Glucocerebrosidase mutations and Parkinson disease

Challenges in Gaucher disease: Perspectives from an expert panel

This focused review concentrates on eight topics of high importance for Gaucher disease (GD) clinicians and researchers: 1) The consideration of GD as distinct types rather than a spectrum. A review of the literature clearly supports the view that there are distinct types of GD. Type 1 is characterized by the absence of primary neuronopathic involvement, while types 2 and 3 are characterized by progressive primary neuronopathic disease. 2) Neurologic and neuronopathic manifestations. A growing body of evidence indicates that the peripheral nervous system may be involved in GD type 1 and that there may also be signs and symptoms of central nervous system (CNS) disease in this group. However, GD type 1 is characterized by the absence of primary neuronopathic disease, whereas GD types 2 and 3 are characterized by progressive, albeit variable, primary neuronopathic disease. Abnormalities in saccadic eye movements have been suggested as being diagnostic for neuronopathic GD, but they may also occur in GD type 1 and in other inflammatory diseases. 3) The importance of whole GBA1 sequencing. This approach is superior to exome sequencing because of potential effects of deep intronic variants on gene expression. It also has the capacity to detect variant alleles that might be missed with gene panels. 4) Monoclonal gammopathy of undetermined significance (MGUS). The risks of MGUS, multiple myeloma, and non-Hodgkin's lymphoma are elevated in patients with GD compared to the general population and strong evidence indicates that lyso-Gb1 stimulates the formation of monoclonal immunoglobulins (M-protein) in patients with GD and MGUS. 5) Pulmonary involvement in GD. Pulmonary complications can be identified through spirometry in up to 45 % of patients with GD type 1 and 55 % of those with GD type 3. Limited evidence exists that enzyme replacement therapy (ERT) reduces the severity of these complications in patients with GD type 1. 6) Gaucheromas. These may occur in patients with GD types 1 or 3, but there is little detailed information about their inception, mechanisms underlying growth, cellular organization, and biochemical activities, and no definitive guidance for their management. Gaucheromas behave like benign (i.e. non-metastasizing) neoplasms, and it may be reasonable to classify them as such. 7) Bone and joint involvement. Dual-energy X-ray absorptiometry scans alone are insufficient for monitoring all changes in bone that may occur in patients with GD. Quantitative magnetic resonance imaging (MRI) techniques using Dixon quantitative chemical shift imaging have provided results that correlate with GD severity scores, bone complications, and biomarkers for GD bone involvement. Thoracic kyphosis is a common complication of GD types 1 and 3, and there is very limited information regarding the effects of ERT or substrate synthesis inhibition therapy (SSIT) on this condition. 8) Treatment initiation, selection, combination, and switching. Prompt initiation of treatment in pediatric patients is important as GD can lead to impaired growth, lower peak bone mass, and delayed puberty. These adverse outcomes can often be ameliorated or prevented with timely treatment. Either ERT or eliglustat, a SSIT agent, is suitable as first-line treatment of adults with GD. Studies of switching from ERT to eliglustat, or between different ERT products, have indicated that changing treatment is safe, although efficacy outcomes vary. A critical remaining issue is the lack of treatments capable of reaching the CNS to slow or halt the progression of neuronopathic disease in patients with GD type 2 or 3 and potentially reduce the risk of Parkinson's disease in GD type 1 patients and heterozygotes for GBA1 variants.

Electric-field induced sleep promotion and lifespan extension in Gaucher's disease model flies

Gaucher's disease (GD) is a genetic disease characterized by a mutation in the metabolic enzyme glucocerebrosidase (GBA1), leading to the accumulation of glucosylceramide in tissues. We previously discovered that a minos-inserted mutation in the GBA1 gene of fruit flies, Drosophila melanogaster, mimics human neuronopathic GD (nGD) characteristics, providing a promising model for studying the molecular mechanisms of the disease. We also reported that extremely low-frequency electric fields (ELF-EFs) promote sleep and extend the lifespan of wild-type flies. In this study, we show that ELF-EFs have health-promoting effects on nGD model flies. Firstly, the total sleep time and sleep episode duration of EF-exposed nGD model flies increased. EFs also extended the lifespans of nGD model flies. Additionally, the expression of the endoplasmic reticulum stress-related gene PERK and autophagy-related gene p62 were elevated after EF exposure. The effects of EF exposure on nGD flies are associated with the change of these genes expression. Our findings suggest that EF exposure may be effective as an additional therapy for nGD.

The RAB32 p.Ser71Arg Variant in Parkinsonisms: Insights from a Large Italian Cohort

BACKGROUND AND OBJECTIVE

Recently, RAB32 has been identified as possibly linked to Parkinson's disease. We studied the prevalence and clinical correlates of the p.Ser71Arg variant in the RAB32 gene in a large case series of Italian patients with Parkinson's disease or atypical parkinsonism.

METHODS

A single-center cohort with a case-control component (consecutively collected at the Parkinson Institute of Milan between 2002 and 2023) was screened for the RAB32 p.Ser71Arg variant. Detailed clinical characteristics of carriers were reviewed. Healthy control subjects were partners or unrelated caregivers. The variant was detected by a TaqMan polymerase chain reaction assay.

