GBA Mutations Research Articles

GBA and APOE Impact Cognitive Decline in Parkinson's Disease: A 10-Year Population-Based Study.

Background:Common genetic variance in apolipoprotein E (APOE), β-glucocerebrosidase (GBA), microtubule-associated protein tau (MAPT), and α-synuclein (SNCA) has been linked to cognitive decline in Parkinson’s disease (PD), although studies have yielded mixed esults.Objectives:To evaluate the effect of genetic variants in APOE, GBA, MAPT, and SNCA on cognitive decline and risk of dementia in a pooled analysis of six longitudinal, non-selective, population-based cohorts of newly diagnosed PD patients.Methods:1002 PD patients, followed for up to 10 years (median 7.2 years), were genotyped for at least one of APOE-ε4, GBA mutations, MAPT H1/H2, or SNCA rs356219. We evaluated the effect of genotype on the rate of cognitive decline (Mini-Mental State Examanation, MMSE) using linear mixed models and the development of dementia (diagnosed using standardized criteria) using Cox regression; multiple comparisons were accounted for using Benjamini–Hochberg corrections.Results:Carriers of APOE-ε4 (n = 281, 29.7%) and GBA mutations (n = 100, 10.3%) had faster cognitive decline and were at higher risk of progression to dementia (APOE-ε4, HR 3.57, P < 0.001; GBA mutations, HR 1.76, P = 0.001) than non-carriers. The risk of cognitive decline and dementia (HR 5.19, P < 0.001) was further increased in carriers of both risk genotypes (n = 23). No significant effects were observed for MAPT or SNCA rs356219.Conclusions:GBA and APOE genotyping could improve the prediction of cognitive decline in PD, which is important to inform the clinical trial selection and potentially to enable personalized treatment

Progranulin deficiency markedly exacerbates Gaucher disease phenotypes in Gba1 mutant mice

Progranulin deficiency markedly exacerbates Gaucher disease phenotypes in Gba1 mutant mice

Gaucher Disease Diagnosis Using Lyso-Gb1 on Dry Blood Spot Samples: Time to Change the Paradigm?

For years, the gold standard for diagnosing Gaucher disease (GD) has been detecting reduced β-glucocerebrosidase (GCase) activity in peripheral blood cells combined with GBA1 mutation analysis. The use of dried blood spot (DBS) specimens offers many advantages, including easy collection, the need for a small amount of blood, and simpler transportation. However, DBS has limitations for measuring GCase activity. In this paper, we recount our cross-sectional study and publish seven years of experience using DBS samples and levels of the deacylated form of glucocerebroside, glucosylsphingosine (lyso-Gb1), for GD diagnosis. Of 444 screened subjects, 99 (22.3%) were diagnosed with GD at a median (range) age of 21 (1–78) years. Lyso-Gb levels for genetically confirmed GD patients vs. subjects negative to GD diagnosis were 252 (9–1340) ng/mL and 5.4 (1.5–16) ng/mL, respectively. Patients diagnosed with GD1 and mild GBA1 variants had lower median (range) lyso-Gb1, 194 (9–1050), compared to GD1 and severe GBA1 variants, 447 (38–1340) ng/mL, and neuronopathic GD, 325 (116–1270) ng/mL (p = 0.001). Subjects with heterozygous GBA1 variants (carrier) had higher lyso-Gb1 levels, 5.8 (2.5–15.3) ng/mL, compared to wild-type GBA1, 4.9 (1.5–16), ng/mL (p = 0.001). Lyso-Gb1 levels, median (range), were 5 (2.7–10.7) in heterozygous GBA1 carriers with Parkinson’s disease (PD), similar to lyso-Gb1 levels in subjects without PD. We call for a paradigm change for the diagnosis of GD based on lyso-Gb1 measurements and confirmatory GBA1 mutation analyses in DBS. Lyso-Gb1 levels could not be used to differentiate between heterozygous GBA1 carriers and wild type.

Rare PSAP Variants and Possible Interaction with GBA in REM Sleep Behavior Disorder.

