Exploring genetic modifiers of Gaucher disease: The next horizon

Challenges in Gaucher disease: Perspectives from an expert panel

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

Modeling bone marrow microenvironment and hematopoietic dysregulation in Gaucher disease through VavCre mediated Gba deletion

Biallelic mutations in Gba cause Gaucher disease (GD), a lysosomal disorder characterized by deficient glucocerebrosidase activity and the accumulation of glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph), primarily in macrophages. Beyond macrophages, GD pathology affects additional hematopoietic lineages, contributing to immune dysregulation. Existing Mx1-Cre Gba knockout models require induction protocols that lead to gene deletion outside hematopoietic cells, limiting the study of hematopoietic-specific effects. To overcome these limitations, we generated a hematopoietic-specific Gba knockout model by crossing Gbafl/fl mice with Vav-Cre, enabling early deletion of Gba exons 8-11 in hematopoietic stem and progenitor cells. These mice were backcrossed to 129X1/SvJ and C57BL/6 J backgrounds, revealing that genetic background significantly influences disease severity. Efficient Gba excision was confirmed in bone marrow, spleen, and thymus, with minimal recombination in the liver. In VavCre 129 GD mice, glucocerebrosidase activity in the spleen was severely reduced, leading to GlcCer and GlcSph accumulation and Gaucher cell infiltration in the spleen and femurs. Transcriptomic analysis identified upregulation of inflammatory and lysosomal pathways. Immune cell deconvolution from RNA-seq data further revealed an expansion of monocytes, dendritic cells, and pro-inflammatory macrophage subsets, suggesting an altered immune landscape. Additionally, GPNMB, a potential GD biomarker, was significantly elevated in both spleens and sera of VavCre 129 GD mice. This hematopoietic-specific GD model provides a powerful platform for studying GD pathophysiology, modifier genes, and immune dysregulation. It offers new opportunities for biomarker discovery and for developing strategies targeting hematopoietic and immune mechanisms in GD and related lysosomal storage disorders.

Evaluating the Molecular Interactions between Type 2 Diabetes Mellitus and Parkinson's Disease: Role of Antidiabetic Drugs as Promising Therapeutics

Evidence from previous research demonstrates a relationship between diabetes mellitus (DM) and Parkinson's disease (PD). T2DM is associated with chronic glucose dysregulation, as an etiological factor. It inhibits neuronal function through disrupted insulin signaling and oxidative stress, which ultimately lead to the loss of dopaminergic neurons in the substantia nigra (SN). Interactions between T2DM and PD were analyzed by gene expression, coexpression, and gene set enrichment via NCBI and STRING databases following pathways like KEGG and Reactome. The study identified nine key gene interactions through published literature on different databases and search engines that are involved in the progression of these chronic diseases. Furthermore, some genetic and nongenetic risk factors, gene mutations and environmental factors, are also involved in the progression of T2DM and PD. This review highlights the limitations of currently available drug treatments for these diseases and examines modern therapeutic approaches to address neurodegenerative and metabolic abnormalities. We critically assess the current experimental methodologies aimed at unraveling the pathophysiological mechanisms linking PD and T2DM while addressing the key challenges impeding a comprehensive understanding of the concurrent emergence of these debilitating age-related conditions.

Direct and indirect regulation of β-glucocerebrosidase by the transcription factors USF2 and ONECUT2

Mutations in GBA1 encoding the lysosomal enzyme β-glucocerebrosidase (GCase) are among the most prevalent genetic susceptibility factors for Parkinson's disease (PD), with 10-30% of carriers developing the disease. To identify genetic modifiers contributing to the incomplete penetrance, we examined the effect of 1634 human transcription factors (TFs) on GCase activity in lysates of an engineered human glioblastoma line homozygous for the pathogenic GBA1 L444P variant. Using an arrayed CRISPR activation library, we uncovered 11 TFs as regulators of GCase activity. Among these, activation of MITF and TFEC increased lysosomal GCase activity in live cells, while activation of ONECUT2 and USF2 decreased it. While MITF, TFEC, and USF2 affected GBA1 transcription, ONECUT2 might control GCase trafficking. The effects of MITF, TFEC, and USF2 on lysosomal GCase activity were reproducible in iPSC-derived neurons from PD patients. Our study provides a systematic approach to identifying modulators of GCase activity and deepens our understanding of the mechanisms regulating GCase.

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

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

Neuronopathic Gaucher disease: Rare in the West, common in the East

Gaucher disease (GD) stands as one of the most prevalent lysosomal disorders, yet neuronopathic GD (nGD) is an uncommon subset characterized by a wide array of clinical manifestations that complicate diagnosis, particularly when neurological symptoms are understated. nGD may manifest as the acute neuronopathic type, or GD type 2 (GD2), either prenatally or within the first weeks to months of life, whereas GD type 3 (GD3) symptoms may emerge at any point during childhood or occasionally in adolescence. The clinical presentation encompasses severe systemic involvement to mild visceral disease, often coupled with a spectrum of progressive neurological signs and symptoms such as cognitive impairment, ataxia, seizures, myoclonus, varying degrees of brainstem dysfunction presenting with stridor, apneic episodes, and/or impaired swallowing. This manuscript aims to provide a comprehensive review of the incidence, distinctive presentations, and diverse clinical phenotypes of nGD across various countries and regions. It will explore the natural history of the neurodegenerative process in GD, shedding light on its various manifestations during infancy and childhood, and offer insights into the diagnostic journey, the challenges faced in the clinical management, and current and investigative therapeutic approaches for GD's neurological variants.

Gaucher disease provides a unique window into Parkinson disease pathogenesis

An exciting development in the field of neurodegeneration is the association between the rare monogenic disorder Gaucher disease and the common complex disorder Parkinson disease (PD). Gaucher disease is a lysosomal storage disorder resulting from an inherited deficiency of the enzyme glucocerebrosidase, encoded by GBA1, which hydrolyses the glycosphingolipids glucosylceramide and glucosylsphingosine. The observation of parkinsonism in a rare subgroup of individuals with Gaucher disease first directed attention to the role of glucocerebrosidase deficiency in the pathogenesis of PD. PD occurs more frequently in people heterozygous for Gaucher GBA1 mutations, and 3-25% of people with Parkinson disease carry a GBA1 variant. However, only a small percentage of individuals with GBA1 variants develop parkinsonism, suggesting that the penetrance is low. Despite over a decade of intense research in this field, including clinical and radiological evaluations, genetic studies and investigations using model systems, the mechanism underlying GBA1-PD is still being pursued. Insights from this association have emphasized the role of lysosomal pathways in parkinsonism. Furthermore, different therapeutic strategies considered or developed for Gaucher disease can now inform drug development for PD.

