Clinicogenetic study of GBA mutations in patients with familial Parkinson's disease

Literature review and meta-analysis of environmental toxins associated with increased risk of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder and leading cause of death worldwide, whose pathogenesis has been linked to toxic environmental exposures. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (i) to compile, and group by exposure setting (non-specified general; residential; occupational), environmental factors reported to modulate the risk of developing PD and (ii) to map and geospatially analyze global regions of both research activity and paucity. Among the broader environmental settings, occupational exposures had the highest average odds ratio value at 3.82, followed by general (non-specified or mixed) exposures at 3.07, and residential exposures at 2.36. Occupational exposure to industrial toxins was the highest ranked subset of exposures with an odds ratio of 10.74. Among the studies meeting the inclusion criteria, 75 % were conducted in Europe or the Western United States. The number of individuals partaking per study ranged from a high of 55,585 (Taiwan) to a low of 233 (Faroe Islands), with a mean of n = 14,462. The top three environmental factors associated with high odds ratios for increased risk of developing PD were (i) exposure to dyes (25.33), (ii) methylene chloride (16.5) and specifically in adult men (iii) consumption of fatty whale meat (10.57), which is known to harbor a broad spectrum of so called persistent, bioaccumulative, toxic (PBT) pollutants. Geospatially, the highest odds ratio values were identified in European countries, whereas notable data gaps were revealed for South America, Australia, Africa, and the majority of Asia with the exception of Taiwan. Whereas occupational exposures to industrial chemicals, such as harmful dyes and methylene chloride, ranked highest in risk values, available data suggest notable opportunities for reducing PD cases globally by limiting harmful environmental exposures to a spectrum of toxic chemicals, particularly via the food intake route. Thus, current efforts in improving environmental quality globally by limiting toxic emission may deliver the added benefit of helping to reign in PD. Agents of concern in this respect include pesticides (e.g., paraquat, demeton, monocrotophos), particulate matter associated with air pollution, and a spectrum of organic and inorganic neurotoxins including heavy metals.

The Degree of Cardiovascular Autonomic Dysfunction is not Different in GBA-Related and Idiopathic Parkinson's Disease Patients: A Case-Control Instrumental Evaluation

Background

Increased prevalence of cardiovascular autonomic failure might play a key role on Parkinson's disease (PD) progression of glucocerebrosidase gene (GBA)-mutated patients, determining a malignant phenotype of disease in these patients.

Objective

To objectively characterize, for the first time, the cardiovascular autonomic profile of GBA-mutated patients compared to idiopathic PD patients by means of cardiovascular reflex tests (CRTs).

Methods

This is a case-control (1 : 2) study on PD patients belonging to well-characterized prospective cohorts. For each PD patient carrying GBA variants, two idiopathic PD patients, matched for sex and disease duration at CRTs, were selected. Patients recruited in these cohorts underwent a complete clinical and instrumental evaluation including specific autonomic questionnaires, CRTs and extensive genetic analysis.

Results

A total of 23 GBA-PD patients (19 males, disease duration 7.7 years) were included and matched with 46 non-mutated PD controls. GBA-mutated patients were younger than controls (59.9±8.1 vs. 64.3±7.2 years, p = 0.0257) and showed a more severe phenotype. Despite GBA-mutated patients reported more frequently symptoms suggestive of orthostatic hypotension (OH) than non-mutated patients (39.1% vs 6.5%, p = 0.001), the degree of cardiovascular autonomic dysfunction, when instrumentally assessed, did not differ between the two groups, showing the same prevalence of neurogenic OH, delayed OH and cardiovascular reflex impairment (pathological Valsalva maneuver).

Conclusion

GBA-PD patients did not show different instrumental cardiovascular autonomic pattern than non-mutated PD. Our findings suggested that symptoms suggestive of OH should be promptly investigated by clinicians to confirm their nature and improve patient care and management.

Whole Transcriptome Analysis of Substantia Nigra in Mice with MPTP-Induced Parkinsonism Bearing Defective Glucocerebrosidase Activity

Mutations in the GBA1 gene represent the major genetic risk factor for Parkinson's disease (PD). The lysosomal enzyme beta-glucocerebrosidase (GCase) encoded by the GBA1 gene participates in both the endolysosomal pathway and the immune response. Disruption of these mechanisms is involved in PD pathogenesis. However, molecular mechanisms of PD associated with GBA1 mutations (GBA-PD) are unknown today in particular due to the partial penetrance of GBA1 variants in PD. The modifiers of GBA1 penetrance have not been elucidated. We characterized the transcriptomic profiles of cells from the substantia nigra (SN) of mice with co-injection with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and selective inhibitor of GCase activity (conduritol-β-epoxide, (CBE)) to mimic PD bearing GCase dysfunction (MPTP+CBE), mice treated with MPTP, mice treated with CBE and control mice treated with injection of sodium chloride (NaCl) (vehicle). Differential expression analysis, pathway enrichment analysis, and outlier detection were performed. Functional clustering of differentially represented transcripts revealed more processes associated with the functioning of neurogenesis, inflammation, apoptosis and autophagy in MPTP+CBE and MPTP mice than in vehicle mice, with a more pronounced alteration of autophagy processes in MPTP+CBE mice than in MPTP mice. The PI3K-Akt-mTOR signaling pathway may be considered a potential target for therapy in PD with GCase dysfunction.

GBA1 in Parkinson's disease: variant detection and pathogenicity scoring matters

BACKGROUND

GBA1 variants are the strongest genetic risk factor for Parkinson's disease (PD). However, the pathogenicity of GBA1 variants concerning PD is still not fully understood. Additionally, the frequency of GBA1 variants varies widely across populations.

OBJECTIVES

To evaluate Oxford Nanopore sequencing as a strategy, to determine the frequency of GBA1 variants in Norwegian PD patients and controls, and to review the current literature on newly identified variants that add to pathogenicity determination.

METHODS

We included 462 Norwegian PD patients and 367 healthy controls. We sequenced the full-length GBA1 gene on the Oxford Nanopore GridION as an 8.9 kb amplicon. Six analysis pipelines were compared using two aligners (NGMLR, Minimap2) and three variant callers (BCFtools, Clair3, Pepper-Margin-Deepvariant). Confirmation of GBA1 variants was performed by Sanger sequencing and the pathogenicity of variants was evaluated.

RESULTS

We found 95.8% (115/120) true-positive GBA1 variant calls, while 4.2% (5/120) variant calls were false-positive, with the NGMLR/Minimap2-BCFtools pipeline performing best. In total, 13 rare GBA1 variants were detected: two were predicted to be (likely) pathogenic and eleven were of uncertain significance. The odds of carrying one of the two common GBA1 variants, p.L483P or p.N409S, in PD patients were estimated to be 4.11 times the odds of carrying one of these variants in controls (OR = 4.11 [1.39, 12.12]).

CONCLUSIONS

In conclusion, we have demonstrated that Oxford long-read Nanopore sequencing, along with the NGMLR/Minimap2-BCFtools pipeline is an effective tool to investigate GBA1 variants. Further studies on the pathogenicity of GBA1 variants are needed to assess their effect on PD.

A severe neurodegenerative disease with Lewy bodies and a mutation in the glucocerebrosidase gene

Several heterozygous variants of the glucocerebrosidase gene (GBA1) have been reported to increase the risk of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). GBA1-associated PD has been reported to be more severe than idiopathic PD, and more deleterious variants are associated with more severe clinical phenotypes. We report a family with a heterozygous p.Pro454Leu variant in GBA1. The variant was associated with a severe and rapidly progressive neurodegenerative disease with Lewy bodies that were clinically and pathologically diverse. Pathogenicity prediction algorithms and evolutionary analyses suggested that p.Pro454Leu is deleterious.

Dual-phase 18 F-FP-CIT positron emission tomography and cardiac 123 I-MIBG scintigraphy of Parkinson's disease patients with GBA mutations: evidence of the body-first type?