PSAP encodes saposin C, the co-activator of glucocerebrosidase, encoded by GBA. GBA mutations are associated with idiopathic/isolated REM sleep behavior disorder (iRBD), a prodromal stage of synucleinopathy. To examine the role of PSAP mutations in iRBD. We fully sequenced PSAP and performed Optimized Sequence Kernel Association Test in 1,113 iRBD patients and 2,324 controls. We identified loss-of-function (LoF) mutations, which are very rare in PSAP, in three iRBD patients and none in controls (uncorrected p = 0.018). Two variants were stop mutations, p.Gln260Ter and p.Glu166Ter, and one was an in-frame deletion, p.332_333del. All three mutations have a deleterious effect on saposin C, based on in silico analysis. In addition, the two carriers of p.Glu166Ter and p.332_333del mutations also carried a GBA variant, p.Arg349Ter and p.Glu326Lys, respectively. The co-occurrence of these extremely rare PSAP LoF mutations in two (0.2%) GBA variant carriers in the iRBD cohort, is unlikely to occur by chance (estimated co-occurrence in the general population based on gnomAD data is 0.00035%). Although none of the three iRBD patients with PSAP LoF mutations have phenoconverted to an overt synucleinopathy at their last follow-up, all manifested initial signs suggestive of motor dysfunction, two were diagnosed with mild cognitive impairment and all showed prodromal clinical markers other than RBD. Their probability of prodromal PD, according to the Movement Disorder Society research criteria, was 98% or more. These results suggest a possible role of PSAP variants in iRBD and potential genetic interaction with GBA, which requires additional studies.

Bioengineered models of Parkinson's disease using patient-derived dopaminergic neurons exhibit distinct biological profiles in a 3D microenvironment.

Three-dimensional (3D) in vitro culture systems using human induced pluripotent stem cells (hiPSCs) are useful tools to model neurodegenerative disease biology in physiologically relevant microenvironments. Though many successful biomaterials-based 3D model systems have been established for other neurogenerative diseases, such as Alzheimer's disease, relatively few exist for Parkinson's disease (PD) research. We employed tissue engineering approaches to construct a 3D silk scaffold-based platform for the culture of hiPSC-dopaminergic (DA) neurons derived from healthy individuals and PD patients harboring LRRK2 G2019S or GBA N370S mutations. We then compared results from protein, gene expression, and metabolic analyses obtained from two-dimensional (2D) and 3D culture systems. The 3D platform enabled the formation of dense dopamine neuronal network architectures and developed biological profiles both similar and distinct from 2D culture systems in healthy and PD disease lines. PD cultures developed in 3D platforms showed elevated levels of α-synuclein and alterations in purine metabolite profiles. Furthermore, computational network analysis of transcriptomic networks nominated several novel molecular interactions occurring in neurons from patients with mutations in LRRK2 and GBA. We conclude that the brain-like 3D system presented here is a realistic platform to interrogate molecular mechanisms underlying PD biology.

Phenotypic Heterogeneity among GBA p.R202X Carriers in Lewy Body Spectrum Disorders.

We describe the clinical and neuropathologic features of patients with Lewy body spectrum disorder (LBSD) carrying a nonsense variant, c.604C>T; p.R202X, in the glucocerebrosidase 1 (GBA) gene. While this GBA variant is causative for Gaucher’s disease, the pathogenic role of this mutation in LBSD is unclear. Detailed neuropathologic evaluation was performed for one index case and a structured literature review of other GBA p.R202X carriers was conducted. Through the systematic literature search, we identified three additional reported subjects carrying the same GBA mutation, including one Parkinson’s disease (PD) patient with early disease onset, one case with neuropathologically-verified LBSD, and one unaffected relative of a Gaucher’s disease patient. Among the affected subjects carrying the GBA p.R202X, all males were diagnosed with Lewy body dementia, while the two females presented as PD. The clinical penetrance of GBA p.R202X in LBSD patients and families argues strongly for a pathogenic role for this variant, although presenting with a striking phenotypic heterogeneity of clinical and pathological features.