Machine Learning-Driven Biomarker Discovery for Skeletal Complications in Type 1 Gaucher Disease Patients

Type 1 Gaucher disease (GD1) is a rare, autosomal recessive disorder caused by glucocerebrosidase deficiency. Skeletal manifestations represent one of the most debilitating and potentially irreversible complications of GD1. Although imaging studies are the gold standard, early diagnostic/prognostic tools, such as molecular biomarkers, are needed for the rapid management of skeletal complications. This study aimed to identify potential protein biomarkers capable of predicting the early diagnosis of bone skeletal complications in GD1 patients using artificial intelligence. An in silico study was performed using the novel Therapeutic Performance Mapping System methodology to construct mathematical models of GD1-associated complications at the protein level. Pathophysiological characterization was performed before modeling, and a data science strategy was applied to the predicted protein activity for each protein in the models to identify classifiers. Statistical criteria were used to prioritize the most promising candidates, and 18 candidates were identified. Among them, PDGFB, IL1R2, PTH and CCL3 (MIP-1α) were highlighted due to their ease of measurement in blood. This study proposes a validated novel tool to discover new protein biomarkers to support clinician decision-making in an area where medical needs have not yet been met. However, confirming the results using in vitro and/or in vivo studies is necessary.

Long-term effectiveness of eliglustat treatment: A real-world analysis from the International Collaborative Gaucher Group Gaucher Registry

Gaucher disease type 1 (GD1) is known for phenotypic heterogeneity and varied natural history. Registrational clinical trials enrolled narrowly defined phenotypes, but greater diversity is encountered in clinical practice. We report real-world outcomes with long-term eliglustat treatment in adults with GD1 in the International Collaborative Gaucher Group Gaucher Registry. Among 5985 GD1 patients in the Registry as of January 6, 2023, 872 started eliglustat at ≥18 years old; of these, 469 met inclusion criteria. We compared clinical parameters at eliglustat initiation (i.e., baseline) and follow-up in treatment-naïve patients and used linear mixed models to estimate annual change from baseline in parameters among patients who switched to eliglustat after ≥1 year on enzyme replacement therapy. Over 4 years of follow-up in non-splenectomized treatment-naïve patients, hemoglobin and platelet count increased, liver and spleen volume decreased, and total lumbar spine bone mineral density (BMD) Z-score decreased slightly. Among non-splenectomized switch patients, on average, hemoglobin decreased -0.030 (95% CI: -0.053, -0.008) g/dL (N = 272) and platelet count increased 2.229 (95% CI: 0.751, 3.706) × 103/mm3 (N = 262) annually up to 10 years; liver volume decreased (-0.009 [95% CI: -0.015, -0.003] MN) (N = 102) and spleen volume remained stable (-0.070 [95% CI: -0.150, 0.010] MN) (N = 106) annually up to 7 years; and total lumbar spine BMD Z-score increased 0.041 (95% CI: 0.015, 0.066) (N = 183) annually up to 8 years. Among splenectomized switch patients, clinical parameters were stable over time. These long-term, real-world outcomes are consistent with the eliglustat clinical trials and emerging real-world experience across the GD phenotypic spectrum.

Soluble mannose receptor: A potential biomarker in Gaucher disease

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

An increase in ER stress and unfolded protein response in iPSCs-derived neuronal cells from neuronopathic Gaucher disease patients

Gaucher disease (GD) is a lysosomal storage disorder caused by a mutation in the GBA1 gene, responsible for encoding the enzyme Glucocerebrosidase (GCase). Although neuronal death and neuroinflammation have been observed in the brains of individuals with neuronopathic Gaucher disease (nGD), the exact mechanism underlying neurodegeneration in nGD remains unclear. In this study, we used two induced pluripotent stem cells (iPSCs)-derived neuronal cell lines acquired from two type-3 GD patients (GD3-1 and GD3-2) to investigate the mechanisms underlying nGD by biochemical analyses. These iPSCs-derived neuronal cells from GD3-1 and GD3-2 exhibit an impairment in endoplasmic reticulum (ER) calcium homeostasis and an increase in unfolded protein response markers (BiP and CHOP), indicating the presence of ER stress in nGD. A significant increase in the BAX/BCL-2 ratio and an increase in Annexin V-positive cells demonstrate a notable increase in apoptotic cell death in GD iPSCs-derived neurons, suggesting downstream signaling after an increase in the unfolded protein response. Our study involves the establishment of iPSCs-derived neuronal models for GD and proposes a possible mechanism underlying nGD. This mechanism involves the activation of ER stress and the unfolded protein response, ultimately leading to apoptotic cell death in neurons.

Delivery of DNA-Based Therapeutics for Treatment of Chronic Diseases

Gene therapy and its role in the medical field have evolved drastically in recent decades. Studies aim to define DNA-based medicine as well as encourage innovation and the further development of novel approaches. Gene therapy has been established as an alternative approach to treat a variety of diseases. Its range of mechanistic applicability is wide; gene therapy has the capacity to address the symptoms of disease, the body's ability to fight disease, and in some cases has the ability to cure disease, making it a more attractive intervention than some traditional approaches to treatment (i.e., medicine and surgery). Such versatility also suggests gene therapy has the potential to address a greater number of indications than conventional treatments. Many DNA-based therapies have shown promise in clinical trials, and several have been approved for use in humans. Whereas current treatment regimens for chronic disease often require frequent dosing, DNA-based therapies can produce robust and durable expression of therapeutic genes with fewer treatments. This benefit encourages the application of DNA-based gene therapy to manage chronic diseases, an area where improving efficiency of current treatments is urgent. Here, we provide an overview of two DNA-based gene therapies as well as their delivery methods: adeno associated virus (AAV)-based gene therapy and plasmid DNA (pDNA)-based gene therapy. We will focus on how these therapies have already been utilized to improve treatment of chronic disease, as well as how current literature supports the expansion of these therapies to treat additional chronic indications in the future.

A review on Gaucher disease: therapeutic potential of β-glucocerebrosidase-targeted mRNA/saRNA approach

Gaucher disease (GD), a rare hereditary lysosomal storage disorder, occurs due to a deficiency in the enzyme β-glucocerebrosidase (GCase). This deficiency leads to the buildup of substrate glucosylceramide (GlcCer) in macrophages, eventually resulting in various complications. Among its three types, GD2 is particularly severe with neurological involvements. Current treatments, such as enzyme replacement therapy (ERT), are not effective for GD2 and GD3 due to their inability to cross the blood-brain barrier (BBB). Other treatment approaches, such as gene or chaperone therapies are still in experimental stages. Additionally, GD treatments are costly and can have certain side effects. The successful use of messenger RNA (mRNA)-based vaccines for COVID-19 in 2020 has sparked interest in nucleic acid-based therapies. Remarkably, mRNA technology also offers a novel approach for protein replacement purposes. Additionally, self-amplifying RNA (saRNA) technology shows promise, potentially producing more protein at lower doses. This review aims to explore the potential of a cost-effective mRNA/saRNA-based approach for GD therapy. The use of GCase-mRNA/saRNA as a protein replacement therapy could offer a new and promising direction for improving the quality of life and extending the lifespan of individuals with GD.

