Natural history of GM1 gangliosidosis-Retrospective cohort study of 61 French patients from 1998 to 2019

A Case for Automated Segmentation of MRI Data in Neurodegenerative Diseases: Type II GM1 Gangliosidosis

BACKGROUND

Volumetric analysis and segmentation of magnetic resonance imaging (MRI) data is an important tool for evaluating neurological disease progression and neurodevelopment. Fully automated segmentation pipelines offer faster and more reproducible results. However, since these analysis pipelines were trained on or run based on atlases consisting of neurotypical controls, it is important to evaluate how accurate these methods are for neurodegenerative diseases. In this study, we compared five fully automated segmentation pipelines, including FSL, Freesurfer, volBrain, SPM12, and SimNIBS, with a manual segmentation process in GM1 gangliosidosis patients and neurotypical controls.

METHODS

We analyzed 45 MRI scans from 16 juvenile GM1 gangliosidosis patients, 11 MRI scans from 8 late-infantile GM1 gangliosidosis patients, and 19 MRI scans from 11 neurotypical controls. We compared the results for seven brain structures, including volumes of the total brain, bilateral thalamus, ventricles, bilateral caudate nucleus, bilateral lentiform nucleus, corpus callosum, and cerebellum.

RESULTS

We found volBrain's vol2Brain pipeline to have the strongest correlations with the manual segmentation process for the whole brain, ventricles, and thalamus. We also found Freesurfer's recon-all pipeline to have the strongest correlations with the manual segmentation process for the caudate nucleus. For the cerebellum, we found a combination of volBrain's vol2Brain and SimNIBS' headreco to have the strongest correlations, depending on the cohort. For the lentiform nucleus, we found a combination of recon-all and FSL's FIRST to give the strongest correlations, depending on the cohort. Lastly, we found segmentation of the corpus callosum to be highly variable.

CONCLUSIONS

Previous studies have considered automated segmentation techniques to be unreliable, particularly in neurodegenerative diseases. However, in our study, we produced results comparable to those obtained with a manual segmentation process. While manual segmentation processes conducted by neuroradiologists remain the gold standard, we present evidence to the capabilities and advantages of using an automated process that includes the ability to segment white matter throughout the brain or analyze large datasets, which pose feasibility issues to fully manual processes. Future investigations should consider the use of artificial intelligence-based segmentation pipelines to determine their accuracy in GM1 gangliosidosis, lysosomal storage disorders, and other neurodegenerative diseases.

Natural history progression of MRI brain volumetrics in type II late-infantile and juvenile GM1 gangliosidosis patients

OBJECTIVE

GM1 gangliosidosis is a rare lysosomal storage disorder characterized by the accumulation of GM1 gangliosides in neuronal cells, resulting in severe neurodegeneration. Currently, limited data exists on the brain volumetric changes associated with this disease. This study focuses on the late-infantile and juvenile subtypes of type II GM1 gangliosidosis, aiming to quantify brain volumetric characteristics to track disease progression.

METHODS

Brain volumetric analysis was conducted on 56 MRI scans from 24 type II GM1 patients (8 late-infantile and 16 juvenile) and 19 healthy controls over multiple time points. The analysis included the use of semi-automated segmentation of the whole brain, ventricles, cerebellum, corpus callosum, thalamus, caudate, and lentiform nucleus. A generalized linear model was used to compare the volumetric measurements between the patient groups and healthy controls, accounting for age as a confounding factor.

RESULTS

Both late-infantile and juvenile GM1 patients exhibited significant whole-brain atrophy compared to healthy controls, even after adjusting for age. Notably, the late-infantile subtype displayed more pronounced atrophy in the cerebellum, thalamus, and corpus callosum compared to the juvenile subtype. Both late-infantile and juvenile subtypes showed significantly higher ventricular volumes and a significant reduction in all other structure volumes compared to the healthy controls. The volumetric measurements also correlated well with disease severity based on clinical metrics.

CONCLUSIONS

The findings underscore the distinct brain volumetrics of the late-infantile and juvenile subtypes of GM1 gangliosidosis compared to healthy controls. These quantifications can be used as reliable imaging biomarkers to track disease progression and evaluate responses to therapeutic interventions.

A Case for Automated Segmentation of MRI Data in Milder Neurodegenerative Diseases

Background

Volumetric analysis and segmentation of magnetic resonance imaging (MRI) data is an important tool for evaluating neurological disease progression and neurodevelopment. Fully automated segmentation pipelines offer faster and more reproducible results. However, since these analysis pipelines were trained on or run based on atlases consisting of neurotypical controls, it is important to evaluate how accurate these methods are for neurodegenerative diseases. In this study, we compared 5 fully automated segmentation pipelines including FSL, Freesurfer, volBrain, SPM12, and SimNIBS with a manual segmentation process in GM1 gangliosidosis patients and neurotypical controls.

