Do Not Miss the (Genetic) Diagnosis of Gaucher Syndrome: A Narrative Review on Diagnostic Clues and Management in Severe Prenatal and Perinatal-Lethal Sporadic Cases

With a growing number of proved therapies and clinical trials for many lysosomal storage disorders (LSDs), a lot of hope for many patients and families exists. However, there are sometimes cases with poor prognosis, fatal outcomes when our efforts must be directed towards a prompt and correct genetic diagnosis, which offers the only possibility of providing the family with appropriate prevention and treatment. To address this issue, in this article, we present the clinical and genetic hallmarks of the lethal form of Gaucher disease (PLGD) and discuss the potential management. We hope that this will draw attention to its specific manifestations (such as collodion-baby phenotype, ichthyosis, arthrogryposis), which differ from best-known GD complications and ensure appropriate diagnostic assessment to provide families at risk with reliable counselling and treatment to avoid the medical complication of GD.

Mapping the Diverse and Inclusive Future of Parkinson's Disease Genetics and Its Widespread Impact

Over the last decades, genetics has been the engine that has pushed us along on our voyage to understand the etiology of Parkinson's disease (PD). Although a large number of risk loci and causative mutations for PD have been identified, it is clear that much more needs to be done to solve the missing heritability mystery. Despite remarkable efforts, as a field, we have failed in terms of diversity and inclusivity. The vast majority of genetic studies in PD have focused on individuals of European ancestry, leading to a gap of knowledge on the existing genetic differences across populations and PD as a whole. As we move forward, shedding light on the genetic architecture contributing to PD in non-European populations is essential, and will provide novel insight into the generalized genetic map of the disease. In this review, we discuss how better representation of understudied ancestral groups in PD genetics research requires addressing and resolving all the challenges that hinder the inclusion of these populations. We further provide an overview of PD genetics in the clinics, covering the current challenges and limitations of genetic testing and counseling. Finally, we describe the impact of worldwide collaborative initiatives in the field, shaping the future of the new era of PD genetics as we advance in our understanding of the genetic architecture of PD.

The remote assessment of parkinsonism supporting 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 PD relies 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.

Glucocerebrosidase 1 and leucine-rich repeat kinase 2 in Parkinson disease and interplay between the two genes

The glucocerebrosidase 1 gene (GBA1), bi-allelic variants of which cause Gaucher disease (GD), encodes the lysosomal enzyme glucocerebrosidase (GCase) and is a risk factor for Parkinson Disease (PD). GBA1 variants are linked to a reduction in GCase activity in the brain. Variants in Leucine-Rich Repeat Kinase 2 (LRRK2), such as the gain-of-kinase-function variant G2019S, cause the most common familial form of PD. In patients without GBA1 and LRRK2 mutations, GCase and LRRK2 activity are also altered, suggesting that these two genes are implicated in all forms of PD and that they may play a broader role in PD pathogenesis. In this review, we review the proposed roles of GBA1 and LRRK2 in PD, focussing on the endolysosomal pathway. In particular, we highlight the discovery of Ras-related in brain (Rab) guanosine triphosphatases (GTPases) as LRRK2 kinase substrates and explore the links between increased LRRK2 activity and Rab protein function, lysosomal dysfunction, alpha-synuclein accumulation and GCase activity. We also discuss the discovery of RAB10 as a potential mediator of LRRK2 and GBA1 interaction in PD. Finally, we discuss the therapeutic implications of these findings, including current approaches and future perspectives related to novel drugs targeting LRRK2 and GBA1.

Inhibition of microglial β-glucocerebrosidase hampers the microglia-mediated antioxidant and protective response in neurons

BACKGROUND

Homozygotic mutations in the GBA gene cause Gaucher's disease; moreover, both patients and heterozygotic carriers have been associated with 20- to 30-fold increased risk of developing Parkinson's disease. In homozygosis, these mutations impair the activity of β-glucocerebrosidase, the enzyme encoded by GBA, and generate a lysosomal disorder in macrophages, which changes morphology towards an engorged phenotype, considered the hallmark of Gaucher's disease. Notwithstanding the key role of macrophages in this disease, most of the effects in the brain have been attributed to the β-glucocerebrosidase deficit in neurons, while a microglial phenotype for these mutations has never been reported.

METHODS

We applied the bioluminescence imaging technology, immunohistochemistry and gene expression analysis to investigate the consequences of microglial β-glucocerebrosidase inhibition in the brain of reporter mice, in primary neuron/microglia cocultures and in cell lines. The use of primary cells from reporter mice allowed for the first time, to discriminate in cocultures neuronal from microglial responses consequent to the β-glucocerebrosidase inhibition; results were finally confirmed by pharmacological depletion of microglia from the brain of mice.

RESULTS

Our data demonstrate the existence of a novel neuroprotective mechanism mediated by a direct microglia-to-neuron contact supported by functional actin structures. This cellular contact stimulates the nuclear factor erythroid 2-related factor 2 activity in neurons, a key signal involved in drug detoxification, redox balance, metabolism, autophagy, lysosomal biogenesis, mitochondrial dysfunctions, and neuroinflammation. The central role played by microglia in this neuronal response in vivo was proven by depletion of the lineage in the brain of reporter mice. Pharmacological inhibition of microglial β-glucocerebrosidase was proven to induce morphological changes, to turn on an anti-inflammatory/repairing pathway, and to hinder the microglia ability to activate the nuclear factor erythroid 2-related factor 2 response, thus increasing the neuronal susceptibility to neurotoxins.

CONCLUSION

This mechanism provides a possible explanation for the increased risk of neurodegeneration observed in carriers of GBA mutations and suggest novel therapeutic strategies designed to revert the microglial phenotype associated with β-glucocerebrosidase inhibition, aimed at resetting the protective microglia-to-neuron communication.

Glucocerebrosidase Activity is not Associated with Parkinson's Disease Risk or Severity

Background

Mutations in the GBA gene, which encodes the lysosomal enzyme glucocerebrosidase (GCase), are risk factors for Parkinson's disease (PD).

Objective

To explore the association between GCase activity, PD phenotype, and probability for prodromal PD among carriers of mutations in the GBA and LRRK2 genes.

Methods

Participants were genotyped for the G2019S‐LRRK2 and nine GBA mutations common in Ashkenazi Jews. Performance‐based measures enabling the calculation of the Movement Disorder Society (MDS) prodromal probability score were collected.

Results

One hundred and seventy PD patients (102 GBA‐PD, 38 LRRK2‐PD, and 30 idiopathic PD) and 221 non‐manifesting carriers (NMC) (129 GBA‐NMC, 45 LRRK2‐NMC, 15 GBA‐LRRK2‐NMC, and 32 healthy controls) participated in this study. GCase activity was lower among GBA‐PD (3.15 ± 0.85 μmol/L/h), GBA‐NMC (3.23 ± 0.91 μmol/L/h), and GBA‐LRRK2‐NMC (3.20 ± 0.93 μmol/L/h) compared to the other groups of participants, with no correlation to clinical phenotype.

