Accumulation Of GM2 Ganglioside Research Articles

Development of an Infantile GM2 Clinical Rating Scale: Remote Assessment of Clinically Meaningful Health-Related Function.

GM2 gangliosidoses (GM2) are a group of rare lysosomal storage disorders in which accumulation of GM2 gangliosides results in progressive central nervous system damage. The infantile GM2 phenotype is characterized by delays in milestones by 6 months of age, followed by rapid loss of motor, cognitive, and visual function. Advancements in early diagnosis and pharmacotherapies provide promise for improved outcomes. However, the lack of feasible and clinically meaningful clinical outcome assessments for GM2 poses a challenge to characterizing GM2 natural history and selecting clinical trial endpoints. The purpose of this study was to develop a remotely administered infantile GM2 rating scale to measure health-related function in children with infantile GM2. A 2-phase mixed methods design was employed. In phase 1 of the study, 8 families of children with Infantile GM2 completed a natural history survey and a 1:1 semistructured interview to provide caregiver perspectives on the impacts of GM2 on health-related function. In phase 2 of the study, 8 expert clinicians provided feedback via surveys and participated in videoconference-hosted focus groups to refine scale administration and scoring procedures. These methods guided the development of 16 scale items to assess function in 5 health-related function domains: vision, hand and arm use, communication, gross motor, and feeding. This study used caregiver perspectives and expert clinician feedback to develop a remotely administered clinical outcome assessment of clinically meaningful health-related function in children with infantile GM2. Future studies will further evaluate the feasibility, reliability, and validity of the Infantile GM2 Clinical Rating Scale.

Aβ peptide enhances GluA1 internalization via lipid rafts in Alzheimer's-related hippocampal LTP dysfunction.

Amyloid β (Aβ) is a central contributor to neuronal damage and cognitive impairment in Alzheimer's disease (AD). Aβ disrupts AMPA receptor-mediated synaptic plasticity, a key factor in early AD progression. Numerous studies propose that Aβ oligomers hinder synaptic plasticity, particularly long-term potentiation (LTP), by disrupting GluA1 (encoded by GRIA1) function, although the precise mechanism remains unclear. In this study, we demonstrate that Aβ mediates the accumulation of GM1 ganglioside in lipid raft domains of cultured cells, and GluA1 exhibits preferential localization in lipid rafts via direct binding to GM1. Aβ enhances the raft localization of GluA1 by increasing GM1 in these areas. Additionally, chemical LTP stimulation induces lipid raft-dependent GluA1 internalization in Aβ-treated neurons, resulting in reduced cell surface and postsynaptic expression of GluA1. Consistent with this, disrupting lipid rafts and GluA1 localization in rafts rescues Aβ-mediated suppression of hippocampal LTP. These findings unveil a novel functional deficit in GluA1 trafficking induced by Aβ, providing new insights into the mechanism underlying AD-associated cognitive dysfunction.

Silencing of B4Galnt1 Gene Prevents GM2 Accumulation in Tay-Sachs Cells

Introduction. The Tay-Sachs disease (TSD) is a progressive neurodegenerative disorder resulting from genetic mutations in the HEXA gene encoding the α-subunit of β-hexosaminidase A leading to the accumulation of GM2 ganglioside in the central nervous system. Multiple therapeutical strategies have been investigated such as gene therapy for Tay-Sachs patients; however, there is still no cure. In the present study, we suggest a new approach for the treatment of the Tay-Sachs disease with the concept of substrate reduction therapy by using AAV9-mediated RNAi technology targeting the B4Galnt1 gene at the upstream of the enzymatic defect in TSD pathology to decrease GM2 biosynthesis and accumulation in cell models of TSD. Material and Methods. We employed AAV9-mediated shRNA transduction for mice and human Tay-Sachs cells. After transduction, expression levels of ganglioside metabolism genes were analyzed by RT-PCR and GM2 and lysosome-associated membrane protein 1 (LAMP1) protein levels were evaluated by immunocytochemistry analysis. Results. Here, we have shown that AAV9-shRNA transduction effectively reduced B4Galnt1 expression in TSD cells demonstrating a reduction in GM2 accumulation and LAMP1. Discussion. Our data shows that AAV-mediated B4Galnt1-shRNA transduction can ameliorate disease pathologies by decreasing the lysosomal accumulation of GM2 through selectively reducing B4Gant1 activity in cell models of the Tay-Sachs disease. Therefore, we suggest promising novel experimental therapy for this devastating disease using a mouse model in the future.