RESULTS

A total of 4600 patients (3762 with PD and 838 with atypical parkinsonisms) and 1722 healthy control subjects were consecutively included in the study. We identified 20 new variant carriers that, together with the 8 previously identified, had younger age at onset than noncarriers (51.0 ± 10.7 vs. 58.3 ± 11.0 years, respectively; P = 0.01). All carriers had a good response to dopaminergic therapy and device-aided therapies. Carriers had mild or no cognitive decline and mild or no depressive symptoms; six had impulse control disorders and one a REM behavior disorder. Family history was positive in 55.5% of cases versus 22.0% of patients without the variant (P < 0.001) and was compatible with a dominant pattern of inheritance. The variant was not identified in patients with atypical parkinsonisms.

CONCLUSIONS

This study confirms that RAB32 is associated with a relatively young adult-onset PD with a favorable therapeutic response. This variant should be included in genetic panels used for the diagnosis of familial and/or relatively young-onset PD. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Early-onset Parkinson's disease in a patient with a rare homozygous pathogenic GBA1 variant and no Gaucher disease symptoms

Parkinson's disease (PD) is a multifaceted neurodegenerative disorder with both non-motor and motor symptoms. Variants in the glucosylceramidase beta 1 (GBA1) gene are the strongest genetic risk factor for PD, while homozygous or compound heterozygous variants in this gene classically cause Gaucher disease (GD). This study presents an early-onset PD patient with a homozygous GBA1 deletion. Whole-exome sequencing (WES) was performed, and the identified variant was validated via Sanger sequencing. The variant was classified according to ACMG guidelines and ClinGen updates. The patient, a Brazilian female of mixed ethnicity, exhibited the full spectrum of classical motor and non-motor PD symptoms without evident hallmarks of GD. The identified homozygous GBA1 variant (NM_000157.4:c.222_224del; p.T75del; rs761621516) has a very low global allele frequency (0.00003284) and is associated with reduced enzymatic activity. This variant exhibits a founder effect among individuals of African descent. This case highlights an intricate genotype-phenotype landscape for GBA1 variants, underscoring the role of homozygous GBA1 variants in PD pathogenesis.

Multivalent GCase Enhancers: Synthesis and Evaluation of Glyco-Gold Nanoparticles Decorated with Trihydroxypiperidine Iminosugars

The present study reports the preparation of the first multivalent iminosugars built onto a glyco-gold nanoparticle core (glyco-AuNPs) capable of stabilizing or enhancing the activity of the lysosomal enzyme GCase, which is defective in Gaucher disease. An N-nonyltrihydroxypiperidine was selected as the bioactive iminosugar unit and further functionalized, via copper-catalyzed alkyne-azide cycloaddition, with a thiol-ending linker that allowed the conjugation to the gold core. These bioactive ligands were obtained with either a linear monomeric or dendritic trimeric arrangement of the iminosugar. The concentration of the bioactive iminosugar on the gold surface was modulated with different amounts of a glucoside bearing a short thiol-ending spacer as the inner ligand. The new mixed-ligand coated glyco-AuNPs were fully characterized, and those with the highest colloidal stability in aqueous medium were subjected to biological evaluation. Glyco-AuNPs with trimeric iminosugar bioactive units showed the ability to stabilize recombinant GCase in a thermal denaturation assay, while Glyco-AuNPs with monomeric iminosugar bioactive units were able to enhance the activity of mutant GCase in Gaucher patient's fibroblasts by 1.9-fold at 2.2 μM.

Mitochondrial oxidant stress promotes α-synuclein aggregation and spreading in mice with mutated glucocerebrosidase

In this study, heterozygous expression of a common Parkinson-associated GBA1 variant, the L444P mutation, was found to exacerbate α-synuclein aggregation and spreading in a mouse model of Parkinson-like pathology targeting neurons of the medullary vagal system. These neurons were also shown to become more vulnerable to oxidative and nitrative stress after L444P expression. The latter paralleled neuronal formation of reactive oxygen species and led to a pronounced accumulation of nitrated α-synuclein. A causal relationship linked mutation-induced oxidative/nitrative stress to enhanced α-synuclein aggregation and spreading that could indeed be rescued by neuronal overexpression of mitochondrial superoxide dismutase 2. Further evidence supported a key involvement of mitochondria as sources of reactive oxygen species as well as targets of oxidative and nitrative damage within L444P-expressing neurons. These findings support the conclusion that enhanced vulnerability to mitochondrial oxidative stress should be considered an important mechanism predisposing to pathology conversion in carriers of GBA1 mutations.