A double-hit in vivo model of GBA viral microRNA-mediated downregulation and human alpha-synuclein overexpression demonstrates nigrostriatal degeneration

Preclinical and clinical studies support a strong association between mutations in the GBA1 gene that encodes beta-glucocerebrosidase (GCase) (EC 3.2.1.45; glucosylceramidase beta) and Parkinson's disease (PD). Alpha-synuclein (AS), a key player in PD pathogenesis, and GBA1 mutations may independently and synergistically cause lysosomal dysfunction and thus, embody clinically well-validated targets of the neurodegenerative disease process in PD. However, in vivo models, recapitulating pathological features of PD that can be used to dissect the nature of the complex relationship between GCase and AS on the nigrostriatal axis, the region particularly vulnerable in PD, are direly needed. To address this, we implemented a bidirectional approach in mice to examine the effects of: 1) GCase overexpression (wild-type and mutant N370S GBA) on endogenous AS levels and 2) downregulation of endogenous GCase (Gba) combined with AS overexpression. Striatal delivery of viral-mediated GCase overexpression revealed minimal effects on cortical and nigrostriatal AS tissue levels and no significant effect on dopaminergic system integrity. On the other hand, microRNA (miR)-mediated Gba1 downregulation (miR Gba), combined with virus-mediated human AS overexpression (+AS), yields decreased GCase activity in the cortex, mimicking levels seen in GBA1 heterozygous carriers (30–40%), increased astrogliosis and microgliosis, decreased striatal dopamine levels (50% compared to controls) and loss of nigral dopaminergic neurons (~33%)- effects that were all reversible with miR rescue. Most importantly, the synergistic neurodegeneration of miR Gba + AS correlated with augmented AS accumulation and extracellular release in the striatum. Collectively, our results suggest that GCase downregulation alone is not sufficient to recapitulate key pathological features of PD in vivo, but its synergistic interplay with AS, via increased AS levels and extracellular release, drives nigrostriatal neurodegeneration. Furthermore, we report a novel double-hit GBA-AS model that can be used to identify putative mechanisms driving PD pathophysiology and can be subsequently used to test novel therapeutic approaches.

The epidemiology of cognitive function in Parkinson's disease.

Epidemiology is the study of the distribution of disease in human populations, which is important in evaluating burden of illness, identifying modifiable risk factors, and planning for current and projected needs of the health care system. Parkinson's disease (PD) is the second most common serious neurodegenerative illness and is expected to further increase in prevalence. Cognitive changes are increasingly viewed as an integral non-motor feature in PD, emerging even in the prodromal phase of the disease. The prevalence of PD-MCI ranges from 20% to 40% depending on the population studied. The incidence of PD-dementia increases with duration of disease, with estimates growing from 3% to 30% of individuals followed for 5 years or less to over 80% after 20 years. There are several challenges in estimating the frequency of cognitive change, including only recently standardized diagnostic criteria, variation depending on exact neuropsychological evaluations performed, and differences in population sampling. Clinical features associated with cognitive decline include older age, increased disease duration and severity, early gait dysfunction, dysautonomia, hallucinations and other neuropsychiatric features, the presence of REM behavior disorder, and posterior predominant dysfunction on neuropsychological testing. There is increasing evidence that genetic risk factors, in particular GBA and MAPT mutations, contribute to cognitive change. Possible protective factors include higher cognitive reserve and regular exercise. Important sequelae of cognitive decline in PD include higher caregiver burden, decreased functional status, and increased risk of institutionalization and mortality. Many remaining uncertainties regarding the epidemiology of cognitive change in PD require future research, with improved biomarkers and more sensitive and convenient outcome measures.

Generation of induced pluripotent stem cell line, ICGi034-A, by reprogramming peripheral blood mononuclear cells from a patient with Parkinson’s disease associated with GBA mutation

Mutation in the glucocerebrosidase encoding gene (GBA) is one of the most frequent genetic cause of Parkinson's disease. ICGi034-A induced pluripotent stem cell (iPSC) line obtained by reprogramming peripheral blood mononuclear cells (PBMCs) of a patient with heterozygous c.1226A > G (p.N370S) mutation in the GBA gene can be used for studying the fundamental mechanisms of the pathogenesis of GBA-associated Parkinson's disease, and for potential drug screening. The iPSCs express pluripotency markers (NANOG, SSEA4, TRA-1-60, OCT4, SOX2), have a normal karyotype, and are capable of producing derivatives of three germ layers.

Cognitive Impairment in Genetic Parkinson's Disease.