BACKGROUND AND PURPOSE

Parkinson's disease (PD) with glucocerebrosidase (GBA) gene mutation (GBA-PD) is known to show more rapid clinical progression than sporadic PD without GBA mutation (sPD). This study was performed to delineate the specific patterns of cortical hypoperfusion, dopamine transporter uptake and cardiac meta-iodobenzylguanidine (MIBG) uptake of GBA-PD in comparison to sPD.

METHODS

Through next-generation sequencing analysis targeting 41 genes, a total of 16 GBA-PD and 24 sPD patients (sex, age matched) were enrolled in the study, and the clinical, dual-phase [¹⁸ F]-N-(3-fluoropropyl)-2β-carboxymethoxy-3β-(4-iodophenyl) nortropane (^{1 8} F-FP-CIT) positron emission tomography (PET) and cardiac ¹²³ I-MIBG scintigraphy results were compared between the two groups.

RESULTS

The GBA-PD group had higher rates of rapid eye movement sleep behavior disorder, orthostatic hypotension and neuropsychiatric symptoms than the sPD group. Early-phase ¹⁸ F-FP-CIT PET showed significantly lower standard uptake value ratio on bilateral posterior parietal cortex (0.94 ± 0.05 vs. 1.02 ± 0.04, p = 0.011) and part of the occipital cortex (p < 0.05) in the GBA-PD group than the sPD group. In striatal dopamine transporter uptake, the regional standard uptake value ratio, asymmetry index and caudate-to-putamen ratio were similar between the two groups. The GBA-PD group had a lower heart-to-mediastinum uptake ratio in ¹²³ I-MIBG scintigraphy than the sPD group.

CONCLUSIONS

The GBA-PD patients showed decreased regional perfusion in the bilateral posterior parietal and occipital cortex. Cardiac sympathetic denervation and non-motor symptoms (orthostatic hypotension, rapid eye movement sleep behavior disorder) were more common in GBA-PD than sPD. These findings suggest that GBA-PD patients have more widespread peripheral (extranigral) α-synuclein accumulation, representing a body-first PD subtype.

GBA inhibition suppresses ovarian cancer growth, survival and receptor tyrosine kinase AXL-mediated signaling pathways

The poor outcome of advanced ovarian cancer under conventional therapy necessitates new strategies to improve therapeutic efficacy. β-glucosidase (encoded by GBA) is a lysosomal enzyme and is involved in sphingolipids metabolism. Recent studies revealed that β-glucosidase plays a role in cancer development and chemoresistance. In this work, we systematically evaluated the expression and role of GBA in ovarian cancer. Our work demonstrates that inhibition of β-glucosidase has therapeutic potential for ovarian cancer. Gene Expression Profiling Interactive Analysis database, western blot and immunohistochemistry analyses of patient samples demonstrated that GBA mRNA and protein expression levels were significantly increased in ovarian cancer compared to normal tissues. Functional studies using gain-of- function and loss-of-function approaches demonstrated that GBA overexpression did not affect growth and migration but alleviated cisplatin's efficacy in ovarian cancer cells. In addition, GBA depletion resulted in growth inhibition, apoptosis induction, and enhancement of cisplatin's efficacy. Of note, we found that GBA inhibition specifically decreased receptor tyrosine kinase AXL level, leading to the suppression of AXL-mediated signaling pathways. Our data suggest that GBA represents a promising target to inhibit AXL signaling and overcome cisplatin resistance in ovarian cancer.

Unraveling Parkinson's Disease Neurodegeneration: Does Aging Hold the Clues?

Aging is the greatest risk factor for Parkinson's disease (PD), suggesting that mechanisms driving the aging process promote PD neurodegeneration. Several lines of evidence support a role for aging in PD. First, hallmarks of brain aging such as mitochondrial dysfunction and oxidative stress, loss of protein homeostasis, and neuroinflammation are centrally implicated in PD development. Second, mutations that cause monogenic PD are present from conception, yet typically only cause disease following a period of aging. Third, lifespan-extending genetic, dietary, or pharmacological interventions frequently attenuate PD-related neurodegeneration. These observations support a central role for aging in disease development and suggest that new discoveries in the biology of aging could be leveraged to elucidate novel mechanisms of PD pathophysiology. A recent rapid growth in our understanding of conserved molecular pathways that govern model organism lifespan and healthspan has highlighted a key role for metabolism and nutrient sensing pathways. Uncovering how metabolic pathways involving NAD+ consumption, insulin, and mTOR signaling link to the development of PD is underway and implicates metabolism in disease etiology. Here, we assess areas of convergence between nervous system aging and PD, evaluate the link between metabolism, aging, and PD and address the potential of metabolic interventions to slow or halt the onset of PD-related neurodegeneration drawing on evidence from cellular and animal models.

A Paper-Based Analytical Device Integrated with Smartphone: Fluorescent and Colorimetric Dual-Mode Detection of β-Glucosidase Activity

In this work, indoxyl-glucoside was used as the substrate to develop a cost-effective, paper-based analytical device for the fluorescent and colorimetric dual-mode detection of β-glucosidase activity through a smartphone. The β-glucosidase can hydrolyze the colorless substrate indoxyl-glucoside to release indoxyl, which will be self-oxidized to generate green products in the presence of oxygen. Meanwhile, the green products emit bright blue-green fluorescence under ultraviolet-visible light irradiation at 365 nm. Fluorescent or colorimetric images were obtained by a smartphone, and the red-green-blue channels were analyzed by the Adobe Photoshop to quantify the β-glucosidase activity. Under the optimum conditions, the relative fluorescent and colorimetric signals have a good linear relationship with the activity of β-glucosidase, in the range of 0.01-1.00 U/mL and 0.25-5.00 U/mL, and the limits of detection are 0.005 U/mL and 0.0668 U/mL, respectively. The activities of β-glucosidase in a crude almond sample measured by the fluorescent and colorimetric methods were 23.62 ± 0.53 U/mL and 23.86 ± 0.25 U/mL, respectively. In addition, the spiked recoveries of normal human serum and crude almond samples were between 87.5% and 118.0%. In short, the paper-based device, combined with a smartphone, can provide a simple, environmentally friendly, and low-cost method for the fluorescent and colorimetric dual-mode detection of β-glucosidase activity.

Transcriptome deregulation of peripheral monocytes and whole blood in GBA-related Parkinson's disease

BACKGROUND

Genetic mutations in beta-glucocerebrosidase (GBA) represent the major genetic risk factor for Parkinson's disease (PD). GBA participates in both the endo-lysosomal pathway and the immune response, two important mechanisms involved in the pathogenesis of PD. However, modifiers of GBA penetrance have not yet been fully elucidated.

METHODS

We characterized the transcriptomic profiles of circulating monocytes in a population of patients with PD and healthy controls (CTRL) with and without GBA variants (n = 23 PD/GBA, 13 CTRL/GBA, 56 PD, 66 CTRL) and whole blood (n = 616 PD, 362 CTRL, 127 PD/GBA, 165 CTRL/GBA). Differential expression analysis, pathway enrichment analysis, and outlier detection were performed. Ultrastructural characterization of isolated CD14+ monocytes in the four groups was also performed through electron microscopy.

RESULTS

We observed hundreds of differentially expressed genes and dysregulated pathways when comparing manifesting and non-manifesting GBA mutation carriers. Specifically, when compared to idiopathic PD, PD/GBA showed dysregulation in genes involved in alpha-synuclein degradation, aging and amyloid processing. Gene-based outlier analysis confirmed the involvement of lysosomal, membrane trafficking, and mitochondrial processing in manifesting compared to non-manifesting GBA-carriers, as also observed at the ultrastructural levels. Transcriptomic results were only partially replicated in an independent cohort of whole blood samples, suggesting cell-type specific changes.

CONCLUSIONS

Overall, our transcriptomic analysis of primary monocytes identified gene targets and biological processes that can help in understanding the pathogenic mechanisms associated with GBA mutations in the context of PD.