Exploring the efficacy and safety of Ambroxol in Gaucher disease: an overview of clinical studies

Gaucher disease (GD) is mainly caused by glucocerebrosidase (GCase) enzyme deficiency due to genetic variations in the GBA1 gene leading to the toxic accumulation of sphingolipids in various organs, which causes symptoms such as anemia, thrombocytopenia, hepatosplenomegaly, and neurological manifestations. GD is clinically classified into the non-neuronopathic type 1, and the acute and chronic neuronopathic forms, types 2 and 3, respectively. In addition to the current approved GD medications, the repurposing of Ambroxol (ABX) has emerged as a prospective enzyme enhancement therapy option showing its potential to enhance mutated GCase activity and reduce glucosylceramide accumulation in GD-affected tissues of different GBA1 genotypes. The variability in response to ABX varies across different variants, highlighting the diversity in patients' therapeutic outcomes. Its oral availability and safety profile make it an attractive option, particularly for patients with neurological manifestations. Clinical trials are essential to explore further ABX's potential as a therapeutic medication for GD to encourage pharmaceutical companies' investment in its development. This review highlights the potential of ABX as a pharmacological chaperone therapy for GD and stresses the importance of addressing response variability in clinical studies to improve the management of this rare and complex disorder.

Is Gauchian genotyping of GBA1 variants reliable?

Biallelic mutations in GBA1 result in Gaucher disease (GD), the inherited deficiency of glucocerebrosidase. Variants in GBA1 are also a common genetic risk factor for Parkinson disease (PD). Currently, some PD centers screen for mutant GBA1 alleles to stratify patients who may ultimately benefit from GBA1-targeted therapeutics. However, accurately detecting variants, especially recombinant alleles resulting from a crossover between GBA1 and its pseudogene, is challenging, impacting studies of both GD and GBA1-associated parkinsonism. Recently, the software tool Gauchian was introduced to identify GBA1 variants from whole genome sequencing. We evaluated Gauchian in 90 Sanger-sequenced patients with GD and five GBA1 heterozygotes. While Gauchian genotyped most patients correctly, it missed some rare or de novo mutations due to its limited internal database and over-reliance on intergenic structural variants. This resulted in misreported homozygosity, incomplete genotypes, and undetected recombination events, limiting Gauchian's utility in variant screening and precluding its use in diagnostics.

Clinical Outcomes of Patients with Chronic Neuropathic Form of Gaucher Disease in the Spanish Real-World Setting: A Retrospective Study

This was a retrospective, multicenter study that aimed to report the characteristics of type 3 Gaucher disease (GD3) patients in Spain, including the genotype, phenotype, therapeutic options, and treatment responses. A total of 19 patients with GD3 from 10 Spanish hospitals were enrolled in the study (14 men, 5 women). The median age at disease onset and diagnosis was 1 and 1.2 years, respectively, and the mean age at follow-up completion was 12.37 years (range: 1-25 years). Most patients exhibited splenomegaly (18/19) and hepatomegaly (17/19) at the time of diagnosis. The most frequent neurological abnormalities at onset were psychomotor retardation (14/19) and extrinsic muscle disorders (11/19), including oculomotor apraxia, supranuclear palsy, and strabismus. The L444P (c.1448T>C) allele was predominant, with the L444P (c.1448T>C) homozygous genotype mainly associated with visceral manifestations like hepatosplenomegaly, anemia, and thrombocytopenia. All patients received enzyme replacement therapy (ERT); other treatments included miglustat and the chaperone (ambroxol). Visceral manifestations, including hepatosplenomegaly and hematological and bone manifestations, were mostly controlled with ERT, except for kyphosis. The data from this study may help to increase the evidence base on this rare disease and contribute to improving the clinical management of GD3 patients.

Identification of genetic variants associated with a wide spectrum of phenotypes clinically diagnosed as Sanfilippo and Morquio syndromes using whole genome sequencing

Mucopolysaccharidoses (MPSs) are inherited lysosomal storage disorders (LSDs). MPSs are caused by excessive accumulation of mucopolysaccharides due to missing or deficiency of enzymes required for the degradation of specific macromolecules. MPS I-IV, MPS VI, MPS VII, and MPS IX are sub-types of mucopolysaccharidoses. Among these, MPS III (also known as Sanfilippo) and MPS IV (Morquio) syndromes are lethal and prevalent sub-types. This study aimed to identify causal genetic variants in cases of MPS III and MPS IV and characterize genotype-phenotype relations in Pakistan. We performed clinical, biochemical and genetic analysis using Whole Genome Sequencing (WGS) in 14 Pakistani families affected with MPS III or MPS IV. Patients were classified into MPS III by history of aggressive behaviors, dementia, clear cornea and into MPS IV by short trunk, short stature, reversed ratio of upper segment to lower segment with a short upper segment. Data analysis and variant selections were made based on segregation analysis, examination of known MPS III and MPS IV genes, gene function, gene expression, the pathogenicity of variants based on ACMG guidelines and in silico analysis. In total, 58 individuals from 14 families were included in the present study. Six families were clinically diagnosed with MPS III and eight families with MPS IV. WGS revealed variants in MPS-associated genes including NAGLU, SGSH, GALNS, GNPTG as well as the genes VWA3B, BTD, and GNPTG which have not previously associated with MPS. One family had causal variants in both GALNS and BTD. Accurate and early diagnosis of MPS in children represents a helpful step for designing therapeutic strategies to protect different organs from permanent damage. In addition, pre-natal screening and identification of genetic etiology will facilitate genetic counselling of the affected families. Identification of novel causal MPS genes might help identifying new targeted therapies to treat LSDs.

Case report: Exome sequencing revealed disease-causing variants in a patient with spondylospinal thoracic dysostosis

Background

Spondylocostal dysostosis is a rare genetic disorder caused by mutations in DLL3, MESP2, LFNG, HES7, TBX6, and RIPPLY2. A particular form of this disorder characterized by the association of spondylocostal dysostosis with multiple pterygia has been reported and called spondylospinal thoracic dysostosis. Both disorders affect the spine and ribs, leading to abnormal development of the spine. Spondylospinal thoracic dysostosis is a rare syndrome characterized by the association of multiple vertebral segmentation defects, thoracic cage deformity, and multiple pterygia. This syndrome can be considered a different form of the described spondylocostal dysostosis. However, no genetic testing has been conducted for this rare disorder so far.