Conclusions

Low GCase activity does not explain the clinical phenotype or risk for prodromal PD in this cohort. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Protein structural features predict responsiveness to pharmacological chaperone treatment for three lysosomal storage disorders

Three-dimensional structures of proteins can provide important clues into the efficacy of personalized treatment. We perform a structural analysis of variants within three inherited lysosomal storage disorders, comparing variants responsive to pharmacological chaperone treatment to those unresponsive to such treatment. We find that predicted ΔΔG of mutation is higher on average for variants unresponsive to treatment, in the case of datasets for both Fabry disease and Pompe disease, in line with previous findings. Using both a single decision tree and an advanced machine learning approach based on the larger Fabry dataset, we correctly predict responsiveness of three Gaucher disease variants, and we provide predictions for untested variants. Many variants are predicted to be responsive to treatment, suggesting that drug-based treatments may be effective for a number of variants in Gaucher disease. In our analysis, we observe dependence on a topological feature reporting on contact arrangements which is likely connected to the order of folding of protein residues, and we provide a potential justification for this observation based on steady-state cellular kinetics.

Pharmacological chaperones are small molecule drugs that bind to proteins to help stabilize the folded state. One set of diseases for which this treatment has been effective is the lysosomal storage disorders, which are caused by defective lysosomal enzymes. However, not all genotypes are equally responsive to treatment. For instance, missense mutants that are particularly destabilized relative to WT are less likely to respond. The availability of datasets containing responsiveness data for large numbers of mutants, along with crystal structures of the protein involved in each disease, make machine learning methods incorporating sequence-based and structural data feasible. We hypothesize that data from two diseases, Fabry and Pompe disease, may be useful for predicting responsiveness of variants in the related Gaucher disease. Results suggest that many rare variants in Gaucher disease could be amenable to existing drugs. Results also suggest that drug responsiveness depends on protein topology in such a way that mutations in early-to-fold residues are more likely to be non-responsive to pharmacological chaperone treatment, which is consistent with a simple kinetic model of stability rescue. This study provides an example of how machine learning can be used to inform further studies towards personalized treatment in medicine.

Gaucher disease type 1: the first experience of enzyme replacement therapy in pediatric practice in Moldova - case report

We report on a case of a little girl patient diagnosed with Gaucher disease (GD) type 1 in her early childhood and our first experience with enzyme replacement therapy (ERT). She was first diagnosed accidentally with enlarged spleen during a pediatric examination when she was three years old, but the family ignored investigations; she was hospitalized for diagnosis at six years old. The GD was confirmed based on: clinical manifestations of left abdominal flank pain, multiple bruising, general weakness, bone pain, low appetite, failure to thrive <5^th percentile, minor hepato- and severe splenomegaly, enlarged submaxillary lymph nodes, associated by anemia with normal platelets; low activity of beta-Glucosidase, two found mutations in GBA gene, Gaucher cells in bone marrow. The ERT was initiated with Imiglucerase (54 UI/kg/2 wks) two years later after diagnosis, avoiding the splenectomy. Subsequently, the platelets showed the first a promising result, gradually increasing their number every 2 weeks and maintaining it in good parameters till the reported moment (2.5 yrs from the start). The hemoglobin level was appreciated within normal ranges 3 months after ERT start and stabilized completely after 6 months. On the other hand, the red blood count normalized within 20 months of applied therapy. The Lyso-GL-1 decreased by 30% after three months of therapy, no antibodies to Imiglucerase were found. The initial spleen volume (1178.19 cm³) decreased by almost 60% in 6 months of ERT, reaching absolutely normal dimensions after 9 months. The ERT with Imiglucerase was tolerated very well by the patient, showing a clear improvement of clinical symptoms after 4-6 months of therapy, hematological picture and splenomegaly solving. Even if the little patient had to come every 2 weeks for infusion, her quality of life improved a lot, being a totally happy child, going to school and having friends. The ERT should be initiated immediately after diagnosis to prevent the multisystem complications.

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.

Recapture Lysosomal Enzyme Deficiency via Targeted Gene Disruption in the Human Near-Haploid Cell Line HAP1

BACKGROUND

Advancement in genome engineering enables rapid and targeted disruption of any coding sequences to study gene functions or establish human disease models. We explored whether this approach can be used to study Gaucher disease, one of the most common types of lysosomal storage diseases (LSDs) in a near-haploid human cell line (HAP1).

RESULTS

CRISPR-Cas9 targeting to coding sequences of β-glucocerebrosidase (GBA), the causative gene of Gaucher disease, resulted in an insertional mutation and premature termination of GBA. We confirmed the GBA knockout at both the gene and enzyme levels by genotyping and GBA enzymatic assay. Characterization of the knockout line showed no significant changes in cell morphology and growth. Lysosomal staining revealed more granular lysosomes in the cytosol of the GBA-knockout line compared to its parental control. Flow cytometry analysis further confirmed that more lysosomes accumulated in the cytosol of the knockout line, recapturing the disease phenotype. Finally, we showed that this knockout cell line could be used to evaluate a replacement therapy by recombinant human GBA.

CONCLUSIONS

Targeted gene disruption in human HAP1 cells enables rapid establishment of the Gaucher model to capture the key pathology and to test replacement therapy. We expect that this streamlined method can be used to generate human disease models of other LSDs, most of which are still lacking both appropriate human disease models and specific treatments to date.

The Genetics of Parkinson's Disease and Implications for Clinical Practice

The genetic landscape of Parkinson’s disease (PD) is characterised by rare high penetrance pathogenic variants causing familial disease, genetic risk factor variants driving PD risk in a significant minority in PD cases and high frequency, low penetrance variants, which contribute a small increase of the risk of developing sporadic PD. This knowledge has the potential to have a major impact in the clinical care of people with PD. We summarise these genetic influences and discuss the implications for therapeutics and clinical trial design.

Ceramide Metabolism and Parkinson's Disease-Therapeutic Targets

Ceramide is a bioactive sphingolipid involved in numerous cellular processes. In addition to being the precursor of complex sphingolipids, ceramides can act as second messengers, especially when they are generated at the plasma membrane of cells. Its metabolic dysfunction may lead to or be a consequence of an underlying disease. Recent reports on transcriptomics and electrospray ionization mass spectrometry analysis have demonstrated the variation of specific levels of sphingolipids and enzymes involved in their metabolism in different neurodegenerative diseases. In the present review, we highlight the most relevant discoveries related to ceramide and neurodegeneration, with a special focus on Parkinson's disease.

Exploring the Genotype-Phenotype Correlation in GBA-Parkinson Disease: Clinical Aspects, Biomarkers, and Potential Modifiers

Variants in the glucocerebrosidase (GBA) gene are the most common genetic risk factor for Parkinson disease (PD). These include pathogenic variants causing Gaucher disease (GD) (divided into “severe,” “mild,” or “complex”—resulting from recombinant alleles—based on the phenotypic effects in GD) and “risk” variants, which are not associated with GD but nevertheless confer increased risk of PD. As a group, GBA-PD patients have more severe motor and nonmotor symptoms, faster disease progression, and reduced survival compared with noncarriers. However, different GBA variants impact variably on clinical phenotype. In the heterozygous state, “complex” and “severe” variants are associated with a more aggressive and rapidly progressive disease. Conversely, “mild” and “risk” variants portend a more benign course. Homozygous or compound heterozygous carriers usually display severe phenotypes, akin to heterozygous “complex” or “severe” variants carriers. This article reviews genotype–phenotype correlations in GBA-PD, focusing on clinical and nonclinical aspects (neuroimaging and biochemical markers), and explores other disease modifiers that deserve consideration in the characterization of these patients.

Gaucher disease: Identification and novel variants in Mexican and Spanish patients

BACKGROUND

Gaucher disease (GD) is the most prevalent lysosomal storage disorder, affecting all ethnic groups, although its prevalence is higher in Ashkenazi Jewish populations. Three clinical forms of GD have been described: Type 1 non-neuronopathic, type 2 acute neuronopathic, and type 3 subacute neuronopathic. An autosomal recessive disorder is caused by variants in the human glucocerebrosidase gene (GBA; MIM*606463) located on chromosome 1q21, resulting from deficit or lack of activity of the β-glucocerebrosidase enzyme, leading to the accumulation of glucocerebroside substrate in the cells of the macrophage-monocyte system. The aim was to determine variants in Mexican and Spanish populations with GD.

