti-PD therapy. The significance and future strategies of α-Syn SAA protocol are highlighted and proposed, whereas challenges and limitations of the assay are discussed.

LRRK2 Inhibitors as Promising Treatment for Parkinson's Disease.

Parkinson's disease (PD) is one of the most prevalent neurodegenerative disorders, with current treatments offering only temporary symptomatic relief. There is an urgent need for the development of novel therapeutic approaches. Abnormal increases in LRRK2 kinase activity have been identified in both sporadic and familial PD patients, suggesting that inhibiting LRRK2 kinase activity presents a promising avenue for the pursuit of effective PD treatment strategies. In this Viewpoint, we discuss the exciting new insights regarding the development of LRRK2 kinase inhibitors as a treatment for Parkinson's disease.

CSF GPNMB in Parkinson's disease: A potential association with age and microglial activation.

Recent evidence suggests a link between glycoprotein non-metastatic melanoma protein B (GPNMB) and Parkinson's disease (PD) pathogenesis. Although elevated plasma GPNMB levels associated with disease severity have been reported in PD, cerebrospinal fluid (CSF) alterations remain elusive. To explore CSF GPNMB alterations and its clinical significance in PD. This study enrolled 118 sporadic PD patients and 40 controls. We examined the potential associations between CSF GPNMB levels and the clinical characteristics or biomarkers of neurodegenerative pathogenesis. PD patients had higher CSF GPNMB levels than controls (p = 0.0159). In the PD group, CSF GPNMB levels correlated with age (age at examination: rs = 0.2511, p = 0.0061; age at onset: rs = 0.2800, p = 0.0021) and the severity of motor and cognitive dysfunction (MDS-UPDRS III score: rs = 0.1998, p = 0.0347; Mini-Mental State Examination score: rs = -0.1922, p = 0.0370). After correcting for multiple comparisons, the correlation with age at onset remained significant. CSF GPNMB levels were also positively correlated with CSF soluble triggering receptor expressed on myeloid cells 2 (sTREM2) levels in both the PD (rs = 0.3582, p < 0.0001) and control (rs = 0.4743, p = 0.0023) groups. Furthermore, multiple regression analysis revealed CSF sTREM2 level as the strongest determinant of CSF GPNMB levels in the PD group (t-value = 3.49, p = 0.0007). Elevated CSF GPNMB levels, linked with age and microglial activation, may be a valuable marker for understanding the interplay between aging, neuroinflammation, and PD pathology.

Aggregation-resistant alpha-synuclein tetramers are reduced in the blood of Parkinson’s patients

Synucleinopathies such as Parkinson’s disease (PD) are defined by the accumulation and aggregation of the α-synuclein protein in neurons, glia and other tissues. We have previously shown that destabilization of α-synuclein tetramers is associated with familial PD due to SNCA mutations and demonstrated brain-region specific alterations of α-synuclein multimers in sporadic PD patients following the classical Braak spreading theory. In this study, we assessed relative levels of disordered and higher-ordered multimeric forms of cytosolic α-synuclein in blood from familial PD with G51D mutations and sporadic PD patients. We used an adapted in vitro-cross-linking protocol for human EDTA-whole blood. The relative levels of higher-ordered α-synuclein tetramers were diminished in blood from familial PD and sporadic PD patients compared to controls. Interestingly, the relative amount of α-synuclein tetramers was already decreased in asymptomatic G51D carriers, supporting the hypothesis that α-synuclein multimer destabilization precedes the development of clinical PD. Our data, therefore suggest that measuring α-synuclein tetramers in blood may have potential as a facile biomarker assay for early detection and quantitative tracking of PD progression.

Using Extracellular miRNA Signatures to Identify Patients with LRRK2-Related Parkinson's Disease.