Cinnamic acid, a natural plant compound, exhibits neuroprotection in a mouse model of Sandhoff disease via PPARα.

Tay-Sachs disease (TSD) and its severe form Sandhoff disease (SD) are autosomal recessive lysosomal storage metabolic disorders, which often result into excessive GM2 ganglioside accumulation predominantly in lysosomes of nerve cells. Although patients with these diseases appear normal at birth, the progressive accumulation of undegraded GM2 gangliosides in neurons leads to early death accompanied by manifestation of motor difficulties and gradual loss of behavioral skills. Unfortunately, there is still no effective treatment available for TSD/SD. The present study highlights the importance of cinnamic acid (CA), a naturally occurring aromatic fatty acid present in a number of plants, in inhibiting the disease process in a transgenic mouse model of SD. Oral administration of CA significantly attenuated glial activation and inflammation and reduced the accumulation of GM2 gangliosides/glycoconjugates in the cerebral cortex of Sandhoff mice. Besides, oral CA also improved behavioral performance and increased the survival of Sandhoff mice. While assessing the mechanism, we found that oral administration of CA increased the level of peroxisome proliferator-activated receptor α (PPARα) in the brain of Sandhoff mice and that oral CA remained unable to reduce glycoconjugates, improve behavior and increase survival in Sandhoff mice lacking PPARα. Our results indicate a beneficial function of CA that utilizes a PPARα-dependent mechanism to halt the progression of SD and thereby increase the longevity of Sandhoff mice.

Lithium treatment rescues dysfunctional autophagy in the cell models of Tay-Sachs disease

Tay-Sachs disease is a rare lysosomal storage disorder (LSD) caused by a mutation in the HexA gene coding β-hexosaminidase A enzyme. The disruption of the HexA gene causes the accumulation of GM2 ganglioside resulting in progressive neurodegeneration in humans. Surprisingly, Hexa−/− mice did not show neurological phenotypes. Our group recently generated a murine model of Tay-Sachs disease exhibiting excessive GM2 accumulation and severe neuropathological abnormalities mimicking Tay-Sachs patients. Previously, we reported impaired autophagic flux in the brain of Hexa/-Neu3−/− mice. However, regulation of autophagic flux using inducers has not been clarified in Tay-Sachs disease cells. Here, we evaluated the effects of lithium treatment on dysfunctional autophagic flux using LC3 and p62 in the fibroblast and neuroglia of Hexa−/-Neu3−/− mice and Tay-Sachs patients. We discovered the clearance of accumulating autophagosomes, aggregate-prone metabolites, and GM2 ganglioside under lithium-induced conditions. Our data suggest that targeting autophagic flux with an autophagy inducer might be a rational therapeutic strategy for the treatment of Tay-Sachs disease.

Increasing β-hexosaminidase A activity using genetically modified mesenchymal stem cells.