Comprehensive Analysis and Experimental Validation of the Parkinson's Disease Lysosomal Gene ACP2 and Pan-cancer

The pivotal role of lysosomal function in preserving neuronal homeostasis is recognized, with its dysfunction being implicated in neurodegenerative processes, notably in Parkinson's disease (PD). Yet, the molecular underpinnings of lysosome-related genes (LRGs) in the context of PD remain partially elucidated. We collected RNA-seq data from the brain substantia nigra of 30 PD patients and 20 normal subjects from the GEO database. We obtained molecular classification clusters from the screened lysosomal expression patterns. The lysosome-related diagnostic model of Parkinson's disease was constructed by XGBoost and Random Forest. And we validated the expression patterns of signature LRGs in the diagnostic model by constructing a PD rat model. Finally, the linkage between PD and cancer through signature genes was explored. The expression patterns of the 33 LRGs screened can be divided into two groups of PD samples, enabling exploration of the variance in biological processes and immune elements. Cluster A had a higher disease severity. Subsequently, critical genes were sieved through the application of machine learning methodologies culminating in the identification of two intersecting feature genes (ACP2 and LRP2). A PD risk prediction model was constructed grounded on these signature genes. The model's validity was assessed through nomogram evaluation, which demonstrated robust confidence validity. Then we analyzed the correlation analysis, immune in-filtration, biological function, and rat expression validation of the two genes with common pathogenic genes in Parkinson's disease, indicating that these two genes play an important role in the pathogenesis of PD. We then selected ACP2, which had a significant immune infiltration correlation, as the entry gene for the pan-cancer analysis. The pan-cancer analysis revealed that ACP2 has profound associations with prognostic indicators, immune infiltration, and tumor-related regulatory processes across various neoplasms, suggesting its potential as a therapeutic target in a range of human diseases, including PD and cancers. Our study comprehensively analyzed the molecular grouping of LRGs expression patterns in Parkinson's disease, and the disease progression was more severe in cluster A. And the PD diagnosis model related to LRGs is constructed. Finally, ACP2 is a potential target for the relationship between Parkinson's disease and tumor.

Clinical, mechanistic, biomarker, and therapeutic advances in GBA1-associated Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease. The development of PD is closely linked to genetic and environmental factors, with GBA1 variants being the most common genetic risk. Mutations in the GBA1 gene lead to reduced activity of the coded enzyme, glucocerebrosidase, which mediates the development of PD by affecting lipid metabolism (especially sphingolipids), lysosomal autophagy, endoplasmic reticulum, as well as mitochondrial and other cellular functions. Clinically, PD with GBA1 mutations (GBA1-PD) is characterized by particular features regarding the progression of symptom severity. On the therapeutic side, the discovery of the relationship between GBA1 variants and PD offers an opportunity for targeted therapeutic interventions. In this review, we explore the genotypic and phenotypic correlations, etiologic mechanisms, biomarkers, and therapeutic approaches of GBA1-PD and summarize the current state of research and its challenges.

The Molecular Impact of Glucosylceramidase Beta 1 (Gba1) in Parkinson's Disease: a New Genetic State of the Art

Parkinson's disease (PD) is a neurodegenerative disorder affecting 2-3% of those aged over 65, characterized by motor symptoms like slow movement, tremors, and muscle rigidity, along with non-motor symptoms such as anxiety and dementia. Lewy bodies, clumps of misfolded proteins, contribute to neuron loss in PD. Mutations in the GBA1 gene are considered the primary genetic risk factor of PD. GBA1 mutations result in decreased activity of the lysosomal enzyme glucocerebrosidase (GCase) resulting in α-synuclein accumulation. We know that α-synuclein aggregation, lysosomal dysfunction, and endoplasmic reticulum disturbance are recognized factors to PD susceptibility; however, the molecular mechanisms connecting GBA1 gene mutations to increased PD risk remain partly unknown. Thus, in this narrative review conducted according to a systematic review method, we aimed to present the main contributions arising from the molecular impact of the GBA1 gene to the pathogenesis of PD providing new insights into potential impacts for advances in the clinical care of people with PD, a neurological disorder that has contributed to the substantial increase in the global burden of disease accentuated by the aging population. In summary, this narrative review highlights the multifaceted impact of GBA1 mutations in PD, exploring their role in clinical manifestations, genetic predispositions, and molecular mechanisms. The review emphasizes the importance of GBA1 mutations in both motor and non-motor symptoms of PD, suggesting broader therapeutic and management strategies. It also discusses the potential of CRISPR/Cas9 technology in advancing PD treatment and the need for future research to integrate these diverse aspects for improved diagnostics and therapies.

The GBA1 K198E Variant Is Associated with Suppression of Glucocerebrosidase Activity, Autophagy Impairment, Oxidative Stress, Mitochondrial Damage, and Apoptosis in Skin Fibroblasts