Methods

We report here the case of an 18-month-old female patient presenting the clinical and radiological features of spondylospinal thoracic dysostosis. To determine the underlying genetic etiology, whole exome sequencing (WES) and Sanger sequencing were performed.

Results

Using WES, we identified a variant in the TPM2 gene c. 628C>T, already reported in the non-lethal form of multiple pterygium syndrome. In addition, following the analysis of WES data, using bioinformatic tools, for oligogenic diseases, we identified candidate modifier genes, CAP2 and ADCY6, that could impact the clinical manifestations.

Conclusion

We showed a potential association between TPM2 and the uncommon spondylocostal dysostosis phenotype that would require further validation on larger cohort.

Omics-Based Approaches for the Characterization of Pompe Disease Metabolic Phenotypes

Lysosomal storage disorders (LSDs) constitute a large group of rare, multisystemic, inherited disorders of metabolism, characterized by defects in lysosomal enzymes, accessory proteins, membrane transporters or trafficking proteins. Pompe disease (PD) is produced by mutations in the acid alpha-glucosidase (GAA) lysosomal enzyme. This enzymatic deficiency leads to the aberrant accumulation of glycogen in the lysosome. The onset of symptoms, including a variety of neurological and multiple-organ pathologies, can range from birth to adulthood, and disease severity can vary between individuals. Although very significant advances related to the development of new treatments, and also to the improvement of newborn screening programs and tools for a more accurate diagnosis and follow-up of patients, have occurred over recent years, there exists an unmet need for further understanding the molecular mechanisms underlying the progression of the disease. Also, the reason why currently available treatments lose effectiveness over time in some patients is not completely understood. In this scenario, characterization of the metabolic phenotype is a valuable approach to gain insights into the global impact of lysosomal dysfunction, and its potential correlation with clinical progression and response to therapies. These approaches represent a discovery tool for investigating disease-induced modifications in the complete metabolic profile, including large numbers of metabolites that are simultaneously analyzed, enabling the identification of novel potential biomarkers associated with these conditions. This review aims to highlight the most relevant findings of recently published omics-based studies with a particular focus on describing the clinical potential of the specific metabolic phenotypes associated to different subgroups of PD patients.

Polygenic Parkinson's Disease Genetic Risk Score as Risk Modifier of Parkinsonism in Gaucher Disease

BACKGROUND

Biallelic pathogenic variants in GBA1 are the cause of Gaucher disease (GD) type 1 (GD1), a lysosomal storage disorder resulting from deficient glucocerebrosidase. Heterozygous GBA1 variants are also a common genetic risk factor for Parkinson's disease (PD). GD manifests with considerable clinical heterogeneity and is also associated with an increased risk for PD.

OBJECTIVE

The objective of this study was to investigate the contribution of PD risk variants to risk for PD in patients with GD1.

METHODS

We studied 225 patients with GD1, including 199 without PD and 26 with PD. All cases were genotyped, and the genetic data were imputed using common pipelines.

RESULTS

On average, patients with GD1 with PD have a significantly higher PD genetic risk score than those without PD (P = 0.021).

CONCLUSIONS

Our results indicate that variants included in the PD genetic risk score were more frequent in patients with GD1 who developed PD, suggesting that common risk variants may affect underlying biological pathways. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Case Report: Novel Pathogenic Variant Detected in Two Siblings with Type 1 Gaucher Disease

BACKGROUND

Gaucher disease (GD) is an autosomal recessive lysosomal storage disease. The disease develops due to glucocerebrosidase enzyme deficiency caused by biallelic pathogenic variants in the glucosylceramidase beta 1 (GBA1) gene, which encodes the glucocerebrosidase enzyme. The GBA1 gene is located at chromosomal location 1q22 and consists of 11 exons. In this article, we report a novel pathogenic variant in the GBA1 gene.

CASE PRESENTATIONS

A 32-year-old female patient with no known chronic disease was admitted with complaints of weakness, bone pain, and abdominal pain. Her evaluation included hepatosplenomegaly, thrombocytopenia, osteoporosis, and anemia. The clinical suspicion of Gaucher disease was confirmed by glucocerebrosidase enzyme level and genetic testing. In her family screening, her sister also had hepato-splenomegaly, osteoporosis, thrombocytopenia, and anemia. Both sisters had no neurological symptoms. As a result of GBA1 gene sequence analysis in two of our patients, a missense variant was detected in the c.593C > A homozygous genotype. This variant has not been reported in any previously published case.

CONCLUSION

In this case report, we aimed to contribute to the literature by reporting a new novel pathogenic variant in the GBA1 gene leading to type 1 Gaucher disease that has not been described before.

Epigallocatechin gallate for Parkinson's disease

In the last couple of decades, we have experienced increased use of nutraceuticals worldwide with a demand for organic foods, which has been elevated to an extent probably unmatched with other periods of our civilization. One of the nutraceuticals that gained attention is epigallocatechin gallate (EGCG), a polyphenol in green tea. It has been suggested that diseases of the central nervous system can benefit from consuming some antioxidants, despite current results showing little evidence for their use in preventing and treating these diseases. ECGC may be beneficial in delaying the neurodegeneration of the substantia nigra regardless of the origin of Parkinson's disease (PD). This review covers the effect of EGCG on vitro and animal models of PD, the potential mechanisms of neuroprotection involved and summaries recent clinical trials in human PD. This review also aims to provide an investigative analysis of the current knowledge in this field and to identify putative crucial issues. Environmental factors such as dietary habits, drug use and social interaction are all factors that influence the evolution of neurodegenerative diseases. Therefore, the use of nutraceuticals requires further investigation.

A versatile fluorescence-quenched substrate for quantitative measurement of glucocerebrosidase activity within live cells

Loss of activity of the lysosomal glycosidase β-glucocerebrosidase (GCase) causes the lysosomal storage disease Gaucher disease (GD) and has emerged as the greatest genetic risk factor for the development of both Parkinson disease (PD) and dementia with Lewy bodies. There is significant interest into how GCase dysfunction contributes to these diseases, however, progress toward a full understanding is complicated by presence of endogenous cellular factors that influence lysosomal GCase activity. Indeed, such factors are thought to contribute to the high degree of variable penetrance of GBA mutations among patients. Robust methods to quantitatively measure GCase activity within lysosomes are therefore needed to advance research in this area, as well as to develop clinical assays to monitor disease progression and assess GCase-directed therapeutics. Here, we report a selective fluorescence-quenched substrate, LysoFQ-GBA, which enables measuring endogenous levels of lysosomal GCase activity within living cells. LysoFQ-GBA is a sensitive tool for studying chemical or genetic perturbations of GCase activity using either fluorescence microscopy or flow cytometry. We validate the quantitative nature of measurements made with LysoFQ-GBA using various cell types and demonstrate that it accurately reports on both target engagement by GCase inhibitors and the GBA allele status of cells. Furthermore, through comparisons of GD, PD, and control patient-derived tissues, we show there is a close correlation in the lysosomal GCase activity within monocytes, neuronal progenitor cells, and neurons. Accordingly, analysis of clinical blood samples using LysoFQ-GBA may provide a surrogate marker of lysosomal GCase activity in neuronal tissue.

