PSEN1 G417S mutation in a Chinese pedigree causing early-onset parkinsonism with cognitive impairment.

Presenilin 1 (PSEN1) mutations are a major cause of familial Alzheimer's disease. The pathogenic variant, PSEN1 p.G417S, has been reported to be associated with spastic paraparesis and cotton wool plaques in Japan. Here, we report a 3 generation Chinese pedigree that included 10 patients presenting with early-onset and rapid progression of parkinsonism with cognitive impairment in their third or fourth decade of life. Three additional living patients developed different degrees of cognitive impairment, without movement disorders. Magnetic resonance imaging of the brain showed white matter hyperintensities, multiple microbleeds, and enlarged perivascular spaces. Whole exome sequencing analysis of the proband detected the mutation, p.G417S, in PSEN1, which was completely co-segregated with the disease phenotype within the family by Sanger sequencing. 3D protein structures predicted that the mutation might influence contact with the lipid membrane and the interaction with beta-catenin. Our study provides insights into the heterogeneity in clinical presentation and imaging associated with mutations in PSEN1.

Evaluating the role of ARSA in Chinese patients with Parkinson's disease.

Recent studies have suggested ARSA, a gene responsible for metachromatic leukodystrophy, could be a genetic modifier of Parkinson's disease (PD) pathogenesis, acting as a molecular chaperone for α-synuclein. To elucidate the role of ARSA variants in PD, we did a comprehensive analysis of ARSA variants by performing next-generation sequencing on 477 PD families, 1440 sporadic early-onset PD patients and 1962 sporadic late-onset PD patients and 2636 controls from Chinese mainland, as well as the association between ARSA variants and cognitive function of PD patients. We identified 2 familial PD following autosomal dominant inherence carrying rare variants of ARSA, but they had limited clinical significance. We detected a total of 81 coding variants of ARSA in our subjects but none of the identified variants were associated with either susceptibility or cognitive performance of PD, while loss-of-function variants showed slightly increased burden in late-onset PD (0.25% vs. 0%, p = 0.08). Our results suggested ARSA may not play important roles in PD of Chinese population.

Low-frequency and rare coding variants of NUS1 contribute to susceptibility and phenotype of Parkinson's disease.

NUS1 has been recently identified as a candidate gene for Parkinson's disease (PD). Few studies have examined the association of NUS1 variants with PD susceptibility and phenotypes. In the first cohort, whole-exome sequencing was performed to identify variants in NUS1 exon-coding and exon-intron regions in 1542 cases and 1625 controls. 13 variants were totally detected, of which 10 rare variants and 3 low-frequency variants. Burden analysis showed that rare NUS1 variants significantly enriched in PD (p=0.016). We also performed a meta-analysis based on previous and our studies to correlate NUS1 mutations with PD susceptibility. Integrating our previous cohort (3210 cases and 2807 controls) and the first cohort identified the significant association of rs539668656 with PD risk (odds ratio (OR) = 2.82, p = 0.016). The genotype-phenotype association analysis showed that patients carrying rare variants, or rs539668656 were significantly associated with earlier onset age, depression, emotional impairment and severe disease condition. Our results support the role of NUS1 rare variants and rs539668656 towards PD susceptibility and phenotype.

The Association Between Lysosomal Storage Disorder Genes and Parkinson's Disease: A Large Cohort Study in Chinese Mainland Population.

Background: Recent years have witnessed an increasing number of studies indicating an essential role of the lysosomal dysfunction in Parkinson's disease (PD) at the genetic, biochemical, and cellular pathway levels. In this study, we investigated the association between rare variants in lysosomal storage disorder (LSD) genes and Chinese mainland PD. Methods: We explored the association between rare variants of 69 LSD genes and PD in 3,879 patients and 2,931 controls from Parkinson's Disease & Movement Disorders Multicenter Database and Collaborative Network in China (PD-MDCNC) using next-generation sequencing, which were analyzed by using the optimized sequence kernel association test. Results: We identified the significant burden of rare putative LSD gene variants in Chinese mainland patients with PD. This association was robust in familial or sporadic early-onset patients after excluding the GBA variants but not in sporadic late-onset patients. The burden analysis of variant sets in genes of LSD subgroups revealed a suggestive significant association between variant sets in genes of sphingolipidosis deficiency disorders and familial or sporadic early-onset patients. In contrast, variant sets in genes of sphingolipidoses, mucopolysaccharidoses, and post-translational modification defect disorders were suggestively associated with sporadic late-onset patients. Then, SMPD1 and other four novel genes (i.e., GUSB, CLN6, PPT1, and SCARB2) were suggestively associated with sporadic early-onset or familial patients, whereas GALNS and NAGA were suggestively associated with late-onset patients. Conclusion: Our findings supported the association between LSD genes and PD and revealed several novel risk genes in Chinese mainland patients with PD, which confirmed the importance of lysosomal mechanisms in PD pathogenesis. Moreover, we identified the genetic heterogeneity in early-onset and late-onset of patients with PD, which may provide valuable suggestions for the treatment.