Parkinson's disease (PD) is a multifactorial, chronic, and progressive neurodegenerative disorder inducing movement alterations as a result of the loss of dopaminergic (DAergic) neurons of the pars compacta in the substantia nigra and protein aggregates of alpha synuclein (α-Syn). Although its etiopathology agent has not yet been clearly established, environmental and genetic factors have been suggested as the major contributors to the disease. Mutations in the glucosidase beta acid 1 (GBA1) gene, which encodes the lysosomal glucosylceramidase (GCase) enzyme, are one of the major genetic risks for PD. We found that the GBA1 K198E fibroblasts but not WT fibroblasts showed reduced catalytic activity of heterozygous mutant GCase by -70% but its expression levels increased by 3.68-fold; increased the acidification of autophagy vacuoles (e.g., autophagosomes, lysosomes, and autolysosomes) by +1600%; augmented the expression of autophagosome protein Beclin-1 (+133%) and LC3-II (+750%), and lysosomal-autophagosome fusion protein LAMP-2 (+107%); increased the accumulation of lysosomes (+400%); decreased the mitochondrial membrane potential (∆Ψm) by -19% but the expression of Parkin protein remained unperturbed; increased the oxidized DJ-1Cys106-SOH by +900%, as evidence of oxidative stress; increased phosphorylated LRRK2 at Ser935 (+1050%) along with phosphorylated α-synuclein (α-Syn) at pathological residue Ser129 (+1200%); increased the executer apoptotic protein caspase 3 (cleaved caspase 3) by +733%. Although exposure of WT fibroblasts to environmental neutoxin rotenone (ROT, 1 μM) exacerbated the autophagy-lysosomal system, oxidative stress, and apoptosis markers, ROT moderately increased those markers in GBA1 K198E fibroblasts. We concluded that the K198E mutation endogenously primes skin fibroblasts toward autophagy dysfunction, OS, and apoptosis. Our findings suggest that the GBA1 K198E fibroblasts are biochemically and molecularly equivalent to the response of WT GBA1 fibroblasts exposed to ROT.

Iron Dyshomeostasis in Neurodegeneration with Brain Iron Accumulation (NBIA): Is It the Cause or the Effect?

Iron is an essential metal ion implicated in several cellular processes. However, the reactive nature of iron renders this metal ion potentially dangerous for cells, and its levels need to be tightly controlled. Alterations in the intracellular concentration of iron are associated with different neuropathological conditions, including neurodegeneration with brain iron accumulation (NBIA). As the name suggests, NBIA encompasses a class of rare and still poorly investigated neurodegenerative disorders characterized by an abnormal accumulation of iron in the brain. NBIA is mostly a genetic pathology, and to date, 10 genes have been linked to familial forms of NBIA. In the present review, after the description of the principal mechanisms implicated in iron homeostasis, we summarize the research data concerning the pathological mechanisms underlying the genetic forms of NBIA and discuss the potential involvement of iron in such processes. The picture that emerges is that, while iron overload can contribute to the pathogenesis of NBIA, it does not seem to be the causal factor in most forms of the pathology. The onset of these pathologies is rather caused by a combination of processes involving the interplay between lipid metabolism, mitochondrial functions, and autophagic activity, eventually leading to iron dyshomeostasis.

The lysosomal β-glucocerebrosidase strikes mitochondria: implications for Parkinson's therapeutics

Parkinson's disease is a neurodegenerative disorder primarily known for typical motor features that arise due to the loss of dopaminergic neurons in the substantia nigra. However, the precise molecular aetiology of the disease is still unclear. Several cellular pathways have been linked to Parkinson's disease, including the autophagy-lysosome pathway, α-synuclein aggregation and mitochondrial function. Interestingly, the mechanistic link between GBA1, the gene that encodes for lysosomal β-glucocerebrosidase (GCase), and Parkinson's disease lies in the interplay between GCase functions in the lysosome and mitochondria. GCase mutations alter mitochondria-lysosome contact sites. In the lysosome, reduced GCase activity leads to glycosphingolipid build-up, disrupting lysosomal function and autophagy, thereby triggering α-synuclein accumulation. Additionally, α-synuclein aggregates reduce GCase activity, creating a self-perpetuating cycle of lysosomal dysfunction and α-synuclein accumulation. GCase can also be imported into the mitochondria, where it promotes the integrity and function of mitochondrial complex I. Thus, GCase mutations that impair its normal function increase oxidative stress in mitochondria, the compartment where dopamine is oxidized. In turn, the accumulation of oxidized dopamine adducts further impairs GCase activity, creating a second cycle of GCase dysfunction. The oxidative state triggered by GCase dysfunction can also induce mitochondrial DNA damage which, in turn, can cause dopaminergic cell death. In this review, we highlight the pivotal role of GCase in Parkinson's disease pathogenesis and discuss promising examples of GCase-based therapeutics, such as gene and enzyme replacement therapies, small molecule chaperones and substrate reduction therapies, among others, as potential therapeutic interventions.