Mutations in the Leucine Rich Repeat Kinase 2 gene are highly relevant in both sporadic and familial cases of Parkinson's disease. Specific therapies are entering clinical trials but patient stratification remains challenging. Dysregulated microRNA expression levels have been proposed as biomarker candidates in sporadic Parkinson's disease. In this proof-of concept study we evaluate the potential of extracellular miRNA signatures to identify LRRK2-driven molecular patterns in Parkinson's disease. We measured expression levels of 91 miRNAs via RT-qPCR in ten individuals with sporadic Parkinson's disease, ten LRRK2 mutation carriers and eleven healthy controls using both plasma and cerebrospinal fluid. We compared miRNA signatures using heatmaps and t-tests. Next, we applied group sorting algorithms and tested sensitivity and specificity of their group predictions. miR-29c-3p was differentially expressed between LRRK2 mutation carriers and sporadic cases, with miR-425-5p trending towards significance. Individuals clustered in principal component analysis along mutation status. Group affiliation was predicted with high accuracy in the prediction models (sensitivity up to 89%, specificity up to 70%). miRs-128-3p, 29c-3p, 223-3p, and 424-5p were identified as promising discriminators among all analyses. LRRK2 mutation status impacts the extracellular miRNA signature measured in plasma and separates mutation carriers from sporadic Parkinson's disease patients. Monitoring LRRK2 miRNA signatures could be an interesting approach to test drug efficacy of LRRK2-targeting therapies. In light of small sample size, the suggested approach needs to be validated in larger cohorts.

Alterations in Blood Methylome as Potential Epigenetic Biomarker in Sporadic Parkinson's Disease.

To characterize DNA methylation (DNAm) differences between sporadic Parkinson's disease (PD) and healthy control (HC) individuals enrolled in the Parkinson's Progression Markers Initiative (PPMI). Using whole blood, we characterized longitudinal differences in DNAm between sporadic PD patients (n = 196) and HCs (n = 86) enrolled in PPMI. RNA sequencing (RNAseq) was used to conduct gene expression analyses for genes mapped to differentially methylated cytosine-guanine sites (CpGs). At the time of patient enrollment, 5,178 CpGs were differentially methylated (2,683 hypermethylated and 2,495 hypomethylated) in PD compared to HC. Of these, 579 CpGs underwent significant methylation changes over 3 years. Several differentially methylated CpGs were found near the cytochrome P450 family 2 subfamily E member 1 (CYP2E1) gene. Additionally, multiple hypermethylated CpGs were associated with the N-myc downregulated gene family member 4 (NDRG4) gene. RNA-Seq analyses showed 75 differentially expressed genes in PD patients compared to controls. An integrative analysis of both differentially methylated sites and differentially expressed genes revealed 20 genes that exhibited hypomethylation concomitant with overexpression. Additionally, 1 gene, cathepsin H (CTSH), displayed hypermethylation that was associated with its decreased expression. We provide initial evidence of alterations in DNAm in blood of PD patients that may serve as potential epigenetic biomarker of disease. To evaluate the significance of these changes throughout the progression of PD, additional profiling at longer intervals and during the prodromal stages of disease will be necessary. ANN NEUROL 2024;95:1162-1172.

Synaptic dysfunction and extracellular matrix dysregulation in dopaminergic neurons from sporadic and E326K-GBA1 Parkinson's disease patients.

Parkinson's disease (PD) is a neurodegenerative disease with both genetic and sporadic origins. In this study, we investigated the electrophysiological properties, synaptic activity, and gene expression differences in dopaminergic (DA) neurons derived from induced pluripotent stem cells (iPSCs) of healthy controls, sporadic PD (sPD) patients, and PD patients with E326K-GBA1 mutations. Our results demonstrate reduced sodium currents and synaptic activity in DA neurons derived from PD patients with E326K-GBA1 mutations, suggesting a potential contribution to PD pathophysiology. We also observed distinct electrophysiological alterations in sPD DA neurons, which included a decrease in synaptic currents. RNA sequencing analysis revealed unique dysregulated pathways in sPD neurons and E326K-GBA1 neurons, further supporting the notion that molecular mechanisms driving PD may differ between PD patients. In agreement with our previous reports, Extracellular matrix and Focal adhesion pathways were among the top dysregulated pathways in DA neurons from sPD patients and from patients with E326K-GBA1 mutations. Overall, our study further confirms that impaired synaptic activity is a convergent functional phenotype in DA neurons derived from PD patients across multiple genetic mutations as well as sPD. At the transcriptome level, we find that the brain extracellular matrix is highly involved in PD pathology across multiple PD-associated mutations as well as sPD.

Altered Sphingolipid Hydrolase Activities and Alpha-Synuclein Level in Late-Onset Schizophrenia.

