Gangliosides and Autoimmune Peripheral Nerve Diseases

Association Between NK Cell Genetic Variants and the Development of Long COVID Associated- and Prepandemic Small Fiber Neuropathy

Long coronavirus disease 2019 (COVID) (LC) symptoms including pain and autonomic dysfunction are in some patients associated with small-fiber neuropathy (SFN). The pathomechanisms underlying SFN are mostly unclear. Natural killer (NK) cells play a crucial role in immune regulation, viral clearance and nerve metabolism. The aim of this study was to identify associations between development of small-fiber dysfunction dependent and independent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and human genetic markers associated with specific NK cell functions. The genetic markers assessed in all cohorts included: FCGR3A, IGHG1, HLA-E, NKG2C, and rs9916629. Genotyping was performed using TaqMan assays, Sanger sequencing and touchdown polymerase chain reaction. We assessed human cytomegalovirus (HCMV) IgG serostatus in all participants, and screened for anti-neuronal, anti-glial and anti-ganglioside autoantibodies in both patient cohorts. We included 50 LC patients with newly-emerged symptoms of small-fiber dysfunction after SARS-CoV-2 infection, 27 prepandemic SFN patients and 320 control persons. Markers associated with low NKG2C response, that is, deletion of the NKG2C gene and lack of prior HCMV infection (IgG seronegativity), occurred significantly more frequently in prepandemic SFN patients compared to LC patients and controls (p = 0.0109 and 0.0005, respectively). In conclusion, markers of impaired NKG2C pathways are associated with prepandemic SFN, but not with Long COVID-associated small-fiber dysfunction.

Neurological features of Hansen disease: a retrospective, multicenter cohort study

To elucidate the neurological features of Hansen disease. The medical records of patients with confirmed Hansen disease transferred from the neurology department were reviewed, and all medical and neurological manifestations of Hansen disease were assessed. Eleven patients with confirmed Hansen disease, 10 with newly detected Hansen disease and 1 with relapsed Hansen disease, who visited neurology departments were enrolled. The newly detected patients with Hansen disease were classified as having lepromatous leprosy (LL, n = 1), borderline lepromatous leprosy (BL, n = 2), borderline leprosy (BB, n = 2), borderline tuberculoid leprosy (BT, n = 1), tuberculoid leprosy (TT, n = 2), or pure neural leprosy (PNL, n = 2). All of the patients with confirmed Hansen were diagnosed with peripheral neuropathy (100.00%, 11/11). The symptoms and signs presented were mainly limb numbness (100.00%, 11/11), sensory and motor dysfunction (100.00%, 11/11), decreased muscle strength (90.90%, 10/11), and skin lesions (81.81%, 9/11). Nerve morphological features in nerve ultrasonography (US) included peripheral nerve asymmetry and segmental thickening (100.00%, 9/9). For neuro-electrophysiology feature, the frequency of no response of sensory nerves was significantly higher than those of motor nerves [(51.21% 42/82) vs (24.70%, 21/85)(P = 0.0183*)] by electrodiagnostic (EDX) studies. Nerve histological features in nerve biopsy analysis included demyelination (100.00%, 5/5) and axonal damage (60.00%, 3/5). In addition to confirmed diagnoses by acid-fast bacteria (AFB) staining (54.54%, 6/11) and skin pathology analysis (100.00%, 8/8), serology and molecular technology were positive in 36.36% (4/11) and 100.00% (11/11) of confirmed patients of Hansen disease, respectively. It is not uncommon for patients of Hansen disease to visit neurology departments due to peripheral neuropathy. The main pathological features of affected nerves are demyelination and axonal damage. The combination of nerve US, EDX studies, nerve biopsy, and serological and molecular tests can improve the diagnosis of Hansen disease.