Clinical Manifestations and Molecular Backgrounds of Parkinson's Disease Regarding Genes Identified From Familial and Population Studies

Over the past 20 years, numerous robust analyses have identified over 20 genes related to familial Parkinson's disease (PD), thereby uncovering its molecular underpinnings and giving rise to more sophisticated approaches to investigate its pathogenesis. α-Synuclein is a major component of Lewy bodies (LBs) and behaves in a prion-like manner. The discovery of α-Synuclein enables an in-depth understanding of the pathology behind the generation of LBs and dopaminergic neuronal loss. Understanding the pathophysiological roles of genes identified from PD families is uncovering the molecular mechanisms, such as defects in dopamine biosynthesis and metabolism, excessive oxidative stress, dysfunction of mitochondrial maintenance, and abnormalities in the autophagy–lysosome pathway, involved in PD pathogenesis. This review summarizes the current knowledge on familial PD genes detected by both single-gene analyses obeying the Mendelian inheritance and meta-analyses of genome-wide association studies (GWAS) from genome libraries of PD. Studying the functional role of these genes might potentially elucidate the pathological mechanisms underlying familial PD and sporadic PD and stimulate future investigations to decipher the common pathways between the diseases.

Pronounced Orthostatic Hypotension in GBA-Related Parkinson's Disease

Patients with Parkinson's disease (PD) carrying variants in the Glucocerebrosidase (GBA) gene (GBA-PD) suffer from orthostatic symptoms more frequently than idiopathic PD patients (IPD). Systematic measurements of the blood pressure have not yet been performed. In the present study, a prospective analysis of 33 GBA-PD and 313 IPD patients was carried out. Systolic blood pressure upon changing from the supine to the upright position dropped more strongly in GBA-PD compared to IPD patients. Diastolic blood pressure and heart rate did not differ between groups. This study provides further evidence for a pronounced involvement of the autonomic nervous system in GBA-PD.

Clinical and molecular genetic findings of hereditary Parkinson's patients from Turkey

INTRODUCTION

The majority of Parkinson's disease (PD) ensue late-onset with a complex spectrum of environmental and genetic risk factors. Awareness of genetic causes in patients with PD is essential for genetic counseling and future genotype-oriented therapeutic developments.

METHODS

Large pathogenic changes in eight PD-related genes and small pathogenic sequence variants in 22 PD-related genes were investigated simultaneously in 82 PD patients from 79 families where clinical evaluations were performed. The phenotypic characteristics of the patients with molecular changes were examined for genotype-phenotype relations.

RESULTS

Pathogenic variants in SNCA, PRKN, DJ-1, FBXO7, and GBA genes were determined in 25 patients from 24 families (24/79, 30%). Associated variants were found in PRKN in 14, SNCA in three, FBXO7 in two, and DJ-1 in one patient. A novel homozygous deletion (c.491delT, p.(V164Dfs*13) (SCV001733595)) leading to protein truncation in the PRKN gene was identified in two patients from the same family. Furthermore, heterozygous GBA gene variants were detected in five patients from different families.

CONCLUSION

It has been shown that the most common cause of genetically transmitted PD is the PRKN gene, while LRRK2 does not play an essential role in this selected population. It has been suggested that even if the autosomal recessive inheritance is expected, genes with autosomal dominant effects such as SNCA should not be overlooked and suggested for investigation. Our study is also the first for evaluating the pathogenic GBA variants' frequency in PD patients from Turkey.

Gaucher disease: an update

Gaucher disease is a lysosomal storage disease affecting the bone marrow, spleen, liver, and nervous system. In Romania we follow up over 70 adult patients with Gaucher disease, who benefit from fully covered therapy. There is a need to screen for Gaucher disease, to diagnose early the condition and to use the best available therapy. This is a review of recent studies on Gaucher disease and is dedicated to trainees in medicine.

Lack of Association Between GBA Mutations and Motor Complications in European and American Parkinson's Disease Cohorts

Background:

Motor complications are a consequence of the chronic dopaminergic treatment of Parkinson’s disease (PD) and include levodopa-induced dyskinesia (LIDs) and motor fluctuations (MF). Currently, evidence is on lacking whether patients with GBA-associated PD differ in their risk of developing motor complications compared to the general PD population.

Objective:

To evaluate the association of GBA carrier status with the development of LIDS and MFs from early PD.

Methods:

Motor complications were recorded prospectively in 884 patients with PD from four longitudinal cohorts using part IV of the UPDRS or MDS-UPDRS. Subjects were followed for up to 11 years and the associations of GBA mutations with the development of motor complications were assessed using parametric accelerated failure time models.

Results:

In 439 patients from Europe, GBA mutations were detected in 53 (12.1%) patients and a total of 168 cases of LIDs and 258 cases of MF were observed. GBA carrier status was not associated with the time to develop LIDs (HR 0.78, 95%CI 0.47 to 1.26, p = 0.30) or MF (HR 1.19, 95%CI 0.84 to 1.70, p = 0.33). In the American cohorts, GBA mutations were detected in 36 (8.1%) patients and GBA carrier status was also not associated with the progression to LIDs (HR 1.08, 95%CI 0.55 to 2.14, p = 0.82) or MF (HR 1.22, 95%CI 0.74 to 2.04, p = 0.43).

Conclusion:

This study does not provide evidence that GBA-carrier status is associated with a higher risk of developing motor complications. Publication of studies with null results is vital to develop an accurate summary of the clinical features that impact patients with GBA-associated PD.

Glucocerebrosidase Gene Therapy Induces Alpha-Synuclein Clearance and Neuroprotection of Midbrain Dopaminergic Neurons in Mice and Macaques

Mutations in the GBA1 gene coding for glucocerebrosidase (GCase) are the main genetic risk factor for Parkinson’s disease (PD). Indeed, identifying reduced GCase activity as a common feature underlying the typical neuropathological signatures of PD—even when considering idiopathic forms of PD—has recently paved the way for designing novel strategies focused on enhancing GCase activity to reduce alpha-synuclein burden and preventing dopaminergic cell death. Here we have performed bilateral injections of a viral vector coding for the mutated form of alpha-synuclein (rAAV9-SynA53T) for disease modeling purposes, both in mice as well as in nonhuman primates (NHPs), further inducing a progressive neuronal death in the substantia nigra pars compacta (SNpc). Next, another vector coding for the GBA1 gene (rAAV9-GBA1) was unilaterally delivered in the SNpc of mice and NHPs one month after the initial insult, together with the contralateral delivery of an empty/null rAAV9 for control purposes. Obtained results showed that GCase enhancement reduced alpha-synuclein burden, leading to improved survival of dopaminergic neurons. Data reported here support using GCase gene therapy as a disease-modifying treatment for PD and related synucleinopathies, including idiopathic forms of these disorders.

Glucocerebrosidase Gene Therapy Induces Alpha-Synuclein Clearance and Neuroprotection of Midbrain Dopaminergic Neurons in Mice and Macaques

Mutations in the GBA1 gene coding for glucocerebrosidase (GCase) are the main genetic risk factor for Parkinson's disease (PD). Indeed, identifying reduced GCase activity as a common feature underlying the typical neuropathological signatures of PD-even when considering idiopathic forms of PD-has recently paved the way for designing novel strategies focused on enhancing GCase activity to reduce alpha-synuclein burden and preventing dopaminergic cell death. Here we have performed bilateral injections of a viral vector coding for the mutated form of alpha-synuclein (rAAV9-SynA53T) for disease modeling purposes, both in mice as well as in nonhuman primates (NHPs), further inducing a progressive neuronal death in the substantia nigra pars compacta (SNpc). Next, another vector coding for the GBA1 gene (rAAV9-GBA1) was unilaterally delivered in the SNpc of mice and NHPs one month after the initial insult, together with the contralateral delivery of an empty/null rAAV9 for control purposes. Obtained results showed that GCase enhancement reduced alpha-synuclein burden, leading to improved survival of dopaminergic neurons. Data reported here support using GCase gene therapy as a disease-modifying treatment for PD and related synucleinopathies, including idiopathic forms of these disorders.