METHODS

We report the molecular analysis by a direct automatic method sequenced of both chains of the GBA gene, in 69 Mexican and 369 Spanish patients with GD.

RESULTS

We detected 75 variants with pathogenic or likely pathogenic effect and, identified 3 new variants c.408_412del/p.Asn136Lysfs*15; c.820G>A/p.Glu274Lys and c.1058T>G/p*. The most frequent variants were c.1448T>C/p.Leu483Pro/L444P and c.1226A>G/p.Asn409Ser/N370S. The detected genotypes were compared with data from both GD registries to define similarities and differences in both populations.

CONCLUSIONS

We defined the variant profile in patients with GD in a Mexican and a Spanish population and compared them. The screening permitted the detection of common variants and the report of three new variants, in addition to a variant associated with Parkinson disease but not with GD. Since molecular diagnosis has considerable predictive value in GD, it is important to study the genotype-phenotype correlations, establishing the severity of the variant.

Neuronal autophagy and mitophagy in Parkinson's disease

Autophagy is the process by which cells can selectively or non-selectively remove damaged proteins and organelles. As the cell's main means of sequestering damaged mitochondria for removal, mitophagy is central to cellular function and survival. Research on autophagy and mitochondrial quality control has increased exponentially in relation to the pathogenesis of numerous disease conditions, from cancer and immune diseases to chronic neurodegenerative diseases like Parkinson's disease (PD). Understanding how components of the autophagic/mitophagic machinery are affected during disease, as well as the contextual relationship of autophagy with determining neuronal health and function, is essential to the goal of designing therapies for human disease. In this review, we will summarize key signaling molecules that consign damaged mitochondria for autophagic degradation, describe the relationship of genes linked to PD to autophagy/mitophagy dysfunction, and discuss additional roles of both mitochondrial and cytosolic pools of PTEN-induced kinase 1 (PINK1) in mitochondrial homeostasis, dendritic morphogenesis and inflammation.

Neurodegenerative Disease Risk in Carriers of Autosomal Recessive Disease

Genetics has driven significant discoveries in the field of neurodegenerative diseases (NDDs). An emerging theme in neurodegeneration warrants an urgent and comprehensive update: that carrier status of early-onset autosomal recessive (AR) disease, typically considered benign, is associated with an increased risk of a spectrum of late-onset NDDs. Glucosylceramidase beta (GBA1) gene mutations, responsible for the AR lysosomal storage disorder Gaucher disease, are a prominent example of this principle, having been identified as an important genetic risk factor for Parkinson disease. Genetic analyses have revealed further examples, notably GRN, TREM2, EIF2AK3, and several other LSD and mitochondria function genes. In this Review, we discuss the evidence supporting the strikingly distinct allele-dependent clinical phenotypes observed in carriers of such gene mutations and its impact on the wider field of neurodegeneration.

Metabolizing profile of the cytochrome pathway CYP2D6, CYP3A4 and the ABCB 1 transporter in Spanish patients affected by Gaucher disease

Several therapeutic options are available for type 1 Gaucher disease (GD1), including enzymatic replacement therapy (ERT) and substrate reduction therapy (SRT). Eliglustat is a selective inhibitor of glucosylceramide synthase that is extensively metabolized by CYP2D6 and, to a lesser extent by CYP3A4; it is also an inhibitor of the P-gp transporter. The aim of this study is to evaluate the metabolizer profile of these cytochrome isoforms in 61 GD1 patients, and to analyze interferences with concomitant therapies. Patients were selected from the Spanish Gaucher Disease Registry considering clinical data, GBA genotype, severity score index, comorbidities, concomitant drugs, type and response to therapy and adverse effects. The polymorphisms of CYP2D6, CYP3A4 and three ABCB1 transporter variants were analyzed by Polymerase Chain Reaction (PCR). The most frequent metabolizer profile was extensive or intermediate for CYP2D6, extensive for CYP3A4*1B and CYP3A4*22 and normal activity for ABCB1. Correlations between metabolizer profile and other variables were analyzed by multiple regression study. Twenty-eight patients received ERT, 17 eliglustat and seven miglustat. Forty-two patients (68.8%) had associated diseases and 54.5% were taking daily concomitant medication. Nine patients under eliglustat therapy received concomitant drugs that interact with the CYPs and/or ABCB1, five of these did not reach therapeutic goals and three presented mild or moderate adverse effects (headache and gastrointestinal disorders). Detailed analysis in four patients with TTT haplotype, corresponding to lack of activity of the transporter, was performed. In order to apply personalized medicine and avoid interferences and adverse effects, the individual CYP metabolizer profile and transporter must be considered when choosing the concomitant medication and/or making dose adjustments.

Elevated holo-transcobalamin in Gaucher disease type II: A case report

Gaucher disease (GD), one of the most common lysosomal disorders, is caused by deficiency of β-glucocerebrosidase. Based on the presence and severity of neurological complications, GD is classified into types I, II (the most severe form), and III. Abnormalities in systemic markers of vitamin B₁₂ (B₁₂ ) metabolism have been reported in GD type I patients, suggesting a higher prevalence of B₁₂ deficiency in these patients. A 2-month-old male with GD type II was admitted to the hospital presenting jaundice, hepatosplenomegaly, and ichthyosis. At admission, cholestasis and ascites, abnormal liver function enzymes, prolonged prothrombin time, and high levels of B₁₂ were confirmed. Analysis of biomarkers of B₁₂ status revealed elevated B₁₂ and holo-transcobalamin (holo-TC) levels. The B₁₂ profile found in our patient is the opposite to what is described for GD type I patients. Holo-TC may increase in inflammatory states or due to liver diseases. In GD, the accumulation of glucocerebroside may be a trigger that initiates a systemic inflammatory reaction, characterized by macrophage activation. We suggest higher levels of holo-TC could be associated with a more severe (neuronopathic) GD, and be a biomarker of GD type II.

Aberrant proteins expressed in skin fibroblasts of Parkinson's disease patients carrying heterozygous variants of glucocerebrosidase and parkin genes

Parkinson's disease (PD) is a neurodegenerative disorder that affects movement, and its development is associated with environmental and genetic factors. Genetic variants in GBA and PARK2 are important risk factors implicated in the development of PD; however, their precise roles have yet to be elucidated. The present study aimed to identify and analyse proteins from the skin fibroblasts of patients with PD carrying heterozygous GBA and PARK2 variants, and from healthy controls. Liquid chromatography coupled with tandem mass spectrometry and label-free quantitative proteomics were performed to identify and compare differential protein expression levels. Moreover, protein-protein interaction networks were assessed using Search Tool for Retrieval of Interacting Genes analysis. Using these proteomic approaches, 122 and 119 differentially expressed proteins from skin fibroblasts of patients with PD carrying heterozygous GBA and PARK2 variants, respectively, were identified and compared. According to the results of protein-protein interaction and Gene Ontology analyses, 14 proteins involved in the negative regulation of macromolecules and mRNA metabolic processes, and protein targeting to the membrane exhibited the largest degree of differential expression in the fibroblasts of patients with PD with a GBA variant, whereas 20 proteins involved in the regulation of biological quality, NAD metabolic process and cytoskeletal organization exhibited the largest degree of differential expression in the fibroblasts of patients with PD with a PARK2 variant. Among these, the expression levels of annexin A2 and tubulin β chain, were most strongly upregulated in the fibroblasts of patients with GBA-PD and PARK2-PD, respectively. Other predominantly expressed proteins were confirmed by western blotting, and the results were consistent with those of the quantitative proteomic analysis. Collectively, the results of the present study demonstrated that the proteomic patterns of fibroblasts of patients with PD carrying heterozygous GBA and PARK2 variants are different and unique. Aberrant expression of the proteins affected by these variants may reflect physiological changes that also occur in neurons, resulting in PD development and progression.