Neuroimmune regulation in the pancreas

The pancreas exerts endocrine and exocrine functions in energy balance. The neural innervation and immune milieu are both crucial in supporting pancreatic homeostasis. The neuronal network connects the pancreas with the central nervous system (CNS) and the enteric nervous system (ENS) and sustains metabolic activities. The nerves in the pancreas are categorized as spinal sensory afferent fibers, vagal sensory afferent nerves, autonomic fibers of both sympathetic and parasympathetic divisions, and fibers from the ENS and intrapancreatic ganglia. They innervate different regions and various cell types, which collectively determine physiological functions. Studies have established that the diverse pathological conditions, including pancreatitis, diabetes, and pancreatic tumor, are attributed to aberrant immune reactions; however, it is largely not clear how the neuronal network may influence the disease conditions. Enlightened by the recent advances illuminating the organ-wide neuronal architecture and the dysfunctions in pancreatic disorders, this review will highlight emerging opportunities to explore the cellular interrelationship, particularly the neuroimmune components in pancreatic health and diseases.

Ganglioside GM1 and the Central Nervous System

GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

Ganglioside analysis in body fluids by liquid-phase separation techniques hyphenated to mass spectrometry

The expression of gangliosides in central nervous system is a few times higher than in the extraneural tissue, a characteristic highlighting their major role at this level. Although in very low amounts, gangliosides are ubiquitously distributed in body fluids too, where, depending on many factors, including pathological states, their composition fluctuates, thus having diagnostic value. Ganglioside investigation in biological fluids, which, except for cerebrospinal fluid (CSF), may be sampled noninvasively, was for years impeded by the limited sensitivity of the analytical instrumentation available in glycomics. However, because the last decade has witnessed significant developments in biological mass spectrometry (MS) and the hyphenated separation techniques, marked by a major increase in sensitivity, reproducibility, and data reliability, ganglioside research started to be focused on biofluid analysis by separation techniques coupled to MS. In this context, our review presents the achievements in this emerging field of gangliosidomics, with a particular emphasis on modern liquid chromatography (LC), thin-layer chromatography, hydrophilic interaction LC, and ion mobility separation coupled to high-performance MS, as well as the results generated by these systems and allied experimental procedures in profiling and structural analysis of gangliosides in healthy or diseased body fluids, such as CSF, plasma/serum, and milk.

Acute Bulbar Palsy and Ophtalmoplegia Associated With Anti-GT1a IgG Antibodies

INTRODUCTION

Although several variants of Guillain-Barré syndrome (GBS) have been described, they are uncommon, and the atypical clinical presentation of patients makes the diagnosis challenging. This article reports a case of acute bulbar palsy plus (ABPp) syndrome.

CASE REPORT

A 18-year-old patient was admitted to our hospital because of difficulty swallowing, slurred speech, tingling of the extremities of the 4 limbs, and diplopia. He reported abdominal pain and diarrhea 2 weeks earlier. Physical examination showed a low-pitched voice, palsy elevation of the soft palate and complete palsy of the abduction of the left eye. Electromyography and cerebrospinal fluid examination were unremarkable, but Campylobacter jejuni serology was positive, and we found an isolated immunoglobulin G (IgG) anti-GT1a antibodies positivity. A diagnosis of ABPp was finally made, and the patient fully recovered early after receiving polyvalent immunoglobulins infusion.

CONCLUSIONS

ABPp is classified as subtype of GBS. The most frequent clinical signs of ABPp are ophthalmoplegia, facial palsy, and ataxia. IgG anti-GT1a and/or anti-GQ1b are positive in a majority of patients with ABPp; however, these antibodies are not specific and can found in other subtypes of GBS.

Early targeting of endoneurial macrophages alleviates the neuropathy and affects abnormal Schwann cell differentiation in a mouse model of Charcot-Marie-Tooth 1A