Glucocerebrosidase Gene Therapy Induces Alpha-Synuclein Clearance and Neuroprotection of Midbrain Dopaminergic Neurons in Mice and Macaques

Mutations in the GBA1 gene coding for glucocerebrosidase (GCase) are the main genetic risk factor for Parkinson’s disease (PD). Indeed, identifying reduced GCase activity as a common feature underlying the typical neuropathological signatures of PD—even when considering idiopathic forms of PD—has recently paved the way for designing novel strategies focused on enhancing GCase activity to reduce alpha-synuclein burden and preventing dopaminergic cell death. Here we have performed bilateral injections of a viral vector coding for the mutated form of alpha-synuclein (rAAV9-SynA53T) for disease modeling purposes, both in mice as well as in nonhuman primates (NHPs), further inducing a progressive neuronal death in the substantia nigra pars compacta (SNpc). Next, another vector coding for the GBA1 gene (rAAV9-GBA1) was unilaterally delivered in the SNpc of mice and NHPs one month after the initial insult, together with the contralateral delivery of an empty/null rAAV9 for control purposes. Obtained results showed that GCase enhancement reduced alpha-synuclein burden, leading to improved survival of dopaminergic neurons. Data reported here support using GCase gene therapy as a disease-modifying treatment for PD and related synucleinopathies, including idiopathic forms of these disorders.

Inhibition of β-glucosidase overcomes gastric cancer chemoresistance through inducing lysosomal dysfunction

OBJECTIVE

The clinical management of gastric cancer still remains challenge due to its poor response to chemotherapy. Better understanding the underlying mechanisms is required for the identification of more comprehensive therapies to overcome chemoresistance in gastric cancer.

MATERIALS AND METHODS

GBA1 level was systematically analyzed in gastric cancer patients before and after chemotherapy, and gastric cancer cells exposed to long-term chemo agent's treatment. The roles of GBA1 and its downstream mechanisms were investigated using pharmacological and genetic approaches.

RESULTS

We observed the time-dependent upregulation of GBA1 expression and enzyme activity in multiple gastric cancer cell lines in response to prolonged exposure of 5-FU. It is noted that this phenomenon was also observed in gastric cancer patients after chemotherapy. Interestingly, no significant differences on GBA1 expression were detected between normal and malignant gastric tissues. These suggest that the predominant role of GBA1 is in the development of gastric cancer chemoresistance rather than tumorigenesis. Functional analysis demonstrated that GBA1 inhibition suppressed gastric cancer growth and survival without affecting migration, and augmented 5-FU's efficacy. Consistently, GBA1 inhibition was active against 5-FU-resistant gastric cancer cells. Mechanism studies showed that GBA1 inhibition led to loss of lysosomal integrity and function in 5-FU-resistant gastric cancer cells.

CONCLUSIONS

We are the first to show that inhibition of β-glucosidase (encoded by GBA1) sensitizes gastric cancer to chemotherapy. Our findings demonstrate the therapeutic value of inhibiting GBA1 in gastric cancer, particularly in those who develop chemoresistance.

Brain-First versus Gut-First Parkinson's Disease: A Hypothesis

Parkinson’s disease (PD) is a highly heterogeneous disorder, which probably consists of multiple subtypes. Aggregation of misfolded alpha-synuclein and propagation of these proteinacious aggregates through interconnected neural networks is believed to be a crucial pathogenetic factor. It has been hypothesized that the initial pathological alpha-synuclein aggregates originate in the enteric or peripheral nervous system (PNS) and invade the central nervous system (CNS) via retrograde vagal transport. However, evidence from neuropathological studies suggests that not all PD patients can be reconciled with this hypothesis. Importantly, a small fraction of patients do not show pathology in the dorsal motor nucleus of the vagus. Here, it is hypothesized that PD can be divided into a PNS-first and a CNS-first subtype. The former is tightly associated with REM sleep behavior disorder (RBD) during the prodromal phase and is characterized by marked autonomic damage before involvement of the dopaminergic system. In contrast, the CNS-first phenotype is most often RBD-negative during the prodromal phase and characterized by nigrostriatal dopaminergic dysfunction prior to involvement of the autonomic PNS. The existence of these subtypes is supported by in vivo imaging studies of RBD-positive and RBD-negative patient groups and by histological evidence— reviewed herein. The present proposal provides a fresh hypothesis-generating framework for future studies into the etiopathogenesis of PD and seems capable of explaining a number of discrepant findings in the neuropathological literature.

Glucocerebrosidase Defects as a Major Risk Factor for Parkinson's Disease

Heterozygous mutations of the GBA1 gene, encoding for lysosomal enzyme glucocerebrosidase (GCase), occur in a considerable percentage of all patients with sporadic Parkinson's disease (PD), varying between 8% and 12% across the world. Genome wide association studies have confirmed the strong correlation between PD and GBA1 mutations, pointing to this element as a major risk factor for PD, possibly the most important one after age. The pathobiological mechanisms underlying the link between a defective function of GCase and the development of PD are still unknown and are currently the focus of intense investigation in the community of pre-clinical and clinical researchers in the PD field. A major controversy regards the fact that, despite the unequivocal correlation between the presence of GBA1 mutations and the risk of developing PD, only a minority of asymptomatic carriers with GBA1 mutations convert to PD in their lifetime. GBA1 mutations reduce the enzymatic function of GCase, impairing lysosomal efficiency and the cellular ability to dispose of pathological alpha-synuclein. Changes in the cellular lipidic content resulting from the accumulation of glycosphingolipids, triggered by lysosomal dysfunction, may contribute to the pathological modification of alpha-synuclein, due to its ability to interact with cell membrane lipids. Mutant GCase can impair mitochondrial function and cause endoplasmic reticulum stress, thereby impacting on cellular energy production and proteostasis. Importantly, reduced GCase activity is associated with clear activation of microglia, a major mediator of neuroinflammatory response within the brain parenchyma, which points to neuroinflammation as a major consequence of GCase dysfunction. In this present review article, we summarize the current knowledge on the role of GBA1 mutations in PD development and their phenotypic correlations. We also discuss the potential role of the GCase pathway in the search for PD biomarkers that may enable the development of disease modifying therapies. Answering these questions will aid clinicians in offering more appropriate counseling to the patients and their caregivers and provide future directions for PD preclinical research.

Relationship between the washout rate of I-123 MIBG scans and autonomic function in Parkinson's disease

Purpose

We have evaluated the clinical significance of the washout rate (WR) on I-123 MIBG scans through the analysis of the relationship between the I-123 MIBG scans and autonomic status in patients with Parkinson’s disease (PD).

Materials and methods

Sixty patients with clinical PD who had decreased HMR were enrolled. An autonomic symptom was evaluated using a head-up tilt test and the Composite Autonomic Severity Score (CASS). An I-123 MIBG scan and F-18 FP-CIT positron emission tomography (PET) were performed. All of the patients were classified into three groups according to the WR. The differences in patient characteristics and the imaging parameters among the three groups were evaluated, and a correlation analysis was also performed.

Results

The frequency of orthostatic hypotension was significantly different among the three groups. The difference in systolic pressure (dSysPr) and the difference in diastolic pressure (dDiaPr) of group 3 was significantly larger than those of groups 1 and 2. From the correlation analysis, it can be seen that age, Hoehn and Yahr (H&Y) stage, dSysPr, and dDiaPr had a weak positive correlation with the WR. The total CASS score was significantly higher in group 3 compared with groups 1 and 2. The WR had a moderate positive correlation with the cardiosympathetic score and the total CASS score.

Conclusion

The WR is related to autonomic dysfunction. An I-123 MIBG cardiac scan is considered to be a good method to evaluate not only the differential diagnosis of Parkinson's disease but also the degree of autonomic dysfunction.