Parkinson's Disease Associated with GBA Gene Mutations: Molecular Aspects and Potential Treatment Approaches

Parkinson's disease (PD) is a multifactorial neurodegenerative disease. To date, genome-wide association studies have identified more than 70 loci associated with the risk of PD. Variants in the GBA gene encoding glucocerebrosidase are quite often found in PD patients in all populations across the world, which justifies intensive investigation of this gene. A number of biochemical features have been identified in patients with GBA-associated Parkinson's disease (GBA-PD). In particular, these include decreased activity of glucocerebrosidase and accumulation of the glucosylceramide substrate. These features were the basis for putting forward a hypothesis about treatment of GBA-PD using new strategies aimed at restoring glucocerebrosidase activity and reducing the substrate concentration. This paper discusses the molecular and genetic mechanisms of GBA-PD pathogenesis and potential approaches to the treatment of this form of the disease.

The Uncovered Function of the Drosophila GBA1a-Encoded Protein

Human GBA1 encodes lysosomal acid β-glucocerebrosidase (GCase), which hydrolyzes cleavage of the beta-glucosidic linkage of glucosylceramide (GlcCer). Mutations in this gene lead to reduced GCase activity, accumulation of glucosylceramide and glucosylsphingosine, and development of Gaucher disease (GD). Drosophila melanogaster has two GBA1 orthologs. Thus far, GBA1b was documented as a bone fide GCase-encoding gene, while the role of GBA1a encoded protein remained unclear. In the present study, we characterized a mutant variant of the fly GBA1a, which underwent ERAD and mildly activated the UPR machinery. RNA-seq analyses of homozygous mutant flies revealed upregulation of inflammation-associated as well as of cell-cycle related genes and reduction in programmed cell death (PCD)-associated genes, which was confirmed by qRT-PCR. We also observed compromised cell death in the midgut of homozygous larvae and a reduction in pupation. Our results strongly indicated that GBA1a-encoded protein plays a role in midgut maturation during larvae development.

A randomized single and multiple ascending dose study in healthy volunteers of LTI-291, a centrally penetrant glucocerebrosidase activator

AIMS

A mutation in the GBA1 gene is the most common genetic risk factor for developing Parkinson's disease. GBA1 encodes the lysosomal enzyme glucosylceramidase beta (glucocerebrosidase, GCase) and mutations decrease enzyme activity. LTI-291 is an allosteric modulator of GCase, enhancing its activity. These first-in-human studies evaluated the safety, tolerability, pharmacokinetics and pharmacodynamics of single and multiple ascending doses of LTI-291 in healthy volunteers.

METHODS

In the single ascending dose (SAD) study, 40 healthy volunteers were randomly assigned to LTI-291 (n = 8 per dose level) or placebo (n = 2 per dose level). Single doses of 3, 10, 30 and 90 mg LTI-291 were investigated. In the multiple ascending dose (MAD) study, 40 healthy middle-aged or elderly volunteers were randomly assigned to LTI-291 (n = 8 per dose level) or placebo (n = 2 per dose level). Fourteen consecutive daily doses of 3, 10, 30 and 60 mg LTI-291 or placebo were administered. In both the SAD and MAD studies, glycosphingolipid levels were measured and a test battery of neurocognitive tasks was performed.

RESULTS

LTI-291 was generally well tolerated and no deaths or treatment-related SAEs occurred and no subject withdrew from a study due to AEs. C_max , AUC_0-24 and AUC_0-inf increased in a dose proportional manner. The median half-life was 28.0 hours after multiple dosing. No dose-dependent glycosphingolipid changes occurred. No neurocognitive adverse effects were detected.

CONCLUSIONS

These first-in-human studies demonstrated that LTI-291 was well tolerated when given orally once daily for 14 consecutive days. This supports the continued clinical development and the exploration of LTI-291 effects in a GBA1-mutated Parkinson population.

Structure, metabolism and biological functions of steryl glycosides in mammals

Steryl glycosides (SGs) are sterols glycosylated at their 3β-hydroxy group. They are widely distributed in plants, algae, and fungi, but are relatively rare in bacteria and animals. Glycosylation of sterols, resulting in important components of the cell membrane SGs, alters their biophysical properties and confers resistance against stress by freezing or heat shock to cells. Besides, many biological functions in animals have been suggested from the observations of SG administration. Recently, cholesteryl glucosides synthesized via the transglycosidation by glucocerebrosidases (GBAs) were found in the central nervous system of animals. Identification of patients with congenital mutations in GBA genes or availability of respective animal models will enable investigation of the function of such endogenously synthesized cholesteryl glycosides by genetic approaches. In addition, mechanisms of the host immune responses against pathogenic bacterial SGs have partially been resolved. This review is focused on the biological functions of SGs in mammals taking into consideration their therapeutic applications in the future.

Screening for Gaucher Disease Using Dried Blood Spot Tests: A Japanese Multicenter, Cross-sectional Survey

Objective For patients with Gaucher disease (GD), a rare, inherited lysosomal storage disease, obtaining a definitive diagnosis is currently time-consuming and costly. A simplified screening method to measure the glucocerebrosidase (GBA) activity using dried blood spots (DBS) on filter paper has recently been developed. Using this newly developed screening method, we evaluated real-world GD screening in patients suspected of having GD. Methods This multicenter, cross-sectional, observational study with a diagnostic intervention component evaluated real-world screening in patients suspected of having GD based on their clinical symptoms and a platelet count <120,000/μL. The endpoint was the number of patients with low GBA activity determined using DBS. Results In 994 patients who underwent initial DBS screening, 77 had low GBA activity. The assay was not repeated in 1 patient who was diagnosed as having a high possibility of GD due to clinical symptoms, and a further 21 patients completed the study without undergoing the second assay. Of the remaining 55 patients who had 2 DBS assays performed, 11 had a low GBA activity in both assays. Overall, DBS screening identified 12 (1.2%) patients with a low GBA activity, a proportion consistent with prior screening studies. Conclusion These results suggest that the simplified DBS method was less burdensome to patients, was easily utilized by many physicians, and could be a useful first-tier screening assay for GD prior to initiating burdensome genetic testing.

Novel β-Glucocerebrosidase Activators That Bind to a New Pocket at a Dimer Interface and Induce Dimerization

Genetic, preclinical and clinical data link Parkinson's disease and Gaucher's disease and provide a rational entry point to disease modification therapy via enhancement of β-Glucocerebrosidase (GCase) activity. We discovered a new class of pyrrolo[2,3-b]pyrazine activators effecting both Vmax and Km. They bind to human GCase and increase substrate metabolism in the lysosome in a cellular assay. We obtained the first crystal structure for an activator and identified a novel non-inhibitory binding mode at the interface of a dimer, rationalizing the observed structure-activity relationship (SAR). The compound binds GCase inducing formation of a dimeric state at both endoplasmic reticulum (ER) and lysosomal pHs, as confirmed by analytical ultracentrifugation. Importantly, the pyrrolo[2,3-b]pyrazines have central nervous system (CNS) drug-like properties. Our findings are important for future drug discovery efforts in the field of GCase activation and provide a deeper mechanistic understanding of the requirements for enzymatic activation, pointing to the relevance of dimerization.