GM2 gangliosidoses are a group of autosomal-recessive lysosomal storage disorders. These diseases result from a deficiency of lysosomal enzyme β-hexosaminidase A (HexA), which is responsible for GM2 ganglioside degradation. HexA deficiency causes the accumulation of GM2-gangliosides mainly in the nervous system cells, leading to severe progressive neurodegeneration and neuroinflammation. To date, there is no treatment for these diseases. Cell-mediated gene therapy is considered a promising treatment for GM2 gangliosidoses. This study aimed to evaluate the ability of genetically modified mesenchymal stem cells (MSCs-HEXA-HEXB) to restore HexA deficiency in Tay-Sachs disease patient cells, as well as to analyze the functionality and biodistribution of MSCs in vivo. The effectiveness of HexA deficiency cross-correction was shown in mutant MSCs upon interaction with MSCs-HEXA-HEXB. The results also showed that the MSCs-HEXA-HEXB express the functionally active HexA enzyme, detectable in vivo, and intravenous injection of the cells does not cause an immune response in animals. These data suggest that genetically modified mesenchymal stem cells have the potentials to treat GM2 gangliosidoses.

Intrathecal delivery of a bicistronic AAV9 vector expressing β-hexosaminidase A corrects Sandhoff disease in a murine model: A dosage study

The pathological accumulation of GM2 ganglioside associated with Tay-Sachs disease (TSD) and Sandhoff disease (SD) occurs in individuals who possess mutant forms of the heterodimer β-hexosaminidase A (Hex A) because of mutation of the HEXA and HEXB genes, respectively. With a lack of approved therapies, patients experience rapid neurological decline resulting in early death. A novel bicistronic vector carrying both HEXA and HEXB previously demonstrated promising results in mouse models of SD following neonatal intravenous administration, including significant reduction in GM2 accumulation, increased levels of Hex A, and a 2-fold extension of survival. The aim of the present study was to identify an optimal dose of the bicistronic vector in 6-week-old SD mice by an intrathecal route of administration along with transient immunosuppression, to inform possible clinical translation. Three doses of the bicistronic vector were tested: 2.5e11, 1.25e11, and 0.625e11 vector genomes per mouse. The highest dose provided the greatest increase in biochemical and behavioral parameters, such that treated mice lived to a median age of 56weeks (>3 times the lifespan of the SD controls). These results have direct implications in deciding a human equivalent dose for TSD/SD and have informed the approval of a clinical trial application (NCT04798235).

Characterization of a phenotypically severe animal model for human AB-Variant GM2 gangliosidosis

AB-Variant GM2 gangliosidosis (ABGM2) is a rare and lethal genetic disorder caused by mutations in the GM2A gene that lead to fatal accumulation of GM2 gangliosides (GM2) in neurons of the central nervous system (CNS). GM2A encodes a transport protein known as GM2 activator (GM2A) protein, which is essential for degrading GM2 into their GM3 form. ABGM2 presents in infantile-, juvenile-, and adult-onset forms; of the three, the infantile-onset is the most prominent, and by far the most severe, as evidenced by high levels of GM2 accumulation, widespread neurodegeneration, and death by the age of 4. Gm2a−/− mice are commonly used as a model of ABGM2. These mice are characterized by phenotypes most representative of predicted adult-onset form of ABGM2, which include moderate GM2 accumulation and mild neurological defects. This mild phenotype has been attributed to compensation by alternative GM2 degradation pathways mediated by sialidase, neuraminidase 3 (NEU3), a pathway that is more prominent in mice than humans. To assess the extent to which NEU3 contributes to GM2 degradation, we generated double knock-out (Gm2a−/−Neu3−/−) mice. Compellingly, these mice present with a clinical phenotype resembling that of a more severe ABGM2, including ataxia, reduced mobility and coordination, weight loss, poor body scores, and lethality by 6–7 months. Furthermore, these phenotypes correlate with a dramatic increase in GM2 accumulation in the CNS compared to levels observed in either Gm2a−/− or Neu3−/− mice. Taken together, these studies, for the first-time, confirm that the mild neurological phenotype of Gm2a−/− mice is due to compensatory activity on GM2 catabolism through an alternate breakdown pathway involving NEU3. These studies support the use of double knockout mice as a novel and highly relevant model for pre-clinical drug studies in a more severe form of ABGM2.