Cognitive impairment is common in idiopathic Parkinson's disease (PD). Knowledge of the contribution of genetics to cognition in PD is increasing in the last decades. Monogenic forms of genetic PD show distinct cognitive profiles and rate of cognitive decline progression. Cognitive impairment is higher in GBA- and SNCA-associated PD, lower in Parkin- and PINK1-PD, and possibly milder in LRRK2-PD. In this review, we summarize data regarding cognitive function on clinical studies, neuroimaging, and biological markers of cognitive decline in autosomal dominant PD linked to mutations in LRRK2 and SNCA, autosomal recessive PD linked to Parkin and PINK1, and also PD linked to GBA mutations.

Glucocerebrosidase dysfunction in neurodegenerative disease.

Parkinson's disease (PD) and related neurodegenerative disorders, termed the synucleinopathies, are characterized pathologically by the accumulation of protein aggregates containing α-synuclein (aSyn), resulting in progressive neuronal loss. There is considerable need for the development of neuroprotective strategies to halt or slow disease progression in these disorders. To this end, evaluation of genetic mutations associated with the synucleinopathies has helped to elucidate crucial mechanisms of disease pathogenesis, revealing key roles for lysosomal and mitochondrial dysfunction. The GBA1 gene, which encodes the lysosomal hydrolase β-glucocerebrosidase (GCase) is the most common genetic risk factor for PD and is also linked to other neurodegenerative disorders including dementia with Lewy bodies (DLB). Additionally, homozygous mutations in GBA1 are associated with the rare lysosomal storage disorder, Gaucher's disease (GD). In this review, we discuss the current knowledge in the field regarding the diverse roles of GCase in neurons and the multifactorial effects of loss of GCase enzymatic activity. Importantly, GCase has been shown to have a bidirectional relationship with aSyn, resulting in a pathogenic feedback loop that can lead to progressive aSyn accumulation. Alterations in GCase activity have furthermore been linked to multiple distinct pathways involved in neurodegeneration, and therefore GCase has emerged as a promising target for therapeutic drug development for PD and related neurodegenerative disorders, particularly DLB.

Pathological α-syn aggregation is mediated by glycosphingolipid chain length and the physiological state of α-syn in vivo

GBA1 mutations that encode lysosomal β-glucocerebrosidase (GCase) cause the lysosomal storage disorder Gaucher disease (GD) and are strong risk factors for synucleinopathies, including Parkinson's disease and Lewy body dementia. Only a subset of subjects with GBA1 mutations exhibit neurodegeneration, and the factors that influence neurological phenotypes are unknown. We find that α-synuclein (α-syn) neuropathology induced by GCase depletion depends on neuronal maturity, the physiological state of α-syn, and specific accumulation of long-chain glycosphingolipid (GSL) GCase substrates. Reduced GCase activity does not initiate α-syn aggregation in neonatal mice or immature human midbrain cultures; however, adult mice or mature midbrain cultures that express physiological α-syn oligomers are aggregation prone. Accumulation of long-chain GSLs (≥C22), but not short-chain species, induced α-syn pathology and neurological dysfunction. Selective reduction of long-chain GSLs ameliorated α-syn pathology through lysosomal cathepsins. We identify specific requirements that dictate synuclein pathology in GD models, providing possible explanations for the phenotypic variability in subjects with GCase deficiency.

Longitudinal clinical, cognitive and neuroanatomical changes over five years in GBA‐positive Parkinson’s disease patients