Cytokines and Gaucher Biomarkers in Glucocerebrosidase Carriers with and Without Parkinson Disease

BACKGROUND

Homozygous and compound heterozygous variants in glucocerebrosidase (GBA) can cause Gaucher disease (GD), whereas heterozygous variants increase the risk of developing Parkinson's disease (PD). GD patients display altered peripheral immune proteins. However, it is unknown if these are altered in GBA carriers with PD.

OBJECTIVES

To determine whether plasma cytokines and immune biomarkers associated with GD are also altered in GBA carriers with or without PD.

METHODS

Inflammatory cytokines and established GD biomarkers, ferritin, CD162, CCL18, and chitotriosidase (28 biomarkers) were measured in GBA pathogenic variant carriers with (n = 135) and without (n = 83) PD, and non-carriers with (n = 75) and without PD (n = 77).

RESULTS

PD patients with biallelic pathogenic variants in GBA had elevated plasma levels of ferritin, CCL18, and MIP1α. These biomarkers were not elevated in heterozygous GBA carriers.

CONCLUSION

GD plasma biomarkers are not promising candidates for stratifying the risk for PD in carriers of heterozygous GBA pathogenic variants. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Gaucher earlier diagnosis consensus point-scoring system (GED-C PSS): Evaluation of a prototype in Finnish Gaucher disease patients and feasibility of screening retrospective electronic health record data for the recognition of potential undiagnosed patients in Finland

Background

Gaucher disease (GD) is a rare inherited multiorgan disorder, yet a diagnosis can be significantly delayed due to a broad spectrum of symptoms and lack of disease awareness. Recently, the prototype of a GD point-scoring system (PSS) was established by the Gaucher Earlier Diagnosis Consensus (GED-C) initiative, and more recently, validated in Gaucher patients in UK. In our study, the original GED-C PSS was tested in Finnish GD patients. Furthermore, the feasibility of point scoring large electronic health record (EHR) data set by data mining to identify potential undiagnosed GD cases was evaluated.

Methods

This biobank study was conducted in collaboration with two Finnish biobanks. Five previously diagnosed Finnish GD patients and ~ 170,000 adult biobank subjects were included in the study. The original PSS was locally adjusted due to data availability issues and applied to the Finnish EHR data representing special health care recordings.

Results

All GD patients had high levels of the biomarker lyso-Gb1 and deleterious GBA mutations. One patient was a compound heterozygote with a novel variant, potentially pathogenic mutation. Finnish EHR data allowed the retrospective assessment of 27–30 of the 32 original GED-C signs/co-variables. Total point scores of GD patients were high but variable, 6–18.5 points per patient (based on the available data on 28–29 signs/co-variables per patient). All GD patients had been recorded with anaemia while only three patients had a record of splenomegaly. 0.72% of biobank subjects were assigned at least 6 points but none of these potential “GD suspects” had a point score as high as 18.5. Splenomegaly had been recorded for 0.25% of biobank subjects and was associated with variable point score distribution and co-occurring ICD-10 diagnoses.

Discussion

This study provides an indicative GED-C PSS score range for confirmed GD patients, also representing potential mild cases, and demonstrates the feasibility of scoring Finnish EHR data by data mining in order to screen for undiagnosed GD patients. Further prioritisation of the “GD suspects” with more developed algorithms and data-mining approaches is needed.

Funding

This study was funded by Shire (now part of Takeda).

c-Abl activates RIPK3 signaling in Gaucher disease

Gaucher disease (GD) is caused by homozygous mutations in the GBA1 gene, which encodes the lysosomal β-glucosidase (GBA) enzyme. GD affects several organs and tissues, including the brain in certain variants of the disease. Heterozygous GBA1 variants are a major genetic risk factor for developing Parkinson's disease. The RIPK3 kinase is relevant in GD and its deficiency improves the neurological and visceral symptoms in a murine GD model. RIPK3 mediates necroptotic-like cell death: it is unknown whether the role of RIPK3 in GD is the direct induction of necroptosis or if it has a more indirect function by mediating necrosis-independent. Also, the mechanisms that activate RIPK3 in GD are currently unknown. In this study, we show that c-Abl tyrosine kinase participates upstream of RIPK3 in GD. We found that the active, phosphorylated form of c-Abl is increased in several GD models, including patient's fibroblasts and GBA null mice. Furthermore, its pharmacological inhibition with the FDA-approved drug Imatinib decreased RIPK3 signaling. We found that c-Abl interacts with RIPK3, that RIPK3 is phosphorylated at a tyrosine site, and that this phosphorylation is reduced when c-Abl is inhibited. Genetic ablation of c-Abl in neuronal GD and GD mice models significantly reduced RIPK3 activation and MLKL downstream signaling. These results showed that c-Abl signaling is a new upstream pathway that activates RIPK3 and that its inhibition is an attractive therapeutic approach for the treatment of GD.

Successful treatment of Gaucher disease type 1 by enzyme replacement therapy over a 10-year duration in a Japanese pediatric patient: A case report

The prevalence of Gaucher disease (GD) in Japan is much lower than that in Western countries; therefore, data on Japanese pediatric patients with GD type 1 are currently limited. The present study reports on the case of a Japanese pediatric patient with GD type 1 who was diagnosed when she presented with hepatosplenomegaly, thrombocytopenia and slight anemia at the age of 2 years. Serology tests revealed high levels of acid phosphatase (ACP) and angiotensin-converting enzyme (ACE). A bone marrow biopsy revealed the presence of Gaucher cells. Abdominal MRI indicated huge hepatosplenomegaly. Erlenmeyer flask deformity was observed on X-ray examination. MRI of the femora featured a high-intensity area within the diaphysis region. The enzymatic activity of leukocyte β-glucosidase, the measurement of which is necessary for a definitive diagnosis of GD, had decreased to 186.7 nmol/h/mg (reference range, 1,424.0-2,338.0 nmol/h/mg). Based on these results, the patient was clinically diagnosed with GD. Glucocerebrosidase gene analysis identified the compound heterozygote mutation of F213I (c.754T>A) on exon 7 and L444P (c.1448T>C) on exon 11. Enzyme replacement therapy (ERT) along with an intravenous infusion of 60 U/kg of imiglucerase every other week was initiated following diagnosis. Hemoglobin levels and the platelet count gradually improved and normalized after two years. ACP and ACE levels, biomarkers of the progression of GD, also improved. Abdominal MRI at six months after the initiation of ERT revealed a decrease in the size of the liver and spleen, which normalized after 1 year. Conversely, MRI of the femora indicated no improvement in the high-intensity area within the diaphysis region for 10 years.