Activation and Purification of ß-Glucocerebrosidase by Exploiting its Transporter LIMP-2 - Implications for Novel Treatment Strategies in Gaucher's and Parkinson's Disease

Genetic variants of GBA1 can cause the lysosomal storage disorder Gaucher disease and are among the highest genetic risk factors for Parkinson's disease (PD). GBA1 encodes the lysosomal enzyme beta-glucocerebrosidase (GCase), which orchestrates the degradation of glucosylceramide (GluCer) in the lysosome. Recent studies have shown that GluCer accelerates α-synuclein aggregation, exposing GCase deficiency as a major risk factor in PD pathology and as a promising target for treatment. This study investigates the interaction of GCase and three disease-associated variants (p.E326K, p.N370S, p.L444P) with their transporter, the lysosomal integral membrane protein 2 (LIMP-2). Overexpression of LIMP-2 in HEK 293T cells boosts lysosomal abundance of wt, E326K, and N370S GCase and increases/rescues enzymatic activity of the wt and E326K variant. Using a novel purification approach, co-purification of untagged wt, E326K, and N370S GCase in complex with His-tagged LIMP-2 from cell supernatant of HEK 293F cells is achieved, confirming functional binding and trafficking for these variants. Furthermore, a single helix in the LIMP-2 ectodomain is exploited to design a lysosome-targeted peptide that enhances lysosomal GCase activity in PD patient-derived and control fibroblasts. These findings reveal LIMP-2 as an allosteric activator of GCase, suggesting a possible therapeutic potential of targeting this interaction.

Soluble mannose receptor: A potential biomarker in Gaucher disease

PURPOSE

Soluble mannose receptor (sMR) relates to mannose receptor expression on macrophages, and is elevated in inflammatory disorders. Gaucher disease (GD) has altered macrophage function and utilises mannose receptors for enzyme replacement therapy (ERT) endocytosis. sMR has not previously been studied in GD.

METHODS

sMR was measured by ELISA and correlated with GD clinical features including spleen and liver volume, haemoglobin and platelet count, bone marrow burden (BMB) scores and immunoglobulin levels. sMR was compared with biomarkers of GD: chitotriosidase, lyso-GL1, PARC, CCL3, CCL4, osteoactivin, serum ACE and ferritin.

RESULTS

Median sMR in untreated GD patients was 303.0 ng/mL compared to post-treatment 190.9 ng/mL (p = .02) and healthy controls 202 ng/mL. Median sMR correlated with median spleen volume 455 mL (r = .70, p = .04), liver volume 2025 mL (r = .64, p = .04), BMB 7 (r = .8, p = .03), IgA 1.9 g/L (r = .54, p = .036), IgG 9.2 g/L (r = .57, p = .027), IgM 1.45 g/L (r = .86, p < .0001), with inverse correlation to median platelet count of 125 × 109/L (r = -.47, p = .08) and haemoglobin of 137 g/L (r = -.77, p = .0008). sMR correlated with established biomarkers: osteoactivin 107.8 ng/mL (r = .58, p = .0006), chitotriosidase 3042 nmol/mL/h (r = .52, p = .0006), PARC 800 ng/mL (r = .67, p = .0068), ferritin 547 μg/L (r = .72, p = .002) and CCL3 50 pg/mL (r = .67, p = .007).

CONCLUSIONS

sMR correlates with clinical features and biomarkers of GD and reduces following therapy.

Role of GBA variants in Lewy body disease neuropathology

Rare and common GBA variants are risk factors for both Parkinson's disease (PD) and dementia with Lewy bodies (DLB). However, the degree to which GBA variants are associated with neuropathological features in Lewy body disease (LBD) is unknown. Herein, we assessed 943 LBD cases and examined associations of 15 different neuropathological outcomes with common and rare GBA variants. Neuropathological outcomes included LBD subtype, presence of a high likelihood of clinical DLB (per consensus guidelines), LB counts in five cortical regions, tyrosine hydroxylase immunoreactivity in the dorsolateral and ventromedial putamen, ventrolateral substantia nigra neuronal loss, Braak neurofibrillary tangle (NFT) stage, Thal amyloid phase, phospho-ubiquitin (pS65-Ub) level, TDP-43 pathology, and vascular disease. Sequencing of GBA exons revealed a total of 42 different variants (4 common [MAF > 0.5%], 38 rare [MAF < 0.5%]) in our series, and 165 cases (17.5%) had a copy of the minor allele for ≥ 1 variant. In analysis of common variants, p.L483P was associated with a lower Braak NFT stage (OR = 0.10, P < 0.001). In gene-burden analysis, presence of the minor allele for any GBA variant was associated with increased odds of a high likelihood of DLB (OR = 2.00, P < 0.001), a lower Braak NFT stage (OR = 0.48, P < 0.001), a lower Thal amyloid phase (OR = 0.55, P < 0.001), and a lower pS65-Ub level (β: -0.37, P < 0.001). Subgroup analysis revealed that GBA variants were most common in LBD cases with a combination of transitional/diffuse LBD and Braak NFT stage 0-II or Thal amyloid phase 0-1, and correspondingly that the aforementioned associations of GBA gene-burden with a decreased Braak NFT stage and Thal amyloid phase were observed only in transitional or diffuse LBD cases. Our results indicate that in LBD, GBA variants occur most frequently in cases with greater LB pathology and low AD pathology, further informing disease-risk associations of GBA in PD, PD dementia, and DLB.