Constructing Prediction Models for Freezing of Gait by Nomogram and Machine Learning: A Longitudinal Study.

Objectives: Although risk factors for freezing of gait (FOG) have been reported, there are still few prediction models based on cohorts that predict FOG. This 1-year longitudinal study was aimed to identify the clinical measurements closely linked with FOG in Chinese patients with Parkinson's disease (PD) and construct prediction models based on those clinical measurements using Cox regression and machine learning. Methods: The study enrolled 967 PD patients without FOG in the Hoehn and Yahr (H&Y) stage 1-3 at baseline. The development of FOG during follow-up was the end-point. Neurologists trained in movement disorders collected information from the patients on a PD medication regimen and their clinical characteristics. The cohort was assessed on the same clinical scales, and the baseline characteristics were recorded and compared. After the patients were divided into the training set and test set by the stratified random sampling method, prediction models were constructed using Cox regression and random forests (RF). Results: At the end of the study, 26.4% (255/967) of the patients suffered from FOG. Patients with FOG had significantly longer disease duration, greater age at baseline and H&Y stage, lower proportion in Tremor Dominant (TD) subtype, a higher proportion in wearing-off, levodopa equivalent daily dosage (LEDD), usage of L-Dopa and catechol-O-methyltransferase (COMT) inhibitors, a higher score in scales of Unified Parkinson's Disease Rate Scale (UPDRS), 39-item Parkinson's Disease Questionnaire (PDQ-39), Non-Motor Symptoms Scale (NMSS), Hamilton Depression Rating Scale (HDRS)-17, Parkinson's Fatigue Scale (PFS), rapid eye movement sleep behavior disorder questionnaire-Hong Kong (RBDQ-HK), Epworth Sleepiness Scale (ESS), and a lower score in scales of Parkinson's Disease Sleep Scale (PDSS) (P < 0.05). The risk factors associated with FOG included PD onset not being under the age of 50 years, a lower degree of tremor symptom, impaired activities of daily living (ADL), UPDRS item 30 posture instability, unexplained weight loss, and a higher degree of fatigue. The concordance index (C-index) was 0.68 for the training set (for internal validation) and 0.71 for the test set (for external validation) of the nomogram prediction model, which showed a good predictive ability for patients in different survival times. The RF model also performed well, the C-index was 0.74 for the test set, and the AUC was 0.74. Conclusions: The study found some new risk factors associated with the FOG including a lower degree of tremor symptom, unexplained weight loss, and a higher degree of fatigue through a longitudinal study, and constructed relatively acceptable prediction models.

Contribution of coding/non-coding variants in NUS1 to late-onset sporadic Parkinson's disease.

INTRODUCTION: A recent study reported that rare variants in NUS1 were associated with Parkinson's disease (PD). We aimed to assess the relative contribution of rare and common coding/non-coding variants of NUS1 to late-onset PD patients (LOPD). METHODS: Whole genome sequencing data were analyzed for target NUS1 regions, derived from a cohort of 1962 cases and 1279 controls. The genetic association analyses were performed using logistic regression analysis and Sequence Kernel association test. Expression quantitative trait loci (eQTL) analysis was conducted to further explore the association of variants with NUS1 expression based on the data from GTEx database. RESULTS: We identified 18 rare coding variants. p.Y131C was first identified in LOPD. However, no significant burden of rare NUS1 coding variants in LOPD was found. The rare variant sets of two regulatory elements (GH06J117605 and GH06J117674) were significantly enriched in LOPD even after Bonferroni correction (adjusted P = 0.013; adjusted P = 0.010). Considering the joint effect of rare and common variants, all variant sets within GH06J117605 and GH06J117674 showed association with LOPD but were no longer significant after Bonferroni correction. None of the common variants within coding/non-coding regions were significant after Bonferroni correction. The eQTL results suggested these variants in GH06J117605 and GH06J117674 could potentially have eQTL effects on the brain tissues. CONCLUSIONS: These findings provide novel insight into the role of NUS1 regulatory regions in the development of LOPD and indicate that the variants in regulatory elements of NUS1 may be associated with LOPD by influencing the gene expression level.