We have previously shown that targeting endoneurial macrophages with the orally applied CSF-1 receptor specific kinase (c-FMS) inhibitor PLX5622 from the age of 3 months onwards led to a substantial alleviation of the neuropathy in mouse models of Charcot-Marie-Tooth (CMT) 1X and 1B disease, which are genetically-mediated nerve disorders not treatable in humans. The same approach failed in a model of CMT1A (PMP22-overexpressing mice, line C61), representing the most frequent form of CMT. This was unexpected since previous studies identified macrophages contributing to disease severity in the same CMT1A model. Here we re-approached the possibility of alleviating the neuropathy in a model of CMT1A by targeting macrophages at earlier time points. As a proof-of-principle experiment, we genetically inactivated colony-stimulating factor-1 (CSF-1) in CMT1A mice, which resulted in lower endoneurial macrophage numbers and alleviated the neuropathy. Based on these observations, we pharmacologically ablated macrophages in newborn CMT1A mice by feeding their lactating mothers with chow containing PLX5622, followed by treatment of the respective progenies after weaning until the age of 6 months. We found that peripheral neuropathy was substantially alleviated after early postnatal treatment, leading to preserved motor function in CMT1A mice. Moreover, macrophage depletion affected the altered Schwann cell differentiation phenotype. These findings underscore the targetable role of macrophage-mediated inflammation in peripheral nerves of inherited neuropathies, but also emphasize the need for an early treatment start confined to a narrow therapeutic time window in CMT1A models and potentially in respective patients.

The impact of the glycan headgroup on the nanoscopic segregation of gangliosides

Gangliosides form an important class of receptor lipids containing a large oligosaccharide headgroup whose ability to self-organize within lipid membranes results in the formation of nanoscopic platforms. Despite their biological importance, the molecular basis for the nanoscopic segregation of gangliosides is not clear. In this work, we investigated the role of the ganglioside headgroup on the nanoscale organization of gangliosides. We studied the effect of the reduction in the number of sugar units of the ganglioside oligosaccharide chain on the ability of gangliosides GM1, GM2, and GM3 to spontaneously self-organize into lipid nanodomains. To reach nanoscopic resolution and to identify molecular forces that drive ganglioside segregation, we combined an experimental technique, Förster resonance energy transfer analyzed by Monte-Carlo simulations offering high lateral and trans-bilayer resolution with molecular dynamics simulations. We show that the ganglioside headgroup plays a key role in ganglioside self-assembly despite the negative charge of the sialic acid group. The nanodomains range from 7 to 120 nm in radius and are mostly composed of the surrounding bulk lipids, with gangliosides being a minor component of the nanodomains. The interactions between gangliosides are dominated by the hydrogen bonding network between the headgroups, which facilitates ganglioside clustering. The N-acetylgalactosamine sugar moiety of GM2, however, seems to impair the stability of these clusters by disrupting hydrogen bonding of neighboring sugars, which is in agreement with a broad size distribution of GM2 nanodomains. The simulations suggest that the formation of nanodomains is likely accompanied by several conformational changes in the gangliosides, which, however, have little impact on the solvent exposure of these receptor groups. Overall, this work identifies the key physicochemical factors that drive nanoscopic segregation of gangliosides.

Ganglioside-monosialic acid (GM1) for prevention of chemotherapy-induced peripheral neuropathy: a meta-analysis with trial sequential analysis

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting side effect that largely remains an unresolved clinical issue, leading to long-term morbidity. This meta-analysis aimed to evaluate the efficacy and safety of Ganglioside-monosialic acid (GM1) in preventing CIPN.

METHODS

Systematic literature searches of PubMed, Web of Science, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov were performed to identify randomized controlled trials and cohort studies that evaluated the efficacy of GM1 for preventing CIPN. Conventional meta-analysis with a random-effects model and trial sequential analysis (TSA) were performed.

RESULTS

A total of five studies involving 868 participants were included. The results showed that GM1 did not reduce the overall incidence of grade ≥ 2 CIPN when the common terminology criteria for adverse events (CTCAE) was used (OR 0.34, 95% CI 0.34-1.11). Subgroup analyses showed that GM1 could not reduce the risk of CTCAE grade ≥ 2 CIPN (OR 0.63, 95% CI 0.35-1.13) and neurotoxicity criteria of Debiopharm (DEB-NTC) grade ≥ 2 CIPN (OR 0.25, 95% CI 0.01-7.10) in oxaliplatin-treated patients, despite that GM1 was associated with a reduced risk of CTCAE grade ≥ 2 CIPN in the taxane subgroup of one study (OR 0.003, 95% CI 0.00-0.05). These results were confirmed by the sub-analysis of randomized controlled trials (RCTs). In TSA, the z-curve for the taxane subgroup crossed the upper trial sequential monitoring boundary (TSMB) but do not reach the required information size (RIS). The z-curves for the oxaliplatin subgroup remained in the nonsignificant area and did not reach the RIS. Further, GM1 did not influence the rate of response to chemotherapy and CTCAE grade ≥ 2 adverse events such as fatigue, nausea, diarrhea, and rash.