Autophagic- and Lysosomal-Related Biomarkers for Parkinson's Disease: Lights and Shadows

Parkinson’s disease (PD) is a neurodegenerative disorder that currently affects 1% of the population over the age of 60 years, for which no disease-modifying treatments exist. This lack of effective treatments is related to the advanced stage of neurodegeneration existing at the time of diagnosis. Thus, the identification of early stage biomarkers is crucial. Biomarker discovery is often guided by the underlying molecular mechanisms leading to the pathology. One of the central pathways deregulated during PD, supported both by genetic and functional studies, is the autophagy-lysosomal pathway. Hence, this review presents different studies on the expression and activity of autophagic and lysosomal proteins, and their functional consequences, performed in peripheral human biospecimens. Although most biomarkers are inconsistent between studies, some of them, namely HSC70 levels in sporadic PD patients, and cathepsin D levels and glucocerebrosidase activity in PD patients carrying GBA mutations, seem to be consistent. Hence, evidence exists that the impairment of the autophagy-lysosomal pathway underlying PD pathophysiology can be detected in peripheral biosamples and further tested as potential biomarkers. However, longitudinal, stratified, and standardized analyses are needed to confirm their clinical validity and utility.

Parkinson's disease in the Western Pacific Region

1·8 billion people of diverse ethnicities and cultures live in the Western Pacific Region. The increasing longevity of populations in this region is a major contributor to the exponential increase in Parkinson's disease prevalence worldwide. Differences exist between Parkinson's disease in the Western Pacific Region and in Europe and North America that might provide important insights into our understanding of the disease and approaches to management. For example, some genetic factors (such as LRRK2 mutations or variants) differ, environmental exposures might play differential roles in modulating the risk of Parkinson's disease, and fewer dyskinesias are reported, with some differences in the profile of non-motor symptoms and comorbidities. Gaps in awareness of the disease and inequitable access to treatments pose challenges. Further improvements in infrastructure, clinical governance, and services, and concerted collaborative efforts in training and research, including greater representation of the Western Pacific Region in clinical trials, will improve care of patients with Parkinson's disease in this region and beyond.

GBA, Gaucher Disease, and Parkinson's Disease: From Genetic to Clinic to New Therapeutic Approaches

Parkinson’s disease (PD) is the second most common degenerative disorder. Although the disease was described more than 200 years ago, its pathogenetic mechanisms have not yet been fully described. In recent years, the discovery of the association between mutations of the GBA gene (encoding for the lysosomal enzyme glucocerebrosidase) and PD facilitated a better understating of this disorder. GBA mutations are the most common genetic risk factor of the disease. However, mutations of this gene can be found in different phenotypes, such as Gaucher’s disease (GD), PD, dementia with Lewy bodies (DLB) and rapid eye movements (REM) sleep behavior disorders (RBDs). Understanding the pathogenic role of this mutation and its different manifestations is crucial for geneticists and scientists to guide their research and to select proper cohorts of patients. Moreover, knowing the implications of the GBA mutation in the context of PD and the other associated phenotypes is also important for clinicians to properly counsel their patients and to implement their care. With the present review we aim to describe the genetic, clinical, and therapeutic features related to the mutation of the GBA gene.

[The genetic predictors of cognitive impairment in Parkinson's disease]

Parkinson's disease (PD) is a common neurodegenerative disorder that can be both sporadic and familial. A number of studies are devoted to the study of non-motor symptoms in PD today. Cognitive deficits, and especially dementia, are one of the most severe and disabling non-motor symptoms of PD. More than a quarter of patients in the early stages of PD have a moderate cognitive impairment, more than half of patients with PD develop dementia within 10 years from the date of diagnosis. Using genome-wide association studies (GWAS), a number of genes associated with cognitive impairment have been identified based on a comparison of genetic and clinical phenotypes. These genes can be divided into three groups: genes that lead to the development of PD and are inherited according to the laws of Mendel (SNCA), genes that are risk factors for PD development (GBA, MAPT) and genes associated with the development of cognitive impairment, but not with PD (COMT, APOE, BDNF). This review examines the effect of genetic variants in the above-mentioned genes on cognitive functions in patients with PD. The elucidation of the genetic basis of cognitive deficits in PD could help in choice of treatment tactics and in development of new therapeutic strategies.

Glucocerebrosidase mutations and synucleinopathies: Toward a model of precision medicine

Glucocerebrosidase is a lysosomal enzyme. The characterization of a direct link between mutations in the gene coding for glucocerebrosidase (GBA1) with the development of Parkinson's disease and dementia with Lewy bodies has heightened interest in this enzyme. Although the mechanisms through which glucocerebrosidase regulates the homeostasis of α-synuclein remains poorly understood, the identification of reduced glucocerebrosidase activity in the brains of patients with PD and dementia with Lewy bodies has paved the way for the development of novel therapeutic strategies directed at enhancing glucocerebrosidase activity and reducing α-synuclein burden, thereby slowing down or even preventing neuronal death. Here we reviewed the current literature relating to the mechanisms underlying the cross talk between glucocerebrosidase and α-synuclein, the GBA1 mutation-associated clinical phenotypes, and ongoing therapeutic approaches targeting glucocerebrosidase. © 2018 International Parkinson and Movement Disorder Society.

Clinical implementation of gene panel testing for lysosomal storage diseases

Background

The diagnostic workup in patients with a clinical suspicion of lysosomal storage diseases (LSD) is often difficult due to the variability in the clinical phenotype. The gold standard for diagnosis of LSDs consists of enzymatic testing. However, due to the sequential nature of this methodology and inconsistent genotype–phenotype correlations of certain LSDs, finding a diagnosis can be challenging.

Method

We developed and clinically implemented a gene panel covering 50 genes known to cause LSDs when mutated. Over a period of 18 months, we analyzed 150 patients who were referred for LSD testing and compared these results with the data of patients who were previously enrolled in a scheme of classical biochemical testing.

Results

Our panel was able to determine the molecular cause of the disease in 22 cases (15%), representing an increase in diagnostic yield compared to biochemical tests developed for 21 LSDs (4.6%). We were furthermore able to redirect the diagnosis of a mucolipidosis patient who was initially suspected to be affected with galactosialidosis. Several patients were identified as being affected with neuronal ceroid lipofuscinosis, which cannot readily be detected by enzyme testing. Finally, several carriers of pathogenic mutations in LSD genes related to the disease phenotype were identified as well, thus potentially increasing the diagnostic yield of the panel as heterozygous deletions cannot be detected.

Conclusion

We show that the implementation of a gene panel for LSD diagnostics results in an increased yield in comparison to classical biochemical testing. As the panel is able to cover a wider range of diseases, we propose to implement this methodology as a first‐tier test in cases of an aspecific LSD presentation, while enzymatic testing remains the first choice in patients with a more distinctive clinical presentation. Positive panel results should however still be enzymatically confirmed whenever possible.

A Meta-Analysis of GBA-Related Clinical Symptoms in Parkinson's Disease

Background

GBA gene had been proved to be a crucial gene to the risk of PD. Numerous studies had discussed about the unique clinical characteristics of PD patients with GBA carriers (GBA + PD). However, there was lack of updated comprehensive analysis on the topic. In order to clarify the association between GBA variants and the clinical phenotypes of PD, we conducted this comprehensive meta-analysis.

Method

Medline, Embase, and Cochrane were used to perform the searching. Strict selection criteria were followed in screening for new published articles or data. Revman 5.3 software was applied to perform the total statistical analysis, and funnel plots in the software were used to assess the publication biases.