Neutral sphingomyelinase inhibition promotes local and network degeneration in vitro and in vivo

BackgroundCell-to-cell communication is vital for tissues to respond, adapt, and thrive in the prevailing milieu. Several mechanisms mediate intercellular signaling, including tunneling nanotubes, gap junctions, and extracellular vesicles (EV). Depending on local and systemic conditions, EVs may contain cargoes that promote survival, neuroprotection, or pathology. Our understanding of pathologic intercellular signaling has been bolstered by disease models using neurons derived from human pluripotent stems cells (hPSC).MethodsHere, we used hPSC-derived retinal ganglion cells (hRGC) and the mouse visual system to investigate the influence of modulating EV generation on intercellular trafficking and cell survival. We probed the impact of EV modulation on cell survival by decreasing the catabolism of sphingomyelin into ceramide through inhibition of neutral sphingomyelinase (nSMase), using GW4869. We assayed for cell survival in vitro by probing for annexin A5, phosphatidylserine, viable mitochondria, and mitochondrial reactive oxygen species. In vivo, we performed intraocular injections of GW4869 and measured RGC and superior colliculus neuron density and RGC anterograde axon transport.ResultsFollowing twenty-four hours of dosing hRGCs with GW4869, we found that inhibition of nSMase decreased ceramide and enhanced GM1 ganglioside accumulation. This inhibition also reduced the density of small EVs, increased the density of large EVs, and enriched the pro-apoptotic protein, annexin A5. Reducing nSMase activity increased hRGC apoptosis initiation due to enhanced density and uptake of apoptotic particles, as identified by the annexin A5 binding phospholipid, phosphatidylserine. We assayed intercellular trafficking of mitochondria by developing a coculture system of GW4869-treated and naïve hRGCs. In treated cells, inhibition of nSMase reduced the number of viable mitochondria, while driving mitochondrial reactive oxygen species not only in treated, but also in naive hRGCs added in coculture. In mice, 20 days following a single intravitreal injection of GW4869, we found a significant loss of RGCs and their axonal recipient neurons in the superior colliculus. This followed a more dramatic reduction in anterograde RGC axon transport to the colliculus.ConclusionOverall, our data suggest that perturbing the physiologic catabolism of sphingomyelin by inhibiting nSMase reorganizes plasma membrane associated sphingolipids, alters the profile of neuron-generated EVs, and promotes neurodegeneration in vitro and in vivo by shifting the balance of pro-survival versus -degenerative EVs.8WXtUmcgzqdrdTPfGd7tbXVideo

Targeting GM2 Ganglioside Accumulation in Dementia: Current Therapeutic Approaches and Future Directions.

Dementia in neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and dementia with Lewy bodies (DLB) is a progressive neurological condition affecting millions worldwide. The amphiphilic molecule GM2 gangliosides are abundant in the human brain and play important roles in neuronal development, intercellular recognition, myelin stabilization, and signal transduction. GM2 ganglioside's degradation requires hexosaminidase A (HexA), a heterodimer composed of an α subunit encoded by HEXA and a β subunit encoded by HEXB. The hydrolysis of GM2 also requires a non-enzymatic protein, the GM2 activator protein (GM2-AP), encoded by GM2A. Pathogenic mutations of HEXA, HEXB, and GM2A are responsible for autosomal recessive diseases known as GM2 gangliosidosis, caused by the excessive intralysosomal accumulation of GM2 gangliosides. In AD, PD and DLB, GM2 ganglioside accumulation is reported to facilitate Aβ and α-synuclein aggregation into toxic oligomers and plaques through activation of downstream signaling pathways, such as protein kinase C (PKC) and oxidative stress factors. This review explored the potential role of GM2 ganglioside alteration in toxic protein aggregations and its related signaling pathways leading to neurodegenerative diseases. Further review explored potential therapeutic approaches, which include synthetic and phytomolecules targeting GM2 ganglioside accumulation in the brain, holding a promise for providing new and effective management for dementia.