Methods

We analyzed 45 MRI scans from 16 juvenile GM1 gangliosidosis patients, 11 MRI scans from 8 late-infantile GM1 gangliosidosis patients, and 19 MRI scans from 11 neurotypical controls. We compared results for 7 brain structures including volumes of the total brain, bilateral thalamus, ventricles, bilateral caudate nucleus, bilateral lentiform nucleus, corpus callosum, and cerebellum.

Results

We found volBrain's vol2Brain pipeline to have the strongest correlations with the manual segmentation process for the whole brain, ventricles, and thalamus. We also found Freesurfer's recon-all pipeline to have the strongest correlations with the manual segmentation process for the caudate nucleus. For the cerebellum, we found a combination of volBrain's vol2Brain and SimNIBS' headreco to have the strongest correlations depending on the cohort. For the lentiform nucleus, we found a combination of recon-all and FSL's FIRST to give the strongest correlations depending on the cohort. Lastly, we found segmentation of the corpus callosum to be highly variable.

Conclusion

Previous studies have considered automated segmentation techniques to be unreliable, particularly in neurodegenerative diseases. However, in our study we produced results comparable to those obtained with a manual segmentation process. While manual segmentation processes conducted by neuroradiologists remain the gold standard, we present evidence to the capabilities and advantages of using an automated process including the ability to segment white matter throughout the brain or analyze large datasets, which pose feasibility issues to fully manual processes. Future investigations should consider the use of artificial intelligence-based segmentation pipelines to determine their accuracy in GM1 gangliosidosis, lysosomal storage disorders, and other neurodegenerative diseases.

Base editing of the GLB1 gene is therapeutic in GM1 gangliosidosis patient-derived cells

GM1 gangliosidosis is an autosomal recessive neurodegenerative lysosomal storage disease caused by pathogenic variants in the GLB1 gene, limiting the production of active lysosomal β-galactosidase. Phenotypic heterogeneity is due in part to variant type, location within GLB1, and the amount of residual enzyme activity; in the most severe form, death occurs in infancy. With no FDA approved therapeutics, development of efficacious strategies for the disease is pivotal. CRISPR/Cas based approaches have revolutionized precision medicine and have been indispensable to the development of treatments for several monogenic disorders with bespoke strategies central to current research pipelines. We used CRISPR/Cas-adenine base editing to correct the GLB1 c.380G>A (p.Cys127Tyr) variant in patient-derived dermal fibroblasts compound heterozygous with the GLB1 c.481T>G (p.Trp161Gly) pathogenic variant. Nucleofection of plasmids encoding the target sgRNA and ABEmax restored the canonical guanine (32.2 ± 2.2 % of the target allele) and synthesis of active β-galactosidase. Analysis of cellular markers of pathology revealed normalization of both primary glycoconjugate storage and lysosomal pathology. Furthermore, analysis of off-target sites nominated by the in silico tools Cas-OFFinder and/or CRISTA revealed no significant editing or indels. This study supports the use of CRISPR/Cas-based approaches for the treatment of GM1 gangliosidosis, and provides foundational data for future translational studies.

Differential Tractography: A Biomarker for Neuronal Function in Neurodegenerative Disease

GM1 gangliosidosis is an ultra-rare inherited neurodegenerative lysosomal storage disorder caused by biallelic mutations in the GLB1 gene. GM1 is uniformly fatal and has no approved therapies, although clinical trials investigating gene therapy as a potential treatment for this condition are underway. Novel outcome measures or biomarkers demonstrating the longitudinal effects of GM1 and potential recovery due to therapeutic intervention are urgently needed to establish efficacy of potential therapeutics. One promising tool is differential tractography, a novel imaging modality utilizing serial diffusion weighted imaging (DWI) to quantify longitudinal changes in white matter microstructure. In this study, we present the novel use of differential tractography in quantifying the progression of GM1 alongside age-matched neurotypical controls. We analyzed 113 DWI scans from 16 GM1 patients and 32 age-matched neurotypical controls to investigate longitudinal changes in white matter pathology. GM1 patients showed white matter degradation evident by both the number and size of fiber tract loss. In contrast, neurotypical controls showed longitudinal white matter improvements as evident by both the number and size of fiber tract growth. We also corroborated these findings by documenting significant correlations between cognitive global impression (CGI) scores of clinical presentations and our differential tractography derived metrics in our GM1 cohort. Specifically, GM1 patients who lost more neuronal fiber tracts also had a worse clinical presentation. This result demonstrates the importance of differential tractography as an important biomarker for disease progression in GM1 patients with potential extension to other neurodegenerative diseases and therapeutic intervention.

GM1 gangliosidosis type II: Results of a 10-year prospective study

PURPOSE

GM1 gangliosidosis (GM1) a lysosomal disorder caused by pathogenic variants in GLB1, is characterized by relentless neurodegeneration. There are no approved treatments.

METHODS

Forty-one individuals with type II (late-infantile and juvenile) GM1 participated in a single-site prospective observational study.