Cross-talks among GBA mutations, glucocerebrosidase, and α-synuclein in GBA-associated Parkinson's disease and their targeted therapeutic approaches: a comprehensive review

Current therapies for Parkinson's disease (PD) are palliative, of which the levodopa/carbidopa therapy remains the primary choice but is unable to modulate the progression of neurodegeneration. Due to the complication of such a multifactorial disorder and significant limitations of the therapy, numerous genetic approaches have been proved effective in finding out genes and mechanisms implicated in this disease. Following the observation of a higher frequency of PD in Gaucher's disease (GD), a lysosomal storage condition, mutations of glycosylceramidase beta (GBA) encoding glucocerebrosidase (GCase) have been shown to be involved and have been explored in the context of PD. GBA mutations are the most common genetic risk factor of PD. Various studies have revealed the relationships between PD and GBA gene mutations, facilitating a better understanding of this disorder. Various hypotheses delineate that the pathological mutations of GBA minimize the enzymatic activity of GCase, which affects the proliferation and clearance of α-synuclein; this affects the lysosomal homeostasis, exacerbating the endoplasmic reticulum stress or encouraging the mitochondrial dysfunction. Identification of the pathological mechanisms underlying the GBA-associated parkinsonism (GBA + PD) advances our understanding of PD. This review based on current literature aims to elucidate various genetic and clinical characteristics correlated with GBA mutations and to identify the numerous pathological processes underlying GBA + PD. We also delineate the therapeutic strategies to interfere with the mutant GCase function for further improvement of the related α-synuclein-GCase crosstalks. Moreover, the various therapeutic approaches such as gene therapy, chaperone proteins, and histone deacetylase inhibitors for the treatment of GBA + PD are discussed.

Cross-talks among GBA mutations, glucocerebrosidase, and α-synuclein in GBA-associated Parkinson’s disease and their targeted therapeutic approaches: a comprehensive review

Current therapies for Parkinson’s disease (PD) are palliative, of which the levodopa/carbidopa therapy remains the primary choice but is unable to modulate the progression of neurodegeneration. Due to the complication of such a multifactorial disorder and significant limitations of the therapy, numerous genetic approaches have been proved effective in finding out genes and mechanisms implicated in this disease. Following the observation of a higher frequency of PD in Gaucher’s disease (GD), a lysosomal storage condition, mutations of glycosylceramidase beta (GBA) encoding glucocerebrosidase (GCase) have been shown to be involved and have been explored in the context of PD. GBA mutations are the most common genetic risk factor of PD. Various studies have revealed the relationships between PD and GBA gene mutations, facilitating a better understanding of this disorder. Various hypotheses delineate that the pathological mutations of GBA minimize the enzymatic activity of GCase, which affects the proliferation and clearance of α-synuclein; this affects the lysosomal homeostasis, exacerbating the endoplasmic reticulum stress or encouraging the mitochondrial dysfunction. Identification of the pathological mechanisms underlying the GBA-associated parkinsonism (GBA + PD) advances our understanding of PD. This review based on current literature aims to elucidate various genetic and clinical characteristics correlated with GBA mutations and to identify the numerous pathological processes underlying GBA + PD. We also delineate the therapeutic strategies to interfere with the mutant GCase function for further improvement of the related α-synuclein–GCase crosstalks. Moreover, the various therapeutic approaches such as gene therapy, chaperone proteins, and histone deacetylase inhibitors for the treatment of GBA + PD are discussed.

False negatives in GBA1 sequencing due to polymerase dependent allelic imbalance

A variant in the GBA1 gene is one of the most common genetic risk factors to develop Parkinson’s disease (PD). Here the serendipitous finding is reported of a polymerase dependent allelic imbalance when using next generation sequencing, potentially resulting in false-negative results when the allele frequency falls below the variant calling threshold (by default commonly at 30%). The full GBA1 gene was sequenced using next generation sequencing on saliva derived DNA from PD patients. Four polymerase chain reaction conditions were varied in twelve samples, to investigate the effect on allelic imbalance: (1) the primers (n = 4); (2) the polymerase enzymes (n = 2); (3) the primer annealing temperature (T_a) specified for the used polymerase; and (4) the amount of DNA input. Initially, 1295 samples were sequenced using Q5 High-Fidelity DNA Polymerase. 112 samples (8.6%) had an exonic variant and an additional 104 samples (8.0%) had an exonic variant that did not pass the variant frequency calling threshold of 30%. After changing the polymerase to TaKaRa LA Taq DNA Polymerase Hot-Start Version: RR042B, all samples had an allele frequency passing the calling threshold. Allele frequency was unaffected by a change in primer, annealing temperature or amount of DNA input. Sequencing of the GBA1 gene using next generation sequencing might be susceptible to a polymerase specific allelic imbalance, which can result in a large amount of flase-negative results. This was resolved in our case by changing the polymerase. Regions displaying low variant calling frequencies in GBA1 sequencing output in previous and future studies might warrant additional scrutiny.

Genes causing congenital hydrocephalus: Their chromosomal characteristics of telomere proximity and DNA compositions

Congenital hydrocephalus (CH) is caused by genetic mutations, but whether factors impacting human genetic mutations are disease-specific remains elusive. Given two factors associated with high mutation rates, we reviewed how many disease-susceptible genes match with (i) proximity to telomeres or (ii) high adenine and thymine (A + T) content in human CH as compared to other disorders of the central nervous system (CNS). We extracted genomic information using a genome data viewer. Importantly, 98 of 108 genes causing CH satisfied (i) or (ii), resulting in >90% matching rate. However, such a high accordance no longer sustained as we checked two factors in Alzheimer's disease (AD) and/or familial Parkinson's disease (fPD), resulting in 84% and 59% matching, respectively. A disease-specific matching of telomere proximity or high A + T content predicts causative genes of CH much better than neurodegenerative diseases and other CNS conditions, likely due to sufficient number of known causative genes (n = 108) and precise determination and classification of the genotype and phenotype. Our analysis suggests a need for identifying genetic basis of both factors before human clinical studies, to prioritize putative genes found in preclinical models into the likely (meeting at least one) and more likely candidate (meeting both), which predisposes human genes to mutations.

Genetic characterization of the Albanian Gaucher disease patient population

Gaucher disease (GD) is a recessive metabolic disorder caused by a deficiency of the GBA gene-encoded enzyme β-glucocerebrosidase. We characterized a cohort of 36 Albanian GD patients, 31 with GD type 1 and 5 affected by GD types 2, 3, and an intermediate GD phenotype between type 2 and type 3. Of the 12 different GBA alleles that we detected, the most frequently observed was p.Asn409Ser, followed by p.[Asp448His;His294Gln]. The prevalence of the p.Leu483Pro allele was approximately 10-fold lower than reported in other populations. We identified a novel pathogenic missense variant (c.1129G>A; p.Ala377Thr). All five of our non-type 1 patients had genotypes consisting of the p.[Asp448His;His294Gln] allele in combination with another severe GBA allele. The median Lyso-Gb1 level of treated patients carrying the p.[Asp448His;His294Gln] and no p.Asn409Ser allele was significantly higher than that of treated individuals homozygous or compound heterozygous for the p.Asn409Ser allele. In conclusion, the most important distinguishing features of the Albanian GD patient population are the underrepresentation of the p.Leu483Pro allele and an unusually high number of p.[Asp448His;His294Gln] alleles originating from a common Balkan founder event. The presence of at least one p.Asn409Ser allele is associated with mild disease and low Lyso-Gb1 biomarker levels, while compound heterozygosity involving p.[Asp448His;His294Gln] and no p.Asn409Ser entails severe phenotypes and high Lyso-Gb1 levels.

Lysosomal storage disorders: Novel and frequent pathogenic variants in a large cohort of Indian patients of Pompe, Fabry, Gaucher and Hurler disease

OBJECTIVES

Diagnosis of lysosomal storage disorders (LSDs) remains challenging due to wide clinical, biochemical and molecular heterogeneity. The study applies a combined biochemical and genetic approach to diagnose symptomatic Indian patients of Pompe, Fabry, Gaucher and Hurler disease to generate a comprehensive dataset of pathogenic variants for these disorders.