The international cooperative Gaucher group (ICCG) Gaucher registry

Gaucher disease GD), is a rare lysosomal storage disorder caused by deficient acid β-glucosylceramidase activity and accumulation of glucosylceramide in tissue macrophages. With the 1991 advent of alglucerase enzyme replenishment therapy (ERT), the manufacturer (Genzyme Corporation) created the ICGG Gaucher Registry to collect longitudinal observational "real word" information about GD world-wide in heterogeneous patient populations, to annotate phenotypes and genotypes that define the natural history of GD in untreated patients, and to document and analyze treatment outcomes for alglucerase and any other future treatments. For 32 years, the ICGG Gaucher Registry has functioned as an educational tool for patients, clinicians, and other stakeholders to increase scientific knowledge of GD, to provide practical management guidance, and to positively impact patient care. This paper illustrates how an industry sponsored registry guided by a company independent scientific advisory board has successfully addressed its mission and evolved in step with technologic and scientific advances.

Accurate long-read sequencing identified GBA1 as major risk factor in the Luxembourgish Parkinson's study

Heterozygous variants in the glucocerebrosidase GBA1 gene are an increasingly recognized risk factor for Parkinson's disease (PD). Due to the GBAP1 pseudogene, which shares 96% sequence homology with the GBA1 coding region, accurate variant calling by array-based or short-read sequencing methods remains a major challenge in understanding the genetic landscape of GBA1-associated PD. We analyzed 660 patients with PD, 100 patients with Parkinsonism and 808 healthy controls from the Luxembourg Parkinson's study, sequenced using amplicon-based long-read DNA sequencing technology. We found that 12.1% (77/637) of PD patients carried GBA1 variants, with 10.5% (67/637) of them carrying known pathogenic variants (including severe, mild, risk variants). In comparison, 5% (34/675) of the healthy controls carried GBA1 variants, and among them, 4.3% (29/675) were identified as pathogenic variant carriers. We found four GBA1 variants in patients with atypical parkinsonism. Pathogenic GBA1 variants were 2.6-fold more frequently observed in PD patients compared to controls (OR = 2.6; CI = [1.6,4.1]). Three novel variants of unknown significance (VUS) were identified. Using a structure-based approach, we defined a potential risk prediction method for VUS. This study describes the full landscape of GBA1-related parkinsonism in Luxembourg, showing a high prevalence of GBA1 variants as the major genetic risk for PD. Although the long-read DNA sequencing technique used in our study may be limited in its effectiveness to detect potential structural variants, our approach provides an important advancement for highly accurate GBA1 variant calling, which is essential for providing access to emerging causative therapies for GBA1 carriers.

A Fixable Fluorescence-Quenched Substrate for Quantitation of Lysosomal Glucocerebrosidase Activity in Both Live and Fixed Cells

Fluorogenic substrates are emerging tools that enable studying enzymatic processes within their native cellular environments. However, fluorogenic substrates that function within live cells are generally incompatible with cellular fixation, preventing their tandem application with fundamental cell biology methods such as immunocytochemistry. Here we report a simple approach to enable the chemical fixation of a dark-to-light substrate, LysoFix-GBA, which enables quantification of glucocerebrosidase (GCase) activity in both live and fixed cells. LysoFix-GBA enables measuring responses to both chemical and genetic perturbations to lysosomal GCase activity. Further, LysoFix-GBA permits simple multiplexed co-localization studies of GCase activity with subcellular protein markers. This tool will aid studying the role of GCase activity in Parkinson's Disease, creating new therapeutic approaches targeting the GCase pathway. This approach also lays the foundation for an approach to create fixable substrates for other lysosomal enzymes.

Marine-Derived Components: Can They Be a Potential Therapeutic Approach to Parkinson's Disease?

The increase in the life expectancy average has led to a growing elderly population, thus leading to a prevalence of neurodegenerative disorders, such as Parkinson's disease (PD). PD is the second most common neurodegenerative disorder and is characterized by a progressive degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNpc). The marine environment has proven to be a source of unique and diverse chemical structures with great therapeutic potential to be used in the treatment of several pathologies, including neurodegenerative impairments. This review is focused on compounds isolated from marine organisms with neuroprotective activities on in vitro and in vivo models based on their chemical structures, taxonomy, neuroprotective effects, and their possible mechanism of action in PD. About 60 compounds isolated from marine bacteria, fungi, mollusk, sea cucumber, seaweed, soft coral, sponge, and starfish with neuroprotective potential on PD therapy are reported. Peptides, alkaloids, quinones, terpenes, polysaccharides, polyphenols, lipids, pigments, and mycotoxins were isolated from those marine organisms. They can act in several PD hallmarks, reducing oxidative stress, preventing mitochondrial dysfunction, α-synuclein aggregation, and blocking inflammatory pathways through the inhibition translocation of NF-kB factor, reduction of human tumor necrosis factor α (TNF-α), and interleukin-6 (IL-6). This review gathers the marine natural products that have shown pharmacological activities acting on targets belonging to different intracellular signaling pathways related to PD development, which should be considered for future pre-clinical studies.