Results

A total of 26 articles including 931 GBA + PD and 14861 GBA noncarriers of PD (GBA - PD) were involved in the final meta-analysis, and 14 of them were either newly added publications or related data newly analyzed compared with the version published in 2015. Then, a series of symptoms containing depression, orthostatic hypotension, motor fluctuation, wearing-off, and freezing were newly analyzed due to more articles eligible. Besides, clinical features like family history, AAO, UPDRS-III, H-Y, and dementia previously analyzed were updated with new data added. Significant statistical differences were found in wearing-off, family history, AAO, UPDRS-III, and dementia (OR: 1.14, 1.65; MD: -3.61, 2.17; OR: 2.44; p: 0.03, <0.00001, <0.00001, 0.003, and <0.00001). Depression was slightly associated with GBA + PD (OR: 1.47; p: 0.04). Clinical symptoms such as H-Y, orthostatic hypotension, motor fluctuation, and freezing did not feature GBA + PD.

Conclusion

Our results demonstrated that there were unique clinical features in GBA + PD which can help the management of the whole duration of PD patients.

GBA-Associated Parkinson's Disease and Other Synucleinopathies

PURPOSE OF REVIEW

GBA mutations are the most common known genetic cause of Parkinson's disease (PD). Its biological pathway may be important in idiopathic PD, since activity of the enzyme encoded by GBA, glucocerebrosidase, is reduced even among PD patients without GBA mutations. This article describes the structure and function of GBA, reviews recent literature on the clinical phenotype of GBA PD, and suggests future directions for research, counseling, and treatment.

RECENT FINDINGS

Several longitudinal studies have shown that GBA PD has faster motor and cognitive progression than idiopathic PD and that this effect is dose dependent. New evidence suggests that GBA mutations may be important in multiple system atrophy. Further, new interventional studies focusing on GBA PD are described. These studies may increase the interest of PD patients and caregivers in genetic counseling. GBA mutation status may help clinicians estimate PD progression, though mechanisms underlying GBA and synucleinopathy require further understanding.

Glucocerebrosidase Mutations in Parkinson Disease

Following the discovery of a higher than expected incidence of Parkinson Disease (PD) in Gaucher disease, a lysosomal storage disorder, mutations in the glucocerebrocidase (GBA) gene, which encodes a lysosomal enzyme involved in sphingolipid degradation were explored in the context of idiopathic PD. GBA mutations are now known to be the single largest risk factor for development of idiopathic PD. Clinically, on imaging and pharmacologically, GBA PD is almost identical to idiopathic PD, other than certain features that can be identified in the specialist research setting but not in routine clinical practice. In patients with a known GBA mutation, it is possible to monitor for prodromal signs of PD. The clinical similarity with idiopathic PD and the chance to identify PD at a pre-clinical stage provides a unique opportunity to research therapeutic options for early PD, before major irreversible neurodegeneration occurs. However, to date, the molecular mechanisms which lead to this increased PD risk in GBA mutation carriers are not fully elucidated. Experimental models to define the molecular mechanisms and test therapeutic options include cell culture, transgenic mice and other in vivo models amenable to genetic manipulation, such as drosophilia. Some key pathological pathways of interest in the context of GBA mutations include alpha synuclein aggregation, lysosomal-autophagy axis changes and endoplasmic reticulum stress. Therapeutic agents that exploit these pathways are being developed and include the small molecule chaperone Ambroxol. This review aims to summarise the main features of GBA-PD and provide insights into the pathological relevance of GBA mutations on molecular pathways and the therapeutic implications for PD resulting from investigation of the role of GBA in PD.

The Association between E326K of GBA and the Risk of Parkinson's Disease

It is reported that both the homozygous and heterozygous states of GBA mutations which are the causes of Gaucher disease (GD) are linked to the risk of PD. However, the GBA variant p.E326K (c.1093G > A, rs2230288), which does not result in GD in homozygous carriers, has triggered debate among experts studying Parkinson's disease (PD). In order to determine if the E326K variant of GBA is associated with the risk of PD, a standard meta-analysis was conducted by searching and screening publications, data extraction, and statistical analysis. Finally, a total of 15 publications, containing 5,908 PD patients and 5,605 controls, were included in this analysis. The pooled OR of the E326K genotype analysis was 1.99 (95% CI: 1.57–2.51). The minor allele frequencies of E326K for PD patients and controls were 1.67% and 1.03%, respectively. The pooled OR for the minor allele A was 1.99 (95% CI: 1.58–2.50). According to the subgroup analysis, we found that the significant differences between PD patients and controls for both genotype and allele of E326K also exist in Asians and Caucasians, respectively. In this study, we found that E326K of GBA is associated with the risk of PD in total populations, Asians, and Caucasians, respectively. Further studies are needed to clarify the role of GBA in the pathogenesis of PD.

Glucocerebrosidase mutations and neuropsychiatric phenotypes in Parkinson's disease and Lewy body dementias: Review and meta-analyses

Heterozygous mutations in glucocerebrosidase gene (GBA) are a major genetic risk factor for Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Recently, there has been a considerable focus on the relationship between GBA mutations and emergence of cognitive impairment and neuropsychiatric symptoms in these diseases. Here, we review the literature in this area, with a particular focus, including meta-analysis, on the key neuropsychiatric symptoms of cognitive impairment, psychosis, and depression in Parkinson's disease. Our meta-analysis demonstrated that GBA mutations are associated with a 2.4-fold increased risk of cognitive impairment. In addition, our novel meta-analyses of psychosis and depression showed a 1.8- and 2.2-fold increased risk respectively associated with GBA mutations, although due to possible bias and heterogeneity the depression findings should be interpreted with caution. While the precise mechanisms which increase susceptibility to neurodegeneration in GBA carriers are not known, evidence of greater cortical Lewy body pathology, reduced patterns of cortical activation, and hippocampal pathology in animal models are all consistent with a direct effect of GBA mutations on these symptoms. Extension of this work in DLB and individuals without neurodegeneration will be important in further characterizing how GBA mutations increase risk for PD and DLB and influence disease course.

Integrated Genetic Analysis of Racial Differences of Common GBA Variants in Parkinson's Disease: A Meta-Analysis

Background: Numerous studies have indicated that there is a possible relationship between GBA variants and Parkinson's disease (PD), however, most of them focused on a few variants such as L444P, N370S. We performed a comprehensive pooled analysis to clarify the relationship between variations of GBA and the risk of PD in different racial groups.

Methods: Standard meta-analysis was conducted, including generating inclusion and exclusion criteria, searching literature, extracting and analyzing data.

Results: Fifty studies containing 20,267 PD patients and 24,807 controls were included. We found that variants 84insGG, IVS2+1G>A, R120W, H255Q, E326K, T369M, N370S, D409H, L444P, R496H and RecNciI increased the risk of PD in total populations (OR: 1.78–10.49; p: <0.00001, 0.00005, 0.0008, 0.005, <0.00001, 0.004, <0.00001, 0.0003, <0.00001, <0.0001, 0.0001). In subgroup analysis by ethnicity, in AJ populations, variants 84insGG, R496H, N370S increased the risk of PD (OR: 9.26–3.51; p: <0.00001, <0.0001, <0.00001). In total non-AJ populations, variants L444P, R120W, IVS2+1G>A, H255Q, N370S, D409H, RecNciI, E326K, T369M increased the risk of PD (OR: 8.66–1.89; p: <0.00001, 0.0008, 0.02, 0.005, <0.00001, 0.001, 0.0001, <0.00001, 0.002). Among the non-AJ populations, pooled analysis from five different groups were done separately. Variants L444P, N370S, H255Q, D409H, RecNciI, E326K increased risk of PD (OR: 6.52–1.84; p: <0.00001, <0.00001, 0.005, 0.005, 0.04, <0.00001) in European/West Asians while R120W and RecNciI in East Asians (OR: 14.93, 3.56; p: 0.001, 0.003). L444P increased the risk of PD in Hispanics, East Asians and Mixed populations (OR: 15.44, 12.43, 7.33; p: 0.00004, <0.00001, 0.009). Lacking of enough original studies, we failed to conduct quantitative analysis in Africa.