CONCLUSIONS

GM1 seemed to be well-tolerated and did not influence the anti-cancer effects of chemotherapeutic agents. Although the data did not confirm the effectiveness of GM1 in preventing oxaliplatin-induced peripheral neuropathy, GM1 might be able to prevent taxane-induced peripheral neuropathy. More studies are required in different ethnic populations receiving taxane-based chemotherapy to confirm these findings.

Characterization of Gangliosides in Three Sea Urchin Species by HILIC-ESI-MS/MS

Sea urchin gangliosides (SU-GLSs) are well acknowledged for their nerve regeneration activity and neuroprotective property. The present study sought to characterize and semi-quantitate different SU-GLS subclasses in three sea urchin species, including Strongylocentrotus nudus, Hemicentrotus pulcherrimus, and Glyptocidaris crenularis. A total of 14 SU-GLS subclasses were identified by a hydrophilic interaction liquid chromatography-Q-Exactive tandem mass spectrometry method. Three sialic acid (Sia) structures, including Neu5Ac, Neu5Gc, and KDN, were identified in SU-GLSs, of which Neu5Ac and Neu5Gc had their corresponding sulfated forms. The linkage among Sias was determined to be 2-8. Additionally, KDN2-6Glc1-1Cer, KDN2-8Neu5Gc2-6Glc1-1Cer, and KDN2-8Neu5Gc2-8Neu5Gc2-6Glc-1Cer were speculated to be novel SU-GLS structures. Furthermore, the total SU-GLS content was 2.0-7.3 mg/g in the three sea urchin species. These results will provide useful data for developing a SU-GLS database of aquatic products. Besides, this study will provide a theoretical basis to explore the nutritional values of seafood products further.

An incomplete form of anti-ganglioside antibody-positive Miller Fisher syndrome after an Epstein-Barr virus infection: A case report

RATIONALE

The Miller Fisher syndrome (MFS) is an acute polyradiculoneuritis regarded as an uncommon clinical variant of the Guillain-Barre syndrome (GBS). It is characterized by the clinical triad of ophthalmoplegia, ataxia, and areflexia. The diagnosis of MFS is based on clinical presentation, presence of albuminocytologic dissociation in the cerebrospinal fluid (CSF), and normal brain imaging results. The presence of anti-ganglioside antibodies (GQlb) in the serum is helpful for the diagnosis. A history of upper respiratory tract infection or diarrhea 3 days to 6 weeks before the onset of MFS is common. However, there are some patients with atypical manifestations who are difficult to diagnose. Here, we present an incomplete form of MFS where antibodies against GQ1b were detected in the serum following an Epstein Barr virus (EBV) infection.

PATIENT CONCERNS

A 77-year-old Chinese woman was admitted to the hospital with acute diplopia and right blepharoptosis. She had a history of mild upper respiratory tract infection 2 weeks ago. In 1 week, the symptoms rapidly progressed into bilateral ophthalmoplegia and hyporeflexia of the limbs without ataxia. CSF analysis on the third day after onset was normal, without albuminocytologic dissociation. EBV immunoglobulin G (IgG) antibodies were detected in the CSF. GQ1b and GD1b IgG antibodies were positive in the serum and negative in the CSF. No responsible lesion was found on brain imaging examination.

DIAGNOSES

In accordance with the progressive bilateral ophthalmoplegia and hyporeflexia, the history of upper respiratory tract infection, the detection of EBV and GQ1b antibodies, and the negative brain imaging examination, the diagnosis of MFS was confirmed.

INTERVENTIONS

The patient was administered intravenous immunoglobulin for 5 days.

OUTCOMES

She had a favorable outcome after treatment. At the 6-week follow-up, bilateral ocular movement limitation and tendon reflexes had recovered.