Assessment of the association between NUS1 variants and essential tremor.

BACKGROUND: A recent study on early onset Parkinson's disease (PD) revealed that NUS1 is a risk gene for PD. Clinically, essential tremor (ET) is closely related to PD. In this study, we aimed to detect NUS1 variants and assess the effect of those variants on patients with ET. METHODS: The 5 coding regions and the exon-intron boundaries of NUS1 were directly sequenced in 395 patients with ET and an equal number of healthy controls, matched for age and sex. The function of variants was assessed by pathogenic predictive software programs. Genetic analysis of variants was used to evaluate susceptibility to ET. RESULTS: A total of 6 exonic variants were identified, including 3 synonymous and 3 missense variants. The non-synonymous variants were predicted to be tolerable. No variants had significant association with ET (none of the p-values were less than 0.05, using Fisher's exact test). CONCLUSION: Our study suggested that NUS1 variants may not contribute to the risk of ET.

GCH1 variants contribute to the risk and earlier age-at-onset of Parkinson's disease: a two-cohort case-control study.

BACKGROUND: Common and rare variants of guanosine triphosphate cyclohydrolase 1 (GCH1) gene may play important roles in Parkinson's disease (PD). However, there is a lack of comprehensive analysis of GCH1 genotypes, especially in non-coding regions. The aim of this study was to explore the genetic characteristics of GCH1, including rare and common variants in coding and non-coding regions, in a large population of PD patients in Chinese mainland, as well as the phenotypic characteristics of GCH1 variant carriers. METHODS: In the first cohort of this case-control study, we performed whole-exome sequencing in 1555 patients with early-onset or familial PD and 2234 healthy controls; then in the second cohort, whole-genome sequencing was performed in sporadic late-onset PD samples (1962 patients), as well as 1279 controls. Variants at target GCH1 regions were extracted, and then genetic and detailed phenotypic data were analyzed using regression models and the sequence kernel association test. We also performed a meta-analysis to correlate deleterious GCH1 variants with age at onset (AAO) in PD patients. RESULTS: For coding variants, we identified a significant burden of GCH1 deleterious variants in early-onset or familial PD cases compared to controls (1.2% vs 0.1%, P < 0.0001). In the analysis of possible regulatory variants in GCH1 non-coding regions, rs12323905 (P = 0.001, odds ratio = 1.19, 95%CI 1.07-1.32) was significantly associated with PD, and variant sets in untranslated regions and intron regions, GCH1 brain-specific expression quantitative trait loci, and two possible promoter/enhancer (GH14J054857 and GH14J054880) were suggestively associated with PD. Genotype-phenotype correlation analysis revealed that the carriers of GCH1 deleterious variants manifested younger AAO (P < 0.0001), and had milder motor symptoms, milder fatigue symptoms and more autonomic nervous dysfunctions. Meta-analysis of six studies demonstrated 6.4-year earlier onset in GCH1 deleterious variant carriers (P = 0.0009). CONCLUSIONS: The results highlight the importance of deleterious variants and non-coding variants of GCH1 in PD in Chinese mainland and suggest that GCH1 mutation can influence the PD phenotype, which may help design experimental studies to elucidate the mechanisms of GCH1 in the pathogenesis of PD.

Expansion of GGC repeat in the human-specific NOTCH2NLC gene is associated with essential tremor.

Essential tremor is one of the most common movement disorders. Despite its high prevalence and heritability, the genetic aetiology of essential tremor remains elusive. Up to now, only a few genes/loci have been identified, but these genes have not been replicated in other essential tremor families or cohorts. Here we report a genetic study in a cohort of 197 Chinese pedigrees clinically diagnosed with essential tremor. Using a comprehensive strategy combining linkage analysis, whole-exome sequencing, long-read whole-genome sequencing, repeat-primed polymerase chain reaction and GC-rich polymerase chain reaction, we identified an abnormal GGC repeat expansion in the 5' region of the NOTCH2NLC gene that co-segregated with disease in 11 essential tremor families (5.58%) from our cohort. Clinically, probands that had an abnormal GGC repeat expansion were found to have more severe tremor phenotypes, lower activities of daily living ability. Obvious genetic anticipation was also detected in these 11 essential tremor-positive families. These results indicate that abnormal GGC repeat expansion in the 5' region of NOTCH2NLC gene is associated with essential tremor, and provide strong evidence that essential tremor is a family of diseases with high clinical and genetic heterogeneities.

Expansion of Human-Specific GGC Repeat in Neuronal Intranuclear Inclusion Disease-Related Disorders.