Glycolipid Metabolite β-Glucosylceramide Is a Neutrophil Extracellular Trap-Inducing Ligand of Mincle Released during Bacterial Infection and Inflammation

Neutrophil extracellular traps (NETs) are implicated in host defense and inflammatory pathologies alike. A wide range of pathogen- and host-derived factors are known to induce NETs, yet the knowledge about specific receptor-ligand interactions in this response is limited. We previously reported that macrophage-inducible C-type lectin (Mincle) regulates NET formation. In this article, we identify glycosphingolipid β-glucosylceramide (β-GlcCer) as a specific NET-inducing ligand of Mincle. We found that purified β-GlcCer induced NETs in mouse primary neutrophils in vitro and in vivo, and this effect was abrogated in Mincle deficiency. Cell-free β-GlcCer accumulated in the lungs of pneumonic mice, which correlated with pulmonary NET formation in wild-type, but not in Mincle^-/-, mice infected intranasally with Klebsiella pneumoniae Although leukocyte infiltration by β-GlcCer administration in vivo did not require Mincle, NETs induced by this sphingolipid were important for bacterial clearance during Klebsiella infection. Mechanistically, β-GlcCer did not activate reactive oxygen species formation in neutrophils but required autophagy and glycolysis for NET formation, because ATG4 inhibitor NSC185058, as well as glycolysis inhibitor 2-deoxy-d-glucose, abrogated β-GlcCer-induced NETs. Forced autophagy activation by tamoxifen could overcome the inhibitory effect of glycolysis blockage on β-GlcCer-mediated NET formation, suggesting that autophagy activation is sufficient to induce NETs in response to this metabolite in the absence of glycolysis. Finally, β-GlcCer accumulated in the plasma of patients with systemic inflammatory response syndrome, and its levels correlated with the extent of systemic NET formation in these patients. Overall, our results posit β-GlcCer as a potent NET-inducing ligand of Mincle with diagnostic and therapeutic potential in inflammatory disease settings.

The diagnosis and management of Gaucher disease in pediatric patients: Where do we go from here?

Gaucher disease (GD) is an autosomal recessive inherited lysosomal storage disease that often presents in early childhood and is associated with damage to multiple organ systems. Many challenges associated with GD diagnosis and management arise from the considerable heterogeneity of disease presentations and natural history. Phenotypic classification has traditionally been based on the absence (in type 1 GD) or presence (in types 2 and 3 GD) of neurological involvement of varying severity. However, patient management and prediction of prognosis may be best served by a dynamic, evolving definition of individual phenotype rather than by a rigid system of classification. Patients may experience considerable delays in diagnosis, which can potentially be reduced by effective screening programs; however, program implementation can involve ethical and practical challenges. Variation in the clinical course of GD and an uncertain prognosis also complicate decisions concerning treatment initiation, with differing stakeholder perspectives around efficacy and acceptable cost/benefit ratio. We review the challenges faced by physicians in the diagnosis and management of GD in pediatric patients. We also consider future directions and goals, including acceleration of accurate diagnosis, improvements in the understanding of disease heterogeneity (natural history, response to treatment, and prognosis), the need for new treatments to address unmet needs for all forms of GD, and refinement of the tools for monitoring disease progression and treatment efficacy, such as specific biomarkers.

RNA sequencing and its applications in cancer and rare diseases

With the invention of RNA sequencing over a decade ago, diagnosis and identification of the gene-related diseases entered a new phase that enabled more accurate analysis of the diseases that are difficult to approach and analyze. RNA sequencing has availed in-depth study of transcriptomes in different species and provided better understanding of rare diseases and taxonomical classifications of various eukaryotic organisms. Development of single-cell, short-read, long-read and direct RNA sequencing using both blood and biopsy specimens of the organism together with recent advancement in computational analysis programs has made the medical professional's ability in identifying the origin and cause of genetic disorders indispensable. Altogether, such advantages have evolved the treatment design since RNA sequencing can detect the resistant genes against the existing therapies and help medical professions to take a further step in improving methods of treatments towards higher effectiveness and less side effects. Therefore, it is of essence to all researchers and scientists to have deeper insight in all available methods of RNA sequencing while taking a step-in therapy design.

Screening, patient identification, evaluation, and treatment in patients with Gaucher disease: Results from a Delphi consensus

Several guidelines are available for identification and management of patients with Gaucher disease, but the most recent guideline was published in 2013. Since then, there have been significant advances in newborn screening, phenotypic characterization, identification of biomarkers and their integration into clinical practice, and the development and approval of new treatment options. Accordingly, the goal of this Delphi consensus exercise was to extend prior initiatives of this type by addressing issues related to newborn screening, diagnostic evaluations, and treatment (both disease directed and adjunctive). The iterative Delphi process involved creation of an initial slate of statements, review by a steering committee, and three rounds of consensus development by an independent panel. A preliminary set of statements was developed by the supporting agency based on literature searches covering the period from 1965 to 2020. The Delphi process reduced an initial set of 185 statements to 65 for which there was unanimous support from the panel. The statements supported may ultimately provide a framework for more detailed treatment guidelines. In addition, the statements for which unanimous support could not be achieved help to identify evidence gaps that are targets for future research.

A Comprehensive, Targeted NGS Approach to Assessing Molecular Diagnosis of Lysosomal Storage Diseases

With over 60 different disorders and a combined incidence occurring in 1:5000-7000 live births, lysosomal storage diseases (LSDs) represent a major public health problem and constitute an enormous burden for affected individuals and their families. Several reasons make the diagnosis of LSDs an arduous task for clinicians, including the phenotype and penetrance variability, the shared signs and symptoms, and the uncertainties related to biochemical enzymatic assay results. Developing a powerful diagnostic tool based on next generation sequencing (NGS) technology may help reduce the delayed diagnostic process for these families, leading to better outcomes for current therapies and providing the basis for more appropriate genetic counseling. Herein, we employed a targeted NGS-based panel to scan the coding regions of 65 LSD-causative genes. A reference group sample (n = 26) with previously known genetic mutations was used to test and validate the entire workflow. Our approach demonstrated elevated analytical accuracy, sensitivity, and specificity. We believe the adoption of comprehensive targeted sequencing strategies into a routine diagnostic route may accelerate both the identification and management of LSDs with overlapping clinical profiles, producing a significant reduction in delayed diagnostic response with beneficial results in the treatment outcome.