LESSONS

The diagnosis of MFS can be challenging, especially when encountered with incomplete symptoms and normal CSF results. Attention should be paid to the presence of anti-GQ1b IgG antibodies when the clinical manifestations are incomplete. Furthermore, EBV primary infection could be associated with MFS and considered a potential causative agent.

Role of 1-Deoxysphingolipids in docetaxel neurotoxicity

A major dose-limiting side effect of docetaxel chemotherapy is peripheral neuropathy. Patients' symptoms include pain, numbness, tingling and burning sensations, and motor weakness in the extremities. The molecular mechanism is currently not understood, and there are no treatments available. Previously, we have shown an association between neuropathy symptoms of patients treated with paclitaxel and the plasma levels of neurotoxic sphingolipids, the 1-deoxysphingolipids (1-deoxySL) (Kramer et al, FASEB J, 2015). 1-DeoxySL are produced when the first enzyme of the sphingolipid biosynthetic pathway, serine palmitoyltransferase (SPT), uses L-alanine as a substrate instead of its canonical amino acid substrate, L-serine. In the current investigation, we tested whether 1-deoxySL accumulate in the nervous system following systemic docetaxel treatment in mice. In dorsal root ganglia (DRG), we observed that docetaxel (45 mg/kg cumulative dose) significantly elevated the levels of 1-deoxySL and L-serine-derived ceramides, but not sphingosine-1-phosphate (S1P). S1P is a bioactive sphingolipid and a ligand for specific G-protein-coupled receptors. In the sciatic nerve, docetaxel decreased 1-deoxySL and ceramides. Moreover, we show that in primary DRG cultures, 1-deoxysphingosine produced neurite swellings that could be reversed with S1P. Our results demonstrate that docetaxel chemotherapy up-regulates sphingolipid metabolism in sensory neurons, leading to the accumulation of neurotoxic 1-deoxySL. We suggest that the neurotoxic effects of 1-deoxySL on axons can be reversed with S1P.

Axonal degeneration in Guillain-Barré syndrome: a reappraisal

The aim of this review was to analyse the pathophysiology of axonal degeneration in Guillain-Barré syndrome (GBS) with emphasis on early stages (≤ 10 days after onset). An overview of experimental autoimmune neuritis (EAN) models is provided. Originally GBS and acute inflammatory demyelinating polyneuropathy were equated, presence of axonal degeneration being attributed to a "bystander" effect. Afterwards, primary axonal GBS forms were reported, designated as acute motor axonal neuropathy/acute motor-sensory axonal neuropathy. Revision of the first pathological description of axonal GBS indicates the coexistence of active axonal degeneration and demyelination in spinal roots, and pure Wallerian-like degeneration in peripheral nerve trunks. Nerve conduction studies are essential for syndrome subtyping, though their sensitivity is scanty in early GBS. Serum markers of axonal degeneration include increased levels of neurofilament light chain and presence of anti-ganglioside reactivity. According to nerve ultrasonographic features and autopsy studies, ventral rami of spinal nerves are a hotspot in early GBS. In P₂-induced EAN models, the initial pathogenic change is inflammatory oedema of spinal roots and sciatic nerve, which is followed by demyelination, and Wallerian-like degeneration in nerve trunks possessing epi-perineurium; a critical elevation of endoneurial fluid pressure is a pre-requisite for inducing ischemic axonal degeneration. Similar lesion topography may occur in GBS. The repairing role of adaxonal Schwann cytoplasm in axonal degeneration is analysed. A novel pathophysiological mechanism for nerve trunk pain in GBS, including pure motor forms, is provided. The potential therapeutic role of intravenous boluses of methylprednisolone for early severe GBS and intractable pain is argued.

Laboratory Tests for Neuropathies: What to do and to Avoid

OBJECTIVES

laboratory tests for work-up of hereditary and acquired neuropathies of peripheral nerves are frequently uncritically utilized. This overview focuses on the most common laboratory tests and investigations needed for diagnosing PNPs by the general neurologist.

METHOD

Literature search.