Recent data described that patients with lysosomal storage disorders (LSDs) may have clinical schizophrenia (SCZ) features. Disruption of lipid metabolism in SCZ pathogenesis was found. Clinical features of schizophrenia (SCZ) have been demonstrated in patients with several lysosomal storage disorders (LSDs). Taking into account the critical role of lysosomal function for neuronal cells' lysosomal dysfunction could be proposed in SCZ pathogenesis. The current study analyzed lysosomal enzyme activities and the alpha-synuclein level in the blood of patients with late-onset SCZ. In total, 52 SCZ patients with late-onset SCZ, 180 sporadic Parkinson's disease (sPD) patients, and 176 controls were recruited. The enzymatic activity of enzymes associated with mucopolysaccharidosis (alpha-L-Iduronidase (IDUA)), glycogenosis (acid alpha-glucosidase (GAA)) and sphingolipidosis (galactosylceramidase (GALC), glucocerebrosidase (GCase), alpha-galactosidase (GLA), acid sphingomyelinase (ASMase)) and concentration of lysosphingolipids (hexosylsphingosine (HexSph), globotriaosylsphingosine (LysoGb3), and lysosphingomyelin (LysoSM)) were measured using LC-MS/MS. The alpha-synuclein level was estimated in magnetically separated CD45+ blood cells using the enzyme-linked immunosorbent assay (ELISA). Additionally, NGS analysis of 11 LSDs genes was conducted in 21 early-onset SCZ patients and 23 controls using the gene panel PGRNseq-NDD. Decreased ASMase, increased GLA activities, and increased HexSpn, LysoGb3, and LysoSM concentrations along with an accumulation of the alpha-synuclein level were observed in late-onset SCZ patients in comparison to the controls (p < 0.05). Four rare deleterious variants among LSDs genes causing mucopolysaccharidosis type I (IDUA (rs532731688, rs74385837) and type III (HGSNAT (rs766835582)) and sphingolipidosis (metachromatic leukodystrophy (ARSA (rs201251634)) were identified in five patients from the group of early-onset SCZ patients but not in the controls. Our findings supported the role of sphingolipid metabolism in SCZ pathogenesis. Aberrant enzyme activities and compounds of sphingolipids associated with ceramide metabolism may lead to accumulation of alpha-synuclein and may be critical in SCZ pathogenesis.

GGC expansions in NOTCH2NLC contribute to Parkinson disease and dopaminergic neuron degeneration.

The role of GGC repeat expansions within NOTCH2NLC in Parkinson's disease (PD) and the substantia nigra (SN) dopaminergic neuron remains unclear. Here, we profile the NOTCH2NLC GGC repeat expansions in a large cohort of patients with PD. We also investigate the role of GGC repeat expansions within NOTCH2NLC in the dopaminergic neurodegeneration of SN. A total of 2,522 patients diagnosed with PD and 1,085 health controls were analyzed for the repeat expansions of NOTCH2NLC by repeat-primed PCR and GC-rich PCR assay. Furthermore, the effects of GGC repeat expansions in NOTCH2NLC on dopaminergic neurons were investigated by using recombinant adeno-associated virus (AAV)-mediated overexpression of NOTCH2NLC with 98 GGC repeats in the SN of mice by stereotactic injection. Four PD pedigrees (4/333, 1.2%) and three sporadic PD patients (3/2189, 0.14%) were identified with pathogenic GGC repeat expansions (larger than 60 GGC repeats) in the NOTCH2NLC gene, while eight PD patients and one healthy control were identified with intermediate GGC repeat expansions ranging from 41 to 60 repeats. No significant difference was observed in the distribution of intermediate NOTCH2NLC GGC repeat expansions between PD cases and controls (Fisher's exact test p-value = 0.29). Skin biopsy showed P62-positive intranuclear NOTCH2NLC-polyGlycine (polyG) inclusions in the skin nerve fibers of patient. Expanded GGC repeats in NOTCH2NLC produced widespread intranuclear and perinuclear polyG inclusions, which led to a severe loss of dopaminergic neurons in the SN. Consistently, polyG inclusions were presented in the SN of EIIa-NOTCH2NLC-(GGC)98 transgenic mice and also led to dopaminergic neuron loss in the SN. Overall, our findings provide strong evidence that GGC repeat expansions within NOTCH2NLC contribute to the pathogenesis of PD and cause degeneration of nigral dopaminergic neurons.

Enzymatic properties and clinical associations of serum alpha-galactosidase A in Parkinson's disease.