Epistasis for head morphology in Drosophila melanogaster

Epistasis-gene-gene interaction-is common for mutations with large phenotypic effects in humans and model organisms. Epistasis impacts quantitative genetic models of speciation, response to natural and artificial selection, genetic mapping, and personalized medicine. However, the existence and magnitude of epistasis between alleles with small quantitative phenotypic effects are controversial and difficult to assess. Here, we use the Drosophila melanogaster Genetic Reference Panel of sequenced inbred lines to evaluate the magnitude of naturally occurring epistasis modifying the effects of mutations in jing and inv, two transcription factors that have subtle quantitative effects on head morphology as homozygotes. We find significant epistasis for both mutations and performed single marker genome-wide association analyses to map candidate modifier variants and loci affecting head morphology. A subset of these loci was significantly enriched for a known genetic interaction network, and mutations of the candidate epistatic modifier loci also affect head morphology.

Intracerebral Gene Therapy in Four Children with Sanfilippo B Syndrome: 5.5-Year Follow-Up Results

We report the safety (primary endpoint) and efficacy (secondary endpoint) of a novel intracerebral gene therapy at 5.5 years of follow-up in children with Sanfilippo B. An uncontrolled, phase 1/2 clinical trial was performed in four patients aged 20, 26, 30, and 53 months. Treatment consisted of 16 intracerebral and cerebellar deposits of a recombinant adeno-associated viral vector encoding human α-N-acetylglucosaminidase (rAAV2/5-hNAGLU) plus immunosuppression. An intermediate report at 30 months was previously published. Thirty treatment-emergent adverse events were reported between 30 and 66 months after surgery, including three classified as severe with no serious drug reactions. At 5.5 years, NAGLU activity was persistently detected in the lumbar cerebrospinal fluid (18% of unaffected control level). Circulating T cells reacting against NAGLU peptides were present, indicating a lack of acquired tolerance. Patients 2, 3, and 4 showed progressive brain atrophy and neurocognitive evolution that did not differ from untreated Sanfilippo A/B children. Patient 1, enrolled at 20 months of age, had a milder disease with normal brain imaging and a significantly better cognitive outcome than the three other patients and untreated patients, although not equivalent to normal children. After 5.5 years, the primary endpoint of this study was achieved with a good safety profile of the proposed treatment. We have also observed sustained enzyme production in the brain and absence of immunological tolerance. Cognitive benefit was not confirmed in the three oldest patients. Milder disease in the youngest patient supports further investigations of adeno-associated vector-mediated intracerebral gene therapy in Sanfilippo B.

Gaucher disease: achievements and prospects

Gaucher disease (GD) is the most common lysosomal storage disorder, resulting from a deficiency in the activity of a lysosomal enzyme glucocerebrosidase, which is involved in the catabolism of sphingolipids. The phenomenal progress in understanding the pathogenesis and development of specific therapy of this disease over the past 60 years dramatically changed the clinical phenotype of GD, turning a severe progressive disorder into an asymptomatic metabolic defect. The evolution of the understanding of GD associated with fundamental discoveries in the field of cell biology, biochemistry and genetics may be of interest to a wide audience as a model of the effective work of the scientific community in the treatment of rare metabolic pathology.

Diffusion tensor imaging of vertebral bone marrow in children with Gaucher's disease type I and III: Pre- and post-therapy

PURPOSE

To assess diffusion tensor imaging (DTI) of the vertebral bone marrow (BM) in children with Gaucher's disease (GD) types I and III before and after therapy.

METHODS

Prospective study was conducted upon 25 children with GD type I (n = 17) and III (n = 8) and 13 age and sex-matched controls underwent DTI of vertebral BM. Mean diffusivity (MD) and fractional anisotropy (FA) of vertebral BM was calculated and correlated with genotyping, chitotriosidase, hemoglobin (HB) and, platelet count.

RESULTS

There was a statistically significant difference in MD and FA of BM between patients and controls (P = 0.001 and 0.02). The area under the curve (AUC) of MD and FA used to differentiate untreated patients from controls was 0.902 and 0.68 with sensitivity, specificity, and, accuracy 92%, 84.6%, and, 89.5% respectively. There was a significant difference in MD and FA of BM between untreated and treated patients (P = 0.001 and 0.02). AUC of MD and FA used to differentiate untreated from treated patients was 0.93 and 0.649 with sensitivity, specificity, and accuracy of 92%, 80%, and 86% respectively. There was a significant difference in MD and FA (P = 0.03, 0.001 respectively) of BM in GD with homozygous L444P mutation (n = 9) and other mutations (n = 14). Chiotriptase, HB and platelet count of patients was correlated with MD (r = -0.36, 0.42, -0.41) and FA (r = -0.47, -0.37, -0.46) respectively.

CONCLUSION

DTI of vertebral BM can help in diagnosis and monitoring patients with GD after therapy and correlated with genotyping, and hematological biomarkers of GD.

Multiple Structural Microform Defects Suggest Role of Modifier Genes

ABSTRACT

One of the biggest challenges in clinical genetics is establishing associations between specific germline mutations and the resulting spectrum of phenotypes. The careful characterization of clinical presentations continues to be a tool for establishing these genotype phenotype correlations. The authors intend, by presenting a case study, proposing that the concomitant occurrence of a combinations of mild structural anomalies in the same individual may be due to changes in genes that can be linked by related pathways. A new born with cleft lip and palate was referred at the Cleft Lip and Palate Center. The anamnese was performed and collected data of familiar history, parental consanguinity, and information about pregnancy period. The careful characterization of clinical presentations and the genetic pathways was studied. It is possible that there is no single mutation that can be clearly identified as the etiology of the combination of the defects displayed in the present case.

The rapidly evolving view of lysosomal storage diseases

Lysosomal storage diseases are a group of metabolic disorders caused by deficiencies of several components of lysosomal function. Most commonly affected are lysosomal hydrolases, which are involved in the breakdown and recycling of a variety of complex molecules and cellular structures. The understanding of lysosomal biology has progressively improved over time. Lysosomes are no longer viewed as organelles exclusively involved in catabolic pathways, but rather as highly dynamic elements of the autophagic-lysosomal pathway, involved in multiple cellular functions, including signaling, and able to adapt to environmental stimuli. This refined vision of lysosomes has substantially impacted on our understanding of the pathophysiology of lysosomal disorders. It is now clear that substrate accumulation triggers complex pathogenetic cascades that are responsible for disease pathology, such as aberrant vesicle trafficking, impairment of autophagy, dysregulation of signaling pathways, abnormalities of calcium homeostasis, and mitochondrial dysfunction. Novel technologies, in most cases based on high-throughput approaches, have significantly contributed to the characterization of lysosomal biology or lysosomal dysfunction and have the potential to facilitate diagnostic processes, and to enable the identification of new therapeutic targets.