AbstractBackgroundGlucocerebrosidase gene (GBA) mutations are the greatest genetic cause of Parkinson’s disease (PD). The aim of this study was to monitor the longitudinal disease course of PD patients with GBA mutation (GBA‐positive) at diagnosis compared to PD noncarriers (GBA‐negative) along a 5‐year follow‐up, evaluating changes in clinical and cognitive outcomes, cortical thickness, and subcortical volumes.Method10 GBA‐positive and 20 GBA‐negative PD at diagnosis underwent clinical, neuropsychological and brain MRI assessments at study entry and once a year for 5 years. At baseline and at the last visit, each group of patients was compared in terms of cortical thickness and subcortical volumes to a group of 22 age‐matched healthy controls (HC). Clinical, cognitive and cortical/subcortical MRI features were compared between groups at baseline and over time.ResultAt baseline, GBA‐positive and GBA‐negative patients had similar clinical and cognitive profiles. Compared to GBA‐negative and HC, GBA‐positive patients showed cortical thinning of left temporal, parietal and occipital gyri. Over time, compared to GBA‐negative, GBA‐positive worsened significantly in motor and cognitive symptoms, and showed a greater pattern of bilateral cortical thinning involving also frontal cortices. After 60 months, compared to HC, GBA‐negative PD patients showed a pattern of cortical thinning similar to that shown by GBA‐positive at baseline. The two groups of patients showed similar patterns of subcortical volume loss over time.ConclusionCompared to GBA‐negative patients, GBA‐positive PD showed a greater and earlier cortical thinning which worsened over time. GBA‐negative PD patients reached the pattern of cortical thinning of GBA‐positive at the baseline only after 5 years, reflecting a slower disease progression. This study highlights the importance of the early detection of GBA mutation in PD patients. Funding: This study was supported by the Ministry of Education and Science of the Republic of Serbia (Grant #175090).

Genetic Analysis of Acid β-Glucosidase in Patients with Multiple Myeloma from Central Taiwan: A Small-Cohort Case-Control Study

Introduction: Multiple myeloma (MM) is an incurable, biologically heterogeneous disease of the plasma cells, associated with older age and is more common in men. Gaucher disease, caused by mutation in acid β-glucosidase (glucocerebrosidase, GBA) gene, has been linked to multiple cancers, especially MM. Pathological accumulation of glucosylceramide and complex glycosphingolipids coupled with chronic inflammation may be the cause of cancer in patients with Gaucher disease. In this study, we hypothesized patients with MM have mutations in the GBA gene and analyzed patients with MM to determine whether they have a higher frequency of GBA variants. Methods: Twenty-four MM samples were acquired from the Human Biobank, China Medical University Hospital, Taichung, Taiwan. GBA mutations were detected by polymerase chain reaction-directed DNA sequencing. Results: We found no mutations in the coding regions of GBA in any of the 24 study subjects. However, two single-nucleotide polymorphisms, rs2070679 and rs2361534, were identified. A significant difference was observed between the study and control groups (p = 0.0028) in rs2361534 allele distribution, with the C allele frequency being higher in patients (1/48, 2.1%) than in the control group (5/3030, 0.16%, Taiwan Biobank). Conclusion: In this study, the sample size was limited and GBA enzyme activity was not measured; therefore, we could not establish a direct correlation between MM and GBA mutations. However, the association of rs2361534 suggests that regions around this single-nucleotide polymorphism may be involved in MM. The relationship between MM and GBA mutations remains unclear. A large sample is required for a detailed analysis of this potential relationship.

Glitazone Treatment Rescues Phenotypic Deficits in a Fly Model of Gaucher/Parkinson's Disease.

Parkinson’s Disease (PD) is the most common movement disorder, and the strongest genetic risk factor for PD is mutations in the glucocerebrosidase gene (GBA). Mutations in GBA also lead to the development of Gaucher Disease (GD), the most common type of lysosomal storage disorder. Current therapeutic approaches fail to address neurological GD symptoms. Therefore, identifying therapeutic strategies that improve the phenotypic traits associated with GD/PD in animal models may provide an opportunity for treating neurological manifestations of GD/PD. Thiazolidinediones (TZDs, also called glitazones) are a class of compounds targeted for the treatment of type 2 diabetes, and have also shown promise for the treatment of neurodegenerative disease, including PD. Here, we tested the efficacy of glitazone administration during development in a fly GD model with deletions in the GBA homolog, dGBA1b (GBA1ΔTT/ΔTT). We observed an optimal dose of pioglitazone (PGZ) at a concentration of 1 μM that reduced sleep deficits, locomotor impairments, climbing defects, and restoration of normal protein levels of Ref(2)P, a marker of autophagic flux, in GBA1ΔTT/ΔTT mutant flies, compared to GBA1+/+ control flies. These data suggest that PGZ may represent a potential compound with which to treat GD/PD by improving function of lysosomal-autophagy pathways, a cellular process that removes misfolded or aggregated proteins.