Neuronal intranuclear inclusion disease (NIID) is a slowly progressing neurodegenerative disease characterized by eosinophilic intranuclear inclusions in the nervous system and multiple visceral organs. The clinical manifestation of NIID varies widely, and both familial and sporadic cases have been reported. Here we have performed genetic linkage analysis and mapped the disease locus to 1p13.3-q23.1; however, whole-exome sequencing revealed no potential disease-causing mutations. We then performed long-read genome sequencing and identified a large GGC repeat expansion within human-specific NOTCH2NLC. Expanded GGC repeats as the cause of NIID was further confirmed in an additional three NIID-affected families as well as five sporadic NIID-affected case subjects. Moreover, given the clinical heterogeneity of NIID, we examined the size of the GGC repeat among 456 families with a variety of neurological conditions with the known pathogenic genes excluded. Surprisingly, GGC repeat expansion was observed in two Alzheimer disease (AD)-affected families and three parkinsonism-affected families, implicating that the GGC repeat expansions in NOTCH2NLC could also contribute to the pathogenesis of both AD and PD. Therefore, we suggest defining a term NIID-related disorders (NIIDRD), which will include NIID and other related neurodegenerative diseases caused by the expanded GGC repeat within human-specific NOTCH2NLC.

Clinical Features and Correlates of Excessive Daytime Sleepiness in Parkinson's Disease.

Objective: To explore the clinical features and correlates of excessive daytime sleepiness (EDS) in a Chinese population of Parkinson's disease (PD) patients. Methods: Patients with clinically established or clinically probable PD were recruited. Clinical and demographic data were collected, and participants were evaluated using standardized assessment protocols. Patients were divided into PD with EDS and PD without EDS groups based on the Epworth sleepiness scale (ESS) scores, with a cutoff score of 10. Clinical manifestations were compared between patients with and without EDS, and correlates of EDS were also studied. In addition, the relationship between EDS and poor nighttime sleep quality was analyzed. Results: A total of 1,221 PD patients were recruited in our study. The mean ESS (min, max) score was 7.6 ± 6.1 (0, 24), and 34.1% of the patients had ESS scores ≥10. No difference was seen in lifestyle (except for alcohol consumption), environmental factors, BMI, levodopa equivalent dose (LED), initial presentation of motor symptoms, motor subtype, and wearing off between patients with and without EDS. The PD with EDS group had a higher proportion of male patients and a higher average patient age. Moreover, the PD with EDS group showed older age at PD onset, lower educational level, and longer disease duration. Patients with EDS had higher scores on the Hoehn-Yahr scale and the Unified Parkinson's Disease Rating Scale (UPDRS) parts I, II, and III score, more severe non-motor symptoms, and poorer quality of sleep and life. Logistic regression analyses demonstrated that EDS was associated with male sex, age, cognitive impairment, PD-related sleep problems, rapid eye movement sleep behavior disorder (RBD), and worse quality of life (QoL). Conclusion: EDS is a general clinical manifestation in PD, and there were significant differences in clinical features between patients with and without EDS. Moreover, our study proved that many factors were associated with EDS, including male sex, age, cognitive impairment, PD-related sleep problems, RBD, and worse QoL. Understanding the clinical characteristics of EDS in PD patients may help identify EDS early, improve QoL, and reduce the occurrence of accidents.

Impaired iPLA2ß activity affects iron uptake and storage without iron accumulation: An in vitro study excluding decreased iPLA2ß activity as the cause of iron deposition in PLAN.

PLA2G6-associated neurodegeneration (PLAN, NBIA2) is the second most common type of neurodegeneration with brain iron accumulation (NBIA), caused by recessive mutations of PLA2G6 gene, which encodes Ca2+-independent phospholipase A2ß (iPLA2ß). In most PLAN cases, decreased iPLA2ß activity and iron deposition was observed meanwhile, and researchers also identified a PLA2G6 mutation family without iron deposition shown by MRI images. This brought us the question of whether decreased iPLA2ß activity was the cause of iron deposition in PLAN. In this study, we used S-BEL as the antagonist of iPLA2ß to block its activity and used SH-SY5Y cells as the expression system. We incubated SH-SY5Y cells with different concentrations of S-BEL. The results showed that decreased iPLA2ß activity led no obvious iron accumulation, while changes of cells state and activation of apoptosis were observed. To further investigate the cause of unchanged iron level, we examined the cellular iron regulatory proteins involved in iron uptake, storage and export. The results were as follows: TfR1 (iron uptake protein) expression was decreased, the expression of ferritin heavy chain and light chain (iron storage protein) was increased. There was no alteration of the expression of DMT1 (iron uptake protein) and FPN1 (iron export protein). Under the condition of decreased iPLA2ß activity, there was no obvious iron accumulation but iron uptake activity decreased and iron storage activity increased. Therefore, we speculate that the decreased iPLA2ß activity may not be the main reason for iron deposition in PLAN.