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.

Outcomes of screening for gammopathies in children and adults with Gaucher disease type 1 in a cohort from Brazil and the United States

Multiple myeloma is the most common hematological malignancy in Gaucher disease type 1 (GD1). There is a lack of outcome data and consensus regarding screening of gammopathies. This study explores utility of screening in Porto Alegre, Brazil, and Cincinnati, Ohio. A retrospective analysis of clinical information and laboratory data from GD1 patients was performed. Over 19 years, 68 individuals with GD1 (31 males, 37 females) underwent screening, and 20 (29.4%) had abnormalities. Twelve (17.6%) had polyclonal gammopathy (mean age 24.2 years, p = .02), seven (10%) had monoclonal gammopathy of uncertain significance (MGUS; mean age 52.7 years, p = .009). One had multiple myeloma (age 61 years). Risk factors for MGUS included male gender (p = .05), p.N409S allele (p = .032). MGUS developed in six of 62 treated and two of four untreated individuals. Of those with MGUS receiving treatment, four were on enzyme replacement therapy (ERT) and one on substrate reduction therapy (SRT). Gammopathy normalized in 13 treated individuals (10 polyclonal, three MGUS) and remained abnormal in two treated individuals (two polyclonal, two MGUS). Gammopathy relapse was seen in one individual with MGUS and three with polyclonal gammopathy. This study describes screening for gammopathies and identifies risk factors in individuals with GD1.

The morphogenesis of granular and lattice corneal dystrophy - A mutation combination hypothesis

Mutations in the BIGH3 gene encoding for keratoepithelin protein have been described in different corneal dystrophies viz. granular corneal dystrophy, lattice corneal dystrophy, and their different clinical subtypes. Even though linked to the BIGH3 gene, the role of BIGH3 gene in the pathogenesis of corneal lattice dystrophy and corneal granular dystrophy remains to be elucidated. We describe the probable functions of a mutated BIGH3 gene in disease pathogenesis, postulate the existence of other phenotype modifier mutations in these dystrophies, and how the coinheritance of these mutations in different combinations along with a normal/mutated BIGH3 gene can lead to the different morphologic patterns seen in these corneal dystrophies and their subtypes.

Highlights on Genomics Applications for Lysosomal Storage Diseases

Lysosomal storage diseases (LSDs) are a heterogeneous group of rare multisystem genetic disorders occurring mostly in infancy and childhood, characterized by a gradual accumulation of non-degraded substrates inside the lysosome. Although the cellular pathogenesis of LSDs is complex and still not fully understood, the approval of disease-specific therapies and the rapid emergence of novel diagnostic methods led to the implementation of extensive national newborn screening (NBS) programs in several countries. In the near future, this will help the development of standardized workflows aimed to more timely diagnose these conditions. Hereby, we report an overview of LSD diagnostic process and treatment strategies, provide an update on the worldwide NBS programs, and discuss the opportunities and challenges arising from genomics applications in screening, diagnosis, and research.

Genetic Modifiers and Rare Mendelian Disease

Despite advances in high-throughput sequencing that have revolutionized the discovery of gene defects in rare Mendelian diseases, there are still gaps in translating individual genome variation to observed phenotypic outcomes. While we continue to improve genomics approaches to identify primary disease-causing variants, it is evident that no genetic variant acts alone. In other words, some other variants in the genome (genetic modifiers) may alleviate (suppress) or exacerbate (enhance) the severity of the disease, resulting in the variability of phenotypic outcomes. Thus, to truly understand the disease, we need to consider how the disease-causing variants interact with the rest of the genome in an individual. Here, we review the current state-of-the-field in the identification of genetic modifiers in rare Mendelian diseases and discuss the potential for future approaches that could bridge the existing gap.

A Novel Homozygous Missense Variant in the NAGA Gene with Extreme Intrafamilial Phenotypic Heterogeneity

Schindler disease is a rare autosomal recessive lysosomal storage disorder caused by a deficiency in alpha-N-acetylgalactosaminidase (α-NAGA) activity due to defects in the NAGA gene. Accumulation of the enzyme's substrates results in clinically heterogeneous symptoms ranging from asymptomatic individuals to individuals with severe neurological manifestations. Here, a 5-year-old Emirati male born to consanguineous parents presented with congenital microcephaly and severe neurological manifestations. Whole genome sequencing revealed a homozygous missense variant (c.838C>A; p.L280I) in the NAGA gene. The allele is a reported SNP in the ExAC database with a 0.0007497 allele frequency. The proband's asymptomatic sister and cousin carry the same genotype in a homozygous state as revealed from the family screening. Due to the extreme intrafamilial heterogeneity of the disease as seen in previously reported cases, we performed further analyses to establish the pathogenicity of this variant. Both the proband and his sister showed abnormal urine oligosaccharide patterns, which is consistent with the diagnosis of Schindler disease. The α-NAGA activity was significantly reduced in the proband and his sister with 5.9% and 12.1% of the mean normal activity, respectively. Despite the activity loss, p.L280I α-NAGA processing and trafficking were not affected. However, protein molecular dynamic simulation analysis revealed that this amino acid substitution is likely to affect the enzyme's natural dynamics and hinders its ability to bind to the active site. Functional analysis confirmed the pathogenicity of the identified missense variant and the diagnosis of Schindler disease. Extreme intrafamilial clinical heterogeneity of the disease necessitates further studies for proper genetic counseling and management.

Bone development and remodeling in metabolic disorders

There are many metabolic disorders that present with bone phenotypes. In some cases, the pathological bone symptoms are the main features of the disease whereas in others they are a secondary characteristic. In general, the generation of the bone problems in these disorders is not well understood and the therapeutic options for them are scarce. Bone development occurs in the early stages of embryonic development where the bone formation, or osteogenesis, takes place. This osteogenesis can be produced through the direct transformation of the pre-existing mesenchymal cells into bone tissue (intramembranous ossification) or by the replacement of the cartilage by bone (endochondral ossification). In contrast, bone remodeling takes place during the bone's growth, after the bone development, and continues throughout the whole life. The remodeling involves the removal of mineralized bone by osteoclasts followed by the formation of bone matrix by the osteoblasts, which subsequently becomes mineralized. In some metabolic diseases, bone pathological features are associated with bone development problems but in others they are associated with bone remodeling. Here, we describe three examples of impaired bone development or remodeling in metabolic diseases, including work by others and the results from our research. In particular, we will focus on hereditary multiple exostosis (or osteochondromatosis), Gaucher disease, and the susceptibility to atypical femoral fracture in patients treated with bisphosphonates for several years.