Sialidase NEU3 action on GM1 ganglioside is neuroprotective in GM1 gangliosidosis

GM1 gangliosidosis is a neurodegenerative disorder caused by mutations in the GLB1 gene, which encodes lysosomal β-galactosidase. The enzyme deficiency blocks GM1 ganglioside catabolism, leading to accumulation of GM1 ganglioside and asialo-GM1 ganglioside (GA1 glycolipid) in brain. This disease can present in varying degrees of severity, with the level of residual β-galactosidase activity primarily determining the clinical course. Glb1 null mouse models, which completely lack β-galactosidase expression, exhibit a less severe form of the disease than expected from the comparable deficiency in humans, suggesting a potential species difference in the GM1 ganglioside degradation pathway. We hypothesized this difference may involve the sialidase NEU3, which acts on GM1 ganglioside to produce GA1 glycolipid. To test this hypothesis, we generated Glb1/Neu3 double KO (DKO) mice. These mice had a significantly shorter lifespan, increased neurodegeneration, and more severe ataxia than Glb1 KO mice. Glb1/Neu3 DKO mouse brains exhibited an increased GM1 ganglioside to GA1 glycolipid ratio compared with Glb1 KO mice, indicating that NEU3 mediated GM1 ganglioside to GA1 glycolipid conversion in Glb1 KO mice. The expression of genes associated with neuroinflammation and glial responses were enhanced in Glb1/Neu3 DKO mice compared with Glb1 KO mice. Mouse NEU3 more efficiently converted GM1 ganglioside to GA1 glycolipid than human NEU3 did. Our findings highlight NEU3’s role in ameliorating the consequences of Glb1 deletion in mice, provide insights into NEU3’s differential effects between mice and humans in GM1 gangliosidosis, and offer a potential therapeutic approach for reducing toxic GM1 ganglioside accumulation in GM1 gangliosidosis patients.

The diagnostic journey for patients with late-onset GM2 Gangliosidoses

Late-onset forms of GM2 gangliosidosis―mainly, Tay-Sachs disease and Sandhoff disease―are under-recognized in clinical practice. In these rare lysosomal storage disorders, deficiency of β-hexosaminidase A results in excessive accumulation of GM2 ganglioside primarily within neurons, leading to cell death and progressive neurodegenerative symptoms, including ataxia, dysarthria, muscle weakness, tremors, atrophy, and psychosis. Presentation is variable and often mimics more common neurodegenerative disorders. We conducted semi-structured interviews on GM2 gangliosidoses diagnosis and treatment with five experts, 30 neurologists, and 28 patients and caregivers. Symptom onset occurred during adolescence/early adulthood in 92% of patients (median age: 14 years). Patients first visited a healthcare provider at a median age of 20 years and received a GM2 diagnosis at a median age of 26 years. Nearly all patients reported problems with their legs and balance starting from symptom onset. Problems with memory, attention span, speech and fatigue were reported more after diagnosis. Patients visited an average of eight healthcare providers before receiving a diagnosis; 64% were diagnosed by a neurologist. Four neurologists (13%) in our sample were aware that there are late-onset forms of GM2 gangliosidosis. The path to diagnosis is long for this late-onset form of a classically fatal infantile disease.

Efficacy of Adeno-Associated Virus Serotype 9-Mediated Gene Therapy for AB-Variant GM2 Gangliosidosis.