Conclusions: Obvious racial differences were found for GBA variants in PD. 84insGG and R496H exclusively increased PD risks in AJ populations, so did L444P, R120W, IVS2+1G>A, H255Q, D409H, RecNciI, E326K, T369M in non-AJ populations. N370S increased the risk of PD in both ethnics. In non-AJ subgroup populations, N370S, H255Q, D409H, E326K exclusively increased PD risks in European/West Asians, as were R120W in East Asians. L444P increased the risk of PD in all groups in non-AJ ethnicity. These results will contribute to the future genetic screening of GBA gene in PD.

Glucocerebrosidase and Parkinson Disease: Molecular, Clinical, and Therapeutic Implications

Parkinson disease (PD) is a complex neurodegenerative disease characterised by multiple motor and non-motor symptoms. In the last 20 years, more than 20 genes have been identified as causes of parkinsonism. Following the observation of higher risk of PD in patients affected by Gaucher disease, a lysosomal disorder caused by mutations in the glucocerebrosidase (GBA) gene, it was discovered that mutations in this gene constitute the single largest risk factor for development of idiopathic PD. Patients with PD and GBA mutations are clinically indistinguishable from patients with idiopathic PD, although some characteristics emerge depending on the specific mutation, such as slightly earlier onset. The molecular mechanisms which lead to this increased PD risk in GBA mutation carriers are multiple and not yet fully elucidated, they include alpha-synuclein aggregation, lysosomal-autophagy dysfunction and endoplasmic reticulum stress. Moreover, dysfunction of glucocerebrosidase has also been demonstrated in non-GBA PD, suggesting its interaction with other pathogenic mechanisms. Therefore, GBA enzyme function represents an interesting pharmacological target for PD. Cell and animal models suggest that increasing GBA enzyme activity can reduce alpha-synuclein levels. Clinical trials of ambroxol, a glucocerebrosidase chaperone, are currently ongoing in PD and PD dementia, as is a trial of substrate reduction therapy. The aim of this review is to summarise the main features of GBA-PD and discuss the implications of glucocerebrosidase modulation on PD pathogenesis.

Lysosomal defects in ATP13A2 and GBA associated familial Parkinson's disease

Genes encoding lysosomal proteins, such as ATP13A2 and GBA, are associated with familial Parkinson's disease (PD). Heterozygous mutations in GBA are strongly associated with familial PD. ATP13A2, which encodes a lysosomal P-type ATPase, has been identified as the causative gene for Kufor-Rakeb syndrome. While lysosomal dysfunction due to these mutations exhibited early onset Parkinsonism, each animal model demonstrated different pathological mechanisms. Clinicogenetic and animal model studies recently identified several lysosomal alterations that play a role in the pathogenesis of PD.

The psychosis spectrum in Parkinson disease

In 2007, the clinical and research profile of illusions, hallucinations, delusions and related symptoms in Parkinson disease (PD) was raised with the publication of a consensus definition of PD psychosis. Symptoms that were previously deemed benign and clinically insignificant were incorporated into a continuum of severity, leading to the rapid expansion of literature focusing on clinical aspects, mechanisms and treatment. Here, we review this literature and the evolving view of PD psychosis. Key topics include the prospective risk of dementia in individuals with PD psychosis, and the causal and modifying effects of PD medication. We discuss recent developments, including recognition of an increase in the prevalence of psychosis with disease duration, addition of new visual symptoms to the psychosis continuum, and identification of frontal executive, visual perceptual and memory dysfunction at different disease stages. In addition, we highlight novel risk factors - for example, autonomic dysfunction - that have emerged from prospective studies, structural MRI evidence of frontal, parietal, occipital and hippocampal involvement, and approval of pimavanserin for the treatment of PD psychosis. The accumulating evidence raises novel questions and directions for future research to explore the clinical management and biomarker potential of PD psychosis.

Nine-year experience in Gaucher disease diagnosis at the Spanish reference center Fundación Jiménez Díaz

BACKGROUND

Fundación Jiménez Díaz (FJD) is a reference center for genetic diagnosis of Gaucher disease (GD) in Spain. Genetic analyses of acid β-glucosidase (GBA) gene using different techniques were performed to search for new mutations, in addition to those previously and most frequently found in the Spanish population. Additionally, the study of the chitotriosidase (CHIT1) gene was used to assess the inflammatory status of patients in the follow-up of enzyme replacement therapy (ERT). We present the genetic data gathered during the last nine years at FJD.

METHODS

Blood samples from patients with suspected GD were collected for enzymatic and genetic analyses. The genetic analysis was performed on DNA from 124 unrelated suspected cases and 57 relatives from 2007 to 2015, starting with a mutational screening kit, followed by Sanger sequencing of the entire gene and other techniques to look for deletions. CHIT1 was also studied to assess the reliability of this biomarker.

RESULTS

In 46 out of 93 GD patients (49.5%) the two mutant alleles were found. We detected 21 different mutations. The most common mutation was N370S (c.126A > G; p.Asp409Ser current nomenclature) (in 50.5% of patients), followed by L444P (c.1448T > C; p.Leu483Pro current nomenclature) (in 24.7%). The most common heterozygous compound genotype observed (18.3%) was c.1226A > G/c.1448T > C (N370S/L444P). Two novel mutations were found (del. Ex.4-11 and c.1296G > T; pW432C), as well as p.S146L, only once previously reported. Two patients showed the homozygous state for the duplication of CHIT1.

CONCLUSION

N370S and L444P are the most common mutations and other mutations associated to Parkinson's disease have been observed. This should be taken into account in the genetic counseling of GD patients.

(123)I-meta-iodobenzylguanidine (MIBG) cardiac scintigraphy in α-synucleinopathies

Cardiac meta-iodobenzylguanidine (MIBG) uptake on (123)I-MIBG cardiac scintigraphy is reduced in patients with Lewy body disease such as Parkinson's disease (PD), dementia with Lewy bodies (DLB), and pure autonomic failure, and has been reported to be useful for differentiating PD from other parkinsonian syndromes, as well as DLB from Alzheimer disease (AD). Postmortem studies have shown that the number of tyrosine hydroxylase (TH)-immunoreactive nerve fibers of the heart was decreased in pathologically-confirmed Lewy body disease, supporting the findings of reduced cardiac MIBG uptake in Lewy body diseases. Now, reduced cardiac MIBG uptake can be a potential biomarker for the presence of Lewy bodies in the nervous system. (123)I-MIBG cardiac scintigraphy can allow us to determine the presence of Lewy bodies.

Glucocerebrosidase modulates cognitive and motor activities in murine models of Parkinson's disease

Mutations in GBA1, the gene encoding glucocerebrosidase, are associated with an enhanced risk of developing synucleinopathies such as Parkinson’s disease (PD) and dementia with Lewy bodies. A higher prevalence and increased severity of motor and non-motor symptoms is observed in PD patients harboring mutant GBA1 alleles, suggesting a link between the gene or gene product and disease development. Interestingly, PD patients without mutations in GBA1 also exhibit lower levels of glucocerebrosidase activity in the central nervous system (CNS), implicating this lysosomal enzyme in disease pathogenesis. Here, we investigated whether modulation of glucocerebrosidase activity in murine models of synucleinopathy (expressing wild type Gba1) affected α-synuclein accumulation and behavioral phenotypes. Partial inhibition of glucocerebrosidase activity in PrP-A53T-SNCA mice using the covalent inhibitor conduritol-B-epoxide induced a profound increase in soluble α-synuclein in the CNS and exacerbated cognitive and motor deficits. Conversely, augmenting glucocerebrosidase activity in the Thy1-SNCA mouse model of PD delayed the progression of synucleinopathy. Adeno-associated virus-mediated expression of glucocerebrosidase in the Thy1-SNCA mouse striatum led to decrease in the levels of the proteinase K-resistant fraction of α-synuclein, amelioration of behavioral aberrations and protection from loss of striatal dopaminergic markers. These data indicate that increasing glucocerebrosidase activity can influence α-synuclein homeostasis, thereby reducing the progression of synucleinopathies. This study provides robust in vivo evidence that augmentation of CNS glucocerebrosidase activity is a potential therapeutic strategy for PD, regardless of the mutation status of GBA1.