A transcriptional and post-transcriptional dysregulation of Dishevelled 1 and 2 underlies the Wnt signaling impairment in type I Gaucher disease experimental models

Bone differentiation defects have been recently tied to Wnt signaling alterations occurring in vitro and in vivo Gaucher disease (GD) models. In this work, we provide evidence that the Wnt signaling multi-domain intracellular transducers Dishevelled 1 and 2 (DVL1 and DVL2) may be potential upstream targets of impaired beta glucosidase (GBA1) activity by showing their misexpression in different type 1 GD in vitro models. We also show that in Gba mutant fish a miR-221 upregulation is associated with reduced dvl2 expression levels and that in type I Gaucher patients single-nucleotide variants in the DVL2 3′ untranslated region are related to variable canonical Wnt pathway activity. Thus, we strengthen the recently outlined relation between bone differentiation defects and Wnt/β-catenin dysregulation in type I GD and further propose novel mechanistic insights of the Wnt pathway impairment caused by glucocerebrosidase loss of function.

Impact of genotype on neutropenia in a large cohort of Serbian patients with glycogen storage disease type Ib

BACKGROUND

Glycogen storage disease type Ib (GSD-Ib) is an inherited metabolic disorder caused by autosomal recessive mutations in SLC37A4 coding for the glucose-6-phosphate transporter. Neutropenia represents major feature of GSD-Ib along with metabolic disturbances. Previous research in GSD-Ib patients did not reveal significant genotype-phenotype correlation. Our objective was to explore the frequency and severity of neutropenia and it's complications in relation to genotype of GSD-Ib patients.

METHODS

We estimated cumulative incidence of neutropenia and severe neutropenia, relation of genotype to absolute neutrophil count (ANC), and dynamics of ANC during serious bacterial infections (SBI) in a cohort of Serbian GSD Ib patients. Impact of genotype on GSD Ib-related inflammatory bowel disease (IBD) was also assessed.

RESULTS

Absolute neutrophil count (ANC) < 1500/mm³ was present in all 33 patients, with severe neutropenia (ANC<500/mm³) occurring in 60.6% of patients. The median age at neutropenia onset was 24 months, while severe neutropenia developed at median of 4.5 years. The ANC was elevated during 90.5% episodes of SBI. Genotypes c.81T>A/c.785G>A and c.81T>A/c.1042_1043delCT are associated with earlier onset of neutropenia. Patients carrying c.785G>A mutation express a higher capacity for ANC increase during SBI. Inflammatory bowel disease was diagnosed in 8 patients (24.2% of total) with median age of onset at 7 years. Risk for IBD occurrence was not significantly affected by gender, genotype and severity of neutropenia.

CONCLUSIONS

We may conclude that certain mutations in SLC37A4 influence the risk for severe neutropenia occurrence but also affect the capacity to increase ANC during SBI.

Glucocerebrosidase and its relevance to Parkinson disease

Mutations in GBA1, the gene encoding the lysosomal enzyme glucocerebrosidase, are among the most common known genetic risk factors for the development of Parkinson disease and related synucleinopathies. A great deal is known about GBA1, as mutations in GBA1 are causal for the rare autosomal storage disorder Gaucher disease. Over the past decades, significant progress has been made in understanding the genetics and cell biology of glucocerebrosidase. A least 495 different mutations, found throughout the 11 exons of the gene are reported, including both common and rare variants. Mutations in GBA1 may lead to degradation of the protein, disruptions in lysosomal targeting and diminished performance of the enzyme in the lysosome.

Gaucher disease is phenotypically diverse and has both neuronopathic and non-neuronopathic forms. Both patients with Gaucher disease and heterozygous carriers are at increased risk of developing Parkinson disease and Dementia with Lewy Bodies, although our understanding of the mechanism for this association remains incomplete. There appears to be an inverse relationship between glucocerebrosidase and α-synuclein levels, and even patients with sporadic Parkinson disease have decreased glucocerebrosidase. Glucocerebrosidase may interact with α-synuclein to maintain basic cellular functions, or impaired glucocerebrosidase could contribute to Parkinson pathogenesis by disrupting lysosomal homeostasis, enhancing endoplasmic reticulum stress or contributing to mitochondrial impairment. However, the majority of patients with GBA1 mutations never develop parkinsonism, so clearly other risk factors play a role. Treatments for Gaucher disease have been developed that increase visceral glucocerebrosidase levels and decrease lipid storage, although they have yet to properly address the neurological defects associated with impaired glucocerebrosidase. Mouse and induced pluripotent stem cell derived models have improved our understanding of glucocerebrosidase function and the consequences of its deficiency. These models have been used to test novel therapies including chaperone proteins, histone deacetylase inhibitors, and gene therapy approaches that enhance glucocerebrosidase levels and could prove efficacious in the treatment of forms of parkinsonism. Consequently, this rare monogenic disorder, Gaucher disease, provides unique insights directly applicable to our understanding and treatment of Parkinson disease, a common and complex neurodegenerative disorder.

The Link between Gaucher Disease and Parkinson's Disease Sheds Light on Old and Novel Disorders of Sphingolipid Metabolism

Sphingolipid metabolism starts with the biosynthesis of ceramide, a bioactive lipid and the backbone for the biosynthesis of complex sphingolipids such as sphingomyelin and glycosphingolipids. These are degraded back to ceramide and then to sphingosine, which enters the ceramide–sphingosine-1-phosphate signaling pathway or is further degraded. Several enzymes with multiple catalytic properties and subcellular localizations are thus involved in such metabolism. Hereditary defects of lysosomal hydrolases have been known for several years to be the cause of lysosomal storage diseases such as gangliosidoses, Gaucher disease, Niemann–Pick disease, Krabbe disease, Fabry disease, and Farber disease. More recently, many other inborn errors of sphingolipid metabolism have been recognized, involving enzymes responsible for the biosynthesis of ceramide, sphingomyelin, and glycosphingolipids. Concurrently, epidemiologic and biochemical evidence has established a link between Gaucher disease and Parkinson’s disease, showing that glucocerebrosidase variants predispose individuals to α-synuclein accumulation and neurodegeneration even in the heterozygous status. This appears to be due not only to lysosomal overload of non-degraded glucosylceramide, but to the derangement of vesicle traffic and autophagy, including mitochondrial autophagy, triggered by both sphingolipid intermediates and misfolded proteins. In this review, old and novel disorders of sphingolipid metabolism, in particular those of ganglioside biosynthesis, are evaluated in light of recent investigations of the link between Gaucher disease and Parkinson’s disease, with the aim of better understanding their pathogenic mechanisms and addressing new potential therapeutic strategies.