Coding mutations in NUS1 contribute to Parkinson's disease.

Whole-exome sequencing has been successful in identifying genetic factors contributing to familial or sporadic Parkinson's disease (PD). However, this approach has not been applied to explore the impact of de novo mutations on PD pathogenesis. Here, we sequenced the exomes of 39 early onset patients, their parents, and 20 unaffected siblings to investigate the effects of de novo mutations on PD. We identified 12 genes with de novo mutations (MAD1L1, NUP98, PPP2CB, PKMYT1, TRIM24, CEP131, CTTNBP2, NUS1, SMPD3, MGRN1, IFI35, and RUSC2), which could be functionally relevant to PD pathogenesis. Further analyses of two independent case-control cohorts (1,852 patients and 1,565 controls in one cohort and 3,237 patients and 2,858 controls in the other) revealed that NUS1 harbors significantly more rare nonsynonymous variants (P = 1.01E-5, odds ratio = 11.3) in PD patients than in controls. Functional studies in Drosophila demonstrated that the loss of NUS1 could reduce the climbing ability, dopamine level, and number of dopaminergic neurons in 30-day-old flies and could induce apoptosis in fly brain. Together, our data suggest that de novo mutations could contribute to early onset PD pathogenesis and identify NUS1 as a candidate gene for PD.

Identification of Ser465 as a novel PINK1 autophosphorylation site.

BACKGROUND: PINK1 (PTEN-induced putative kinase 1) gene is the causal gene for recessive familial type 6 of Parkinson's disease (PARK6), which is an early-onset autosomal recessive inherited neurodegenerative disease. PINK1 has been reported to exert both autophosphorylation and phosphorylation activity, affecting cell damage under stress and other physiological responses. However, there has been no report on the identification of PINK1 autophosphorylation sites and their physiological functions. METHODS: (1) We adopted mass spectrometry assay to identify the autophosphorylation site of PINK1, and autoradiography assay was further conducted to confirm this result. (2) Kinase activity assay was used to compare the kinase activity of both Ser465 mutant PINK1 and disease-causing mutant PINK1. (3) We use Pulse-chase analysis to measure whether Ser465 may affect PINK1 degradation. (4) Immunocytochemistry staining was used to study the PINK1 subcellular localization and Parkin transition in subcellular level. RESULT: In our study, we identified the 465th serine residue (Ser465) as one of the autophosphorylation sites in PINK1 protein. The inactivation of Ser465 can decrease the kinase activity of PINK1. Either dissipated or excessive Ser465 site phosphorylation of PINK1 can slow down its degradation. PINK1 autophosphorylation contributes to the transit of Parkin to mitochondria, and has no effect on its subcellular localization. PARK6 causal mutations, T313 M and R492X, display the same characteristics as Ser465A mutation PINK1 protein, such as decreasing PINK1 kinase activity and affecting its interaction with Parkin. CONCLUSION: Ser465 was identified as one of the autophosphorylation sites of PINK1, which affected PINK1 kinase activity. In addition, Ser465 is involved in the degradation of PINK1 and the transit of Parkin to mitochondria. T313 M and R492X, two novel PARK6 mutations on Thr313 and Arg492, were similar to Ser465 mutation, including decreasing PINK1 phosphorylation activity and Parkin subcellular localization.

RAB39B gene mutations are not linked to familial Parkinson's disease in China.

Recently, RAB39B mutations were reported to be a causative factor in patients with Parkinson's disease (PD). To validate the role of RAB39B in familial PD, a total of 195 subjects consisting of 108 PD families with autosomal-dominant (AD) inheritance and 87 PD families with autosomal-recessive (AR) inheritance in the Chinese Han population from mainland China were included in this study. We did not identify any variants in the coding region or the exon-intron boundaries of the gene by Sanger sequencing method in the DNA samples of 180 patients (100 with AD and 80 with AR). Furthermore, we did not find any variants in the RAB39B gene when Whole-exome sequencing (WES) was applied to DNA samples from 15 patients (8 with AD and 7 with AR) for further genetic analysis. Additionally, when quantitative real-time PCR was used to exclude large rearrangement variants in these patients, we found no dosage mutations in RAB39B gene. Our results suggest that RAB39B mutation is very rare in familial PD and may not be a major cause of familial PD in the Chinese Han Population.