DESIGN & METHODS

Symptomatic patients were biochemically diagnosed by fluorometric methods and molecular confirmation was carried out by gene sequencing. Genetic variants were analyzed according to the ACMG/AMP 2015 variant interpretation guidelines.

RESULTS

Amongst the 2181 suspected patients, 285 (13%) were biochemically diagnosed. Of these, 22.5% (64/285) diagnosed with Pompe disease harboured c.1933G>A, c.1A>G, c.1927G>A and c.2783G>C as common and 10 novel pathogenic variants while 7.4% (21/285) patients diagnosed with Fabry disease carried c.851T>C, c.902G>A, c.905A>C and c.1212_1234del as frequent disease-causing variants along with 7 novel pathogenic variants. As many as 48.4% (138/285) patients were diagnosed with Gaucher disease and had c.1448T>C as the most common pathogenic variant followed by c.1342G>C and c.754T>C with 7 previously unreported disease-causing variants and in the 21.7% (62/285) diagnosed cases of Hurler disease, c.1469T>C, c.754delC c.568_581del and c.1898C>T were identified as the most common causative variants along with 21 novel pathogenic variants.

CONCLUSION

This comprehensive data set of disease-causing frequent and novel pathogenic variants reported for the first time in such a large patient cohort for each of these four LSDs from the Indian sub-continent, along with their biochemical and clinical spectrum will contribute towards providing definitive diagnosis and treatment, identifying carrier status, as well as in counselling prenatal cases to reduce the morbidity and mortality associated with these disorders.

Fabry Disease With Concomitant Lewy Body Disease

Although Gaucher disease can be accompanied by Lewy pathology (LP) and extrapyramidal symptoms, it is unknown if LP exists in Fabry disease (FD), another progressive multisystem lysosomal storage disorder. We aimed to elucidate the distribution patterns of FD-related inclusions and LP in the brain of a 58-year-old cognitively unimpaired male FD patient suffering from predominant hypokinesia. Immunohistochemistry (CD77, α-synuclein, collagen IV) and neuropathological staging were performed on 100-µm sections. Tissue from the enteric or peripheral nervous system was unavailable. As controls, a second cognitively unimpaired 50-year-old male FD patient without LP or motor symptoms and 3 age-matched individuals were examined. Inclusion body pathology was semiquantitatively evaluated. Although Lewy neurites/bodies were not present in the 50-year-old individual or in controls, severe neuronal loss in the substantia nigra pars compacta and LP corresponding to neuropathological stage 4 of Parkinson disease was seen in the 58-year-old FD patient. Major cerebrovascular lesions and/or additional pathologies were absent in this individual. We conclude that Lewy body disease with parkinsonism can occur within the context of FD. Further studies determining the frequencies of both inclusion pathologies in large autopsy-controlled FD cohorts could help clarify the implications of both lesions for disease pathogenesis, potential spreading mechanisms, and therapeutic interventions.

Fronto-temporal dementia risk gene TMEM106B has opposing effects in different lysosomal storage disorders

TMEM106B is a transmembrane protein localized to the endo-lysosomal compartment. Genome-wide association studies have identified TMEM106B as a risk modifier of Alzheimer's disease and frontotemporal lobar degeneration, especially with progranulin haploinsufficiency. We recently demonstrated that TMEM106B loss rescues progranulin null mouse phenotypes including lysosomal enzyme dysregulation, neurodegeneration and behavioural alterations. However, the reason whether TMEM106B is involved in other neurodegenerative lysosomal diseases is unknown. Here, we evaluate the potential role of TMEM106B in modifying the progression of lysosomal storage disorders using progranulin-independent models of Gaucher disease and neuronal ceroid lipofuscinosis. To study Gaucher disease, we employ a pharmacological approach using the inhibitor conduritol B epoxide in wild-type and hypomorphic Tmem106b-/- mice. TMEM106B depletion ameliorates neuronal degeneration and some behavioural abnormalities in the pharmacological model of Gaucher disease, similar to its effect on certain progranulin null phenotypes. In order to examine the role of TMEM106B in neuronal ceroid lipofuscinosis, we crossbred Tmem106b-/- mice with Ppt1-/-, a genetic model of the disease. In contrast to its conduritol B epoxide-rescuing effect, TMEM106B loss exacerbates Purkinje cell degeneration and motor deficits in Ppt1-/- mice. Mechanistically, TMEM106B is known to interact with subunits of the vacuolar ATPase and influence lysosomal acidification. In the pharmacological Gaucher disease model, the acidified lysosomal compartment is enhanced and TMEM106B loss rescues in vivo phenotypes. In contrast, gene-edited neuronal loss of Ppt1 causes a reduction in vacuolar ATPase levels and impairment of the acidified lysosomal compartment, and TMEM106B deletion exacerbates the mouse Ppt1-/- phenotype. Our findings indicate that TMEM106B differentially modulates the progression of the lysosomal storage disorders Gaucher disease and neuronal ceroid lipofuscinosis. The effect of TMEM106B in neurodegeneration varies depending on vacuolar ATPase state and modulation of lysosomal pH. These data suggest TMEM106B as a target for correcting lysosomal pH alterations, and in particular for therapeutic intervention in Gaucher disease and neuronal ceroid lipofuscinosis.

The GBA p.G85E mutation in Korean patients with non-neuronopathic Gaucher disease: founder and neuroprotective effects

Background

Gaucher disease (GD) is caused by a deficiency of β-glucocerebrosidase, encoded by GBA. Haplotype analyses previously demonstrated founder effects for particular GBA mutations in Ashkenazi Jewish and French-Canadian populations. This study aimed to investigate the clinical characteristics and mutation spectrum of GBA in Korean GD patients and to identify founder effect of GBA p.G85E in non-neuronopathic GD patients.

Results

The study cohort included 62 GD patients from 58 unrelated families. Among them, 18 patients from 17 families harbored the p.G85E mutation. Haplotype analysis was performed for 9 probands and their parents for whom DNA samples were available. In 58 unrelated probands, the GBA mutation p.L483P was the most common (30/116 alleles, 26%), followed by p.G85E (16%), p.F252I (13%), and p.R296Q (9%). The median age at diagnosis of the 18 patients harboring the p.G85E mutation was 3.8 (range 1.2–57) years. No patients developed neurological symptoms during follow-up periods of 2.2–20.3 (median 13.9) years. The size of the shared haplotype containing GBA p.G85E was 732 kbp, leading to an estimated age of 3075 years.

Conclusion

The GBA p.G85E mutation, which appears to be neuroprotective despite producing distinctive visceromegaly and skeletal symptoms, exhibited a potential founder effect in Korean GD patients.

Neurodegeneration and Inflammation-An Interesting Interplay in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder, caused by, so far, unknown pathogenetic mechanisms. There is no doubt that pro-inflammatory immune-mediated mechanisms are pivotal to the pathogenicity and progression of the disease. In this review, we highlight the binary role of microglia activation in the pathophysiology of the disorder, both neuroprotective and neuromodulatory. We present how the expression of several cytokines implicated in dopaminergic neurons (DA) degeneration could be used as biomarkers for PD. Viral infections have been studied and correlated to the disease progression, usually operating as trigger factors for the inflammatory process. The gut-brain axis and the possible contribution of the peripheral bowel inflammation to neuronal death, mainly dopaminergic neurons, seems to be a main contributor of brain neuroinflammation. The role of the immune system has also been analyzed implicating a-synuclein in the activation of innate and adaptive immunity. We also discuss therapeutic approaches concerning PD and neuroinflammation, which have been studied in experimental and in vitro models and data stemming from epidemiological studies.