Glucocerebrosidase activity and lipid levels are related to protein pathologies in Parkinson's disease

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are progressive neurodegenerative diseases characterized by the accumulation of misfolded α-synuclein in the form of Lewy pathology. While most cases are sporadic, there are rare genetic mutations that cause disease and more common variants that increase incidence of disease. The most prominent genetic mutations for PD and DLB are in the GBA1 and LRRK2 genes. GBA1 mutations are associated with decreased glucocerebrosidase activity and lysosomal accumulation of its lipid substrates, glucosylceramide and glucosylsphingosine. Previous studies have shown a link between this enzyme and lipids even in sporadic PD. However, it is unclear how the protein pathologies of disease are related to enzyme activity and glycosphingolipid levels. To address this gap in knowledge, we examined quantitative protein pathology, glucocerebrosidase activity and lipid substrates in parallel from 4 regions of 91 brains with no neurological disease, idiopathic, GBA1-linked, or LRRK2-linked PD and DLB. We find that several biomarkers are altered with respect to mutation and progression to dementia. We found mild association of glucocerebrosidase activity with disease, but a strong association of glucosylsphingosine with α-synuclein pathology, irrespective of genetic mutation. This association suggests that Lewy pathology precipitates changes in lipid levels related to progression to dementia.

Genetic Evidence for Endolysosomal Dysfunction in Parkinson’s Disease: A Critical Overview

Parkinson’s disease (PD) is the second most common neurodegenerative disorder in the aging population, and no disease-modifying therapy has been approved to date. The pathogenesis of PD has been related to many dysfunctional cellular mechanisms, however, most of its monogenic forms are caused by pathogenic variants in genes involved in endolysosomal function (LRRK2, VPS35, VPS13C, and ATP13A2) and synaptic vesicle trafficking (SNCA, RAB39B, SYNJ1, and DNAJC6). Moreover, an extensive search for PD risk variants revealed strong risk variants in several lysosomal genes (e.g., GBA1, SMPD1, TMEM175, and SCARB2) highlighting the key role of lysosomal dysfunction in PD pathogenesis. Furthermore, large genetic studies revealed that PD status is associated with the overall “lysosomal genetic burden”, namely the cumulative effect of strong and weak risk variants affecting lysosomal genes. In this context, understanding the complex mechanisms of impaired vesicular trafficking and dysfunctional endolysosomes in dopaminergic neurons of PD patients is a fundamental step to identifying precise therapeutic targets and developing effective drugs to modify the neurodegenerative process in PD.

Genetics of Multiple System Atrophy and Progressive Supranuclear Palsy: A Systemized Review of the Literature

Multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) are uncommon multifactorial atypical Parkinsonian syndromes, expressed by various clinical features. MSA and PSP are commonly considered sporadic neurodegenerative disorders; however, our understanding is improving of their genetic framework. The purpose of this study was to critically review the genetics of MSA and PSP and their involvement in the pathogenesis. A systemized literature search of PubMed and MEDLINE was performed up to 1 January 2023. Narrative synthesis of the results was undertaken. In total, 43 studies were analyzed. Although familial MSA cases have been reported, the hereditary nature could not be demonstrated. COQ2 mutations were involved in familial and sporadic MSA, without being reproduced in various clinical populations. In terms of the genetics of the cohort, synuclein alpha (SNCA) polymorphisms were correlated with an elevated likelihood of manifesting MSA in Caucasians, but a causal effect relationship could not be demonstrated. Fifteen MAPT mutations were linked with PSP. Leucine-rich repeat kinase 2 (LRRK2) is an infrequent monogenic mutation of PSP. Dynactin subunit 1 (DCTN1) mutations may imitate the PSP phenotype. GWAS have noted many risk loci of PSP (STX6 and EIF2AK3), suggesting pathogenetic mechanisms related to PSP. Despite the limited evidence, it seems that genetics influence the susceptibility to MSA and PSP. MAPT mutations result in the MSA and PSP pathologies. Further studies are crucial to elucidate the pathogeneses of MSA and PSP, which will support efforts to develop novel drug options.

Genetic Architecture of Parkinson's Disease

Year 2022 marks 25 years since the first mutation in familial autosomal dominant Parkinson's disease was identified. Over the years, our understanding of the role of genetic factors in the pathogenesis of familial and idiopathic forms of Parkinson's disease has expanded significantly - a number of genes for the familial form of the disease have been identified, and DNA markers for an increased risk of developing its sporadic form have been found. But, despite all the success achieved, we are far from an accurate assessment of the contribution of genetic and, even more so, epigenetic factors to the disease development. The review summarizes the information accumulated to date on the genetic architecture of Parkinson's disease and formulates issues that need to be addressed, which are primarily related to the assessment of epigenetic factors in the disease pathogenesis.