RESULTS

Classification of 37 distinct variants using American College of Medical Genetics and Genomics criteria resulted in the upgrade of 6 and the submission of 4 new variants. In contrast to type I infantile disease, children with type II had normal or near normal hearing and did not have cherry-red maculae or hepatosplenomegaly. Some older children with juvenile onset disease developed thickened aortic and/or mitral valves. Serial magnetic resonance images demonstrated progressive brain atrophy, more pronounced in late infantile patients. Magnetic resonance spectroscopy showed worsening elevation of myo-inositol and deficit of N-acetyl aspartate that were strongly correlated with scores on the Vineland Adaptive Behavior Scale, progressing more rapidly in late infantile compared with juvenile onset disease.

CONCLUSION

Serial phenotyping of type II GM1 patients expands the understanding of disease progression and clarifies common misconceptions about type II patients; these are pivotal steps toward more timely diagnosis and better supportive care. The data amassed through this 10-year effort will serve as a robust comparator for ongoing and future therapeutic trials.

Drug Repurposing and Lysosomal Storage Disorders: A Trick to Treat

Rare diseases, or orphan diseases, are defined as diseases affecting a small number of people compared to the general population. Among these, we find lysosomal storage disorders (LSDs), a cluster of rare metabolic diseases characterized by enzyme mutations causing abnormal glycolipid storage. Drug repositioning involves repurposing existing approved drugs for new therapeutic applications, offering advantages in cost, time savings, and a lower risk of failure. We present a comprehensive analysis of existing drugs, their repurposing potential, and their clinical implications in the context of LSDs, highlighting the necessity of mutation-specific approaches. Our review systematically explores the landscape of drug repositioning as a means to enhance LSDs therapies. The findings advocate for the strategic repositioning of drugs, accentuating its role in expediting the discovery of effective treatments. We conclude that drug repurposing represents a viable pathway for accelerating therapeutic discovery for LSDs, emphasizing the need for the careful evaluation of drug efficacy and toxicity in disease-specific contexts.

GM1 Gangliosidosis Type II: Results of a 10-Year Prospective Study

Purpose

GM1 gangliosidosis (GM1) is an ultra-rare lysosomal storage disease caused by pathogenic variants in galactosidase beta 1 (GLB1; NM_000404), primarily characterized by neurodegeneration, often in children. There are no approved treatments for GM1, but clinical trials using gene therapy (NCT03952637, NCT04713475) and small molecule substrate inhibitors (NCT04221451) are ongoing. Understanding the natural history of GM1 is essential for timely diagnosis, facilitating better supportive care, and contextualizing the results of therapeutic trials.

Methods

Forty-one individuals with type II GM1 (n=17 late infantile and n=24 juvenile onset) participated in a single-site prospective observational study. Here, we describe the results of extensive multisystem assessment batteries, including clinical labs, neuroimaging, physiological exams, and behavioral assessments.

Results

Classification of 37 distinct variants in this cohort was performed according to ACMG criteria and resulted in the upgrade of six and the submission of four new variants to pathogenic or likely pathogenic. In contrast to type I infantile, children with type II disease exhibited normal or near normal hearing and did not have cherry red maculae or significant hepatosplenomegaly. Some older children with juvenile onset developed thickened aortic and/or mitral valves with regurgitation. Serial MRIs demonstrated progressive brain atrophy that were more pronounced in those with late infantile onset. MR spectroscopy showed worsening elevation of myo-inositol and deficit of N-acetyl aspartate that were strongly correlated with scores on the Vineland Adaptive Behavior Scale and progress more rapidly in late infantile than juvenile onset disease.

Conclusion

The comprehensive serial phenotyping of type II GM1 patients expands the understanding of disease progression and clarifies some common misconceptions about type II patients. Findings from this 10-year endeavor are a pivotal step toward more timely diagnosis and better supportive care for patients. The wealth of data amassed through this effort will serve as a robust comparator for ongoing and future therapeutic trials.

Gene therapy approaches for GM1 gangliosidosis: Focus on animal and cellular studies

One of the most important inherited metabolic disorders is GM1 gangliosidosis, which is a progressive neurological disorder. The main cause of this disease is a genetic defect in the enzyme β-galactosidase due to a mutation in the glb1 gene. Lack of this enzyme in cells (especially neurons) leads to the accumulation of ganglioside substrate in nerve tissues, followed by three clinical forms of GM1 disease (neonatal, juvenile, and adult variants). Genetically, many mutations occur in the exons of the glb1 gene, such as exons 2, 6, 15, and 16, so the most common ones reported in scientific studies include missense/nonsense mutations. Therefore, many studies have examined the genotype-phenotype relationships of this disease and subsequently using gene therapy techniques have been able to reduce the complications of the disease and alleviate the signs and symptoms of the disease. In this regard, the present article reviews the general features of GM1 gangliosidosis and its mutations, as well as gene therapy studies and animal and human models of the disease.