Glucocerebrosidase and parkinsonism: lessons to learn

Both homo- (causing autosomal-recessive Gaucher's disease; GD) and heterozygous mutations in the glucocerebrosidase gene (GBA) are associated with Parkinson's disease (PD), and represent the most robust known genetic susceptibility factors identified in PD. Since the accumulation of α-synuclein has been considered critical to the pathogenesis of PD among several possible pathways through which glucocerebrosidase (GCase) deficiency may promote the pathogenesis of PD, particular attention was given to the reciprocity with α-synuclein levels, lysosomal dysfunction, endoplasmatic reticulum-Golgi trafficking of GCase, dysregulation of calcium homeostasis and mitochondrial abnormalities. The proportion of PD patients that carry GBA mutations is estimated to be approximately between 5 and 10 %. Individual PD patients with or without GBA mutations cannot be discriminated on clinical or pathological grounds. However, GBA mutation carriers may have slightly earlier age at PD onset, more likely have a positive family history for PD, and more prevalent non-motor symptoms when compared to those patients who are not carriers. Establishing the concept of GBA-related PD promoted a search for the pathogenic mechanisms through which GCase deficiency may influence pathogenesis of PD, suggesting that targeting the GCase-lysosomal pathway might be a rational approach for the development of neuroprotective drugs in PD.

Advances in GBA-associated Parkinson's disease--Pathology, presentation and therapies

GBA mutations are to date the most common genetic risk factor for Parkinson's disease. The GBA gene encodes the lysomal hydrolase glucocerebrosidase. Whilst bi-allelic GBA mutations cause Gaucher disease, both mono- and bi-allelic mutations confer risk for Parkinson's disease. Clinically, Parkinson's disease patients with GBA mutations resemble idiopathic Parkinson's disease patients. However, these patients have a modest reduction in age-of-onset of disease and a greater incidence of cognitive decline. In some cases, GBA mutations are also responsible for familial Parkinson's disease. The accumulation of α-synuclein into Lewy bodies is the central neuropathological hallmark of Parkinson's disease. Pathologic GBA mutations reduce enzymatic function. A reduction in glucocerebrosidase function increases α-synuclein levels and propagation, which in turn inhibits glucocerebrosidase in a feed-forward cascade. This cascade is central to the neuropathology of GBA-associated Parkinson's disease. The lysosomal integral membrane protein type-2 is necessary for normal glucocerebrosidase function. Glucocerebrosidase dysfunction also increases in the accumulation of β-amyloid and amyloid-precursor protein, oxidative stress, neuronal susceptibility to metal ions, microglial and immune activation. These factors contribute to neuronal death. The Mendelian Parkinson's disease genes, Parkin and ATP13A2, intersect with glucocerebrosidase. These factors sketch a complex circuit of GBA-associated neuropathology. To clinically interfere with this circuit, central glucocerebrosidase function must be improved. Strategies based on reducing breakdown of mutant glucocerebrosidase and increasing the fraction that reaches the lysosome has shown promise. Breakdown can be reduced by interfering with the ability of heat-shock proteins to recognize mutant glucocerebrosidase. This underlies the therapeutic efficacy of certain pharmacological chaperones and histone deacetylase inhibitors. These therapies are promising for Parkinson's disease, regardless of mutation status. Recently, there has been a boom in studies investigating the role of glucocerebrosidase in the pathology of Parkinson's disease. This merits a comprehensive review of the current cell biological processes and pathological pictures involving Parkinson's disease associated with GBA mutations.

The Neuropsychiatric and Motor Profile of GBA-Associated Parkinson's Disease: A Review

Background

Cognitive and motor decline, along with psychiatric symptoms, have a major impact on independence, nursing home admission, caregiver burden, and mortality in Parkinson's disease (PD). The single most common genetic risk factor for developing PD is a mutation in the glucocerebrosidase (GBA) gene.

Methods

This work is a literature review regarding "GBA" and "Parkinson's disease" as conducted by PubMed search.

Results

There is a higher prevalence of cognitive decline and more rapid trajectory of disease progression in PD-GBA carriers, compared to noncarriers. PD-GBA carriers also have domain-specific cognitive impairment, particularly in visual memory tasks. PD-GBA carriers may also have a more aggressive motor phenotype than noncarriers.

Conclusions

Early identification of PD-GBA carriers may lead to targeted therapies and development of new treatments.

Impact of glucocerebrosidase mutations on motor and nonmotor complications in Parkinson's disease

Homozygous mutations of the glucocerebrosidase gene (GBA) cause Gaucher disease (GD), and heterozygous mutations of GBA are a major risk factor for Parkinson's disease (PD). This study examined the impact of GBA mutations on the longitudinal clinical course of PD patients by retrospective cohort design. GBA-coding regions were fully sequenced in 215 PD patients and GD-associated GBA mutations were identified in 19 (8.8%) PD patients. In a retrospective cohort study, time to develop dementia, psychosis, wearing-off, and dyskinesia were examined. Survival time analysis followed a maximum 12-year observation (median 6.0 years), revealing that PD patients with GD-associated mutations developed dementia and psychosis significantly earlier than those without mutations (p < 0.001 and p = 0.017, respectively). Adjusted hazard ratios of GBA mutations were 8.3 for dementia (p < 0.001) and 3.1 for psychosis (p = 0.002). No statistically significant differences were observed for wearing-off and dyskinesia between the groups. N-isopropyl-p[(123)I] iodoamphetamine single-photon emission tomography pixel-by-pixel analysis revealed that regional cerebral blood flow was reduced in the bilateral parietal cortex, including the precuneus of GD-associated mutant PD patients, compared with matched PD controls without mutations.

Effect of GBA Mutations on Phenotype of Parkinson's Disease: A Study on Chinese Population and a Meta-Analysis

GBA has been identified as a genetic risk factor for PD. Whether the clinical manifestations of PD patients with or without GBA mutations are different has still not reached a consensus. We firstly detected the GBA mutation L444P in 1147 Chinese PD patients and simultaneously evaluated their corresponding clinical data. Then we compared the phenotypes between 646 PD patients with GBA mutations and 10344 PD patients without GBA mutations worldwide through meta-analysis. Through the method of meta-analysis, there was significant difference in age at onset (MD = -3.10 [95% CI: -4.88, -1.32]), bradykinesia as an initial symptom (OR = 1.49 [95% CI: 1.15, 1.94]), having family history (OR = 1.50 [95% CI: 1.18, 1.91]), and dementia (OR = 3.21 [95% CI: 1.97, 5.24]) during the comparison between PD patients with and without GBA mutations. While, in the aspect of tremor as an initial symptom (OR = 0.81 [95% CI: 0.64, 1.03]), the severity of motor symptoms such as H-Y (MD = 0.06 [95% CI: -0.06, 0.17]) and UPDRS-III (MD = 1.61 [95% CI: -0.65, 3.87]) and having dyskinesia (OR = 1.60 [95% CI: 0.90, 2.84]) during the comparison between the two groups revealed no statistical differences. Our results suggested that the phenotypes of PD patients with GBA mutations are different from GBA noncarriers.

Pathogenic mechanisms of neurodegeneration in Parkinson disease

The last 2 decades represent a period of unparalleled advancement in the understanding of the pathogenesis of Parkinson disease (PD). The discovery of several forms of familial parkinsonism with mendelian inheritance has elucidated insights into the mechanisms underlying the degeneration of dopaminergic neurons of the substantia nigra that histologically characterize PD. α-Synuclein, the principal component of Lewy bodies, remains the presumed pathogen at the heart of the current model; however, concurrently, a diverse range of other mechanisms have been implicated. The creation of a coherent disease model will be crucial to the development of effective disease modifying therapies for sporadic PD.