Neuronopathic GBA1L444P Mutation Accelerates Glucosylsphingosine Levels and Formation of Hippocampal Alpha-Synuclein Inclusions

The most common genetic risk factor for Parkinson's disease (PD) is heterozygous mutations GBA1, which encodes for the lysosomal enzyme, glucocerebrosidase. Reduced glucocerebrosidase activity associates with an accumulation of abnormal α-synuclein (α-syn) called Lewy pathology, which characterizes PD. PD patients heterozygous for the neuronotypic GBA1L444P mutation (GBA1+/L444P) have a 5.6-fold increased risk of cognitive impairments. In this study, we used GBA1+/L444P mice of either sex to determine its effects on lipid metabolism, expression of synaptic proteins, behavior, and α-syn inclusion formation. At 3 months of age, GBA1+/L444P mice demonstrated impaired contextual fear conditioning, and increased motor activity. Hippocampal levels of vGLUT1 were selectively reduced in GBA1+/L444P mice. We show, using mass spectrometry, that GBA1L444P expression increased levels of glucosylsphingosine, but not glucosylceramide, in the brains and serum of GBA1+/L444P mice. Templated induction of α-syn pathology in mice showed an increase in α-syn inclusion formation in the hippocampus of GBA1+/L444P mice compared with GBA1+/+ mice, but not in the cortex, or substantia nigra pars compacta. Pathologic α-syn reduced SNc dopamine neurons by 50% in both GBA1+/+ and GBA1+/L444P mice. Treatment with a GlcCer synthase inhibitor did not affect abundance of α-syn inclusions in the hippocampus or rescue dopamine neuron loss. Overall, these data suggest the importance of evaluating the contribution of elevated glucosylsphingosine to PD phenotypes. Further, our data suggest that expression of neuronotypic GBA1L444P may cause defects in the hippocampus, which may be a mechanism by which cognitive decline is more prevalent in individuals with GBA1-PD.SIGNIFICANCE STATEMENT Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are both pathologically characterized by abnormal α-synuclein (α-syn). Mutant GBA1 is a risk factor for both PD and DLB. Our data show the expression of neuronotypic GBA1L444P impairs behaviors related to hippocampal function, reduces expression of a hippocampal excitatory synaptic protein, and that the hippocampus is more susceptible to α-syn inclusion formation. Further, our data strengthen support for the importance of evaluating the contribution of glucosylsphingosine to PD phenotypes. These outcomes suggest potential mechanisms by which GBA1L444P contributes to the cognitive symptoms clinically observed in PD and DLB. Our findings also highlight the importance of glucosylsphingosine as a relevant biomarker for future therapeutics.

The Consequences of GBA Deficiency in the Autophagy-Lysosome System in Parkinson's Disease Associated with GBA

GBA gene variants were the first genetic risk factor for Parkinson's disease. GBA encodes the lysosomal enzyme glucocerebrosidase (GBA), which is involved in sphingolipid metabolism. GBA exhibits a complex physiological function that includes not only the degradation of its substrate glucosylceramide but also the metabolism of other sphingolipids and additional lipids such as cholesterol, particularly when glucocerebrosidase activity is deficient. In the context of Parkinson's disease associated with GBA, the loss of GBA activity has been associated with the accumulation of α-synuclein species. In recent years, several hypotheses have proposed alternative and complementary pathological mechanisms to explain why lysosomal enzyme mutations lead to α-synuclein accumulation and become important risk factors in Parkinson's disease etiology. Classically, loss of GBA activity has been linked to a dysfunctional autophagy-lysosome system and to a subsequent decrease in autophagy-dependent α-synuclein turnover; however, several other pathological mechanisms underlying GBA-associated parkinsonism have been proposed. This review summarizes and discusses the different hypotheses with a special focus on autophagy-dependent mechanisms, as well as autophagy-independent mechanisms, where the role of other players such as sphingolipids, cholesterol and other GBA-related proteins make important contributions to Parkinson's disease pathogenesis.

Intranasal Administration of Forskolin and Noopept Reverses Parkinsonian Pathology in PINK1 Knockout Rats

Parkinson's Disease (PD) is a brain-degenerative disorder characterized by a progressive loss of midbrain dopamine neurons. Current standard-of-care includes oral administration of Levodopa to address motor symptoms, but this treatment is not disease-modifying. A reduction in Protein Kinase A (PKA) signaling and neurotrophic support contributes to PD pathology. We previously showed that enhancing PKA activity in the brain via intraperitoneal administration of Forskolin in Parkinsonian rats (PINK1 knockout) abrogate motor symptoms and loss of midbrain dopamine neurons. Given that intraperitoneal administration is invasive, we hypothesized that intranasal administration of Forskolin and a second nootropic agent (Noopept) could reverse PD pathology efficiently. Results show that intranasal administration of a formulation (CNS/CT-001) containing Forskolin (10 µM) and Noopept (20 nM) significantly reversed motor symptoms, loss of hind limb strength, and neurodegeneration of midbrain dopamine neurons in PINK1-KO rats and is indistinguishable from wild-type (WT) rats; therapeutic effects associated with increased PKA activity and levels of BDNF and NGF in the brain. Intranasal administration of CNS/CT-001, but not Forskolin, significantly decreased the number of α-synuclein aggregates in the cortex of PINK1-KO rats, and is indistinguishable from WT rats. Overall, we show proof of concept that intranasal administration of CNS/CT-001 is a non-invasive, disease-modifying formulation for PD.

Perspective: Is a Closer Interaction between Experimental and Clinical Research Paradigms in Chronic Neurodegeneration, Such as Parkinson's Disease, Necessary Again?

This editorial discusses the current standstill in research in Parkinson's disease from a clinician's point of view [...].