GM2 gangliosidoses are a group of neurodegenerative lysosomal storage disorders that are characterized by the accumulation of GM2 gangliosides (GM2), leading to rapid neurological decline and death. The hydrolysis of GM2 requires the specific synthesis, processing, and combination of products of three genes-HEXA, HEXB, and GM2A-within the cell's lysosomes. Mutations in these genes result in Tay-Sachs disease, Sandhoff disease, or AB-variant GM2 gangliosidosis (ABGM2), respectively. ABGM2, the rarest of the three types, is characterized by a mutation in the GM2A gene, which encodes the GM2 activator (GM2A) protein. Being a monogenic disease, gene therapy is a plausible and likely effective method of treatment for ABGM2. This study aimed at assessing the effects of administering a one-time intravenous treatment of single-stranded Adeno-associated virus serotype 9 (ssAAV9)-GM2A viral vector at a dose of 1 × 1014 vector genomes (vg) per kilogram per mouse in an ABGM2 mouse model (Gm2a-/-). ssAAV9-GM2A was administered at 1-day (neonatal) or 6-weeks of age (adult-stage). The results demonstrated that, in comparison to Gm2a-/- mice that received a vehicle injection, the treated mice had reduced GM2 accumulation within the central nervous system and had long-term persistence of vector genomes in the brain and liver. This proof-of-concept study is a step forward towards the development of a clinically therapeutic approach for the treatment of patients with ABGM2.

Biochemical Correction of GM2 Ganglioside Accumulation in AB-Variant GM2 Gangliosidosis.

GM2 gangliosidosis is a group of genetic disorders that result in the accumulation of GM2 ganglioside (GM2) in brain cells, leading to progressive central nervous system (CNS) atrophy and premature death in patients. AB-variant GM2 gangliosidosis (ABGM2) arises from loss-of-function mutations in the GM2 activator protein (GM2AP), which is essential for the breakdown of GM2 in a key catabolic pathway required for CNS lipid homeostasis. In this study, we show that intrathecal delivery of self-complementary adeno-associated virus serotype-9 (scAAV9) harbouring a functional human GM2A transgene (scAAV9.hGM2A) can prevent GM2 accumulation in in GM2AP-deficient mice (Gm2a-/- mice). Additionally, scAAV9.hGM2A efficiently distributes to all tested regions of the CNS within 14 weeks post-injection and remains detectable for the lifespan of these animals (up to 104 weeks). Remarkably, GM2AP expression from the transgene scales with increasing doses of scAAV9.hGM2A (0.5, 1.0 and 2.0 × 1011 vector genomes (vg) per mouse), and this correlates with dose-dependent correction of GM2 accumulation in the brain. No severe adverse events were observed, and comorbidities in treated mice were comparable to those in disease-free cohorts. Lastly, all doses yielded corrective outcomes. These data indicate that scAAV9.hGM2A treatment is relatively non-toxic and tolerable, and biochemically corrects GM2 accumulation in the CNS-the main cause of morbidity and mortality in patients with ABGM2. Importantly, these results constitute proof-of-principle for treating ABGM2 with scAAV9.hGM2A by means of a single intrathecal administration and establish a foundation for future preclinical research.

Autophagic flux is impaired in the brain tissue of Tay-Sachs disease mouse model.

Tay-Sachs disease is a lethal lysosomal storage disorder caused by mutations in the HexA gene encoding the α subunit of the lysosomal β-hexosaminidase enzyme (HEXA). Abnormal GM2 ganglioside accumulation causes progressive deterioration in the central nervous system in Tay-Sachs patients. Hexa-/- mouse model failed to display abnormal phenotype. Recently, our group generated Hexa-/-Neu3-/- mouse showed severe neuropathological indications similar to Tay-Sachs patients. Despite excessive GM2 ganglioside accumulation in the brain and visceral organs, the regulation of autophagy has not been clarified yet in the Tay-Sachs disease mouse model. Therefore, we investigated distinct steps of autophagic flux using markers including LC3 and p62 in four different brain regions from the Hexa-/-Neu3-/- mice model of Tay-Sachs disease. Our data revealed accumulated autophagosomes and autophagolysosomes indicating impairment in autophagic flux in the brain. We suggest that autophagy might be a new therapeutic target for the treatment of devastating Tay-Sachs disease.

Plasma GM2 ganglioside potential biomarker for diagnosis, prognosis and disease monitoring of GM2-Gangliosidosis.