Glucosylceramide in cerebrospinal fluid of patients with GBA-associated and idiopathic Parkinson\u2019s disease enrolled in PPMI

Protein-coding variants in the GBA gene modulate susceptibility and progression in ~10% of patients with Parkinson’s disease (PD). GBA encodes the β-glucocerebrosidase enzyme that hydrolyzes glucosylceramide. We hypothesized that GBA mutations will lead to glucosylceramide accumulation in cerebrospinal fluid (CSF). Glucosylceramide, ceramide, sphingomyelin, and lactosylceramide levels were measured by liquid chromatography-tandem mass spectrometry in CSF of 411 participants from the Parkinson’s Progression Markers Initiative (PPMI) cohort, including early stage, de novo PD patients with abnormal dopamine transporter neuroimaging and healthy controls. Forty-four PD patients carried protein-coding GBA variants (GBA-PD) and 227 carried wild-type alleles (idiopathic PD). The glucosylceramide fraction was increased (P = 0.0001), and the sphingomyelin fraction (a downstream metabolite) was reduced (P = 0.0001) in CSF of GBA-PD patients compared to healthy controls. The ceramide fraction was unchanged, and lactosylceramide was below detection limits. We then used the ratio of glucosylceramide to sphingomyelin (the GlcCer/SM ratio) to explore whether these two sphingolipid fractions altered in GBA-PD were useful for stratifying idiopathic PD patients. Idiopathic PD patients in the top quartile of GlcCer/SM ratios at baseline showed a more rapid decline in Montreal Cognitive Assessment scores during longitudinal follow-up compared to those in the lowest quartile with a P-value of 0.036. The GlcCer/SM ratio was negatively associated with α-synuclein levels in CSF of PD patients. This study highlights glucosylceramide as a pathway biomarker for GBA-PD patients and the GlcCer/SM ratio as a potential stratification tool for clinical trials of idiopathic PD patients. Our sphingolipids data together with the clinical, imaging, omics, and genetic characterization of PPMI will contribute a useful resource for multi-modal biomarkers development.

Association between CSF alpha-synuclein seeding activity and genetic status in Parkinson\u2019s disease and dementia with Lewy bodies

The clinicopathological heterogeneity in Lewy-body diseases (LBD) highlights the need for pathology-driven biomarkers in-vivo. Misfolded alpha-synuclein (α-Syn) is a lead candidate based on its crucial role in disease pathophysiology. Real-time quaking-induced conversion (RT-QuIC) analysis of CSF has recently shown high sensitivity and specificity for the detection of misfolded α-Syn in patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). In this study we performed the CSF RT-QuIC assay in 236 PD and 49 DLB patients enriched for different genetic forms with mutations in GBA, parkin, PINK1, DJ1, and LRRK2. A subgroup of 100 PD patients was also analysed longitudinally. We correlated kinetic seeding parameters of RT-QuIC with genetic status and CSF protein levels of molecular pathways linked to α-Syn proteostasis. Overall, 85% of PD and 86% of DLB patients showed positive RT-QuIC α-Syn seeding activity. Seeding profiles were significantly associated with mutation status across the spectrum of genetic LBD. In PD patients, we detected positive α-Syn seeding in 93% of patients carrying severe GBA mutations, in 78% with LRRK2 mutations, in 59% carrying heterozygous mutations in recessive genes, and in none of those with bi-allelic mutations in recessive genes. Among PD patients, those with severe GBA mutations showed the highest seeding activity based on RT-QuIC kinetic parameters and the highest proportion of samples with 4 out of 4 positive replicates. In DLB patients, 100% with GBA mutations showed positive α-Syn seeding compared to 79% of wildtype DLB. Moreover, we found an association between α-Syn seeding activity and reduced CSF levels of proteins linked to α-Syn proteostasis, specifically lysosome-associated membrane glycoprotein 2 and neurosecretory protein VGF.These findings highlight the value of α-Syn seeding activity as an in-vivo marker of Lewy-body pathology and support its use for patient stratification in clinical trials targeting α-Syn.

Cellular and biochemical response to chaperone versus substrate reduction therapies in neuropathic Gaucher disease.