Recent studies have revealed an association between Parkinson's disease (PD) and Fabry disease, a lysosomal storage disorder; however, the underlying mechanisms remain to be elucidated. This study aimed to investigate the enzymatic properties of serum alpha-galactosidase A (GLA) and compared them with the clinical parameters of PD. The study participants consisted of 66 sporadic PD patients and 52 controls. We measured serum GLA activity and calculated the apparent Michaelis constant (Km ) and maximal velocity (Vmax ) by Lineweaver-Burk plot analysis. Serum GLA protein concentration was measured by enzyme-linked immunosorbent assay. We examined the potential correlations between serum GLA activity and GLA protein concentration and clinical features and the plasma neurofilament light chain (NfL) level. Compared to controls, PD patients showed significantly lower serum GLA activity (P < 0.0001) and apparent Vmax (P = 0.0131), but no change in the apparent Km value. Serum GLA protein concentration was lower in the PD group (P = 0.0168) and was positively associated with GLA activity. Serum GLA activity and GLA protein concentration in the PD group showed a negative correlation with age. Additionally, serum GLA activity was negatively correlated with the motor severity score and the level of plasma NfL, and was positively correlated with the score of frontal assessment battery. This study highlights that the lower serum GLA activity in PD is the result of a quantitative decrement of GLA protein in the serum and that it may serve as a biomarker of disease severity.

Gene Panel Sequencing Analysis Revealed a Strong Contribution of Rare Coding Variants to the Risk of Parkinson's Disease in Sporadic Moroccan Patients.

Parkinson's disease (PD) is a neurodegenerative movement disorder which can be either familial or sporadic. While it is well known that monogenic mutations are not a very common cause of PD, GWAS studies have shown that an additional fraction of the PD heritability could be explained by rare or common variants. To identify the rare variants that could influence the risk of PD in the Moroccan population, a cohort of 94 sporadic PD patients negative for the LRRK2 G2019S mutation was subjected to NGS gene panel sequencing, and gene dosage using the MLPA method. Mean age of onset at enrollment was 51.7 ± 11.51years, and 60% of patients were men. We identified 70 rare variants under 0.5% of frequency in 16 of the 20 genes analyzed, of which 7 were novel. Biallelic disease-causing variants in genes with recessive inheritance were found in 5 PD cases (5.31%), whereas 13 patients (13.8%) carried likely pathogenic variants in genes with dominant inheritance. Moreover, 8 patients (8.5%) carried a single variant in MAPT or POLG, whereas co-occurrence of rare variants involving more than one gene was observed in 28 patients (30%). PD patients with variants in recessive genes had a younger mean age at onset than patients with dominant ones (33.40 (12.77) vs. 53.15 (6.63), p < 0.001), while their clinical features were similar. However, patients with rare variants in the risk factor genes or in more than one gene tended to have less resting tremor (p < 0.04), but more dystonia (p < 0.006) and dementia (p < 0.002) than those without any rare variants in known PD-associated genes. Our results showed a significant enrichment of rare variants particularly in LRRK2, VPS13C, POLG, and MAPT and underline their impact on the risk of sporadic form of the disease.

PINK1-Dependent Mitophagy Inhibits Elevated Ubiquitin Phosphorylation Caused by Mitochondrial Damage.

Ubiquitin phosphorylation by the mitochondrial protein kinase PTEN-induced kinase 1 (PINK1), upon mitochondrial depolarization, is an important intermediate step in the recycling of damaged mitochondria via mitophagy. As mutations in PINK1 can cause early-onset Parkinson's disease (PD), there has been a growing interest in small-molecule activators of PINK1-mediated mitophagy as potential PD treatments. Herein, we show that N6-substituted adenosines, such as N6-(2-furanylmethyl)adenosine (known as kinetin riboside) and N6-benzyladenosine, activate PINK1 in HeLa cells and induce PINK1-dependent mitophagy in primary mouse fibroblasts. Interestingly, pre-treatment of HeLa cells and astrocytes with these compounds inhibited elevated ubiquitin phosphorylation that is induced by established mitochondrial depolarizing agents, carbonyl cyanide m-chlorophenyl-hydrazine and niclosamide. Together, this highlights N6-substituted adenosines as progenitor PINK1 activators that could potentially be developed, in the future, as treatments for aged and sporadic PD patients who have elevated phosphorylated ubiquitin levels in the brain.

Unexpected phenotypic and molecular changes of combined glucocerebrosidase and acid sphingomyelinase deficiency.