GM2-Gangliosidosis are a group of inherited lysosomal storage pathologies characterized by a large accumulation of GM2 ganglioside in the lysosome. They are caused by mutation in HEXA or HEXB causing reduced or absent activity of a lysosomal β-hexosaminidase A, or mutation in GM2A causing defect in GM2 activator protein (GM2AP), an essential protein for the activity of the enzyme. Biochemical diagnosis relies on the measurement of β-hexosaminidases A and B activities, which is able to detect lysosomal enzyme deficiency but fails to identify defects in GM2AP. We developed a rapid, specific and sensitive liquid chromatography-mass spectrometry-based method to measure simultaneously GM1, GM2, GM3 and GD3 molecular species. Gangliosides were analysed in plasma from 19 patients with GM2-Gangliosidosis: Tay-Sachs (n = 9), Sandhoff (n = 9) and AB variant of GM2-Gangliosidosis (n = 1) and compared to 20 age-matched controls. Among patients, 12 have a late adult-juvenile-onset and 7 have an infantile early-onset of the disease. Plasma GM2 molecular species were increased in all GM2-Gangliosidosis patients (19/19), including the patient with GM2A mutation, compared to control individuals and compared to patients with different other lysosomal storage diseases. GM234:1 and GM234:1/GM334:1 ratio discriminated patients from controls with 100% sensitivity and specificity. GM234:1 and GM234:1/GM334:1 were higher in patients with early-onset compared to those with late-onset of the disease, suggesting a relationship with severity. Longitudinal analysis in one adult with Tay-Sachs disease over 9 years showed a positive correlation of GM234:1 and GM234:1/GM334:1 ratio with age at sampling. We propose that plasma GM2 34:1 and its ratio to GM3 34:1 could be sensitive and specific biochemical diagnostic biomarkers for GM2-Gangliosidosis including AB variant and could be useful as a first line diagnostic test and potential biomarkers for monitoring upcoming therapeutic efficacy.

Enzyme-responsive polymersomes ameliorate autophagic failure in a cellular model of GM1 gangliosidosis

GM1 gangliosidosis is a lysosomal storage disorder caused by deficiency of β-galactosidase (βgal) and subsequent accumulation of GM1 ganglioside in lysosomes. One of the pathological aspects of GM1 gangliosidosis, and other storage disorders, is impaired autophagy, i.e., a reduced fusion of autophagosomes and lysosomes to degrade cellular waste. Enzyme replacement therapy (ERT) can effectively treat systemic deficiency but is limited by immunogenicity and shortened half-life of intravenously administered enzyme. In this paper, we report a hyaluronic acid-b-polylactic acid (HA-PLA) polymersome delivery system that can achieve an enzyme-responsive and sustained delivery of βgal to promote the cell’s self-healing process of autophagy. HA-PLA polymersomes have an average diameter of 138.0 ± 17.6 nm and encapsulate βgal with an efficiency of 77.7 ± 3.4%. In the presence of model enzyme Hyaluronidase, HA-PLA polymersomes demonstrate a two-fold higher release of encapsulant than without enzyme. We also identified reduced autophagy in a cellular model of GM1 Gangliosidosis (GM1SV3) compared to healthy cells, illustrated using immunofluorescence. Enhanced autophagy was reported in GM1SV3 cells treated with βgal-loaded polymersomes. Most notably, the fusion of lysosomes and autophagosomes in GM1SV3 cells returned to normal levels of healthy cells after 24 h of polymersome treatment. The HA-PLA polymersomes described here can provide a promising delivery system to treat GM1 Gangliosidosis.