Gaucher disease (GD) is caused by deficiency of the lysosomal membrane enzyme glucocerebrosidase (GCase) and the subsequent accumulation of its substrate, glucosylceramide (GC). Mostly missense mutations of the glucocerebrosidase gene (GBA) cause GCase misfolding and inhibition of proper lysosomal trafficking. The accumulated GC leads to lysosomal dysfunction and impairs the autophagy pathway. GD types 2 and 3 (GD2-3), or the neuronopathic forms, affect not only the Central Nervous System (CNS) but also have severe systemic involvement and progressive bone disease. Enzyme replacement therapy (ERT) successfully treats the hematologic manifestations; however, due to the lack of equal distribution of the recombinant enzyme in different organs, it has no direct impact on the nervous system and has minimal effect on bone involvement. Small molecules have the potential for better tissue distribution. Ambroxol (AMB) is a pharmacologic chaperone that partially recovers the mutated GCase activity and crosses the blood-brain barrier. Eliglustat (EGT) works by inhibiting UDP-glucosylceramide synthase, an enzyme that catalyzes GC biosynthesis, reducing GC influx load into the lysosome. Substrate reduction therapy (SRT) using EGT is associated with improvement in GD bone marrow burden score and bone mineral density parallel with the improvement in hematological parameters. We assessed the effects of EGT and AMB on GCase activity and autophagy-lysosomal pathway (ALP) in primary cell lines derived from patients with GD2-3 and compared to cell lines from healthy controls. We found that EGT, same as AMB, enhanced GCase activity in control cells and that an individualized response, that varied with GBA mutations, was observed in cells from patients with GD2-3. EGT and AMB enhanced the formation of lysosomal/late endosomal compartments and improved autophagy, independent of GBA mutations. Both AMB and EGT increased mitochondrial mass and density in GD2-3 fibroblasts, suggesting enhancement of mitochondrial function by activating the mitochondrial membrane potential. These results demonstrate that EGT and AMB, with different molecular mechanisms of action, enhance GCase activity and improve autophagy-lysosome dynamics and mitochondrial functions.

Preclinical pharmacology of glucosylceramide synthase inhibitor venglustat in a GBA-related synucleinopathy model

Mutations in GBA, the gene encoding the lysosomal enzyme glucocerebrosidase (GCase), represent the greatest genetic risk factor for developing synucleinopathies including Parkinson’s disease (PD). Additionally, PD patients harboring a mutant GBA allele present with an earlier disease onset and an accelerated disease progression of both motor and non-motor symptoms. Preclinical studies in mouse models of synucleinopathy suggest that modulation of the sphingolipid metabolism pathway via inhibition of glucosylceramide synthase (GCS) using a CNS-penetrant small molecule may be a potential treatment for synucleinopathies. Here, we aim to alleviate the lipid storage burden by inhibiting the de novo synthesis of the primary glycosphingolipid substrate of GCase, glucosylceramide (GlcCer). We have previously shown that systemic GCS inhibition reduced GlcCer and glucosylsphingosine (GlcSph) accumulation, slowed α-synuclein buildup in the hippocampus, and improved cognitive deficits. Here, we studied the efficacy of a brain-penetrant clinical candidate GCS inhibitor, venglustat, in mouse models of GBA-related synucleinopathy, including a heterozygous Gba mouse model which more closely replicates the typical GBA-PD patient genotype. Collectively, these data support the rationale for modulation of GCase-related sphingolipid metabolism as a therapeutic strategy for treating GBA-related synucleinopathies.

The remote assessment of parkinsonism supporting the ongoing development of interventions in Gaucher disease.

Mutations in GBA which are causative of Gaucher disease in their biallelic form, are the most common genetic risk factor for Parkinson's disease (PD). The diagnosis of PDrelies upon clinically defined motor features which appear after irreversible neurodegeneration. Prodromal symptoms of PD may provide a means to predict latent pathology, years before the onset of motor features. Previous work has reported prodromal features of PD in GBA mutation carriers, however this has been insufficiently sensitive to identify those that will develop PD. The Remote Assessment of Parkinsonism Supporting Ongoing Development of Interventions in Gaucher Disease (RAPSODI GD) study assesses a large cohort of GBA mutation carriers, to aid development of procedures for earlier diagnosis of PD.