RESULTS

laboratory tests recommended for the work-up of hereditary and acquired neuropathies should be chosen according to the individual and family history, clinical presentation, and electrophysiological findings. Laboratory tests should be selected specifically according to the suspected type of neuropathy to avoid unnecessary tests and expenses. Work-up should include as few samples as necessary for uncovering the etiology and should consider the sensitivity/specificity of the tests applied.. Basic screening tests for neuropathies should include a blood cell count, thyroid, renal and liver function tests, blood glucose levels, HbA1c, vitamin-B12, and immunofixation. Other laboratory investigations should be carried out only if a specific phenotype is present or if unexpected changes of the disease course occur. In these cases referral to a neuromuscular center is recommended.

CONCLUSIONS

Laboratory tests are helpful for the diagnosis of acquired and hereditary neuropathies but these tests should be ordered according to the history, clinical presentation and findings on electrophysiological investigations. If basic laboratory parameters fail to uncover the etiology, patients should be referred to a center specialized in neuromuscular disorders.

ANTIBODIES AND RECEPTORS: From Neuromuscular Junction to Central Nervous System

Myasthenia gravis (MG) is a relatively rare neurological disease that is usually associated with antibodies to the acetylcholine receptor (AChR). These antibodies (Abs) cause loss of the AChRs from the neuromuscular junction (NMJ), resulting in muscle weakness that can be life-threatening. Another form of the disease is caused by antibodies to muscle specific kinase (MuSK) that result in impaired AChR clustering and numbers at the NMJ, and may also interfere with presynaptic adaptive mechanisms. Other autoimmune disorders, Lambert Eaton myasthenic syndrome and acquired neuromyotonia, are associated with antibodies to presynaptic voltage-gated calcium and potassium channels respectively. All four conditions can be diagnosed by specific clinical features, electromyography and serum antibody tests, and can be treated effectively by a combination of pharmacological approaches and procedures that reduce the levels of the IgG antibodies. They form the first of a spectrum of diseases in which serum autoantibodies bind to extracellular domains of neuronal proteins throughout the nervous system and lead to constellations of clinical features including paralysis, sensory disturbance and pain, memory loss, seizures, psychiatric disturbance and movement disorders. This review will briefly summarize the ways in which this field has developed, since the 1970s when considerable contributions were made in Ricardo Miledi's laboratory at UCL.

Glycosphingolipids and Infection. Potential New Therapeutic Avenues

Glycosphingolipids (GSLs), the main topic of this review, are a subclass of sphingolipids. With their glycans exposed to the extracellular space, glycosphingolipids are ubiquitous components of the plasma membrane of cells. GSLs are implicated in a variety of biological processes including specific infections. Several pathogens use GSLs at the surface of host cells as binding receptors. In addition, lipid-rafts in the plasma membrane of host cells may act as platform for signaling the presence of pathogens. Relatively common in man are inherited deficiencies in lysosomal glycosidases involved in the turnover of GSLs. The associated storage disorders (glycosphingolipidoses) show lysosomal accumulation of substrate(s) of the deficient enzyme. In recent years compounds have been identified that allow modulation of GSLs levels in cells. Some of these agents are well tolerated and already used to treat lysosomal glycosphingolipidoses. This review summarizes present knowledge on the role of GSLs in infection and subsequent immune response. It concludes with the thought to apply glycosphingolipid-lowering agents to prevent and/or combat infections.

The Biology of Gangliosides

Gangliosides comprise a varied family of glycosphingolipid structures bearing one or more sialic acid residues. They are found in all mammalian tissues but are most abundant in the brain, where they represent the quantitatively major class of sialoglycans. As prominent molecular determinants on cell surfaces, they function as molecular-recognition partners for diverse glycan-binding proteins ranging from bacterial toxins to endogenous cell-cell adhesion molecules. Gangliosides also regulate the activity of plasma membrane proteins, including protein tyrosine kinases, by lateral association in the same membranes in which they reside. Their roles in molecular recognition and membrane protein regulation implicate gangliosides in human physiology and pathology, including infectious diseases, diabetes, cancer, and neurodegeneration. The varied structures and biosynthetic pathways of gangliosides are presented here, along with representative examples of their biological functions in health and disease.