AAVrh10 vector corrects pathology in animal models of GM1 gangliosidosis and achieves widespread distribution in the CNS of nonhuman primates

GM1 gangliosidosis is a rare, inherited neurodegenerative disorder caused by mutations in the GLB1 gene, which encodes the lysosomal hydrolase acid β-galactosidase (β-gal). β-gal deficiency leads to toxic accumulation of GM1 ganglioside, predominantly in the central nervous system (CNS), resulting in progressive neurodegeneration. LYS-GM101 is an AAVrh.10-based gene therapy vector carrying the human GLB1 cDNA. The efficacy of intra-cerebrospinal fluid injection of LYS-GM101 analogs was demonstrated in GM1 mouse and cat models with widespread diffusion of β-gal and correction of GM1 ganglioside accumulation in the CNS without observable adverse effects. Clinical dose selection was performed, based on a good-laboratory-practice study, in nonhuman primates (NHPs) using the clinical LYS-GM101 vector. A broadly distributed increase of β-gal activity was observed in NHP brain 3 months after intra-cisterna magna injection of LYS-GM101 at 1.0×1012 vg/mL CSF and 4.0×1012 vg/mL CSF, with 20% and 60% increases compared with vehicle-treated animals, respectively. Histopathologic examination revealed asymptomatic adverse changes in the sensory pathways of the spinal cord and dorsal root ganglia in both sexes and at both doses. Taken as a whole, these pre-clinical data support the initiation of a clinical study with LYS-GM101 for the treatment of GM1 gangliosidosis.

Infantile Sandhoff disease with ventricular septal defect: a case report

BackgroundInfantile Sandhoff disease is a rare inherited disorder that progressively destroys nerve cells in the brain and spinal cord, and is classified under lysosomal storage disorder. It is an autosomal recessive disorder of sphingolipid metabolism that results from deficiency of the lysosomal enzymes β-hexosaminidase A and B. The resultant accumulation of GM2 ganglioside within both gray matter nuclei and myelin sheaths of the white matter results in eventual severe neuronal dysfunction and neurodegeneration.Case presentationWe evaluated a 3.5-year-old Comorian girl from the United Arab Emirates who presented with repeated chest infections with heart failure due to ventricular septal defect, neuroregression, recurrent seizures, and cherry-red spots over macula. She had macrocephaly, axial hypotonia, hyperacusis, and gastroesophageal reflux. Organomegaly was absent. Brain magnetic resonance imaging, metabolic tests, and genetic mutations confirmed the diagnosis. Despite multidisciplinary therapy, the girl succumbed to her illness.ConclusionThough early cardiac involvement can be seen with novel mutations, it is extremely rare to find association of ventricular septal defect in infantile Sandhoff disease. Neuroregression typically starts around 6 months of age. We report this case because of the unusual association of a congenital heart disease with underlying infantile Sandhoff disease and symptomatic heart failure in the first month of life with eventual fatal outcome.

Preclinical Enzyme Replacement Therapy with a Recombinant β-Galactosidase-Lectin Fusion for CNS Delivery and Treatment of GM1-Gangliosidosis.

GM1-gangliosidosis is a catastrophic, neurodegenerative lysosomal storage disease caused by a deficiency of lysosomal β-galactosidase (β-Gal). The primary substrate of the enzyme is GM1-ganglioside (GM1), a sialylated glycosphingolipid abundant in nervous tissue. Patients with GM1-gangliosidosis present with massive and progressive accumulation of GM1 in the central nervous system (CNS), which leads to mental and motor decline, progressive neurodegeneration, and early death. No therapy is currently available for this lysosomal storage disease. Here, we describe a proof-of-concept preclinical study toward the development of enzyme replacement therapy (ERT) for GM1-gangliosidosis using a recombinant murine β-Gal fused to the plant lectin subunit B of ricin (mβ-Gal:RTB). We show that long-term, bi-weekly systemic injection of mβ-Gal:RTB in the β-Gal−/− mouse model resulted in widespread internalization of the enzyme by cells of visceral organs, with consequent restoration of enzyme activity. Most importantly, β-Gal activity was detected in several brain regions. This was accompanied by a reduction of accumulated GM1, reversal of neuroinflammation, and decrease in the apoptotic marker caspase 3. These results indicate that the RTB lectin delivery module enhances both the CNS-biodistribution pattern and the therapeutic efficacy of the β-Gal ERT, with the potential to translate to a clinical setting for the treatment of GM1-gangliosidosis.