Heterozygous variants in GBA1, encoding glucocerebrosidase (GCase), are the most common genetic risk factor for Parkinson's disease (PD). Moreover, sporadic PD patients also have a substantial reduction of GCase activity. Genetic variants of SMPD1 are also overrepresented in PD cohorts, whereas a reduction of its encoded enzyme (acid sphingomyelinase or ASM) activity is linked to an earlier age of PD onset. Despite both converging on the ceramide pathway, how the combined deficiencies of both enzymes might interact to modulate PD has yet to be explored. Therefore, we created a double-knockout (DKO) zebrafish line for both gba1 (or gba) and smpd1 to test for an interaction in vivo, hypothesising an exacerbation of phenotypes in the DKO line compared to those for single mutants. Unexpectedly, DKO zebrafish maintained conventional swimming behaviour and had normalised neuronal gene expression signatures compared to those of single mutants. We further identified rescue of mitochondrial Complexes I and IV in DKO zebrafish. Despite having an unexpected rescue effect, our results confirm ASM as a modifier of GBA1 deficiency in vivo. Our study highlights the need for validating how genetic variants and enzymatic deficiencies may interact in vivo.

NF-κB/c-Rel DNA-binding is reduced in substantia nigra and peripheral blood mononuclear cells of Parkinson's disease patients

NF-κB/c-Rel DNA-binding is reduced in substantia nigra and peripheral blood mononuclear cells of Parkinson's disease patients

Cryo-EM structure of amyloid fibril formed by α-synuclein hereditary A53E mutation reveals a distinct protofilament interface

Synucleinopathies like Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple systems atrophy (MSA), have the same pathologic feature of misfolded α-synuclein protein (α-syn) accumulation in the brain. PD patients who carry α-syn hereditary mutations tend to have earlier onset and more severe clinical symptoms than sporadic PD patients. Therefore, revealing the effect of hereditary mutations to the α-syn fibril structure can help us understand these synucleinopathies' structural basis. Here, we present a 3.38Å cryo-electron microscopy structure of α-synuclein fibrils containing the hereditary A53E mutation. The A53E fibril is symmetrically composed of two protofilaments, similar to other fibril structures of WT and mutant α-synuclein. The new structure is distinct from all other synuclein fibrils, not only at the interface between proto-filaments, but also between residues packed within the same proto-filament. A53E has the smallest interface with the least buried surface area among all α-syn fibrils, consisting of only two contacting residues. Within the same protofilament, A53E reveals distinct residue re-arrangement and structural variation at a cavity near its fibril core. Moreover, the A53E fibrils exhibit slower fibril formation and lower stability compared to WT and other mutants like A53T and H50Q, while also demonstrate strong cellular seeding in α-synuclein biosensor cells and primary neurons. In summary, our study aims to highlight structural differences - both within and between the protofilaments of A53E fibrils - and interpret fibril formation and cellular seeding of α-synuclein pathology in disease, which could further our understanding of the structure-activity relationship of α-synuclein mutants.

Evaluating the Genetic Role of Circadian Clock Genes in Parkinson's Disease.

Increasing evidence suggests that circadian dysfunction is related to Parkinson's disease (PD). However, the role of circadian clock genes in PD is still poorly understood. This study aimed to illustrate the association between genetic variants of circadian clock genes and PD in a large Chinese population cohort. Ten circadian clock genes were included in this study. Whole-exome sequencing (WES) was conducted in 1997 early-onset or familial PD patients and 1652 controls (WES cohort), and whole-genome sequencing (WGS) was conducted in 1962 sporadic late-onset PD patients and 1279 controls (WGS cohort). Analyses were completed using the optimized sequence kernel association test and regression analyses. In the burden analysis of the circadian clock gene set, we found suggestive significant associations between the circadian clock genes and PD in the WES cohort when considering missense, damaging missense (Dmis), and deleterious variants. Moreover, the burden analysis of single genes revealed suggestive significant associations between PD and the loss-of-function variants of the CRY1 gene, missense, Dmis, and deleterious variants of the PER1 gene, and Dmis and deleterious variants of the PER2 gene in the WES cohort.Rare variants in the WGS cohort and all common variants in the WGS and WES cohorts were unrelated to PD. Phenotypic analysis indicated that deleterious variants of the PER1 gene were associated with dyskinesia in the WES cohort. Our study provides evidence of a potential link between circadian clock genes and PD from a genetic perspective.

Parkinson’s disease-associated 18 bp promoter variant of DJ-1 alters REST binding and regulates its expression

Parkinson’s disease-associated 18 bp promoter variant of DJ-1 alters REST binding and regulates its expression