Trends in Glucocerebrosides Research: A Systematic Review

Glucocerebrosides are sphingolipid components of cell membranes that intervene in numerous cell biological processes and signaling pathways and that deregulation is implicated in human diseases such as Gaucher disease and Parkinson's disease. In the present study, we conducted a systematic review using document co-citation analysis, clustering and visualization tools to explore the trends and knowledge structure of glucocerebrosides research as indexed in the Science Citation Index Expanded database (1956-present). A co-citation network of 5,324 publications related to glucocerebrosides was constructed. The analysis of emerging categories and keywords suggested a growth of research related to neurosciences over the last decade. We identified ten major areas of research (e.g., clusters) that developed over time, from the oldest (i.e., on glucocerebrosidase protein or molecular analysis of the GBA gene) to the most recent ones (i.e., on drug resistance in cancer, pharmacological chaperones, or Parkinson's disease). We provided for each cluster the most cited publications and a description of their intellectual content. We moreover identified emerging trends in glucocerebrosides research by detecting the surges in the rate of publication citations in the most recent years. In conclusion, this study helps to apprehend the most significant lines of research on glucocerebrosides. This should strengthen the connections between scientific communities studying glycosphingolipids to facilitate advances, especially for the most recent researches on cancer drug resistance and Parkinson's disease.

Diffuse large B-cell non-Hodgkin's lymphoma in Gaucher disease

Gaucher disease type 1 (GD1) is the most common lysosomal storage disease and affects nearly 1 in 40,000 live births. In addition, it is the most common genetic disorder in the Ashkenazi Jewish population with phenotypic variation presenting in early childhood to asymptomatic nonagenarians. There have been a number of studies showing an increased risk of certain malignancies in patients, especially non- Hodgkin's lymphoma (NHL) and multiple myeloma. We describe a 66-year-old Ashkenazi Jewish male with GD1 who was first started on enzyme replacement therapy (ERT) with imiglucerase for GD1 at age 57 years, followed a year later by the diagnosis of diffuse large b-cell non-Hodgkin's lymphoma (DLBCL). He was treated with R-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone, plus the monoclonal antibody rituximab), however relapsed and developed myelodysplasia necessitating an allo-stem-cell transplantation but succumbed to severe graft vs. host disease. In addition, we also describe a 38-year-old Ashkenazi Jewish male with GD1 who was diagnosed with DLBCL at age 22 years with Gaucher disease diagnosed on pre-treatment bone marrow biopsy which was confirmed by enzyme assay and genotyping. At age 24 years, he was started on ERT with imiglucerase and at age 35 years, he switched to eliglustat. He has remained in remission from the lymphoma. A meta-analysis of the literature will be elaborated upon and we will discuss the relationship of GD1 to NHL and discuss more recent information regarding lyso-GL1 and the development of NHL and multiple myeloma.

Glycosphingolipids and neuroinflammation in Parkinson's disease

Parkinson's disease is a progressive neurodegenerative disease characterized by the loss of dopaminergic neurons of the nigrostriatal pathway and the formation of neuronal inclusions known as Lewy bodies. Chronic neuroinflammation, another hallmark of the disease, is thought to play an important role in the neurodegenerative process. Glycosphingolipids are a well-defined subclass of lipids that regulate crucial aspects of the brain function and recently emerged as potent regulators of the inflammatory process. Deregulation in glycosphingolipid metabolism has been reported in Parkinson's disease. However, the interrelationship between glycosphingolipids and neuroinflammation in Parkinson's disease is not well known. This review provides a thorough overview of the links between glycosphingolipid metabolism and immune-mediated mechanisms involved in neuroinflammation in Parkinson's disease. After a brief presentation of the metabolism and function of glycosphingolipids in the brain, it summarizes the evidences supporting that glycosphingolipids (i.e. glucosylceramides or specific gangliosides) are deregulated in Parkinson's disease. Then, the implications of these deregulations for neuroinflammation, based on data from human inherited lysosomal glycosphingolipid storage disorders and gene-engineered animal studies are outlined. Finally, the key molecular mechanisms by which glycosphingolipids could control neuroinflammation in Parkinson's disease are highlighted. These include inflammasome activation and secretion of pro-inflammatory cytokines, altered calcium homeostasis, changes in the blood-brain barrier permeability, recruitment of peripheral immune cells or production of autoantibodies.

Precision medicine in Parkinson's disease patients with LRRK2 and GBA risk variants - Let's get even more personal

Parkinson's disease (PD) is characterized by motor deficits and a wide variety of non-motor symptoms. The age of onset, rate of disease progression and the precise profile of motor and non-motor symptoms display considerable individual variation. Neuropathologically, the loss of substantia nigra dopaminergic neurons is a key feature of PD. The vast majority of PD patients exhibit alpha-synuclein aggregates in several brain regions, but there is also great variability in the neuropathology between individuals. While the dopamine replacement therapies can reduce motor symptoms, current therapies do not modify the disease progression. Numerous clinical trials using a wide variety of approaches have failed to achieve disease modification. It has been suggested that the heterogeneity of PD is a major contributing factor to the failure of disease modification trials, and that it is unlikely that a single treatment will be effective in all patients. Precision medicine, using drugs designed to target the pathophysiology in a manner that is specific to each individual with PD, has been suggested as a way forward. PD patients can be stratified according to whether they carry one of the risk variants associated with elevated PD risk. In this review we assess current clinical trials targeting two enzymes, leucine-rich repeat kinase 2 (LRRK2) and glucocerebrosidase (GBA), which are encoded by two most common PD risk genes. Because the details of the pathogenic processes coupled to the different LRRK2 and GBA risk variants are not fully understood, we ask if these precision medicine-based intervention strategies will prove "precise" or "personalized" enough to modify the disease process in PD patients. We also consider at what phases of the disease that such strategies might be effective, in light of the genes being primarily associated with the risk of developing disease in the first place, and less clearly linked to the rate of disease progression. Finally, we critically evaluate the notion that therapies targeting LRRK2 and GBA might be relevant to a wider segment of PD patients, beyond those that actually carry risk variants of these genes.

Role of Genes and Treatments for Parkinson’s Disease

Parkinson’s Disease (PD) is a complex neurodegenerative disorder that mainly results due to the loss of dopaminergic neurons in the substantia nigra of the midbrain. It is well known that dopamine is synthesized in substantia nigra and is transported to the striatumvianigrostriatal tract. Besides the sporadic forms of PD, there are also familial cases of PD and number of genes (both autosomal dominant as well as recessive) are responsible for PD. There is no permanent cure for PD and to date, L-dopa therapy is considered to be the best option besides having dopamine agonists. In the present review, we have described the genes responsible for PD, the role of dopamine, and treatment strategies adopted for controlling the progression of PD in humans.

Emerging Targeted Therapeutics for Genetic Subtypes of Parkinsonism

In recent years, a precision medicine approach, which customizes medical treatments based on patients' individual profiles and incorporates variability in genes, the environment, and lifestyle, has transformed medical care in numerous medical fields, most notably oncology. Applying a similar approach to Parkinson's disease (PD) may promote the development of disease-modifying agents that could help slow progression or possibly even avert disease development in a subset of at-risk individuals. The urgent need for such trials partially stems from the negative results of clinical trials where interventions treat all PD patients as a single homogenous group. Here, we review the current obstacles towards the development of precision interventions in PD. We also review and discuss the clinical trials that target genetic forms of PD, i.e., GBA-associated and LRRK2-associated PD.